Impacts of transgenic Bt cotton on the stylet penetration behaviors of Bemisia tabaci biotype B Evidence from laboratory experiments

Stylet penetration behaviors of Bemisia tabaci biotype B on two transgenic cotton lines ＂GK12＂ and ＂GK19＂ expressing Bt toxic protein CrylA （Bt cotton） and a non-Bt conventional cotton line ＂Simian-3＂ （CK cotton） were recorded with the direct current electrical penetration graph （DC-EPG） technique. Our results suggested that EPG waveform patterns, types and characteristics [non-probe （NP）, pathway （C）, potential drops （pd） and phloem phase （E（pd））] ofBemisia tabaci biotype B were very similar on the three cotton lines. There were no obvious differences of pathway variables among whiteflies on the three cotton lines. Some phloem variables related to E（pd）l differed. Duration of 1st E（pd）l and mean duration of E（pd）l on both GK12 and GK19 were significantly shorter than that on CK cotton （P 〈 0.05）. Fewer whiteflies on GK have long E（pd）l. Other phloem variables including total duration of E（pd） summed, mean E（pd） duration and percentage of whiteflies reaching the phloem phase were similar among the three cotton lines.

Volatiles induced by the larvae of the Asian corn borer （Ostrinia furnacalis） in maize plants affect behavior of conspecific larvae and female adults

Effects of maize （Zea mays L.） volatiles induced by larvae of the Asian corn borer, Ostriniafurnacalis （Guenee）, on the orientation behaviors of Asian corn borer larvae and oviposition of the females were investigated. Nineteen volatile chemicals, with terpenes being the major components, were identified from maize plants attacked by third instar Asian corn borer larvae. Coupled gas chromatographic-electroantennographic detection （GC-EAD） analyses revealed some electroantennographic differences between female and male Asian corn borer antennae in response to larvae-induced maize volatiles; female responded to （E）-2-hexenal, nonanal, （Z）-3-hexen-l-ol and three unknown compounds while the male only responded to （E）-2-hexenal, nonanal and one unknown compound. In laboratory orientation bioassays, Asian corn borer neonate larvae were attracted to extracts collected from Asian corn borer-damaged plants as well as to synthetic farnesene, but were repelled by （Z）-3-hexen- 1 -ol. In laboratory oviposition bioassays, gravid females laid fewer eggs on plants damaged by larvae than on mechanically damaged plants or undamaged plants. Adult Asian corn borer females deposited fewer eggs on wax paper treated with （E）-2-hexenal or （Z）-3-hexen-l-ol than on wax paper treated with hexane （control）. The results suggest that Asian corn borer can affect the behaviors of conspecific larvae and adults by changing host plant volatiles.

Stylet penetration behaviors of the cotton aphid Aphis gossypfi on transgenic Bt cotton

Stylet penetration behaviors of cotton aphids Aphis gossypii Glover on a transgenic cotton line ＂GK-12＂ expressing Bt toxic protein of Cry 1A （Bt cotton） and a non- Bt conventional cotton line ＂Simian-3＂ （CK cotton） were recorded with the direct current electrical penetration graph （DC-EPG） technique. Cotton aphids reared on Bt cotton （abbreviated as Bt-aphids） and its parental non-Bt control line （CK-aphids） for more than 20 generations each, were used for recordings on two cotton lines. Among 47 selected parameters reflecting the activities of aphid stylets within plant tissues, there were eight parameters of CK-aphids showing significant differences between the performances of CK- aphids on Bt cotton and CK cotton, while for Bt-aphids, all the parameters were statistically equal between the performances on the two cotton lines. All parameters with significant differences indicated that CK-aphids could penetrate into Bt cotton more easily, but the phloem saps of Bt cotton were not as good as those of regular cotton for CK-aphids. Based on the present results, we concluded that there were some factors in Bt cotton affecting penetration behaviors of CK-aphids, but it just took several generations for CK-aphids to completely adapt Bt cotton, and Bt-aphids could feed on two cotton lines without difficulty.