Abstract: The decline of disease resistance of transgenic insect-resistant cotton has bec ome one of the important factors restricting China cotton production. With two t ransgenic insect-resistant cotton varieties and their parental conventi onal cotton lines as test materials, the effects of their root exudates on the s pore germination and mycelial growth of Verticillium dahliae Kleb were studi ed, and the components and contents of the amino acids and sugars in the exudate s were determined. Comparing with their parental lines, the two transgenic insec t-resistant varieties had a declined resistance against V. dahliae, and the ir root exudates had promotion effects on V. dahliae spore germination and mycel ial growth. The root exudates of transgenic cotton Zhong-41, compared with thos e of its parent line Zhong-23, contained two additional amino acids Met and Lys , and the contents of Asp, Glu, Ser, Ala, Val, Leu, and Tyr were significantly h igher. Though the components of amino acids in the root exudates of Simian-3 an d transgenic cotton GK-12 were the same, the Tyr, Val, and Leu contents in the root exudates of transgenic cotton GK-12 were significantly lower. Four kinds o f sugar were detected in the root exudates of Zhong-41, while only glucose was detected in the root exudates of Zhong-23. These four kinds of sugar were also detected in the root exudates of Simian-3 and GK12, but their contents differed significantly.

Key words: fade stage, normalized difference vegetation index (NDVI), Inner Mongolia., ecological zone, climate factor