Studies On Wheat Plant-wheat Aphid-natural Enemy Interactions

The wheat aphids such as Sitobion avenae and Rhopalosiphum padi are major pests of wheat in China and many other countries in the world. To meet the demand of sustainable pest control strategy, the wheat plant-wheat aphid -natural enemy interactions are studied in this paper. The results are summarized as follows:Three non-preference resistant wheat cultivars, i.e. KOK-1679, LI and Xiaobaidongmai could make the population growth rate of Sitobion avenae dramatically decreasing, and no negative impacts on parasitoid Aphidius avenae . Moreover, the height growth rate, leaf area, and chlorophyll of wheat plant increased by introducing A. avenae to the host plant. After 9 days of S. avenae (at the beginning of 2nd instar) infestation, the population growth rate of S. avenae in susceptible cultivar Hongmanghong was 94.21%, but in the higher resistant line KOK-1679 was 18.05% . Compared with susceptible cultivars, the wasp revealed increasing emergence rate, shorter emergence time and longer adult life in resistant cultivars (lines). The colonial rate of 5. avenae on non-preference wheat plant was lower which may lead the parasite rate to be lower.As to the main differences between volatiles from wheat cultivars (KOK-1679 and Beijing837) with different resistance level were 6-methyl-5-hepten-2-ol and methyl salicylate in KOK-1679, but 2-camphor, naphthalene and butanoic-Z-3-hexenyl ester in Beijing837. There were much differences between volatiles from Beijing837 with or without aphids infestation. Some new volatiles, 2-camphene, 6-methyl-5-hepten-2-one, 6-methyl-5-hepten-2-ol and methyl salicylate from plant-aphid complex, and the quantity of E-2-hexenal and benzaldehyde increased sharply in plant-aphid complex.The olfactory responses of S. avenae and Rhopalosiphum padi including alatae and apterae to volatiles from seven wheat cultivars(lines) with different resistance levels to aphids were different. KOK-1679 ^ LK Xiaobaidongmai and Zhong4wumang were repellent at some degree. The susceptible cultivars Hongmanghong^ Beijing837 and Mingxianl69 were attractive. Olfactory responses ofR.padi apterae to wheat plant volatiles were higher than alatae. The results of cluster analysis using S/C(stimulus/control) of the two aphid species as variety of the seven wheat cultivars(lines) basically coincided with the evaluation in fields. The volatiles(6-methyl-5-hepten-2-one, 6-methyl-5-hepten-2-ol and methyl salicylate) induced by aphids feeding were more repellent to the two aphid species.E-2-hexenal,E-2-hexenol and E-3-hexenyl-acetate were more attractive to 5. avenae, alatae of R. padi and apterae of R. padi. No effects of Alkyl with long chain, 2-camphene, 2-camphenor and 1-methyl-naphthalene on the two aphid species were found.The electroantennal responses of alate and apterous adult aphids of S. avenae and117R.padi to wheat plant volatiles and volatiles induced by aphid feeding were analysed by BAG techniques. Variation of olfactory responses were also analysed. Electroantennal responses of S. avenae to methyl salicylate, E-2-hexenal, E-2-hexenol, 6-methyl-5-hepten-2-one, 6-methyl-5-hepten-2-ol, and R. padi to methyl salicylate, E-3-hexenyl-acetate, 6-methyl-5-hepten-2-one, 6-methyl-5-hepten-2-ol were larger. The electroantennal responses to 6-methyl-5-Hepten-2-one, E-2-hexenol and methyl salicylate were significantly different between alate and apterous adult aphids of S. avenae , and to E-2-hexenol,octanal, linalol, methyl salicylate , E-3-hexenyl-acetate were also different between alate and apterous adult aphids of R. padi. The electroantennal responses to volatiles from different wheat species were consistant with the behaviour performance hi bioassay test.The responses of female A. avenae to volatiles emanating from undamaged wheat plant, S.avenae, R. padi, aphids-plant complex and aphids damaged plant were investigated hi wind tunnel and Y-tube olfactometer. Volatiles from undamaged wheat plant, S. avenae, R. padi were much less attractive to A. avenae than that from aphids-plant complex and aphi...