Academic literature on the topic 'Wheat – Flowering time'

Flowering time is a critical stage for crop development as it regulates the ability of plants to adapt to an environment. To understand the genetic control of flowering time, a genome-wide association study (GWAS) was conducted to identify the genomic regions associated with the control of this trait in durum wheat (Triticum durum Desf.). A total of 96 landraces and 288 modern lines were evaluated for days to heading, growing degree days, and accumulated day length at flowering across 13 environments spread across Morocco, Lebanon, Mauritania, and Senegal. These environments were grouped into four pheno-environments based on temperature, day length, and other climatic variables. Genotyping with a 35K Axiom array generated 7652 polymorphic single nucleotide polymorphisms (SNPs) in addition to 3 KASP markers associated with known flowering genes. In total, 32 significant QTLs were identified in both landraces and modern lines. Some QTLs had a strong association with already known regulatory photoperiod genes, Ppd-A and Ppd-B, and vernalization genes Vrn-A1 and VrnA7. However, these loci explained only 5% to 20% of variance for days to heading. Seven QTLs overlapped between the two germplasm groups in which Q.ICD.Eps-03 and Q.ICD.Vrn-15 consistently affected flowering time in all the pheno-environments, while Q.ICD.Eps-09 and Q.ICD.Ppd-10 were significant only in two pheno-environments and the combined analysis across all environments. These results help clarify the genetic mechanism controlling flowering time in durum wheat and show some clear distinctions to what is known for common wheat (Triticum aestivum L.).

Growers in the wheatbelt of south-eastern Australia need increases in water-limited potential yield (PYw) in order to remain competitive in a changing climate and with declining terms of trade. In drought-prone regions, flowering time is a critical determinant of yield for wheat (Triticum aestivum L.). Flowering time is a function of the interaction between management (M, establishment date), genotype (G, development rate) and prevailing seasonal conditions. Faced with increasing farm size and declining autumn rainfall, growers are now sowing current fast-developing spring wheat cultivars too early. In order to widen the sowing window and ensure optimum flowering dates for maximum yield, new G × M strategies need to be identified and implemented. This study examined the effect of manipulating genotype (winter vs spring wheat and long vs short coleoptile) and management (sowing date, fallow length and sowing depth) interventions on yield and flowering date in high-, medium- and low-rainfall zones in south-eastern Australia. Twelve strategies were simulated at nine sites over the period 1990–2016. At all sites, the highest yielding strategies involved winter wheats with long coleoptiles established on stored subsoil moisture from the previous rotation, and achieved a mean yield increase of 1200 kg/ha or 42% relative to the baseline strategy. The results show promise for winter wheats with long coleoptiles to widen the sowing window, remove the reliance on autumn rainfall for early establishment and thus stabilise flowering and maximise yield. This study predicts that G × M strategies that stabilise flowering may increase PYw.

SUMMARYFlowering and successful pollination in wheat are key determinants of both quantity and quality of grain. Bread wheat line ‘Paragon’, introgressed with single or multiple daylength insensitivity alleles was used to dissect the effects on the timing and duration of flowering within a hierarchical plant architecture. Flowering of wheat plants was observed in a series of pot-based and field experiments. Ppd-D1a was the most potent known allele affecting the timing of flowering, requiring the least thermal time to flowering across all experiments. The duration of flowering for individual lines was dominated by the shift in the start of flowering in later tillers and the number of tillers per plant, rather than variation in flowering duration of individual spikes. There was a strong relationship between flowering duration and the start of flowering with the earliest lines flowering for the longest. The greatest flowering overlap between tillers was recorded for the Ppd-1b. Across all lines, a warmer environment significantly reduced the duration of flowering and the influence of Ppd-1a alleles on the start of flowering. These findings provide evidence of pleiotropic effects of the Ppd-1a alleles, and have direct implications for breeding for increased stress resilient wheat varieties.

