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KESHAVARZI, MARYAM, RAHELEH TABARIPOUR, and FAZAL ULLAH. "Assessment of SCoT and ISSR molecular markers in genetic diversity of rigid ryegrass (Lolium rigidum Gaud.) in Iran." Phytotaxa 538, no. 3 (March 8, 2022): 182–96. http://dx.doi.org/10.11646/phytotaxa.538.3.2.
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Lolium rigidum (Poaceae) is important forage and weed species grown in different habitats of Iran. Rigid ryegrass originated from the Mediterranean region. They are very resistant to common herbicides. To investigate the genetic variability of L. rigidum, we studied 81 individuals of 18 natural populations from Iran; four ISSR and four SCoT primers were used. These are reproducible and highly polymorphic markers. We examined their gene flow and genetic variation. Genetic diversity among and within populations was determined through different methods. The Mantel test indicated a significant correlation between these populations’ genetic distance and geographical distance and a high correlation between ISSR and SCoT markers. Analyses of molecular variance (AMOVA) produced high genetic differences among the studied populations for both markers. Structure analysis showed population genetic stratification and identified three genetic groups through ISSR molecular markers for L. rigidum in Iran and indicated restricted gene flow. The current investigation revealed the productivity of ISSR and SCoT molecular markers in evaluating genetic variation and grouping of wild populations of L. rigidum and provides detailed data concerning the genetic structure of its populations. The present finding provided useful information for further conservation, selection, and breeding plans.
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Manalil, Sudheesh, Roberto Busi, Michael Renton, and Stephen B. Powles. "An Herbicide-Susceptible Rigid Ryegrass (Lolium rigidum) Population Made Even More Susceptible." Weed Science 60, no. 1 (March 2012): 101–5. http://dx.doi.org/10.1614/ws-d-11-00076.1.
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A wild population of a plant species, especially a cross-pollinated species, can display considerable genetic variation. Genetic variability is evident in differential susceptibility to an herbicide because the population can show continuous phenotypic variation. Recent, recurrent selection studies have revealed that phenotypic variation in response to low herbicide rates is heritable and can result in rapid evolution of herbicide resistance in genetically variable cross-pollinated rigid ryegrass. In this study, the heritable genetic variation in an herbicide-susceptible rigid ryegrass population was exploited to shift the population toward greater herbicide susceptibility by recurrent selection. To enhance herbicide susceptibility, herbicide-susceptible rigid ryegrass plants were divided into two identical clones, and one series of cloned plants was treated with a low rate of herbicide (diclofop). The nontreated clones of individuals that did not survive the herbicide treatment were selected and bulk-crossed to obtain the susceptible progeny. After two cycles of selection, the overall susceptibility to diclofop was doubled. The results indicate that minor genes for resistance are present in an herbicide-susceptible rigid ryegrass population, and their exclusion can increase susceptibility to diclofop.
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Simarmata, Marulak, Suleiman Bughrara, and Donald Penner. "Inheritance of glyphosate resistance in rigid ryegrass (Lolium rigidum) from California." Weed Science 53, no. 5 (October 2005): 615–19. http://dx.doi.org/10.1614/ws-04-187r.1.
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Glyphosate resistance was found in a rigid ryegrass population in northern California. A sample of the resistant plants were collected and grown under greenhouse conditions. The objective of this study was to evaluate glyphosate resistance in the progeny of the collected plants by recurrent selection, obtain the homozygous resistant and sensitive lines to establish dose-response curves, and to determine the inheritance of glyphosate resistance in rigid ryegrass. Diverse levels of resistance were observed in the first generation with survival of 89, 59, 45, and 9% from glyphosate at 1x, 2x, 4x, and 8x respectively, where x = 1.12 kg ha−1isopropylamine salt of glyphosate. Clones of plants that died from 1x were allowed to produce seed and were further subjected to recurrent selection to generate the most sensitive plants (S lines), which died from 0.125x glyphosate. The most resistant plants (R lines) were generated from the survivors receiving 8x glyphosate. The ratio between I50rates for the glyphosate resistant and the glyphosate sensitive plants was > 100-fold. The R and S lines were crossed reciprocally and F1progeny of both (R × S) and (S × R) showed intermediate resistance. These survived up to 2x glyphosate. The F2progeny were generated by intercrossing of F1plants. The ratio of sensitive, intermediate, and resistant plants in the F2population before the treatment of glyphosate at 0.125x followed by 8x was 1 : 16, 14 : 16, and 1 : 16 respectively, which corresponded to the Mendelian segregation ratio of two genes. The results indicated that the inheritance of glyphosate resistance in rigid ryegrass from California appeared to be nuclear, incompletely dominant, multigenic, and pollen-transmitted with no indication of maternal inheritance.
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Brunton, David J., Gurjeet Gill, and Christopher Preston. "Resistance to bixlozone and clomazone in cross-resistant rigid ryegrass (Lolium rigidum) populations from southern Australia." Weed Science 69, no. 3 (January 28, 2021): 284–89. http://dx.doi.org/10.1017/wsc.2021.6.
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AbstractThree resistant (R) rigid ryegrass (Lolium rigidum Gaudin) populations from southern Australia (EP162, 375-14, and 198-15) with cross-resistance to thiocarbamate, chloroacetamide, and sulfonylisoxazoline herbicides displayed reduced sensitivity to the isoxazolidinone herbicides bixlozone and clomazone. Each of these R populations was exposed to two cycles of recurrent selection (RS) in which plants were treated with the field rate of bixlozone, survivors were bulk crossed, and seed was collected. After the first cycle of recurrent selection (RS1), the LD50 to bixlozone in population 198-15 increased to 17.5-fold compared with the S population and increased further to 26.9-fold after a second cycle of recurrent selection (RS2). The recurrent selection process also increased the level of resistance to bixlozone in populations EP162 and 375-14 (7.8- to 18.4-fold) compared with the S population. Phorate antagonized bixlozone and clomazone in SLR4 (34.6- and 28.1-fold increase in LD50) and both herbicides in populations EP162 (36.5- to 46.6-fold), 375-14 (71.4- to 73.9-fold), and 198-15 (86.4- to 91.5-fold) compared with the absence of phorate. The increase in LD50 of all L. rigidum RS populations when treated with phorate suggests a lack of herbicide activation is not the likely resistance mechanism to these herbicides. This research highlights the elevated risk of thiocarbamate-resistant L. rigidum populations to rapidly evolve resistance to the isoxazolidinone herbicides bixlozone and clomazone.
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Bullitta, S. "Response to selection for root dimension in a Mediterranean natural population of Lolium rigidum Gaud." Plant Breeding 115, no. 1 (April 1996): 63–66. http://dx.doi.org/10.1111/j.1439-0523.1996.tb00872.x.
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Broster, J. C., J. E. Pratley, R. H. L. Ip, L. Ang, and K. P. Seng. "Cropping practices influence incidence of herbicide resistance in annual ryegrass (Lolium rigidum) in Australia." Crop and Pasture Science 70, no. 1 (2019): 77. http://dx.doi.org/10.1071/cp18355.
