Nymphiposition and Population Growth of Rhoaplosiphum padi L. (Homoptera: Aphididae) on Conventional Wheat Cultivars and Transgenic Wheat Isolines

Nymphiposition and population growth of bird cherry-oat aphid, Rhoaplosiphum padi L. (Homoptera: Aphididae), were measured in four experiments with conventional, non-transgenic cultivars of wheat (Triticum aestivum L.) and in four separate experiments with isolines of ‘Prospect’ wheat containing the pin2 gene with promoter for potato proteinase inhibitor II. In two experiments with conventional wheat, population growth of R. padi was lower on cultivars ‘Sharp,’ ‘Marshall’ and ‘Ember’ compared to that on ‘Russ.’ Numbers of R. padi were intermediate on ‘2375’ and did not differ from that on other cultivars. In the third and fourth experiments, Sharp and Marshall had less R. padi than ‘Guard’ and ‘Prospect,’ whereas ‘Butte 86’ and ‘Ivan’ had intermediate numbers of R. padi that did not differ from that on other cultivars. Nymphiposition by alate R. padi did not differ among cultivars, indicating a lack of antixenosis. Transgenic isolines did not show resistance to R. padi. Two of three experiments showed no effect of isoline on nymphiposition by R. padi, and three of four experiments showed no effect of isoline on final numbers of R. padi. However, in one experiment, nymphiposition by R. padi was greater on some transgenic isolines than others and, after 13 d, some transgenic isolines had greater populations of R. padi. Mechanical wounding of transgenic plants had no effect on nymphiposition or final numbers of R. padi. Although wheat cultivars Sharp, Marshall and Ember show promise as sources of antibiosis resistance to R. padi, more research is needed to understand potential use of proteinase transgenes in wheat for cereal aphid management.