Field Resistance in Bread Wheat to Russian Wheat Aphid, Diuraphis noxia Under Flood Irrigation
The Russian wheat aphid (RWA) (Diuraphis noxia) is cosmopolitan pest and yield losses of up to 93% have been reported in different wheat growing countries. It also has a high degree of biotypic diversity that necessitates the development and utilization of location specific resistant wheat varieties. Thus, 49 wheat genotypes known to be resistant to RWA in other countries were evaluated using natural infestation in 7x7 Simple Lattice for two seasons under flood irrigation at Debre Zeit, Ethiopia. In both seasons none of the tested genotypes were free of RWA infestations. However, in the 2015 season, there was statistically significant difference among genotypes in RWA intensity in all sampling dates, whereas in the 2016 season there was the statistically significant difference among genotypes in RWA intensity in the first three sampling dates but not in the later three sampling dates. The genotypes CIMMYT 109, CMYRWA-7, CMY RWA 36, CMY RWA 103, Correll, SH01-Correll, IG41560, IG 41556, IG 107166, KRWA-9, KRWA 152, SHK01-A26-15, SHK01-B32-59, SHK01-C96-149 and SHK01-D12-167 were highly susceptible to RWA, while CMY RWA 101, PI 625140-1, R-765-RWA-152, SHK01-A36-22, SHK01-B10-46, SHK01-B30-58, SHK01-B35-60, SHK01-B84-89 and SHK01-D37-184 were highly resistant. The remaining genotypes were moderately resistant/ susceptible. As a result the pattern of population increase on the different genotypes was variable across sampling dates. There was no apparent relationship between percent infested tillers and number of aphids per tiller.