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Herbicide resistance is a common occurrence in southern Australia. The evolution of herbicide resistance is influenced by the selection pressure placed on the weed species controlled by that herbicide. Results from resistance screening of ~4500 annual ryegrass (Lolium rigidum Gaud.) samples were entered in a GIS database, together with several agricultural parameters used in the Australian Bureau of Statistics Agricultural Surveys. This allowed a study of the associations between mode of action of resistance, geographic distribution of resistance across southern Australia, and farming practices employed in particular regions. Cultivation was negatively associated with resistances in acetyl-CoA carboxylase (ACCase)-inhibiting cyclohexanedione and acetolactate synthase (ALS)-inhibiting herbicides. Higher proportions of wheat sown were associated with higher incidences of resistance. ACCase-inhibiting aryloxyphenoxypropionate and cyclohexanedione and ALS-inhibiting resistances were higher in those shires where soils were predominantly acidic. This study demonstrates the association between farm practice and the evolution of herbicide resistance. The analysis provides reinforcement to the principle of rotating chemical modes of action with non-chemical weed control measures to minimise the risk of herbicide resistance evolution in any farming system.
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Burnet, Michael W. M., John T. Christopher, Joseph A. M. Holtum, and Stephen B. Powles. "Identification of Two Mechanisms of Sulfonylurea Resistance Within One Population of Rigid Ryegrass (Lolium rigidum) Using a Selective Germination Medium." Weed Science 42, no. 3 (September 1994): 468–73. http://dx.doi.org/10.1017/s0043174500076785.
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A biotype of rigid ryegrass (Lolium rigidumGaudin biotype VLR69) resistant to some ALS inhibitors was characterized to determine the mechanisms of resistance to the sulfonylurea herbicides. The biotype had a high level of resistance to chlorsulfuron (20×) and triasulfuron (25×), and an intermediate level of resistance to imazaquin (7×) and sulfometuron (7.5×) but exhibited a low level of resistance to imazapyr (2.5×). At 60 to 90 g ai ha-1sulfometuron, 4% of the population survived without apparent herbicidal effect The same response to sulfometuron was also observed when seeds of the resistant biotype VLR69 were germinated on agar containing sulfometuron. At 27 nM sulfometuron, 4% of the seeds germinated and grew normally while the growth of the bulk of the population was retarded. This differential response to sulfometuron at the seedling stage allowed selection of sulfometuron-resistant individuals from the population. Activity of ALS extracted from these sulfometuron-resistant plants was less sensitive to inhibition by chlorsulfuron than ALS extracted from plants considered sulfometuron susceptible in the same system. Unselected plants from the VLR69 population were able to detoxify chlorsulfuron more rapidly than susceptible VLR1 plants. It is apparent that there are at least two mechanisms of sulfonylurea resistance in the resistant biotype VLR69 which occur at different frequencies within the population. These data show that more than one mechanism or resistance may develop in response to herbicide selection pressure and that the resulting populations are not necessarily homogeneous.
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Fernandez-Moreno, Pablo Tomas, Antonia Maria Rojano-Delgado, Julio Menendez, and Rafael De Prado. "First Case of Multiple Resistance to Glyphosate and PPO-inhibiting Herbicides in Rigid Ryegrass (Lolium rigidum) in Spain." Weed Science 65, no. 6 (August 22, 2017): 690–98. http://dx.doi.org/10.1017/wsc.2017.49.
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Five rigid ryegrass populations suspected of being resistant to both glyphosate and oxyfluorfen were collected in southern Spain and tested under laboratory-controlled conditions. Four populations (Depuradora, Condado, AlamoRasilla, and Portichuelo) were treated with glyphosate for at least 15 consecutive years, and treatments during the last 5 yr were mixed with oxyfluorfen. The fifth population (4alamos) followed the same glyphosate treatment, although oxyfluorfen was never used to control it. Dose–response assays confirmed glyphosate resistance in all populations, with resistance indexes ranging from 11.7 to 37.5 (GR90). Shikimate accumulation assays consistently supported these data, as the most glyphosate-resistant populations (Depuradora and Condado) displayed the lowest shikimate levels. Surprisingly, four populations (Depuradora, Condado, AlamoRasilla, and Portichuelo) displayed 7.93- to 70.18-fold more resistance (GR90) to oxyfluorfen, despite limited selection pressure, showing a similar resistance pattern as that for glyphosate. The 4alamos population displayed oxyfluorfen GR90values that were similar to those observed in susceptible plants; however, this population was significantly more resistant in terms of plant survival (LD90). Protoporphyrin IX accumulation assays supported the results of dose–response assays, in that the most oxyfluorfen-resistant populations accumulated less protoporphyrin IX. Although more studies are needed, it seems that these five glyphosate-resistant weed populations display a natural tendency to easily develop resistance to oxyfluorfen, with the populations that have higher resistance to glyphosate also having higher resistance to oxyfluorfen.
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Mahajan, Gulshan, Kerry McKenzie, and Bhagirath S. Chauhan. "Influence of row spacing and cultivar selection on annual ryegrass (Lolium rigidum) control and grain yield in chickpea (Cicer arietinum)." Crop and Pasture Science 70, no. 2 (2019): 140. http://dx.doi.org/10.1071/cp18436.
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Annual ryegrass (ARG) (Lolium rigidum Gaudin) is a problematic weed for chickpea (Cicer arietinum L.) production in Australia. Understanding the critical period of control of ARG in chickpea is important for developing effective integrated management strategies to prevent unacceptable yield loss. Experiments were conducted over 2 years at the research farm of the University of Queensland, Gatton, to evaluate the effect of chickpea row spacing (25 and 75cm) and cultivar (PBA Seamer and PBA HatTrick) and ARG infestation period (from 0, 3 and 6 weeks after planting (WAP), and weed-free) on ARG suppression and grain yield of chickpea. Year×treatment interactions were not significant for any parameter, and none of the treatment combinations showed any interaction for grain yield. Average grain yield was greater (20%) with 25-cm than 75-cm rows. On average, PBA Seamer had 9% higher yield than PBA HatTrick. Average grain yield was lowest in season-long weedy plots (562kg ha–1) and highest in weed-free plots (1849kg ha–1). Grain yield losses were lower when ARG emerged at 3 WAP (1679kg ha–1). Late-emerged ARG (3 and 6 WAP) had lower biomass (4.7–22.2g m–2) and number of spikes (5–24m–2) than ARG that emerged early; at 0 WAP, weed biomass was 282–337g m–2 and number of spikes 89–120m–2. Compared with wide row spacing, narrow row spacing suppressed ARG biomass by 16% and 52% and reduced number of spikes of ARG by 26% and 48% at 0 WAP and 3 WAP, respectively. PBA Seamer suppressed ARG growth more effectively than PBA HatTrick, but only in the season-long weedy plots. Our results imply that in ARG-infested fields, grain yield of chickpea can be increased by exploring narrow row spacing and weed-competitive cultivars. These cultural tools could be useful for developing integrated weed management tactics in chickpea in combination with pre-emergent herbicides.
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Moore, Joseph R., James E. Pratley, Leslie A. Weston, Wade J. Mace, John C. Broster, and Karen A. Kirkby. "Epichloë occultans infection in Australian Lolium rigidum is associated with cropping history and environment but not with herbicide resistance status of host plant." Crop and Pasture Science 69, no. 6 (2018): 642. http://dx.doi.org/10.1071/cp17455.
