IDENTIFICATION OF POWDERY MILDEW RESISTANCE GENES IN COMMON WHEAT (TRITICUM-AESTIVUM L EM THELL) .9. CULTIVARS, LAND RACES AND BREEDING LINES GROWN IN CHINA

The objective of the study was to provide information about the occurr ence and distribution of resistance genes in wheat cultivars, includin g old cultivars, land races and advanced breeding lines grown in China . Ninety-four accessions were analysed with a set of ii differential p owdery mildew isolates. Forty-four cultivars did not possess any major mildew resistance genes. Thirty cultivars revealed the response patte rn of individual resistance genes. The most frequently encountered gen e was Pm8, which occurred singly in 11 cultivars, combined either with Pm4a in three cultivars or with Pm4b in another three cultivars. Howe ver, 12 cultivars possessing the wheat-rye translocated chromosome pai r T1BL.1RS did not express Pm8. Gene Pm2 was found in four cultivars a nd in combination with Pm6 in one cultivar. Genes Pm4a and Pm4b were o bserved in four and five cultivars, respectively. Another six cultivar s carried Pm5. A gene combination of Pm2 + Pm4b + Pm6 was found in one cultivar. Twelve cultivars and breeding lines exhibited a response pa ttern that could not be assigned to resistance genes or gene combinati ons present in the differential cultivars. Five out of these 12 cultiv ars/lines showed resistance to all the isolates tested. There is an ur gent need to search for novel sources of mildew resistance in order to sustain resistance to existing and emerging powdery mildew pathogens.