Abstract
Key messageThe first cytological characterization of the 2NvS segment in hexaploid wheat; complete de novo assembly and annotation of 2NvS segment; 2NvS frequency is increasing 2NvS and is associated with higher yield.The Aegilops ventricosa 2NvS translocation segment has been utilized in breeding disease-resistant wheat crops since the early 1990s. This segment is known to possess several important resistance genes against multiple wheat diseases including root knot nematode, stripe rust, leaf rust and stem rust. More recently, this segment has been associated with resistance to wheat blast, an emerging and devastating wheat disease in South America and Asia. To date, full characterization of the segment including its size, gene content and its association with grain yield is lacking. Here, we present a complete cytological and physical characterization of this agronomically important translocation in bread wheat. We de novo assembled the 2NvS segment in two wheat varieties, ‘Jagger’ and ‘CDC Stanley,’ and delineated the segment to be approximately 33 Mb. A total of 535 high-confidence genes were annotated within the 2NvS region, with > 10% belonging to the nucleotide-binding leucine-rich repeat (NLR) gene families. Identification of groups of NLR genes that are potentially N genome-specific and expressed in specific tissues can fast-track testing of candidate genes playing roles in various disease resistances. We also show the increasing frequency of 2NvS among spring and winter wheat breeding programs over two and a half decades, and the positive impact of 2NvS on wheat grain yield based on historical datasets. The significance of the 2NvS segment in wheat breeding due to resistance to multiple diseases and a positive impact on yield highlights the importance of understanding and characterizing the wheat pan-genome for better insights into molecular breeding for wheat improvement.
Highlights
Bread wheat (Triticum aestivum L.), a crop that provides roughly one-fifth of the calories consumed by humans, has a very large genome of 16 gigabase (IWGSC 2018)
Our results show that there is a 3 to 6 Mb region following the Ae. ventricosa segment that is low in polymorphisms among the four 2NvS carriers (Jagger, CDC Stanley, SY Mattis and Mace) and expected to be wheat chromatin with identity by descent (IBD) from the original VPM1 translocation (Supplemental Figure S4)
To test the hypothesis that 2NvS might carry unique nucleotide-binding leucine-rich repeat (NLR) gene families that are partially responsible for the suite of disease resistance genes found on this segment, we examined the phylogenetic relationships of 2 NvS NLR genes genes compared to Chinese Spring 2AS NLRs
Summary
Bread wheat (Triticum aestivum L.), a crop that provides roughly one-fifth of the calories consumed by humans, has a very large genome of 16 gigabase (IWGSC 2018). The high plasticity of the genome likely contributed to the successful spread of bread wheat as a staple food crop around the globe. This high plasticity readily enables introgression of novel alleles via chromosome translocations from related species (Friebe et al 1996). Over 52 Triticeae species across 13 genera have been successfully utilized to enrich the genetic diversity of cultivated wheat (Wulff and Moscou 2014). A segment from Ae. ventricosa was first introduced into the wheat cultivar VPM1 by the French cytogeneticist G. New reports suggest that this fragment is contributing to lodging resistance in bread wheat (Singh et al 2019)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have