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Annual ryegrass (Lolium rigidum Gaud.) is a troublesome invasive plant in southern Australian cropping systems and is typically infected with a fungal endophyte, Epichloë occultans. Potential links between herbicide resistance and endophyte infection were investigated in this study. We surveyed 391 ryegrass populations from geographically distinct, naturalised pasture and cropping areas across southern Australia and compared frequencies of seed-borne endophyte infection in the collected seed samples from mature annual ryegrass. Data on herbicide resistance from similar seedlots were cross-referenced with endophyte infection frequency to examine the potential relationship between herbicide resistance and endophyte infection. Seeds from cropping paddocks exhibited a significantly higher frequency of endophyte infection than pasture paddocks sampled from the same region. Frequencies of endophyte infection in annual ryegrass declined across Australia during 2001–09, whereas the opposite trend was observed during 2009–12. Impacts of the Australian Millennium Drought, the correspondingly altered rainfall patterns and environmental selection pressures have a role in determining observed endophyte infection frequencies. However, there was no significant correlation between endophyte frequency and herbicide resistance in the populations evaluated. Differences in endophyte infection frequencies were associated with farming practices, and require further examination to determine causative selection pressures encountered in Australian field settings.
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Goggin, D. E., S. B. Powles, and K. J. Steadman. "Selection for low or high primary dormancy in Lolium rigidum Gaud seeds results in constitutive differences in stress protein expression and peroxidase activity." Journal of Experimental Botany 62, no. 3 (October 25, 2010): 1037–47. http://dx.doi.org/10.1093/jxb/erq334.
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Owen, Mechelle J., and Stephen B. Powles. "Lessons learnt: crop-seed cleaning reduces weed-seed contamination in Western Australian grain samples." Crop and Pasture Science 71, no. 7 (2020): 660. http://dx.doi.org/10.1071/cp20093.
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Weeds are a major contributing factor to crop yield loss. Weed control is regularly practiced during the growing season, with many growers making a conscious effort to minimise weed-seed return to the soil seedbank during the cropping program. However, growers may be unintentionally introducing weed seeds through sowing of contaminated crop seed. Using samples of crop seed obtained from 29 growers across two Western Australian grain-growing regions, 81 samples were hand-cleaned to determine weed-seed contamination levels. Of those samples, 41% were weed-free, and in the remaining 59%, the main contaminant was Lolium rigidum (annual ryegrass), occurring in 49% of contaminated samples. Crop type and cleaning method had significant effects on the level of weed-seed contamination, with barley having higher levels of contamination than other crops, and professional contractors providing lower contamination than other methods of cleaning. However, any seed-cleaning method provided significantly cleaner grain samples than no seed cleaning. This study established that crop-seed contamination was evident on Western Australian farms and that growers may be unintentionally sowing weed seeds with their crops. Seed cleaning combined with judicious paddock selection and weed-seed removal during the growing season can lead to weed-free crop seed.
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Coleman, R. K., G. S. Gill, and G. J. Rebetzke. "Identification of quantitative trait loci for traits conferring weed competitiveness in wheat (Triticum aestivum L.)." Australian Journal of Agricultural Research 52, no. 12 (2001): 1235. http://dx.doi.org/10.1071/ar01055.
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As weeds develop resistance to a broad range of herbicides, wheat (Triticum aestivum L.) cultivars with superior weed competitive capacity are needed to complement integrated weed management strategies. In this study, agronomic and morphological traits that enable wheat to compete effectively with weeds were identified. Halberd, Cranbrook, and 161 Cranbrook x Halberd doubled haploid (DH) lines were examined in field experiments conducted over two growing seasons. The weed species Lolium rigidum L. (annual ryegrass) was sown in strips perpendicular to the direction of wheat seeding. Various traits were measured during each season with competitive ability determined by both percent loss in wheat grain yield and suppression of ryegrass growth. Width of leaf 2, canopy height, and light interception at early stem elongation (Z31), and tiller number, height at maturity, and days to anthesis were important for competitive ability in 1999. In the previous year, length of leaf 2 and size of the flag leaf contributed to competitiveness. Seasonal effects appeared to have some impact on the relative contribution of crop traits to competitive ability. The morphological traits involved in maintaining grain yield differed from those that contributed to the suppression of ryegrass growth. Development of the Cranbrook x Halberd chromosomal linkage map enabled the putative identification of quantitative trait loci (QTL) associated with competitive ability in the DH population. Many of the QTL were mapped to similar positions in both years. Further, several traits, including time to anthesis, flag leaf size, height at stem elongation, and the size of the first 2 leaves, were mapped to similar positions on chromosomes 2B and 2D. Narrow-sense heritabilities on an entry-mean basis were typically high within each year for traits associated with weed competitive ability. However, large genotype x year interactions reduced these heritabilities, making genetic gain through phenotypic selection difficult. The identification of QTL repeatable over seasons indicates the potential for marker-assisted selection in a wheat breeding program selecting for improved grain yield and weed competitiveness.
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Gaull, K. R., and T. J. Ridsdill-Smith. "The foraging behaviour of redlegged earth mite, Halotydeus destructor (Acarina: Penthaleidae), in an annual subterranean clover pasture." Bulletin of Entomological Research 86, no. 3 (June 1996): 247–52. http://dx.doi.org/10.1017/s0007485300052524.
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AbstractThe foraging behaviour of the redlegged earth mite, Halotydeus destructor (Tucker), in annual pasture was documented and the relative numbers of individuals foraging on subterranean clover, Trifolium subterraneum (Leguminosae), capeweed, Arctotheca calendula (Compositae) and grasses (mainly Lolium rigidum (Gramineae)), estimated in winter and spring in south-western Australia. The main feature of H. destructor foraging behaviour was the presence of aggregations ranging in size from 3–36 individuals on the adaxial surfaces of the upper canopy of the pasture. Most aggregating individuals were feeding, while most solitary and paired individuals were searching. There was no evidence that individuals aggregated for reproductive behaviour; the adult sex ratio was similar to that of the population even though immatures were under-represented in aggregations. During winter the distribution of numbers of H. destructor on subclover, capeweed and grasses in the upper canopy of pasture was similar to the estimated ground cover of these plant species. However, individuals showed host-plant selection for subclover when feeding. During spring, when the pasture plants were flowering, there were more H. destructor in capeweed flowers than in aggregations on subclover foliage. The capeweed flowers were shown to enhance the rate of H. destructor reproduction in a laboratory experiment. Most H. destructor were on or near the soil surface, with 10% at any one time on the upper canopy of the pasture. H. destructor is polyphagous, and behaved in pasture as a selective opportunist feeder.
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Harries, Martin, Ken C. Flower, Craig A. Scanlan, Michael T. Rose, and Michael Renton. "Interactions between crop sequences, weed populations and herbicide use in Western Australian broadacre farms: findings of a six-year survey." Crop and Pasture Science 71, no. 5 (2020): 491. http://dx.doi.org/10.1071/cp19509.
