POSTULATION OF RESISTANCE GENES TO YELLOW RUST IN WILD EMMER WHEAT DERIVATIVES AND ADVANCED WHEAT LINES FROM NEPAL

Seedlings of 38 wild emmer derivatives, and a total of 53 advanced whe at varieties/lines introduced from the International Maize and Wheat I mprovement Centre (CIMMYT) or other sources, Nepalese breeding lines a nd local cultivars were inoculated with 18 different yellow rust isola tes to postulate yellow rust resistance genes (Yr). Many wild emmer wh eat derivatives used were resistant to all isolates indicating the pre sence of undescribed genes. Some derivatives carried Yr9, Yr6 and/or Y rSU. Genes Yr1, Yr2, Yr6, Yr7, Yr8, Yr15, YrSU and YrA+ are no longer effective in Nepal; Yr4, Yr5, Yr9, Yr10, YrSP and YrSD are still effec tive; the effectiveness of Yr3 remains unclear. This study shows that stripe rust resistance in seedling stage of most Nepalese cultivars an d advanced materials is based on Yr9 with combinations of Yr2, Yr6, Yr 7, and YrA+, of which only Yr9 is still effective in Nepal. In many co untries Yr9 has lost its effectiveness. Therefore the introduction of new Yr-genes from wild emmer wheat in Nepalese cultivars is highly imp ortant.