Abstract Key message This review summarizes the allelic series, effects, interactions between genes and with the environment, for the major flowering time genes that drive phenological adaptation of barley. Abstract The optimization of phenology is a major goal of plant breeding addressing the production of high-yielding varieties adapted to changing climatic conditions. Flowering time in cereals is regulated by genetic networks that respond predominately to day length and temperature. Allelic diversity at these genes is at the basis of barley wide adaptation. Detailed knowledge of their effects, and genetic and environmental interactions will facilitate plant breeders manipulating flowering time in cereal germplasm enhancement, by exploiting appropriate gene combinations. This review describes a catalogue of alleles found in QTL studies by barley geneticists, corresponding to the genetic diversity at major flowering time genes, the main drivers of barley phenological adaptation: VRN-H1 (HvBM5A), VRN-H2 (HvZCCTa-c), VRN-H3 (HvFT1), PPD-H1 (HvPRR37), PPD-H2 (HvFT3), and eam6/eps2 (HvCEN). For each gene, allelic series, size and direction of QTL effects, interactions between genes and with the environment are presented. Pleiotropic effects on agronomically important traits such as grain yield are also discussed. The review includes brief comments on additional genes with large effects on phenology that became relevant in modern barley breeding. The parallelisms between flowering time allelic variation between the two most cultivated Triticeae species (barley and wheat) are also outlined. This work is mostly based on previously published data, although we added some new data and hypothesis supported by a number of studies. This review shows the wide variety of allelic effects that provide enormous plasticity in barley flowering behavior, which opens new avenues to breeders for fine-tuning phenology of the barley crop.

AbstractHarvest weed seed control (HWSC) is a weed management technique that intercepts and destroys weed seeds before they replenish the soil weed seedbank and can be used to control herbicide-resistant weeds in global cropping systems. Wild radish (Raphanus raphanistrum L.) is a problematic, globally distributed weed species that is considered highly susceptible to HWSC, as it retains much of its seed on the plant during grain harvest. However, previous studies have demonstrated that R. raphanistrum is capable of adapting its life cycle, in particular its flowering time, to allow individuals more time to mature and potentially shed seeds before harvest, thereby evading HWSC interception. This study compared the vegetative growth plus physiological and ecological fitness of an early-flowering R. raphanistrum biotype with an unselected genetically related biotype to determine whether physiological costs of early flowering exist when in competition with wheat (Triticum aestivum L.). Early flowering time adaptation in R. raphanistrum did not change the relative growth rate or competitive ability of R. raphanistrum. However, the height of first flower was reduced in the early flowering time–selected population, indicating that this population would retain more pods below the typical harvest cutting height (15 cm) used in HWSC. The presence of wheat competition (160 to 200 plants m−2) increased flowering height in the early flowering time–selected population, which would likely increase the susceptibility of early-flowering R. raphanistrum plants to HWSC. Overall, early-flowering adaption in R. raphanistrum is a possible strategy to escape being captured by the HWSC; however, increasing crop competition is likely to be an effective strategy to maintain the effectiveness of HWSC.