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Six years of survey data taken from 184 paddocks spanning 14 million ha of land used for crop and pasture production in south-west Western Australia were used to assess weed populations, herbicide resistance, integrated weed management (IWM) actions and herbicide use patterns in a dryland agricultural system. Key findings were that weed density within crops was low, with 72% of cropping paddocks containing fewer than 10 grass weeds/m2 at anthesis. Weed density and herbicide resistance were not correlated, despite the most abundant grass weed species (annual ryegrass, Lolium rigidum Gaudin) testing positive for resistance to at least one herbicide chemistry in 92% of monitored paddocks. A wide range of herbicides were used (369 unique combinations) suggesting that the diversity of herbicide modes of action may be beneficial for reducing further development of herbicide resistance. However, there was a heavy reliance on glyphosate, the most commonly applied active ingredient. Of concern, in respect to the evolution of glyphosate resistant weeds, was that 45% of glyphosate applications to canola were applied as a single active ingredient and area sown to canola in Western Australia expanded from 0.4 to 1.4 million hectares from 2005 to 2015. In order to minimise the weed seed bank within crops, pastures were used infrequently in some regions and in 50% of cases pastures were actively managed to reduce weed seed set, by applying a non-selective herbicide in spring. The use of non-selective herbicides in this manner also kills pasture plants, consequently self-regenerating pastures were sparse and contained few legumes where cropping intensity was high. Overall, the study indicated that land use selection and utilisation of associated weed management actions were being used successfully to control weeds within the survey area. However, to successfully manage herbicide resistant weeds land use has become less diverse, with pastures utilised less and crops with efficacious weed control options utilised more. Further consideration needs to be given to the impacts of these changes in land use on other production factors, such as soil nutrient status and plant pathogens to assess sustainability of these weed management practices in a wider context.
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Bullitta, S., R. Floris, M. D. Hayward, and F. Veronesi. "The Reproductive System of a Lolium rigidum Gaud. Population from Sardinia and its Implications for Breeding*." Plant Breeding 111, no. 4 (December 1993): 312–17. http://dx.doi.org/10.1111/j.1439-0523.1993.tb00647.x.
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Tapper, B. A., and G. C. M. Latch. "Selection against toxin production in endophyte-infected perennial ryegrass." NZGA: Research and Practice Series 7 (January 1, 1999): 107–11. http://dx.doi.org/10.33584/rps.7.1999.3389.
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Strains of perennial ryegrass (Lolium perenne L.) endophyte (Neotyphodium lolii) from nature can be selected by analysis of the alkaloid profiles in plants from diverse seed collections. Lolitrem B, ergovaline, and peramine are the alkaloids of primary interest. The selected endophytes can be cultured and transferred into improved cultivars or breeding lines to reduce or eliminate grazing animal toxicoses while significant plant protection qualities can be maintained. Because the endophytes are transmitted only through seed, stable infections with selected endophytes in pastures can be achieved. Keywords: alkaloids, endophyte, ergovaline, lolitrem, Neotyphodium lolii, peramine, perennial ryegrass
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Vandeleur, R. K., and G. S. Gill. "The impact of plant breeding on the grain yield and competitive ability of wheat in Australia." Australian Journal of Agricultural Research 55, no. 8 (2004): 855. http://dx.doi.org/10.1071/ar03136.
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Fourteen wheat (Triticum aestivum L.) cultivars released to Australian growers over the last century were examined to determine the impact of crop breeding on competitive ability with weeds. In 1999 and 2000 the weed used in the field study was annual ryegrass (Lolium rigidum Gaud.) and in 2001 oats (Avena sativa cv. Marloo) was the weedy competitor. In 2 out of 3 years (1999 and 2001), when Puccinia recondita (leaf rust) infection was not a problem, there were consistent trends for improvement in yielding ability through breeding effort over time. In these 2 seasons the yielding ability of wheat increased by around 15 kg/ha.year as compared with a yield increase of only 4.7 kg/ha.year in 2000 due to a heavy P. recondita infection. In 1999 and 2000, when annual ryegrass was used as the weedy competitor, there was no systematic trend for changes in crop yield loss with time (r = 0.47 in 1999; r = 0.08 in 2000, P > 0.05). However, in 2001, when oat was used as the weed, there was a significant positive linear relationship (r = 0.81, P < 0.01) between the year of cultivar release and crop yield loss, indicating inferior competitive ability of the modern cultivars. Old cultivars such as Nabawa not only provided superior weed suppression, they were also more tolerant of weeds as indicated by the smaller yield loss. Plant height appeared to be an important contributor to the superior competitiveness of the standard height, older cultivars. Other morphological traits contributing to superior competitive ability included greater leaf length and width, light interception, and flag leaf length. To improve the competitive ability of modern wheats without compromising their yielding ability, morphological traits that enhance early crop vigour (size of leaf 1 and 2) and light interception without affecting harvest index may need to be incorporated from carefully selected germplasm.
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Sokolovic, Dejan, Zoran Lugic, Jasmina Radovic, Tomislav Zivanovic, Snezana Babic, Aleksandar Simic, and Radojka Maletic. "Evaluation of morphological traits, dry matter yield and quality of Lolium perenne L. autochthonous populations from Serbia through multivariate analysis." Genetika 43, no. 1 (2011): 129–40. http://dx.doi.org/10.2298/gensr1101129s.
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Due to specific climatic conditions, perennial ryegrass breeding in Serbia is focused on resistance or tolerance to abiotic stress factors, especially to drought and high temperatures. These traits should be associated with high dry matter yield and quality. Therefore, most frequently used initial material is autochthonous populations and ecotypes adapted to local agro-ecological conditions, but knowledge about their variability of important traits for breeding is missing. Pre-selection evaluation of ten populations of perennial ryegrass originating from Serbia is presented in this paper. Twenty five traits were investigated during the two-year period and processed using analysis of variance and multivariate statistical methods (cluster and principal components analysis). The goal was to determine diversity and genetic distances of investigated populations by phenotyping and to define traits considerably affecting the variability and discrimination of populations. On cluster diagram two groups of population are observed, but geographic origin of populations (lowland, hilly, mountainous habitat) was not influence to clustering of collection. Factor analysis has clarified that first seven principal components (PC) described almost 95%. The traits which show high correlation coefficients with first principal component were plant height in first cut, leaf length and width, DM of generative tillers, spike and spikelet length and 1000 seed weight, and with second principal component time of heading, terminal internode length, DM of vegetative tillers, spikelet number and FSU. It can be concluded that variability between populations was high and that differences of population were mainly affected by most important traits for breeding, such as components of dry matter production and some seed yield components.
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Marais, J. P., D. C. W. Goodenough, M. de Figueiredo, and C. Hopkins. "The development of a Lolium multiflorum cultivar with a low moisture content and an increased readily digestible energy to protein ratio." Australian Journal of Agricultural Research 54, no. 1 (2003): 101. http://dx.doi.org/10.1071/ar02043.
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A breeding program was conducted to improve the forage quality of Lolium multiflorum. Fifteen cultivars grown in spaced-plant trials were subjected to selection for a low moisture and a high non-structural carbohydrate content. Results showed consistent positive correlations between non-structural carbohydrate content, dry matter content, and digestibility in vitro of the grass. In a small plot trial comparing F6 plants (Selection 121) with 11 commercial L. multiflorum cultivars, Selection 121 gave the second-highest dry matter yield (difference not significant, P > 0.05) of the cultivars tested. The dry matter content of Selection 121 was significantly higher and the acid detergent fibre content significantly lower than that of the commercial cultivars. Furthermore, the total non-structural carbohydrate content was significantly higher and the nitrogen content significantly lower than that of the other L. multiflorum cultivars, giving Selection 121 nutritionally a much more favourable readily digestible energy to protein ratio than the commercial cultivars. Selection 121 was subsequently named 'NCD Enhancer' and is inscribed on the South African Variety List.
