Role Of Beberis Spp. In Virulence Variation Of Puccinia Striiformis And In Occurrence Of Wheat Stripe Rust

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the mostimportant wheat diseases around the world. Wheat cultivar with resistance to stripe rustovercome by new race of Pst due to virulence variation has been considered main element ofburst of the disease. The wheat stripe rust pathogen population of China has been reported tobe a distinct genetic group with higher diversity than those in many other countries. Geneticrecombination in the Pst population has been identified with molecular markers, Berberis spp.play an important role in sexual generation of Pst as alternate host, but the extent and rule ofsexual stage in natural conditions still unknown in China. In this study, we investigated aecialsmaples from rust-infected berberis by molecular techniques and biological process to providea basis of revealing high level of genetic diversity and virulence variation of Chinese Pstpopulation and to improve strategies for a better control of wheat stripe rust in future studiesin China.The main results were as follows:1. Different Berberis species were widely distributed and most surveyed plants hadpycnia and aecia of rust fungi throughout the surveyed regions, especially Gansu, Shaanxi andSichuan provinces as “hot-spot” regions for Pst. B. brachypoda, B. aggregate, B. shensiana, B.potaninii and B. soulieana were the most five berberis among the different kinds of Berberisspp. we found. Rust pathogen can not only infect the leaves, but also other parts of barberryplants except root. Among3,703aecia sampled (corresponding to3,703seedlings) frombarberry plants of five species, B. brachypoda, B. aggregate, B. shensiana, B. potaninii and B.soulieana, under natural infections in Gansu and Shaanxi provinces, four produced Psturedinia on susceptible wheat cultivar Mingxian169， two from B. brachypoda, one from B.shensiana, and one from B. soulieana. After DNA extract and PCR amplification, sequence ofthe ITS regions of the four isolates from barberry shared99%identity with the Pst sequencesin the NCBI database. This result proved that the four isolates were Pst, but shows a very lowinfection rate of Pathogen, and maybe Berberis species had little effect for prevalent striperust.2. We tested Pst isolates obtained from aecia on naturally infected barberry plants on the wheat genotypes used to differentiate Chinese Pst races to determine virulence variations. Thefour isolates had virulence patterns different from each other and all previously reported racescollected from wheat plants. Furthermore,82single uredinium isolates obtained from the fourbarberry isolates had high virulence diversity rates, ranging from9.0%to28.1%, indicatingthat the diverse isolates were produced through sexual reproduction on barberry plants undernatural conditions. In addition to Pst, sequence analysis of PCR products of the ITS regionsand inoculation tests on wheat identified P. graminis (Pg, the stem rust pathogen). Our resultsindicated that Pst can infect some Berberis spp. under natural conditions and the sexual cycleof the fungus may contribute to the diversity of Pst in China.