[Effects of transgenic insect-resistant cotton root exudates on the growth of Verticillium dahliae Kleb].

The decline of disease resistance of transgenic insect-resistant cotton has become one of the important factors restricting China cotton production. With two transgenic insect-resistant cotton varieties and their parental conventional cotton lines as test materials, the effects of their root exudates on the spore germination and mycelial growth of Verticillium dahliae Kleb were studied, and the components and contents of the amino acids and sugars in the exudates were determined. Comparing with their parental lines, the two transgenic insect-resistant varieties had a declined resistance against V. dahliae, and their root exudates had promotion effects on V. dahliae spore germination and mycelial growth. The root exudates of transgenic cotton Zhong-41, compared with those 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 higher. Though the components of amino acids in the root exudates of Simian-3 and 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 of 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.

The effect of root exudates from two transgenic insect-resistant cotton lines on the growth of Fusarium oxysporum.

The attenuation of disease resistance in transgenic insect-resistant cotton has become one of the important factors restricting cotton production in China. Two transgenic insect-resistant cotton lines and their parental conventional cotton lines were used as the testing materials. The effects of root exudates of these cotton lines on the spore germination and mycelial growth of Fusarium oxysporum were studied and the components, contents of amino acids and sugars were determined. The results showed that the resistance of the two insect-resistant cotton lines to F. oxysporum was inferior to the parental lines, and that their root exudates promoted fungal spore germination and mycelial growth. Considerable differences in the components and contents of both, amino acids and sugars were found between the root exudates of transgenic cotton lines and their parental lines, where the disease indices were highly correlated with the total amount of sugars in the root exudates.