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Muylle, H., E. van Bockstaele, and I. Roldan-Ruiz. "Selection of AFLP markers linked with crown rust resistance in Lolium: efficiency of bulk segregant analysis in an Allogamous species." Plant Protection Science 38, SI 1 - 6th Conf EFPP 2002 (January 1, 2002): 161–64. http://dx.doi.org/10.17221/10345-pps.
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Ryegrasses are important forage species. An important foliar disease in Lolium is crown rust, caused by the fungus Puccinia<br />coronata. This cosmopolitan biotrophic fungus causes forage and seed losses, and decoloration of amenity grasslands.<br />In breeding towards resistant cultivars, it is important to know the mode of inheritance of crown rust resistance. A pair<br />cross between a susceptible and a resistant plant resulted in a F1 population segregating for rust resistance. According to<br />the segregation data, major genes were assumed to encode for crown rust resistance. In a bulk segregant analysis (BSA)<br />187 primer combinations revealed AFLP markers linked with resistance. Two groups of genetically unlinked markers<br />were identified, explaining together 35% of the phenotypic variation.
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CASHMAN, P. A., T. J. GILLILAND, M. McEVOY, S. WATSON, and M. O'DONOVAN. "Changes in plant morphological expression in 12 perennial ryegrass cultivars following frequent and infrequent cutting management." Journal of Agricultural Science 154, no. 3 (June 2, 2015): 456–71. http://dx.doi.org/10.1017/s0021859615000386.
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SUMMARYPerennial ryegrass (Lolium perenneL.) cultivars are out-breeding populations of differing phenotypes, potentially allowing for directional selection to occur after sowing. To investigate this, the morphology of individual space plants (i.e. isolated plants sown at 0·75 m row spaces) grown from tillers extracted from single-cultivar swards subjected to frequent cutting (FC) or infrequent cutting (IC) for 5 years (aged accessions) were compared with plants grown from seed (seed accessions). The study examined 12 cultivars, creating 36 ‘accessions’ of 80 plants in each. These plants were examined for 23 morphological measurements to test for and classify directional selection in perennial ryegrass swards. A high degree of separation was achieved between the 12 seed accessions, validating the discriminating power of the experiment. Changes in morphological expression of plants taken from swards indicated selection in favour of particular morphological ideotypes. This directional selection was identified in 10 of the accessions subjected to FC and eight subjected to IC management. Emergence natural height (plant undisturbed height at inflorescence emergence) and plant volume (emergence width × emergence natural height) were the characters modified most between seed and aged accessions. The magnitude of these morphological changes varied between cultivars. Glencar had the greatest number of morphological characters exhibiting directional selection under frequent cutting, whereas Greengold had the greatest number exhibiting directional selection under infrequent cutting. The plants grown from aged swards were also smaller than the seed accessions in all characters, raising the possibility that they may also be less productive. The present study showed that sward management can cause and influence directional selection of plants from within the morphological range of expression within perennial ryegrass cultivars.
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Faville, M. J., A. Koulman, L. Briggs, M. Cao, C. Podmore, and D. Abraham. "Exploring endophyte compatibility in perennial ryegrass." NZGA: Research and Practice Series 13 (January 1, 2007): 143–46. http://dx.doi.org/10.33584/rps.13.2006.3105.
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The association between perennial ryegrass (PRG) and fungal endophyte is an important factor in the protection of New Zealand pastures from insect pests, and the genetic background of the host plant significantly affects endophyte performance. Quantitative trait locus (QTL) analysis of phenotypic data from herbage harvested from a mapping population in autumn 2005 identified loci in the PRG genome influencing three traits: (1) endophyte mycelial mass; (2) ergovaline level; (3) peramine level. Three QTL were identified for each trait. For mycelial mass two QTL accounted for more than 75% of the variation (PV) for in the population and have considerable potential for development as pre-inoculation marker-assisted selection (MAS) tools for endophyte colonisation in PRG breeding programmes. The largest-effect QTL for peramine level (18% PV) coincided with a major mycelial mass QTL, implying peramine concentration is partly determined by endophyte colonisation. All other alkaloid QTL, however, were independent of mycelial mass, indicating it may be possible to develop MAS that will facilitate breeding for alkaloid phenotype, independent of the degree of endophyte colonisation. Keywords: DIMS, ELISA, Lolium, map, metabolic profiling, Neotyphodium, SSR
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Worthington, Margaret L., S. Chris Reberg-Horton, David Jordan, and J. Paul Murphy. "A Comparison of Methods for Evaluating the Suppressive Ability of Winter Wheat Cultivars against Italian Ryegrass (Lolium perenne)." Weed Science 61, no. 3 (September 2013): 491–99. http://dx.doi.org/10.1614/ws-d-12-00167.1.
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Infestations of Italian ryegrass are problematic in both conventional and organic wheat production systems. The development of wheat cultivars with superior competitive ability against Italian ryegrass could play a role in maintaining acceptable yields and suppressing weed populations. Research was conducted in North Carolina to identify indirect methods of selection for Italian ryegrass suppressive ability (hereafter referred to as weed suppressive ability) of winter wheat cultivars that correlate well with Italian ryegrass-to-wheat biomass ratios. Two winter wheat cultivars (Dyna-Gro Baldwin and Dyna-Gro Dominion) and one experimental wheat line (NC05-19684) with differing morphological traits were overseeded with varying densities of Italian ryegrass. Wheat height measured throughout the growing season in weed-free plots was strongly associated with weed suppressive ability, but high wheat tillering capacity had no significant effect on weed suppressive ability in the lines tested in this study. Italian ryegrass seed head density during grain fill was strongly correlated (r= 0.94) with Italian ryegrass-to-wheat biomass ratio, the generally accepted measure of weed suppressive ability. Visual estimates of percent Italian ryegrass biomass relative to the plot with the highest level of Italian ryegrass infestation in each replicate were also strongly correlated with weed suppressive ability at all growth stages, especially during heading (r= 0.87) (Zadoks growth stage [GS] 55). Measurements from nonimaging spectrophotometers and overhead photographs taken from tillering (Zadoks 23 to 25) to early dough development (Zadoks 80) were unreliable estimates of end-of-season Italian ryegrass-to-wheat biomass ratios because they failed to account for wheat cultivar differences in biomass, color, and growth habit. Italian ryegrass seed head density and visual estimates of Italian ryegrass biomass during grain fill are appropriate indirect methods of selection for weed suppressive ability in breeding programs.
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Barrett, B. A., M. J. Faville, S. N. Nichols, W. R. Simpson, G. T. Bryan, and A. J. Conner. "Breaking through the feed barrier: options for improving forage genetics." Animal Production Science 55, no. 7 (2015): 883. http://dx.doi.org/10.1071/an14833.