El blat és un cultiu que aporta el 20% de les proteïnes i les calories per al consum humà a nivell global. L’adaptació de la data de floració a cada ambient en particular forma part d’un mecanisme d’escapament de l’estrès, cosa que podria reduir l’impacte negatiu esperat degut al canvi climàtic. La hipòtesi general sobre la que s’estableix aquest estudi és que un canvi en la data de floració afectaria les condiciones ambientals durant les fases crítiques de desenvolupament del blat, que al seu torn poden tenir un impacte en la formació del rendiment. Un conjunt de línies de blat dur de primavera, amb variacions al·lèliques contrastants per als loci Ppd-1, que afecten la sensibilitat al fotoperíode, es van assajar en un ampli rang de latituds de l’hemisferi Nord (41°N a Espanya, 27°N al noroest de Mèxic, i 19°N al sud de Mèxic, aquesta darrera amb sembra de primavera). Es van portar a terme experiments de camp en regadiu, entre els anys 2007 i 2012, per a investigar l’efecte de les variants al·lèliques en els loci Ppd-A1 i Ppd-B1 sobre la fenologia i la formació del rendiment. Els genotips portadors de l’al·lel Ppd-A1a GS100, causant d’insensibilitat al fotoperíode, van tendir a presentar un pes de gra (PG) i un rendiment superiors a la resta. Les variants al·lèliques per a Ppd-B1 no van afectar la data de floració, però l’al·lel causant d’insensibilitat al fotoperíode (Ppd-B1b) es va associar a un major número de grans per unitat de superfície (NG), degut a un augment en el número d’espiguetes espiga-1. Una floració més precoç (tant si era degut a Ppd-1 com a precocitat intrínseca, Eps), va tendir a una associació amb un rendiment més alt degut a un major PG. Les combinacions al·lèliques GS105/Ppd-B1b i Ppd-A1b/Ppd-B1b es van associar amb un increment del NG degut a un augment del número de grans espigueta-1, però això no es va traduir en un rendiment major, degut a la relació negativa entre NG i PG. Una floració més precoç produïda per gens Eps va resultar en un menor número d’espiguetes espiga-1, però no un menor NG. Quan ambdós al·lels en els loci Ppd-1 presentaven el mateix tipus de resposta al fotoperíode (sensible/sensible o insensible/insensible) es va observar una major estabilitat en el rendiment. Les condicions ambientals durant la primera meitat del període d’ompliment del gra van ser els factors més importants per definir el PG. Un retràs en la data de floració es va associar amb reduccions en la taxa d’ompliment de gra i amb PG. En les latituds amb sembra de tardor, un increment de 1°C en la temperatura mitjana va reduir el PG en 5,2 mg gra-1. L’anàlisi d’associació genotip-fenotip va mostrar que les regions als cromosomes 6A (114 cM) i 6B (126 cM) tenien associacions generals amb el rendiment, esdevenint regions crítiques amb QTLs importants. La detecció de marcadors únics associats a una característica va estar molt lligada a l’ambient, i la interacció entre parells de marcadors va mostrar major efecte que els corresponents marcadors únics.
El trigo es un cultivo que aporta el 20% de las proteínas y calorías para el consumo humano a nivel global. La adaptación de la fecha de floración a cada ambiente en particular forma parte de un mecanismo de escape al estrés, lo que podría reducir el impacto negativo esperado debido al cambio climático. La hipótesis general sobre la que se establece este estudio es que un cambio en la fecha de floración afectaría a las condiciones ambientales durante las fases críticas del desarrollo del trigo, lo que a su vez puede tener un impacto en la formación del rendimiento. Un conjunto de líneas de trigo duro de primavera, con variaciones alélicas contrastantes para loci Ppd-1, que afectan la sensibilidad al fotoperiodo, fueron ensayadas en un amplio rango de latitudes del hemisferio Norte (41°N en España, 27°N en el noroeste de México, y 19°N en el sur de México, esta última con siembra de primavera). Se llevaron a cabo experimentos de campo en regadío, entre los años 2007 y 2012, para investigar el efecto que tuvieron las variantes alélicas en los loci Ppd-A1 y Ppd-B1 sobre la fenología y la formación del rendimiento. Los genotipos con el alelo Ppd-A1a GS100, causante de insensibilidad al fotoperiodo, tendieron a presentar un peso de grano (PG) y un rendimiento superiores al resto. Las variantes alélicas para Ppd-B1 no afectaron a la fecha de floración, pero el alelo causante de insensibilidad al fotoperiodo (Ppd B1b) aumentó el número de granos por unidad de superficie (NG) debido a un aumento de número de espiguillas espiga-1. Una floración más temprana (ya fuera debida a Ppd-1 o a precocidad intrínseca, Eps) tendió a estar asociada con rendimiento más alto debido a un PG mayor. Las combinaciones alélicas GS105/Ppd-B1b y Ppd-A1b/Ppd-B1b se asociaron con un incremento de NG debido a un aumento del número de granos espiguilla-1, pero esto no se tradujo en un mayor rendimiento debido a la relación negativa entre NG y PG. Una floración más temprana producida por genes Eps tuvo como resultado un menor número de espiguillas espiga-1, pero no un menor NG. Cuando ambos alelos en los loci Ppd-1 poseían el mismo tipo de respuesta al fotoperiodo (sensible/sensible o insensible/insensible) se observó una mayor estabilidad en el rendimiento. Las condiciones ambientales durante la primera mitad del periodo de llenado de grano fueron los factores más importantes para definir el PG. Un retraso en la fecha de floración se asoció con reducciones en la tasa de llenado de grano y el PG. En las latitudes donde la siembra se realizó en otoño, un incremento de 1°C en la temperatura media redujo el PG en 5,2 mg grano-1. El análisis de asociación de fenotipo-genotipo mostró que las regiones en los cromosomas 6A (114 cM) y 6B (126 cM) se asociaron en general con el rendimiento, representando regiones críticas con QTLs importantes. La detección de marcadores únicos asociados a una característica estuvo muy ligada al ambiente, y la interacción entre pares de marcadores mostró mayor efecto que sus correspondientes marcadores únicos.
Wheat is a staple crop that provides 20% of proteins and calories to global human diets. Adapting flowering time to each particular environment is one of the stress avoidance mechanisms that could reduce the predicted impact of climate change. The general hypothesis underlying this research was that a change in flowering time would affect environmental conditions of spring durum wheat during critical developmental phases, which in turn would have an impact on yield formation. A set of spring durum wheat lines with contrasting allele variants at Ppd-1 loci, affecting photoperiod sensitivity, were tested at a range of Northern latitudes (41°N in Spain, 27°N in the northwest of Mexico, and 19°N in the south of Mexico, this last site with spring sowing time). Field experiments under irrigation were carried out between the years 2007 and 2012, to investigate the effect of allele variants at Ppd-A1 and Ppd-B1 loci on phenology and yield formation. Genotypes carrying the allele Ppd-A1a GS100, causing photoperiod insensitivity, tended to have high grain weight (GW) and yield. Allele variants at Ppd-B1 locus did not affect flowering time, but the Ppd-B1b allele causing photoperiod sensitivity increased grain number per unit area (GN) due to a higher number of spikelets spike-1. Early flowering (either due to Ppd-1 or earliness per se, Eps) tended to be associated with high yield due to high GW. The allele combinations GS105/Ppd-B1b and Ppd-A1b/Ppd-B1b were associated with higher GN due to an increase in the number of grains spikelet-1, but it did not translate as yield increase due to a trade-off between GN and GW. Early flowering caused by Eps genes resulted in a low number of spikelets spike-1, but not a low GN. Yield stability was enhanced when alleles at Ppd-1 loci conferred a similar photoperiod response (sensitive/sensitive or insensitive/insensitive). The environmental conditions during the first half of the grain filling period were the most critical factors to define GW. Flowering time delays were associated with reductions in grain filling rate and GW. At autumn-sowing sites, an increase of 1°C in mean temperature reduced GW by 5.2 mg grain-1. The analysis of phenotype-genotype associations showed that the regions at chromosomes 6A (114 cM) and 6B (126 cM) were associated with yield across sites, thus representing hotspots for QTL regulating yield performance. The detection of single markers-trait associations (MTAs) was highly affected by environment, and the interactions between pairs of markers showed a stronger effect than the corresponding single MTAs.

