Resistance of wheat cultivars to bird cherry-oat aphid, Rhopalosiphum padi (Hem.: Aphididae)

The bird cherry-oat aphid, Rhopalosiphum padi (L.), is polyphagous with a nearly worldwide distribution and known as an important pest of wheat and the main vector of barley yellow dwarf virus. In this study, the possibility of antixenosis, antibiosis and tolerance of six common wheat cultivars of Chamran, Darab 2, Shiraz, Ghods, Marvdasht and Niknezhad was investigated at 2-3 leaf growth stage in the Fars province, Iran. The experiments were conducted at 24 ± 5°C, 65 ± 5% R.H. and natural light in a greenhouse, using a randomized complete design. The analysis of variance in regard to the number of adult aphids attracted to each cultivar, was indicative of significant differences among the cultivars (P < 0.01). The highest (21 ± 0.71) and the lowest (11.6 ± 0.51) mean number of adult aphids attracted per plant was observed on Shiraz and Darab 2, respectively. The antibiosis test, based on nymphs per female was significantly different among the cultivars (P < 0.01) whose average values were 62.05, 55.84, 49.89, 47.63, 42.76 and 40.65 nymphs per female on Niknezhad, Shiraz, Ghods, Marvdash, Chamran, and Darab 2, respectively. The tolerance studies based on the damage index, showed that Chamran and Darab 2, with the lowest damage index (1.33), were the most tolerant cultivars while Shiraz and Niknezhad, with the highest damage indexes of 3.00 and 3.67 respectively, were the most susceptible cultivars. The cutivars Niknezhad and Shiraz are found to be susceptible, Ghods and Marvdasht partially resistant, and Chamran and Darab 2 resistant to the bird cherry - oat aphid.