Determination of greenbug biotypes in three populations collected in three localities of remarkable cereal in Argentina

The knowledge of the biotypic composition of an aphid population is important to prevent damage that would occur in the cultivars selected for their resistance to different aphids. In order to study the biotypic composition of three greenbug populations (Schizaphis graminum, Rond) the following differential cultivars were used: oats PI 186270, CI 1579, CI 4888, will barley, Insave F.A rye, Amigo wheat and Triticale Gaucho. Ten plants were infested and other ten were kept as controls without infestation. The number of aphids remained constant (10 adults per plant) during all the experiment. The initial and final height, the growth rate, the fresh and dry weights, the level of chlorosis and the plant vigour were recorded during two subsequent weeks. The infested plants of the differential cultivars showed a variable behaviour when infested with the three populations, pointing out the presence of biotypical variability in the composition of these populations. Current results show that the biotype C was the most frequent in Bavio , Bordenave and La Dulce. The B biotype was found in Bordenave and La Dulce, and it could also be present in Bavio population, where the biotype E would be found.

Key words: Schizaphis graminum, greenbug, biotypes, populations, aphids.