Academic literature on the topic 'Amphidiploid'

Eight diploid wild species of groundnut were hybridized to produce eight amphidiploids. Both the parental diploid species and synthetic amphidiploids were screened for foliar diseases viz. early leaf spot and rust, besides for sucking pests viz. thrips and leaf hopper. All the diploid species had high level of resistance for rust disease. Arachis cardenasii registered high level of resistance for both leaf hopper. Those desirable attributes were combined in the amphidiplods. The pollen fertility ranged from 19.0 to 67.4 per cent in the seven amphidiploid involving both 'A' genome species. Whereas it was only 1.5 per cent in A. villosa x A. batizocoi where 'A' and 'B' genomes were involved.

Pollen morphology was examined in amphidiploid and amphidaploid interspecific hybrids between Brassica oleracea L. and B. campestris L. Pollen of the amphidiploid interspecific hybrids between B. oleracea var. capitata and B. campestris var. pekinensis, and between B. campestris var. chinensis and B. oleracea var. capitata, were significantly longer and wider than those of their diploid parents, presumably due to the phenotypic expression of the hybrid genomes and ploidy effects. The exine ridges and pores of the amphidiploids were well-developed and significantly larger than those of their diploid parents, but they were poorly developed in the amphihaploids.

Floral characteristics, meiotic behavior, and sporad formation were compared in three Dendrobium tetraploids (amphidiploids) and their diploid counterparts. Amphidiploid flowers were larger than those of diploids. Diploid meiotic behavior varied; mean configurations at Metaphase I ranged from 14.3 bivalents and 9.4 univalents to 18.9 bivalents and 0.2 univalents. In amphidiploids, nearly all cells had 38 bivalents. Sporad formation also varied; diploids had 36% to 70% tetrads and amphidiploids had 97% to 100% tetrads. Preferential pairing and small chromosome size may promote bivalent formation in amphidiploids.

Abstract Highly gametic sterility of a distant hybrid Populus simonii × P. euphratica cv. ‘Xiaohuyang-2’ restricts its utilization in breeding programs of Populus. Amphidiploid induction by somatic chromosome doubling is expected to restore its gametic fertility. In this study, nodal-segment and leaf explants of ‘Xiaohuyang-2’ were used to induce chromosome doubling with colchicine in vitro. Although chromosome doubling of the nodal-segment explants only produced mixoploids, the treatments of leaf explants on adventitious bud regeneration medium successfully produced 4 amphidiploids, which might be attributed to the direct organogenesis of the adventitious buds on the leaf explants. This is the first report of amphidiploid induction in a distant hybrid between Populus section Tacamahaca and sect. Turanga. The highest amphidiploid induction frequency was 16.7 %. Both the explant survival rate and polyploidization frequency were significantly affected by colchicine concentration and exposure time. The amphidiploid plants significantly differed from the diploid and mixoploid plants in morphological and anatomical characteristics. They had larger, thicker, and greener leaves than the diploids and mixoploids. The increase in ploidy level also resulted in changes in stomatal features. The induced amphidiploid plants of the distant hybrid ‘Xiaohuyang-2’ are expected to play important roles in breeding programs of Populus in the future, which can be used as a bridge parent with the ability of unreduced gamete formation to cross with fast-growth germplasms to produce triploids pyramiding desirable traits of fast growth, easy cutting propagation, and salt and drought tolerances.

Newly resynthesized AC amphihaploids, which were characterized by high meiotic pairing and multivalent formulation, after doubling of their chromosome number showed preferential pairing and bivalent formation in the resynthesized amphidiploid Brassica napus (AACC). However, univalents as well as multivalents were also formed indicating that their chromosome behaviour was not fully diploidized. Stabilization of chromosome pairing in newly resynthesized amphidiploids can be achieved through genetic control or structural modification of the homoeologous chromosomes. A comparison of the meiotic behaviour of spontaneous haploids of natural rapeseed with that of the newly synthesized AC amphihaploids provides some evidence that both processes may be involved in the regulation of chromosome pairing in Brassica.Key words: Brassica, amphihaploid, amphidiploid, meiosis, univalents, multivalents.

