Anatomical and chemical characteristics associated with lodging resistance in wheat

Anatomical and chemical characteristics of stems affect lodging in wheat(Triticum aestivum L.) cultivars. Traits associated with lodging resistance, such as plant height, stem strength, culm wall thickness, pith diameter, and stem diameter, were extensively investigated in earlier studies. However, the solid stem trait was rarely considered. In this study, we measured a range of anatomical and chemical characteristics on solid and hollow stemmed wheat cultivars. Significant correlations were detected between resistance to lodging and several anatomical features, including width of mechanical tissue, weight of low internodes, and width of stem walls. Morphological features that gave the best indication of improved lodging resistance were increased stem width, width of mechanical tissue layer, and stem density. Multiple linear regression analysis showed that 99% of the variation in lodging resistance could be explained by the width of the mechanical tissue layer, suggesting that solid stemmed wheat has several anatomical features for increasing resistance to lodging. In addition, microsatellite markers GWM247 and GWM340 were linked to a single solid stem QTL on chromosome 3BL in a population derived from the cross Xinongshixin(solid stem)/Line 3159(hollow stem). These markers should be valuable in breeding wheat for solid stem.

Novel Natural Allelic Variations at the Rht-1 Loci in Wheat

Plant height is an important agronomic trait. Dramatic increase in wheat yield during the ＂green revolution＂ is mainly due to the widespread utilization of the Reduced height （Rht）-1gene. We analyzed the natural allelic variations of three homoeologous loci Rht-A1, Rht-B1, and Rht-D1 in Chinese wheat （Triticum aestivum L.） micro-core collections and the Rht-B1/D1 genotypes in over 1,500 bred cultivars and germplasms using a modified EcoTILLING. We identified six new Rht-A1 allelic variations （Rht-Alb-g）, eight new Rht-B1 allelic variations （Rht-Blh-o）, and six new Rht-D1 allelic variations （Rht-Dle-j）. These allelic variations contain single nucleotide polymorphisms （SNPs） or small insertions and deletions in the coding or uncoding regions, involving two frame-shift mutations and 15 missenses. Of which, Rht-Dle and Rht-Dlh resulted in the loss of interactions of GID1-DELLA-GID2, Rht-Blicould increase plant height. We found that the Rht-Blh contains the same SNPs and 197 bp fragment insertion as reported in Rht-Blc. Further detection of Rht-Blh in Tibet wheat germplasms and wheat relatives indicated that Rht-Blc may originate from Rht-Blh. These results suggest rich genetic diversity at the Rht-1 loci and provide new resources for wheat breeding.

Whole-genome resequencing of the wheat A subgenome progenitor Triticum urartu provides insights into its demographic history and geographic adaptation

Triticum urartu is the progenitor of the A subgenome in tetraploid and hexaploid wheat.Uncovering the landscape of genetic variations in T.urartu will help us understand the evolutionary and polyploid characteristics of wheat.Here,we investigated the population genomics of T.urartu by genome-wide sequencing of 59 representative accessions collected around the world.A total of 42.2 million highquality single-nucleotide polymorphisms and 3 million insertions and deletions were obtained by mapping reads to the reference genome.The ancient T.urartu population experienced a significant reduction in effective population size(Ne)from3000000 to140000 and subsequently split into eastern Mediterranean coastal and Mesopotamian-Transcaucasian populations during the Younger Dryas period.A map of allelic drift paths displayed splits and mixtures between different geographic groups,and a strong genetic drift towards hexaploid wheat was also observed,indicating that the direct donor of the A subgenome originated from northwestern Syria.Genetic changes were revealed between the eastern Mediterranean coastal and Mesopotamian-Transcaucasian populations in genes orthologous to those regulating plant development and stress responses.A genome-wide association study identified two single-nucleotide polymorphisms in the exonic regions of the SEMI-DWARF 37 ortholog that corresponded to the different T.urartu ecotype groups.Our study provides novel insights into the origin and genetic legacy of the A subgenome in polyploid wheat and contributes a gene repertoire for genomicsenabled improvements in wheat breeding.