Characterization of virulence and diversity of Puccinia triticina on wheat in Bulgaria during 2017/2018 growing season

Leaf rust (Puccinia triticina Eriks.) is one of the most widespread diseases on wheat (Triticum aestivum L.) in Bulgaria and worldwide. The monitoring researches of the pathogen populations have not only scientific significance, but also practical importance in the breeding for resistance and the distribution of the resistant varieties in the agro cenosis. One hundred and twenty isolates of Puccinia triticina were collected from nine agro ecological regions in Bulgaria during vegetative growth seasons 2016/17 and 2017/18. Seventy-nine phenotypically different pathotypes were identified based on the expressed infec-tion type on 20 different varieties (Lr genes). Eight of the races (PKTTS, PHTTS, TKTTS, TKTTT, THTTS, THTTD, TKKTJ and PKKTS) identified in the population, were found in previous investigations as well. Thirty-six new pathotypes were identified in 2017, and in 2018 - 35 new pathotypes. In 2017, with the highest percent of distribution were pathotypes PHKTD and PKTTD (7.9%), and in 2018 - pathotype PKKTS (7.0%). The predominant virulent phenotypes during vegetative growth seasons 2016/17 and 2017/18 were unevenly distributed on the territory of Bulgaria. The genes for resistance varied by their efficiency. During the investigated period, virulence on genes Lr 9, Lr 19 and Lr 43 was not found. Low frequency virulence was determined on genes Lr 2b, Lr 22B, Lr 40, Lr 41 and Lr 47. Genes Lr 1, Lr 2c, Lr 3, Lr 10, Lr 11, Lr 15, Lr 18, Lr 20, Lr 21, Lr 23, Lr 26, Lr 27+31, Lr 29, Lr 30, Lr 36, Lr 37, Lr 44, Lr 45, Lr 51, Lr 60, Lr 63, Lr 64, Lr B were with low efficiency during the studied period, while genes Lr 14a, Lr 16 and Lr 17 were completely inefficient.