Abstract The seedling vigor of the amphidiploid (2n = 4x = 32) green bunching onion, ‘Beltsville Bunching’, surpasses that of its constituent species, Allium cepa L. (common bulb onion, 2n = 16) and A. fistulosum L. (Japanese bunching or Welsh onion, 2n = 16). Released in 1950, ‘Beltsville Bunching’ was developed by Henry A. Jones from a natural amphidiploid discovered in a population of F1 hybrids between A. cepa ‘White Portugal’ inbred 3-203-113-5 and A. fistulosum “Nebuka type” (1, 3). ‘Beltsville Bunching’ is not widely grown, which may be attributed to poor seed productivity. The original cultivar, apparently derived from a single plant, probably does not contain the genetic variability needed to allow improvement by selection alone. Additional germplasm for outcrossing is needed to correct the horticultural defects in this onion. To expand the range of tetraploid germplasm available for developing new ‘Beltsville Bunching’-type amphidiploids, several A. cepa × A. fistulosum and reciprocal crosses were treated with colchicine in the Vegetable Laboratory at the Beltsville Agricultural Research Center beginning in 1981. Seeds of two amphidiploid populations designated f-c 8407 and f-c 8432, were released in Feb. 1987 from that program.

Several colchicine-induced amphidiploids of blackspot-resistant, wild diploid rose species were produced for interbreeding with tetraploid garden roses. Shoot-tip chromosome counts confirmed that 86-7 (Rosa wichuraiana Crep. × R. rugosa rubra Hort.) and 86-3 (R. laevigata Michx. × R. banksiae Aiton) are amphidiploids (2n = 4x = 28), and that 84-1000 (R. roxburghii Tratt. × R. laevigata Michx.) is a mixoploid with diploid (2n = 2x = 14) and hypotetraploid (2n = 4x-1 = 27) sectors. The measured volume of pollen grains and guard cells was higher in the tetraploids. Pollen stainability was higher in amphidiploids 86-3 and 86-7 than in mixoploid 84-1000. The amphidiploid 86-7 has greater pollen fertility as determined by crossing with a range of commercial tetraploid roses than 86-3 and 84-1000, but is less fertile than its parental diploid species. Leaflets of the amphidiploids are larger and more crinkled along the midrib than in their diploid parents. These three amphidiploids provide new additions to tetraploid rose germplasm.

Future genetic progress in wheat grain yield will depend on increasing biomass and this must be achieved without commensurate increases in nitrogen (N) fertilizer inputs to minimize environmental impacts. In recent decades there has been a loss of genetic diversity in wheat through plant breeding. However, new genetic diversity can be created by incorporating genes into bread wheat from wild wheat relatives. Our objectives were to investigate amphidiploids derived from hybrids of bread wheat (Triticum aestivum L.) and related species from the genera Aegilops, Secale, Thinopyrum and Triticum for expression of higher biomass, N-use efficiency (NUE) and leaf photosynthesis rate compared to their bread wheat parents under high and low N conditions. Eighteen amphidiploid lines and their bread wheat parents were examined in high N (HN) and low N (LN) treatments under glasshouse conditions in two years. Averaged across years, grain yield reduced by 38% under LN compared to HN conditions (P = 0.004). Three amphidiploid lines showed positive transgressive segregation compared to their bread wheat parent for biomass per plant under HN conditions. Positive transgressive segregation was also identified for flag-leaf photosynthesis both pre-anthesis and post-anthesis under HN and LN conditions. For N uptake per plant at maturity positive transgressive segregation was identified for one amphidiploid line under LN conditions. Our results indicated that introgressing traits from wild relatives into modern bread wheat germplasm offers scope to raise biomass and N-use effciency in both optimal and low N availability environments.

Intergeneric hybrids and amphidiploid hybrids from crosses of Aegilopstauschii and Secale cereale were produced using young embryo rescue. The hybrids showed complete sets of both parental chromosomes. The dihaploid plants showed an average meiotic pairing configuration of 10.84 I + 1.57 II + 0.01 III. Genomic in situ staining revealed 3 types of bivalent associations, i.e. D-D, R-R and D-R at frequencies of 8.6, 8.2 and 83.3%, respectively. Trivalents consisted of D-R-D or R-D-R associations. These results suggested that both intra- and intergenomic chromosome homology were contributed to chromosome pairing. Derived amphidiploids with 2n = 28 paired at metaphase I of meiosis as 4.51 I + 11.70 II + 0.03 III. Chromosome pairing of amphidiploids appeared more or less regular, i.e. bivalent-like with some trivalent configurations.

