FIRST REPORT OF LEAF RUST PATHOTYPES VIRULENT TO HIGHLY EFFECTIVE LR-GENES TRANSFERRED FROM AGROPYRON SPECIES TO BREAD WHEAT

The gene pool of effective sources of leaf rust resistance used in the breeding of wheat (Triticum aestivum L.) includes several species of the genus Agropyron. The genes deriving therefrom (Lr 19, 19d, 29, Ag( i)1, Ag(i)2, 38) are highly effective to pathotypes of Puccinia recond ita Rob. ex Desm. In the Saratov and Orenbhurg districts of Russia, ho wever, pathotypes virulent to these genes have been discovered. These pathotypes are virulent to Saratov-bred cultivars carrying Lr 19, to ' Indis' (Lr 19d) and RL 6097 (Lr 38). The distribution of virulence on the 'Thatcher' near-isogenic lines with different Lr genes shows that most of the Lr genes tested are susceptible to these new pathotypes of P. recondita, but the Lr genes Lr 9, 23, 24, 26 were exceptions. The inoculation of Mexican bread wheat cultivars, which carry widespread L r gene combinations, by these pathotypes disclosed different infection types. Out of 10 Lr-gene combinations, four were highly effective; na mely the combinations Lr 13+26, Lr 26+?, Lr 23+16 and Lr 23+26+34.