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Title: Identification of eighteen Berberis species as alternate hosts of Puccinia striiformis f. sp. tritici and virulence variation in the pathogen isolates from natural infection of barberry plants in China

Author
item ZHAO, J. - Northwest Agriculture And Forestry University
item WANG, L. - Northwest Agriculture And Forestry University
item WANG, Z. - Northwest Agriculture And Forestry University
item Chen, Xianming
item ZHANG, H. - Northwest Agriculture And Forestry University
item YAO, J. - Northwest Agriculture And Forestry University
item ZHAN, G. - Northwest Agriculture And Forestry University
item CHEN, W. - Northwest Agriculture And Forestry University
item HUANG, L. - Northwest Agriculture And Forestry University
item KANG, Z. - Northwest Agriculture And Forestry University

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2013
Publication Date: 3/20/2013
Citation: Zhao, J., Wang, L., Wang, Z.Y., Chen, X., Zhang, H.C., Yao, J.N., Zhan, G.M., Chen, W., Huang, L.L., Kang, Z.S. 2013. Identification of eighteen Berberis species as alternate hosts of Puccinia striiformis f. sp. tritici and virulence variation in the pathogen isolates from natural infection of barberry plants in China. Phytopathology. 103:935-940.

Interpretive Summary: Barberry has been recognized as an alternate host for wheat stripe rust pathogen under artificial inoculation conditions, but whether sexual reproduction occurs in China is unknown. In this study, a total of 28 Berberis species were identified and of 20 species tested, 18 species were susceptible to stripe rust when inoculated with teliospores of the fungus from wheat plants under greenhouse conditions. Among 3,703 aecia sampled from barberry plants, four produced stripe rust uredinia on a susceptible wheat cultivar. Sequences of the ITS regions of the four isolates from barberry shared 99% identity with the stripe rust pathogen sequences. The four isolates had virulence patterns different from all previously reported races collected from wheat plants. Furthermore, 82 single-uredinium isolates obtained from the four barberry isolates had high virulence diversity rates, ranging from 9.0% to 28.1%, indicating that the diverse isolates were produced through sexual reproduction on barberry plants under natural conditions. In addition to the stripe rust pathogen, sequence analysis of PCR products of the ITS regions and inoculation tests on wheat identified the stem rust pathogen. Our results indicated that the stripe rust pathogen can infect some Berberis spp. under natural conditions and the sexual cycle of the fungus may contribute to the diversity of the stripe rust pathogen in China.

Technical Abstract: The wheat stripe rust pathogen (Puccinia striiformis f. sp. tritici, Pst) population in China has been reported to be a distinct genetic group with higher diversity than those in many other countries. Genetic recombination in the Pst population has been identified with molecular markers, but whether sexual reproduction occurs in China is unknown. In this study, we surveyed barberry plants for infection by rust fungi in the stripe rust “hotspot” regions in Gansu, Sichuan, and Shaanxi provinces; collected barberry plants and inoculated plants of 20 Berberis species with germinated teliospores under controlled greenhouse conditions for susceptibility to Pst; and 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. Different Berberis species were widely distributed and most surveyed plants had pycnia and aecia of rust fungi throughout the surveyed regions. A total of 28 Berberis species were identified during our study. From 20 Berberis species tested with teliospores of Pst from wheat plants, 18 species were susceptible under greenhouse conditions. Among 3,703 aecia sampled from barberry plants of three species, B. shensiana, B. brachypoda, and B. soulieana, under natural infections in Gansu and Shaanxi provinces, four produced Pst uredinia on susceptible wheat cultivar Mingxian 169. Sequence of the ITS regions of the four isolates from barberry shared 99% identity with the Pst sequences in the NCBI database. The four isolates had virulence patterns different from all previously reported races collected from wheat plants. Furthermore, 82 single-uredinium isolates obtained from the four barberry isolates had high virulence diversity rates, ranging from 9.0% to 28.1%, indicating that the diverse isolates were produced through sexual reproduction on barberry plants under natural conditions. In addition to Pst, sequence analysis of PCR products of the ITS regions and inoculation tests on wheat identified P. graminis (Pg, the stem rust pathogen). Our results indicated that Pst can infect some Berberis spp. under natural conditions and the sexual cycle of the fungus may contribute to the diversity of Pst in China.