L’objectiu d’aquesta Tesi Doctoral va ser estudiar l’efecte dels gens Ppd-1 sobre la fenologia i els components del rendiment en blat dur. Es va treballar amb una col•lecció de línies amb diverses combinacions al•lèliques per a Ppd-A1 i Ppd-B1, avaluades en quatre localitats a Espanya i Mèxic durant els anys 2007 i 2008. Els resultats mostren que la temperatura i el fotoperíode van distingir les localitats estudiades. Els gens Ppd-1 van explicar gran part de la variabilitat genètica del període sembra-antesi i l’expressió de Ppd-A1a va augmentar quan el fotoperíode mig fins a floració va ser inferior a 12 h. Els al•lels que confereixen insensibilitat al fotoperíode es van classificar com GS-100>GS- 105>Ppd-B1a segons la potència del seu efecte sobre la fenologia. Els genotips portadors de l’al•lel Ppd-A1b van rendir menys en tots els ambients degut a un menor número d’espigues/m2 i menor pes del gra. Els efectes compensatoris entre components del rendiment van ser menors en ambients favorables.
El objetivo de esta Tesis Doctoral fue estudiar el efecto de los genes Ppd-1 sobre la fenología y los componentes del rendimiento en trigo duro. Se trabajó con una colección de líneas con diversas combinaciones alélicas para Ppd-A1 y Ppd-B1, evaluadas en cuatro localidades en España y México durante los años 2007 y 2008. Los resultados muestran que la temperatura y el fotoperíodo distinguieron las localidades estudiadas. Los genes Ppd-1 explicaron gran parte de la variabilidad genética del período siembra-antesis y la expresión de Ppd-A1a aumentó cuando el fotoperíodo medio hasta floración fue inferior a 12 h. Los alelos que confieren insensibilidad al fotoperíodo se clasificaron como GS-100>GS-105>Ppd-B1a según la potencia de su efecto sobre la fenología. Los genotipos portadores del alelo Ppd-A1b rindieron menos en todos los ambientes, debido al menor número de espigas/m2 y menor peso del grano. Los efectos compensatorios entre componentes del rendimiento fueron menores en ambientes favorables.
The aim of this thesis was to study the effect of Ppd-1 genes on the phenology and yield components of durum wheat. A set of lines carrying different allelic combinations at Ppd-A1 and Ppd-B1 loci were tested in four sites (two in Spain and two in Mexico) during 2007 and 2008. The results showed that meteorological traits mostly distinguishing between sites were temperature and photoperiod. The Ppd-1 genes explained much of the genetic variability of sowing-anthesis period. The expression of Ppd-A1a increased when the average photoperiod until anthesis was lower than 12 h. According to its effect on phenology alleles conferring photoperiod insensitivity were classified as GS-100> GS-105> Ppd-B1a. Genotypes carrying the allele Ppd-A1b resulted consistently in the lowest yields due to their few number of spikes per m2 and light grains. Compensatory effects between yield components were lower under favorable environments.

