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IDENTIFICATION OF SOURCES OF RESISTANCE TO SCALD IN BARLEY GERMPLASM ADAPTED TO STRESS CONDITIONS
IDENTIFICATION OF SOURCES OF RESISTANCE TO SCALD IN BARLEY GERMPLASM ADAPTED TO STRESS CONDITIONS H TOUBIA-RAHME, OF MAMLUK and S GRANDO International Center for Agricultural Research in the Dry Areas, (ICARDA), P. O~ Box 5466, Aleppo, Syria Background and objectives Scald caused by Rhynchosporium secalis (Oud.) Davis is a common disease of barley (Hordeum vulgareR. secalis. The objective of this study was to identify sources of resistance to scald in an already adapted genetic background and in a plant type agronomically acceptable to the farmer. Materials and methods A large number of entries of barley germplasm developed by the breeders are tested every year for resistance to scald under artificial epiphytotics in two locations: ICARDA's principal station at Te Hadya, Syria and on a substation at Terbol, Lebanon. The resistant lines obtained are pooled in special scald disease nursery and retested for 2 consecutive years to confirm their resistance. Plots consisted of short rows (40 cm). Each plot was bordered by a spreader row, which was sown with a mixture of scald susceptible varieties. Inoculations started when plants were in the five-leaf stage and were repeated at times when frequent rainfall was expected. Pathogen strains used for the inoculation originated from different locations in Syria and Lebanon. The inoculum was renewed annually and represented a mixture of indigenous strains. The procedures of [1] were used to isolate the fungus and to produce inoculum. Readings were taken according to the 0-9 disease scoring scale of [2]. Readings were taken when the plants were in the late milk stage (DC77). Results and conclusions After 3 years of testing under artificial epiphytotics in the two locations, 12 lines were identified with high level of resistance to scald. The score of these lines ranged from 0 to 2 on a 0-9 scale. All lines had an acceptable level of resistance to powdery mildew and covered smut and are regarded as lines with multiple disease resistance. Some lines are adapted to low rainfall areas with mild winters, some to low rainfall areas with continental climate, and others to moderate rainfall areas with longer growing season. All represents the peculiar environmental conditions of WANA region. In conclusion, these lines are valuable sources of resistance to be utilized in the breeding programs. The genetics of resistance in these lines are not known and need further investigation. References 1. Schein RD, Kerolo JW, 1956. Plant Disease Reporter 40, 814-815. 2. Saari EE, Prescoft JM, 1975. Plant Disease Reporter 59, 377-380.