Virulence and aggressiveness variability of greenbug under the influence of host plant
Keywords:
cereals, Sсhizaphis graminum, populations, virulence, aggressiveness, selectionAbstract
Patterns of the greenbug (Schizaphis graminum Rondani) selection for aggressiveness and virulence were investigated as influenced by the plant genotypes. The possibility of radical changes in the insect population genetic structure during the host plant vegetation period was revealed. Seasonal differences of Krasnodar aphid population in the frequencies of virulence to the major plant resistance genes have been demonstrated. In the natural populations of greenbug the selection of insect virulence phenotypes was observed which was conditioned by the weakly expressed resistance of host plant. Our study showed that the frequencies of the aphid clones virulent to barley samples change during feeding on another host plant. Significant influence of weakly expressed resistance of host plant on S. graminum fecundity was found. Phytophage clones with wider virulence spectrum were more competitive while reproducing on the susceptible genotypes. Reproduction of the insect population on the relatively resistant forms may result in decreasing frequency of genes responsible for the virulence to major resistance genes of the host. The change of the nonspecific aggressiveness of greenbug was observed during its reproduction on the plants with different resistance level. The increase of nonspecific aggressiveness of S. graminum was routinely observed in compatible phytophage – plant host combinations.