We aim to improve diversity of domesticated wheat by transferring genetic variation for important target traits from related wild and cultivated grass species. The present study describes the development of F1 hybrids between wheat and related species from the genera Aegilops, Secale, Thinopyrum, and Triticum and production of new amphidiploids. Amphidiploid lines were produced from 20 different distant relatives. Both colchicine and caffeine were successfully used to double the chromosome numbers. The genomic constitution of the newly formed amphidiploids derived from seven distant relatives was determined using genomic in situ hybridization (GISH). Altogether, 42 different plants were analysed, 19 using multicolour GISH separating the chromosomes from the A, B, and D genomes of wheat, as well as the distant relative, and 23 using single colour GISH. Restructuring of the allopolyploid genome, both chromosome losses and aneuploidy, was detected in all the genomes contained by the amphidiploids. From the observed chromosome numbers there is an indication that in amphidiploids the B genome of wheat suffers chromosome losses less frequently than the other wheat genomes. Phenotyping to realize the full potential of the wheat – related grass germplasm is underway, linking the analyzed genotypes to agronomically important target traits.

Wheat is one of the most widely consumed staple crops in the world including India and its demand is increasing with increasing population. Increased grain yield (GY) has been associated with increased use of nitrogen (N) fertilizers which represent a significant environmental and production cost. Developing cultivars which have higher grain yield but use N efficiently may allow reduced fertilizer N inputs. The objectives of this study were to: (i) quantify the genetic variability in N use-efficiency (grain dry matter (DM) yield per unit N available from soil and fertilizer, NUE) in a panel of modern Indian wheat cultivars and find new genetic variation in a panel of amphidiploids produced by crossing hexaploid bread wheat with wild wheat relatives and (ii) identify traits and understand physiological mechanisms determining improved NUE to exploit for development of new N efficient cultivars. Thirty Indian elite bread wheat cultivars and 18 amphidiploid lines along with their five respective bread wheat parents were tested under high N (HN) and low N (LN) conditions in two years in field experiments at Agharkar Research Institute, Pune, India (2013 and 2014) and in glasshouse experiments at Nottingham University, UK, (2015 and 2016), respectively. Detailed growth analysis was conducted including GY, above-ground dry matter (AGDM), DM and N partitioning at anthesis and at harvest along with N remobilization efficiency (NRE) in the field experiment. Senescence kinetics of the flag-leaf were assessed from a visual score weekly from anthesis to complete canopy senescence in both sets of experiments. Physiological traits were assessed including flag-leaf light-saturated photosynthetic rate (Amax) under HN conditions in the field experiment and under both HN and LN conditions in glasshouse experiment. Flag-leaf relative chlorophyll content (SPAD) under HN and LN conditions was measured in both experiments; and Normalized Difference Vegetative Index (NDVI) under HN and LN conditions in field experiment. 2D seedling root phenotyping was carried out on subset of 12 genotypes selected based on contrasting performance under LN conditions from both the field and glasshouse experiments. In field experiments, GY was reduced under low N (LN) conditions on average by 1.46 t ha−1 (28%). Crop above-ground N-uptake at harvest on average was reduced from 16.2 kg N ha−1 under HN to 8.5 kg N ha−1 under LN conditions while N-utilization efficiency (grain DM yield per unit above-ground N uptake at harvest; NUtE) increased from 32.7 to 44.6 g DM g−1 N. Significant N × genotype level interaction was observed for GY, N uptake at harvest and NUtE. Overall genetic variability in GY and NUE (which ranged from 15.6 - 23.7 g DM g−1 N under LN; P<0.001) related mainly to differences in N uptake rather than NUtE. Overall, cultivars ranged significantly at anthesis in N accumulation in the flag-leaf N (1.1 -2.2 g N m−2 at HN and 0.5-1.0 g N m−2 at LN), the stem and remaining leaf with sheath (5.78-11.97 at HN and 3.61- 6.33 g N m−2 at LN) (P=0.01), and the ear (2.91-6.13 at HN and 2.06-4.23 g N m−2 at LN) (P<0.001). Cultivars ranged in N partitioning index (proportion of above-ground N in the crop component, NPI) at anthesis for the flag-leaf from 0.08 to 0.16 at HN and 0.07 to 0.13 at LN (P< 0.001); and for the stem-and remaining leaf with sheath from 0.54 to 0.68 at HN and from 0.52 to 0.65 at LN (P<0.001) and for ear from 0.21 to 0.34 at HN and from 0.28 to 0.41 at LN (P<0.001). The post-anthesis NRE was positively associated with the duration of flag-leaf senescence amongst cultivars under LN. Genetic variation in grain yield and grain N% (through N dilution effects) appeared to be mainly influenced by pre-anthesis N accumulation rather than post-anthesis N remobilization under LN conditions. Under N stress conditions, there was evidence that NRE was a determinant of genetic variation in grain N%. Flag-leaf Amax was positively associated with AGDM (P=0.02), GY (P=0.14), and specific leaf N at anthesis (P=0.046). Flag-leaf onset (VS.OnsetRP) and end (VS.EndRP) of senescence was positively associated with GY, AGDM and NRE in both N treatments. In the glasshouse experiments, out of 18 amphidiploid lines, two lines under HN and three lines under LN conditions showed transgressive segregation (TS) above the bread wheat parent for pre-anthesis Amax and 12 lines under HN and 7 lines under LN conditions showed TS for post-anthesis Amax. In addition, higher expression than the bread wheat parent was observed for Thinopyrum turcicum P208/201 x Chinese Spring Eup 94 under HN conditions for GY and for Thinopyrum turcicum P208/201 x Chinese Spring Eup 94, Secale anatolicum P208/142 x Highbury and Secale anatolicum P208/141 x Chinese Spring Eup 94 under HN conditions for AGDM showing potential to exploit these genotypes for wide crossing for NUE wheat breeding. Seedling root architectural traits including seminal root number per plant showed association with field and glasshouse GY and NUE related traits in HN and LN conditions. Overall amphidiploids showed evidence for increased root depth than bread wheat cultivars in the hydroponics seedling platform under both HN and LN conditions. In summary: • N-use efficiency in thirty Indian wheat cultivars in the field was correlated with onset of flag-leaf senescence under high N and low N conditions and senescence timing was correlated with N accumulation at anthesis. • Yield response to N limitation of 30 wheat cultivars was associated with responses in N uptake at anthesis under both N conditions. • The grain yield in N stressed crops for the 30 cultivars was limited by post-anthesis source capacity. • Three amphidiploids lines (Thinopyrum turcicum P208/201 x Chinese Spring Eup 94, Secale anatolicum P208/142 x Highbury and Secale anatolicum P208/141 x Chinese Spring Eup 94) in glasshouse conditions showed higher flag-leaf photosynthesis rate and prolonged flag leaf green area than their recurrent parents. • The 2D seedling RSAT study showed seminal root number was correlated amongst 12 Indian wheat cultivars and amphidiploids with grain yield per shoot under high and low N conditions.

