DONORS OF GREENBUG RESISTANCE IN SORGHUM

Abstract

Background. Greenbug (Sсhizaphis graminum Rondani) is a key pest of sorghum. By now, 15 resistance genes have been identified in this crop. The Sgr5 - Sgr15 resistance genes have not being used in breeding; however, differential interaction with the herbivore was revealed only for the accessions protected by the Sgr7 - Sgr11 genes. The necessity to continue searching for sorghum accessions with new resistance genes is quite obvious. Materials and methods. Under laboratory conditions, resistance to a Krasnodar population of S. graminum was analyzed in 13 accessions weakly damaged by this herbivore. Besides, the resistance of the earlier selected grain sorghum accessions from China and of F₁ hybrids from crosses of these forms with susceptible sterile lines was studied. Segregation for resistance to the aphid population in the F₂ hybrids from crossing the accessions k-1239 and k-1251 with susceptible testers was also analyzed. Segregation for resistance to a clone weakly damaging the cultivar ‘Sarvashi' was studied in the F₂ ‘Sarvashi s' × k-1251. When studying genetic control of sorghum resistance to the aphid, two experimental approaches were applied: examination of the differential insect-host interaction, and hybridological analysis. Results and conclusions. Nine accessions of grain, sweet and wild sorghum, protected by alleles of greenbug resistance genes differing from earlier identified alleles of the Sgr1 - Sgr6 and Sgr12 genes, have been selected. Pure lines k-105, k-533, k-1239, k-3650, k-6339 and k-10524 selected from grain and sweet sorghum samples are most promising for use in breeding for resistance. A dominant inheritance pattern of greenbug resistance was demonstrated by ten grain sorghum accessions from China: k-830, k-831, k-931, k-932, k-933, k-1238, k-1239, k-1241, k-1251 and k-2588. Each of the accessions k-1239 and k-1251 has two highly effective resistance genes (dominant and recessive), which are not identical to alleles of the effective Sgr5 and Sgr6 genes.