关键词: 耕地, 耕地, 细碎化, 景观指数, 临夏北塬

Abstract: To discuss the response mechanism of Bt cotton resistance to Helicoverpa armigera under the diurnal temperature condition, two different Bt cotton varieties were used as materials for mensurating insecticidal protein content from cotton leaves at seedling stage and investigating the death rate of cotton bollworm fed on cotton leaves. In the experiment, temperature stress (35℃/28℃ or 35℃/18℃) were carried out for 96 h in the artificial climatic chamber in order to study the influence of alternating temperatures day and night on cotton bollworm larval mortality and insecticidal protein expression. The results indicated that when day/night temperature was 35℃/18℃, it could significantly affect Cry1Ac protein content and cotton bollworm larval mortality, and in pace with the time extending, Cry1Ac protein content and larval mortality suffered a sharp decline. While 35℃/28℃ of day/night temperature also affected the insecticidal protein expression and larval mortality, but it had only small influence degree. And as the time extended, Cry1Ac protein content had a stable reduction. Between the two Bt cotton varieties from different gene sources, cotton ‘Hanza 154’ from USA had higher insecticidal protein content than ‘Wanmian11’ from Anhui. Bt cotton from USA was less affected by diurnal temperature. The extremely high temperature at daytime and the very low temperature at night might significantly affect Bt cotton resistance to cotton bollworm. What’s more, the longer the stress time, the stronger the effect degree. It will provide a theoretical basis for security applications of Bt cotton in frequently extreme weather during the process of cotton cultivation in China.