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Pasture based on perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) is the foundation for production and profit in the Australasian pastoral sectors. The improvement of these species offers direct opportunities to enhance sector performance, provided there is good alignment with industry priorities as quantified by means such as the forage value index. However, the rate of forage genetic improvement must increase to sustain industry competitiveness. New forage technologies and breeding strategies that can complement and enhance traditional approaches are required to achieve this. We highlight current and future research in plant breeding, including genomic and gene technology approaches to improve rate of genetic gain. Genomic diversity is the basis of breeding and improvement. Recent advances in the range and focus of introgression from wild Trifolium species have created additional specific options to improve production and resource-use-efficiency traits. Symbiont genetic resources, especially advances in grass fungal endophytes, make a critical contribution to forage, supporting pastoral productivity, with benefits to both pastures and animals in some dairy regions. Genomic selection, now widely used in animal breeding, offers an opportunity to lift the rate of genetic gain in forages as well. Accuracy and relevance of trait data are paramount, it is essential that genomic breeding approaches be linked with robust field evaluation strategies including advanced phenotyping technologies. This requires excellent data management and integration with decision-support systems to deliver improved effectiveness from forage breeding. Novel traits being developed through genetic modification include increased energy content and potential increased biomass in ryegrass, and expression of condensed tannins in forage legumes. These examples from the wider set of research emphasise forage adaptation, yield and energy content, while covering the spectrum from exotic germplasm and symbionts through to advanced breeding strategies and gene technologies. To ensure that these opportunities are realised on farm, continuity of industry-relevant delivery of forage-improvement research is essential, as is sustained research input from the supporting pasture and plant sciences.
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Ludemann, C. I., C. M. Wims, and D. F. Chapman. "Validation of perennial ryegrass cultivar Forage Value Index rankings using independent trial data." Journal of New Zealand Grasslands 79 (January 1, 2017): 97–101. http://dx.doi.org/10.33584/jnzg.2017.79.562.
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Abstract The current DairyNZ Forage Value Index (FVI) categorises ryegrass cultivar-endophyte combinations into five, 'star rating' groups for dry matter (DM) yield using data from the National Forage Variety Trial (NFVT) system. However, variability in performance of cultivars between trials raises the question of how cultivars with different star ratings perform against each other under different conditions. The validity of the FVI star rating categories for perennial ryegrass was assessed using cultivar DM yield data from two independent trials outside the NFVT system and under dairy cow grazing with white clover. Results from the trials were used in Monte Carlo simulations to provide a probabilistic determination of the likelihood of high FVI rated cultivars outperforming the low FVI rated cultivars. Results indicate selecting high FVI (5 star) perennial ryegrass cultivars over lower FVI (3 star) cultivars deliver greater contributions to dairy operating profit in over 94% of the simulated iterations for the Waikato and Canterbury. Keywords: Forage Value Index, Lolium perenne, plant breeding, selection, cultivars
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Kosolapov, V. M., V. I. Cherniavskih, and S. I. Kostenko. "Fundamentals for forage crop breeding and seed production in Russia." Vavilov Journal of Genetics and Breeding 25, no. 4 (July 10, 2021): 401–7. http://dx.doi.org/10.18699/vj21.044.
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Plant breeding and seed production of new generation fodder crops is the groundwork for creating a fodder base for livestock production in sufficient quantities. The Federal Williams Research Center of Forage Production and Agroecology founded in 2018 based on of the All-Russia Williams Fodder Research Institute and other scientific institutions is the largest and most comprehensive center in the field of food production. It develops new techniques and methods for creating initial seed material based on a wide use of genetics, biotechnology, microbiology, immunology, ecology, biogeocenology, and cell selection. During the existence of the Fodder Research Institute and its experimental stations, up to 300 varieties of feed crops were created, which occupied leading positions in the production of fodder in meadows, pastures, and hayfields. Eighty-five modern varieties of fodder crops of the latest generation are widely used and zoned in all regions of Russia. However, the destroyed system of elite and commercial seed production does not allow these varieties to take their rightful place in fodder production, and the market still possesses a large share of non-varietal and mass scale reproduction seeds. In addition, imported seeds brought to the Russian market are often disguised as lawn varieties to reduce the cost and simplify their entry to the market. In this way, 107 varieties of winter ryegrass (Lolium perenne L.), 47 varieties of cane fescue (Festuca arundinacea Schreb.), 21 varieties of creeping clover (Trifolium repens L.), etc. appeared in Russia. In such circumstances, the attention of the Williams Center is focused on the development of techniques and methods for creating fundamentally new varieties based on its own research in genetics, biotechnology, immunology, and ecological selection. Much attention is paid to expanding the network of research stations throughout Russia in order to revive the system of elite seed growing, especially in the regions with the most favorable climate for growing seeds of particular crops. A seed production center was organized as a branch of the Williams Center at the end of 2020. In the future, it is planned to create a united coordinated interdepartmental complex for the breeding of fodder crops in accordance with the regional needs of animal husbandry.
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Wang, J., N. O. I. Cogan, L. W. Pembleton, and J. W. Forster. "Variance, inter-trait correlation, heritability and trait-marker association of herbage yield, nutritive values, and morphological characteristics in Italian ryegrass (Lolium multiflorum Lam.)." Crop and Pasture Science 66, no. 9 (2015): 973. http://dx.doi.org/10.1071/cp15070.
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Italian ryegrass (Lolium multiflorum Lam.) is one of the most important temperate forage grasses on a global basis. The present study estimated trait variance, inter-trait correlation and broad-sense heritability (H2) for herbage yield, nutritive values and morphological characteristics of Italian ryegrass, and analysed associations between these traits and single nucleotide polymorphism (SNP) markers. A field-based, spaced-plant nursery experiment was conducted to assess 960 genotypes from seven cultivars and breeding lines, in a randomised complete block design with four replicates. Significant correlations, broad ranges of variation and significant genotypic variance components were identified for 18 measured phenotypic traits. Moderate H2 estimates (0.36–0.52) were obtained for nutritive values, compared with low to high H2 estimates (0.20–0.69) for yield over five cuttings, and moderate to high H2 estimates (0.40–0.78) for morphological traits. Within- and among-cultivar variation ranged from 40.0% to 95.1% and 4.9% to 60.0%, respectively, depending on different traits. Association analysis identified 65 significant SNP–trait gene associations involving multiple genomic regions, which warrant further validation. The implications of trait correlation and heritability for selection and improvement are discussed.
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Jasieniuk, Marie, Riaz Ahmad, Anna M. Sherwood, Jeffrey L. Firestone, Alejandro Perez-Jones, W. Thomas Lanini, Carol Mallory-Smith, and Zachary Stednick. "Glyphosate-Resistant Italian Ryegrass (Lolium multiflorum) in California: Distribution, Response to Glyphosate, and Molecular Evidence for an Altered Target Enzyme." Weed Science 56, no. 4 (August 2008): 496–502. http://dx.doi.org/10.1614/ws-08-020.1.