AbstractCoffee is a perennial (sub)tropical crop and one of the most valuable commodities globally. Coffee is grown by an estimated 25 million farmers, mostly smallholders, and provides livelihoods to about 125 million people. The Coffea genus comprises over 120 species. Two species account for nearly the entire world coffee production: C. arabica L. (Arabica coffee) and C. canephora Pierre ex A. Froehner (Canephora coffee) with the former supplying about 65% of the world’s consumption. Arabica coffee is a self-pollinated, amphidiploid species (2n = 4x = 44) whereas other Coffea species are diploid (2n = 2x = 22) and generally cross-pollinated. Induced mutagenesis using physical and chemical mutagens has been a successful strategy in producing over 3,300 mutant varieties in over 220 crop species with global impact. Spontaneous Arabica coffee mutants of significant economic importance have been found since the early 1900s, following the spread of Arabica coffee cultivation across the globe. However, Arabica coffee has so far not been improved through induced mutagenesis and studies on coffee mutagenesis are scarce. In this chapter, principles and practices of mutation-assisted breeding along with current breeding limitations of Arabica coffee are briefly reviewed, as an introduction to subsequent protocol chapters on mutation induction, advanced cell and tissue culture, Leaf Rust resistance screening and the application of novel molecular/genomics tools supporting mutation-assisted improvement and genetics research of Arabica coffee.

Отдалённая гибридизация, получение удвоенных гаплоидов и амфидиплоидов являются широко распространёнными методами создания исходного материала в селекции злаков. Однако, некоторый ценный генетический материал у отдалённых гибридов мягкой и твёрдой пшеницы, а также других злаков, может теряться из-за проблемы стерильности данных растений, вызванной наличием негомологичных субгеномов и трудностей полиплоидизации. При невозможности получения семян от самоопыления, использование клонального микроразмножения может помочь сохранить и размножить эти растения. Distant hybridization, obtaining doubled haploids and amphidiploids are widely used methods for creating starting material in cereal breeding. However, some valuable genetic material in distant hybrids of soft and durum wheat, as well as other cereals, may be lost due to the problem of sterility of these plants caused by the presence of non-homologous subgenomes and difficulties in polyploidization. If it is not possible to obtain seeds from self-pollination, the use of clonal micropropagation can help to conserve and propagate these plants.