The focus of this chapter is on how languages move and change over time and space. The perceptions of historical linguists have been shaped by what they were observing. During the flowering of comparative linguistics, from the late 19th into the 20th century, the dominant view was that in earlier times when people moved, their languages moved with them, often over long distances, sometimes fast, and that language change was largely internal. That changed in the second half of the 20th century. We now recognize that in recent centuries and millennia, most movements of communities and individuals have been local and shorter. Constant contact between communities resulted in features flowing across language boundaries, especially in crowded and long-settled locations such as most of Central and West Africa. Although communities did mix and people did cross borders, it became clear that language and linguistic features could also move without communities moving.

This chapter examines the factors that affect the timing and patterning of flowering, as well as the effects of different flowering patterns on pollination outcomes. Plants should flower in ways that maximize their own reproductive success. The “flowering pattern” is a composite of the timing and frequency of individual flowers opening, and also of floral longevity. These phenological factors vary between and within species. Flowering phenology can influence the plant’s manipulation of its visitors in ways that should increase either or both of pollen transfer and pollen receipt. The chapter first considers the frequency of flowering and the shape of the flowering period before discussing flower longevity and flowering period. It also explores the question of how big a flower should be, how many flowers a plant should have at any one time, what determines the phenological parameters for a particular plant species, and where the flowers should be placed.

This chapter looks back on the process of becoming a mother, as women come to understand the visions they had — of motherhood as a bed of roses, of birth as agony or ecstasy, of pregnancy as a flowering or a burden. After the event these images are brought sharply into focus by the contrast medium of reality, which exposes the outline of what was, too often, a romantic dream. More than a third of the women interviewed for this study said they found becoming a mother a difficult experience. Eight out of ten said it had been different from what they had expected. The same proportion thought the pictures of pregnancy, birth, and motherhood conveyed in antenatal literature, women's magazines, and the media in general were too romantic, painting an over-optimistic portrait of happy mothers and fathers, quiet contented babies, and neat and shining homes that bore little resemblance to the chaos, disruption, and confusion of first-time motherhood.

