Greenbug resistance in local oat samples from East Asia

Abstract

Genetic uniformity of crops promotes adaptive microevolution in pests and resistant varieties with various genetic bases are to be cultivated. Till now only 4 oat genes for resistance to greenbug (Schizaphis graminum Rond.) are identified. Resistance in sample Russian 77 (CI 2898) to greenbug biotype À is controlled by dominant gene Tg 1 (Gardenhire 1964). Study of inheritance of resistance in 3 oat varieties revealed that lines PI 186270 and CI 1580 had single dominant genes (Grb1 and Grb2 respectively) determining resistance to biotype Ñ; line CI 4888 had dominant gene Grb3 for biotype  resistance. Possible presence of minor genes for resistance in all 3 samples could not be excluded (Boozaya-Angoon et al. 1981). Experiments were conducted in a climate chamber as described by Starks & Burton (1977). Samples at the seedling stage were infested with Krasnodar population of the aphid. When the control plants (cv. Borrus) died damage in experimental plants was estimated according to the scale: 0 no damage, 1 1-10%, 2 11-20 % 10 90-100 % of the leaf surface damaged. Among 277 oat samples most representing local forms from Primorskii krai (Russia), Mongolia, China and Japan, eighty five were heterogeneous for resistance to the greenbug. Damage ratings of resistant components in 42 samples were 1-4, low level of resistance was identified in 43 forms. Wide range of variation for damage ratings (1-10) was characteristic for some samples; it could be result of low expressiveness of genes for resistance and/or difference in virulence pattern among the aphid clones in used population. It was possible to select lines with high and low level of the resistance from that samples indicating to several genes for the trait in at least some oat forms. Half of samples with high level of resistance originated from Mongolia. As genes Grb1 Grb3 were identified in local oat forms from Argentina, Italy and Scotland, we suppose that selected lines have genes for the aphid resistance nonidentical to that described earlier. Gardenhire, J.H. 1964. Crop Science 4: 443; Boozaya-Angoon, D. et al. 1981. Environmental Entomology 10: 557-559; Starks, K.J. & Burton, R.L. 1977. USDA Techn. Bull. 1556: 1-12.