Investigation of the mechanism of adult-stage resistance to barley yellow dwarf virus associated with awheat-Thinopyrum intermedium translocation

Barley yellow dwarf virus(BYDV)can infect wheat(Triticum aestivum L.),leading to yield loss.Among four BYDV strains(GAV,GPV,PAV,and RMV)identified in China,BYDV-GAV is the prevailing isolate.YW642,a wheat–Thinopyrum intermedium translocation line,is resistant to BYDV isolates at both seedling and adult stages.Zhong 8601 is the wheat recurrent parent of YW642 and is susceptible to BYDV.In this study,we investigated the adult-stage resistance mechanism of YW642,measured BYDV titer and hydrogen peroxide(H_2O_2) in adult-stage leaves of YW642 and Zhong 8601 inoculated with BYDV-GAV,and identified transcriptional differences between YW642 and Zhong 8601 using microarray-based comparative transcriptomics.Enzyme-linked immunosorbent assay and H_2O_2assay showed that both BYDV titer and H_2O_2 content were markedly lower in YW642 than in Zhong 8601 at 21,28,35,and 40 days post-inoculation(dpi).The transcriptomic comparison revealed that many types of genes were significantly up-regulated at 35 dpi in adult-stage leaves of YW642 compared to Zhong 8601.The important up-regulated genes associated with the adult-stage resistance encoded 15 resistance-like proteins,pathogenesis-related proteins(such as defensin and lipid transfer proteins),protein kinase homologs,transcription factors,reactive oxygen species scavenging-related proteins,and jasmonic acid and gibberellic acid biosynthesis enzymes.These results suggest that precise expression regulation of these proteins plays a crucial role in adult-stage resistance of YW642 against BYDV infection.

Release of Stem Rust Resistant Wheat Varieties for Commercial Production in Kenya

Detection in 1999 of a new stem rust （Puccinia graminis f. sp. tritici） race Ug99 in Uganda with broad virulence including the virulence for Sr31 and its migration to Kenya and Ethiopia has been recognized as a significant threat to local and world wheat production. All the Current Kenyan commercial varieties are susceptible to this race. This study was aimed at identifying suitable wheat varieties with resistance to Ug99 and replacing the susceptible commercial varieties through multi-locational testing and variety release. Thirty three lines were identified from a prescreen population of 104 lines and tested in 3 wheat growing regions in Kenya for two seasons in 2006 and 2007. The resulting four superior lines were evaluated under the National Performance Trial （NPT） where two lines which out-performed the best check variety were released as for commercial production. ＇Robin＇ was the best line and out yielded the commercial variety by 27%. ＂Eaglel0＂ was the second best and was better significantly than the check variety. These two lines which combined both adult plant resistant gene Sr2 complex and other major genes are expected to have some durable resistance and may be used to replace the current susceptible commercial varieties grown in Kenya.