This is a study of the territorial structures within which past communities managed their landscapes. Today, we live our lives within a complex hierarchy of administrative units that includes parishes, districts, counties, and nations, and while some of these are recent in origin, others are deeply rooted in the past: most parts of England, for example, still have counties that are direct successors to the shires recorded in Domesday and which still form the basis for our local government. These territorial entities are an important part of our history, giving communities a sense of place and identity, and this book will explore where this aspect of our landscape has come from: might county names such as Essex— meaning the ‘East Saxons’—suggest that they originated as early Anglo-Saxon kingdoms, and if so, what was the relationship between these kingdoms and the Romano-British civitates and Iron Age kingdoms that preceded them? The idea that the landscape all around us has a long and complex history is a familiar one. For a long time, however, continuity stretching back to the Roman period and beyond was thought to be rare. Archaeologists and historians have argued that once Britain ceased to be part of the Roman Empire, its economy collapsed, and it was not long before hordes of Angles and Saxons sailed across the North Sea and dispossessed the Britons of their land. This was thought to have marked the onset of the ‘dark ages’ before the flowering of a new era of civilization—the ‘Middle Ages’—a few centuries later. Although this was the view when Hoskins (1955) wrote his Making of the English Landscape, it is noteworthy that in the same year Finberg (1955) published a short paper speculating that there may have been considerable continuitywithin the landscape at Withington in Gloucestershire. Overall, however, while some Romanists saw a degree of overlap and continuity during the Anglo-Saxon colonization, most saw the fifth century as one of dramatic change reflected in the apparent desertion of most towns and villas, the collapse of market-based trade and manufacturing, and the introduction of entirely new forms of architecture, burial practice and material culture (see Esmonde Cleary 2014, 3 for a historiography).

The university is one of Europe’s great gifts to the world. There had been sophisticated centres of learning in Classical Athens and Alexandria, in China, and then in North Africa and Spain during the Islamic world’s scientific flowering. But it is Europe’s universities which gave birth to the humanism of the Renaissance, drove the Reformation, led the rise of empirical science, and promoted the emergence of critical history. They are still extending the boundaries of knowledge today, as part of a global enterprise which is heavily influenced by the European model. They emerged in the twelfth century. The first wave of a dozen or so, including Bologna, Paris, and Oxford, already comprised different types of university, reflecting their different origins depending on which came first, the chicken or the egg, the teacher or the student. In Bologna, reputed to have been founded in 1088 and hence Europe’s oldest university, the student is thought to have come first. Groups of students were looking for training to get qualifications that would help them practise medicine or law and employed teachers to help them. There ‘the lecturing staff had to submit to a competitive trial to win the custom of their fee paying consumers . . . teaching was viewed as a commodity like any other and it was logical that new students should sample lecture courses before making their academic purchase’. They were mature students who had probably already started work and knew what extra training they needed to advance in their profession. By contrast in Northern Europe the university began with teachers setting up universities: they had much younger students who were more dependent on them. (They were called masters, reflecting the origins of the model in apprenticeships.) These universities tended to be less vocational as the routes into professions such as the law or medicine were instead via apprenticeships. Towns gave these new institutions a mixed welcome—and sometimes still do. Tensions between town and gown boiled over into violence. Universities looked to the Church, the major countervailing power of the time, for protection from hostile locals.

The main goal of our research was to identify the relationship between the normalized difference vegetation index (NDVI) and the area of assimilation surface (AS) of spring wheat crops during the growing season, as well as to develop practical application of the findings. Throughout the growing season, the area of assimilation surface of T. aestivum increases much faster than the vegetation index NDVI. The smallest AS (282.7 m2/ha), which corresponded to 0.01 units of the NDVI (calculated factor) was observed during the tillering stage. It reaches its maximum values – 331.7–406.1–383.7 m2/ha (1.20–1.47–1.39 times higher) from stem elongation to the end of flowering. During the grain filling and maturation, these values decrease to 336.2 m2/ha but still are 1.19 times higher than the initial ones.