Virulence and molecular variations of Puccinia triticina, the incitant of wheat leaf rust, in Egypt

Out of 106 isolates of the wheat leaf rust pathogen, Puccinia triticina, collected from five Governorates in Egypt during 2010/11 and 2011/12 growing seasons, 72 physiologic races were identified based on infection types expressed on the series of 20 differential varieties (Lr genes). The highest diversity of races was found in Kafr-Elsheikh and Beheira governorates. race TTTTT was virulent to all 20 Lr genes (100.00%) while, race BBBBB didn't appear any virulence. races, TPTTT and TTTST recorded high frequency (95%), followed by races, FKTTT, KKPTT, KKTST, PTTSS, RTTSS, TKSST, TTPRK and TTTTL (85% each). The raPd analysis of ten P. triticina isolates indicated that four primers, 402, 489, 521 and 538 distinguished molecular phenotypes between isolates that had high virulence to resistance genes, versus isolates that were avirulent or virulent to resistance genes. Primer 521 distinguished unique molecular phenotype among three highly virulent isolates (TTTTT, TTTST and TPTTT). however, primer 538 distinguished unique molecular phenotype among three lowly or avirulent isolates (BBBBB, BLBBQ and MCDLQ). dendrogram clustering determined that at 18.82% similarity there were two groups of P. triticina isolates. isolates in group a consisted of the virulent isolates TTTTT, TTTST, TPTTT, PTTSS, TCBML, TCDML, MCDLQ and MBDLN. however, group B consisted of two avirulent isolates BBBBB and BlBBQ. strong correlation was found between virulence and molecular phenotype of P. triticina isolates. The high diversity and the recurrence of common races in each year is consistent with oversummer survival of P. triticina within egypt or in a neighboring country. The buildup of races virulent on cultivars with the commonly used Lr genes in egypt has had a strong selective effect on virulence in the pathogen population