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Selection by herbicides has resulted in widespread evolution of herbicide resistance in agricultural weeds. In California, resistance to glyphosate was first confirmed in rigid ryegrass in 1998. Objectives of this study were to determine the current distribution and level of glyphosate resistance in Italian ryegrass, and to assess whether resistance could be due to an altered target site. Seeds were sampled from 118 populations and seedlings were treated with glyphosate at 866 g ae ha−1. Percentage of survivors ranged from 5 to 95% in 54 populations. All plants from 64 populations died. One susceptible (S) population, four putatively resistant (R) populations, and one S accession from Oregon were used for pot dose–response experiments, shikimic acid analyses, and DNA sequencing. Seedlings were treated with glyphosate at eight rates, ranging from 108 to 13,856 g ae ha−1. Shoot biomass was evaluated 3 wk after treatment and fit to a log-logistic regression equation. On the basis of GR50(herbicide rate required to reduce growth by 50%) values, seedlings from putatively R populations were roughly two to 15 times more resistant to glyphosate than S plants. Shikimic acid accumulation was similar in all plants before glyphosate treatment, but at 4 and 7 DAT, S plants from California and Oregon accumulated approximately two and three times more shikimic acid, respectively, than R plants. Sequencing of a cDNA fragment of the EPSPS coding region revealed two different codons, both of which encode proline at amino acid position 106 in S individuals. In contrast, all R plants sequenced exhibited missense mutations at site 106. Plants from one population revealed a mutation resulting in a proline to serine substitution. Plants from three R populations exhibited a mutation corresponding to replacement of proline with alanine. Our results indicate that glyphosate resistance is widespread in Italian ryegrass populations of California, and that resistance is likely due to an altered target enzyme.
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Figueiredo Junior, Geide A., Roberto Busi, Danica E. Goggin, Aimone Porri, and Hugh J. Beckie. "Sensitivity of herbicide-resistant Rigid Ryegrass (Lolium rigidum) populations to cinmethylin, a new herbicide site of action." Weed Science, January 26, 2023, 1–20. http://dx.doi.org/10.1017/wsc.2023.2.
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Abstract Rigid ryegrass (Lolium rigidum Gaudin) is the most problematic weed in Australia, with evolved resistance to multiple herbicide sites of action. Selection pressure by cinmethylin (Group 30, a fatty acid thioesterase inhibitor) has been limited because few populations have been exposed to the herbicide since its introduction in 2019. In this study, we examined the sensitivity of L. rigidum populations to this new herbicide. From a screening of almost 500 field populations in 2020, 28 potentially-resistant populations were further investigated in a dose-response experiment. Seedlings from five populations surviving treatments of 250 or 375 g ai ha-1 cinmethylin were grown to maturity and seeds harvested. The level of resistance found among the five putative-resistant parental populations of L. rigidum was negligible. In one population, one round of selection with cinmethylin resulted in a two-fold increase in the lethal dose causing 50% mortality in the progeny population, although this dose was still only one-sixth of the recommended field rate of cinmethylin. Having a unique site of action, cinmethylin is a viable pre-emergence herbicide option to control existing multiple-resistance populations of L. rigidum. Comprehensive field monitoring and recurrent selection studies under controlled environmental conditions are needed to better ascertain the risk of L. rigidum evolving a high level of resistance to cinmethylin, although current data suggest that this risk is relatively low.
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García, Rosa M., Jesús Martínez-Fernández, Antonio Rodríguez, and Ana de la Torre. "Identification of sentinel plant species for evaluating phytotoxicity of veterinary antibiotics in Mediterranean Europe." Environmental Sciences Europe 34, no. 1 (April 14, 2022). http://dx.doi.org/10.1186/s12302-022-00608-0.
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Abstract Background Antibiotics used to treat livestock species enter agricultural fields when they are excreted by grazing animals or are present in manure that is added to fields as fertiliser. In the European Union, the potential effects of such antibiotics on terrestrial plants must be evaluated following the standardised OECD 208 method, which specifies the crop and wild species that should serve as “sentinels” for assessing antibiotic exposure. The present study aimed to compare this approved list of sentinel species against crop and wild plant species actually present in agricultural and pasture lands in Mediterranean Europe in order to identify the most appropriate sentinel plants for the region. The study focused on Spain as a region representative of Mediterranean Europe. Georeferenced layers for wild plant species and cultivated areas (crops), livestock density and land cover were combined, and then selection criteria were applied, leading to the identification of sentinel crop and wild species for crop land and pasture scenarios. Results In the crop land scenario, the sentinel crop species were barley (Hordeum vulgare L.), wheat (Triticum spp.), corn (Zea mays L), sunflower (Helianthus annuus L.), dried pea (Pisum sativum L.), alfalfa (Medicago sativa L.), vetch (Vicia sativa L.), oilseed rape (Brassica napus L.) and sugar beet (Saccharum officinarum L.), all of them listed in the OECD 208 method with the exception of alfalfa; the sentinel wild species were Papaver rhoeas L., Galium aparine L. and Chenopodium album L. In the pasture scenario, sentinel wild species were Bromus tectorum L., Agrostis capillaris L., Trifolium pratense L., Lotus corniculatus L. and Galium aparine L. The following common weed species in field boundaries or in pasture lands also emerged as potential sentinel species for risk assessment, even though they are not listed in the OECD 208 method: Sonchus oleraceus L., Avena sterilis L., Dactylis glomerata L., Hordeum murinum L. and Lolium rigidum Gaudin. Conclusions The sentinel species identified in this study may be useful in risk assessment procedures covering the Mediterranean Europe. The method developed for this study could be applied to identify sentinel species for other representative agroclimatic regions in Europe (such as Atlantic and Continental).
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Barrett, Brent A., Marty J. Faville, Kioumars Ghamkhar, and Marcelo J. Carena. "Developing new tools for pasture plant breeding." Journal of New Zealand Grasslands, December 8, 2018, 255–62. http://dx.doi.org/10.33584/jnzg.2018.80.343.
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The rate of genetic gain represented in the Forage Value Index of perennial ryegrass (Lolium perenne) is a major factor underpinning sustained profitability in pastoral farming. Effective new technologies for trait data acquisition and parent plant selection are used in many animal and crop improvement programmes to lift the rate of gain, but have yet to be developed and integrated in forage breeding. For forage improvement, hypotheses tested were: a) genomic selection (GS) offers a viable breeding strategy, and b) key enabling technologies for non-destructive, high-throughput phenotyping (HTP) in the field will improve trait data acquisition. To evaluate GS, extensive molecular marker and phenotypic datasets in structured populations of perennial ryegrass were developed. Phenotypic data for seasonal dry matter yield (DMY), the core trait in the Dairy NZ Forage Value Index, were obtained replicated field trials. Data on heading date (HD) as a useful trait to assess the efficacy of GS for simply inherited traits, were also collected. Genomic prediction models were developed for seasonal DMY and HD. Application of GS for HD was effective in selecting for both early and late heading, with movement of up to 7 days in a single generation of selection. The HTP research used iterative development of computational methods supporting a repeatable, non-invasive means of accurately and rapidly measuring DMY of perennial ryegrass in single row plots. These findings demonstrate effective genetic prediction and phenotyping approaches which may enable breeders to lift the rate of genetic gain in perennial ryegrass.
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Maity, Aniruddha, Amrit Lamichaney, Dinesh Chandra Joshi, Ali Bajwa, Nithya Subramanian, Michael Walsh, and Muthukumar Bagavathiannan. "Seed Shattering: A Trait of Evolutionary Importance in Plants." Frontiers in Plant Science 12 (June 16, 2021). http://dx.doi.org/10.3389/fpls.2021.657773.
