Advancing Harvest Index in Winter Wheat in High Biomass Backgrounds through Genomics Enabled Breeding

小麦是全球三大主要谷类作物之一，每年产量超过7亿吨。到2050年，全球对小麦的需求将增长到9亿吨，为了实现这一目标，产量必须每年增长1.6%，而目前的年增长率为1%。提高生物量的研究，特别是通过提高小麦光合作用的途径，可能会产生一些产量的增加，但是这不大可能有助于实现产量目标，除非产生的额外生物量是“有用的生物量”，或谷物。收获指数（HI，谷物干物质产量/地上DM）是衡量有用生物量与非有用生物量之比的指标，是产量的关键组成部分。对于冬小麦，HI值很少超过0.55，并且自20世纪90年代以来没有显著增加，尽管理论极限高达0.65。更好地了解HI的遗传基础将有助于在高生物量品种中改进和稳定表达HI，从而导致遗传产量潜力的阶跃变化。有显著的证据表明，产量潜力是一个碳汇限制性状，其中碳积累受到粮食库强度的限制。因此，提高亩产粒数是提高现代冬小麦高产率和产量潜力的重要途径。结果效率是衡量开花时每单位穗干重所结的籽粒数，是另一个特别感兴趣的性状。该项目是与KWS英国有限公司的Ed Byrne博士和Jacob Lage博士合作进行的，并将对KWS英国优质冬小麦双单倍体系的籽粒产量、HI、1000粒重和每平方米粒数进行表型分析；籽粒分配和光合性状，包括穗和茎节间干物质分配指数、结实效率（穗粒数/穗DM）、冠层NDVI和叶片叶绿素含量（SPAD）。该小组（150个品系）代表了整个KWS项目的分层抽样，将进行基因分型。标记-性状分析将通过GWAS进行，以确定籽粒分配性状的标记，这些标记可用于育种计划，以选择高HI，高生物量基因型。更广泛的种质，包括BBSRC育种者工具包面板中的合成衍生和地方衍生品系，也将进行筛选（100个品系），并进行标记-性状分析，以更好地了解潜在位点的范围。我们将在一组DH株系上进行RNAseq实验，并结合孕穗期穗激素浓度分析，进一步研究KWS株系籽粒分配的遗传和生理基础。

Wheat is one of the three major staple cereal crops globally, with excess of 700m tonnes produced per year. Global demand for wheat is set to grow to 900m tonnes by 2050, and in order to meet that target, yields must increase by 1.6% per year, up from current annual increases of 1%. Research to improve biomass, particularly through the avenue of enhancing wheat photosynthesis may generate some yield increases, however this is unlikely to help hit yield targets unless the additional biomass generated is "useful biomass", or grain. Harvest index, (HI, grain dry matter (DM) yield / aboveground DM) is a measure of the ratio of useful biomass to non-useful biomass, and is a key component of yield. For winter wheat, HI values rarely exceed 0.55, and have not increased significantly since the 1990's, despite a theoretical limit as high as 0.65. A better understanding of the genetic basis of HI would allow for the improvement and stable expression of HI in higher biomass varieties, leading to a step change in genetic yield potential. There is significant evidence that yield potential is a sink limited trait, where carbon accumulation is limited by grain sink strength. Therefore improving grains per m2 is an important avenue for increasing the HI and yield potential of modern winter wheat. Fruiting efficiency is a measure of the number of grains set per unit of spike dry weight as anthesis, and is another trait of particular interest. This project is in collaboration with Drs Ed Byrne and Jacob Lage at KWS UK Ltd and will phenotype an association panel of elite KWS UK winter wheat doubled-haploid lines for grain yield, HI, 1000 grain weight and grains per m2; and grain partitioning and photosynthetic traits, including spike and stem-internode dry matter partitioning indices, fruiting efficiency (grains per unto spike DM at anthesis), canopy NDVI and leaf chlorophyll content (SPAD). The panel (150 lines), representing a stratified sampling across the KWS programme, will be genotyped. Marker-trait analysis will be performed via GWAS to identify markers for grain partitioning traits that can be used in breeding programs to select for high HI, high biomass genotypes.Wider germplasm including synthetic-derived and landrace-derived lines in the BBSRC Breders' Toolkit panel will also be screened (100 lines) and marker-trait analysis carried out to gain a better understanding of the range of potential loci. . The genetic and physiological basis of grain partitioning in the KWS panel will be investigated further with an RNAseq experiment on a subset of DH lines, in conjunction with spike hormone concentration analysis at booting.