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Seed shattering refers to the natural shedding of seeds when they ripe, a phenomenon typically observed in wild and weedy plant species. The timing and extent of this phenomenon varies considerably among plant species. Seed shattering is primarily a genetically controlled trait; however, it is significantly influenced by environmental conditions, management practices and their interactions, especially in agro-ecosystems. This trait is undesirable in domesticated crops where consistent efforts have been made to minimize it through conventional and molecular breeding approaches. However, this evolutionary trait serves as an important fitness and survival mechanism for most weeds that utilize it to ensure efficient dispersal of their seeds, paving the way for persistent soil seedbank development and sustained future populations. Weeds have continuously evolved variations in seed shattering as an adaptation under changing management regimes. High seed retention is common in many cropping weeds where weed maturity coincides with crop harvest, facilitating seed dispersal through harvesting operations, though some weeds have notoriously high seed shattering before crop harvest. However, high seed retention in some of the most problematic agricultural weed species such as annual ryegrass (Lolium rigidum), wild radish (Raphanus raphanistrum), and weedy amaranths (Amaranthus spp.) provides an opportunity to implement innovative weed management approaches such as harvest weed seed control, which aims at capturing and destroying weed seeds retained at crop harvest. The integration of such management options with other practices is important to avoid the rapid evolution of high seed shattering in target weed species. Advances in genetics and molecular biology have shown promise for reducing seed shattering in important crops, which could be exploited for manipulating seed shattering in weed species. Future research should focus on developing a better understanding of various seed shattering mechanisms in plants in relation to changing climatic and management regimes.
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Ahmed, Lina Q., and Abraham J. Escobar-Gutiérrez. "Unexpected Intraspecific Variability of Perennial Ryegrass (Lolium perenne L.) in Response to Constant Temperature During Germination and Initial Heterotrophic Growth." Frontiers in Plant Science 13 (April 8, 2022). http://dx.doi.org/10.3389/fpls.2022.856099.
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Lolium perenne (L.) is one of the most important species in temperate grasslands. Temperature is a major factor controlling plant development. Breeding L. perenne cultivars adapted to new ranges of temperature could be necessary under most climate change scenarios. However, before any breeding effort in such direction, knowing the intraspecific variability of responses to temperature is essential. Our objective was to analyze a sample of accessions of L. perenne for their response to constant temperature during germination and initial heterotrophic growth. Eight accessions were taken out from a genebank containing 160 accessions. Six accessions were wild populations collected in different places in France and the other two were populations from a selection program. For germination, four replicates of 100 seeds per accession were tested in Petri dishes in the dark at eight constant temperatures, from 5 to 40°C with increases of 5°C. Germination countings were carried out at variable time intervals and durations that depended on treatments. For initial heterotrophic growth analysis, seeds were germinated at 25°C. Sets of 30 seedlings per accession were placed in polypropylene boxes on blotter blue paper and transferred to each one of the eight treatments in the dark. They were pictured at variable time intervals for root and shoot growth measurement by image analysis. Neither seed germination nor heterotrophic growth was observed at 40°C, for any accession. Temperature and time course response surfaces were markedly different between accessions. Equally, maximum germinability and the shape of the response curves to temperature were significantly different between accessions. This means that limited similarities between responses were observed. Furthermore, germination rates followed the non-linear beta function with significant differences between some accessions. These also showed significant differences in their root and shoot growth rate in response to temperature. In general, the relative growth rates of roots and shoots were slow at 5°C, peaked between 25 and 30°C, and showed a sharp reduction afterward. These results reveal, for the first time, high genetic variability within L. perenne germplasm for the response to temperature in the initial life phases. This discovered variability should serve breeders to create perennial ryegrass varieties for the future.
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Xing, Jing, Ruijie Zhao, Qing Zhang, Xinru Huang, Tingchao Yin, Jing Zhang, and Bin Xu. "Genome-Wide Identification and Characterization of the LpSAPK Family Genes in Perennial Ryegrass Highlight LpSAPK9 as an Active Regulator of Drought Stress." Frontiers in Plant Science 13 (June 2, 2022). http://dx.doi.org/10.3389/fpls.2022.922564.
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SAPK/SnRK2 family genes play crucial roles in plant growth, development, and abiotic stress responses. The objective of this study was to identify and characterize the LpSAPK genes in perennial ryegrass (Lolium perenne L.). The results showed that there are 10 LpSAPKs in perennial ryegrass that could be classified into three groups with similar genic (exon–intron) structures to their orthologous genes in Arabidopsis and other grass species. Ka/Ks analysis suggested that the LpSAPKs and their orthologs were under purifying selection to maintain their conserved function during evolution. Nine out of ten LpSAPKs were localized in the cytoplasm and nucleus with the exception of LpSAPK5 which was only observed in the cytoplasm. Most LpSAPKs were responsive to various abiotic stress and hormonal (ABA, cytokinin, and ethylene) treatments but were downregulated in leaves and upregulated in roots, suggesting that there were unknown cis elements in promoters of these genes or unidentified post-transcriptional mechanism responsible for the tissue-dependent stress-regulated expression of these LpSAPKs. Furthermore, LpSAPK9 was identified as a candidate positive regulator in drought tolerance using a yeast ectopic expression system, and LpSAPK9 showed contrasting expression changes in drought-sensitive and -tolerant ryegrass varieties, suggesting that expression levels of LpSAPK9 were related to ryegrass drought tolerance. These results will facilitate further functional analysis of LpSAPKs for molecular breeding of ryegrass and other related grass species.
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Faville, M., B. Barrett, A. Griffiths, M. Schreiber, C. Mercer, I. Baird, N. Ellison, et al. "Implementing molecular marker technology in forage improvement." Proceedings of the New Zealand Grassland Association, January 1, 2003, 229–38. http://dx.doi.org/10.33584/jnzg.2003.65.2498.
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Accelerated improvement of two cornerstones of New Zealand's pastoral industries, per ennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.), may be realised through the application of markerassisted selection (MAS) strategies to enhance traditional plant breeding programmes. Genome maps constructed using molecular markers represent the enabling technology for such strategies and we have assembled maps for each species using EST-SSR markers - simple sequence repeat (SSR) markers developed from expressed sequence tags (ESTs) representing genes. A comprehensive map of the white clover genome has been completed, with 464 EST-SSR and genomic SSR marker loci spanning 1125 cM in total, distributed across 16 linkage groups. These have been further classified into eight pairs of linkage groups, representing contributions from the diploid progenitors of this tetraploid species. In perennial ryegrass a genome map based exclusively on EST-SSR loci was constructed, with 130 loci currently mapped to seven linkage groups and covering a distance of 391 cM. This map continues to be expanded with the addition of ESTSSR loci, and markers are being concurrently transferred to other populations segregating for economically significant traits. We have initiated gene discovery through quantitative trait locus (QTL) analysis in both species, and the efficacy of the white clover map for this purpose was demonstrated with the initial identification of multiple QTL controlling seed yield and seedling vigour. One QTL on linkage group D2 accounts for 25.9% of the genetic variation for seed yield, and a putative QTL accounting for 12.7% of the genetic variation for seedling vigour was detected on linkage group E1. The application of MAS to forage breeding based on recurrent selection is discussed. Keywords: genome map, marker-assisted selection, perennial ryegrass, QTL, quantitative trait locus, SSR, simple sequence repeat, white clover