The Effects Of Transgenic Insect-resistant Cotton On Soil Organisms

According to cotton's different vegetal period, we gathered the cotton field surface layer soil (0 - 20cm) on November 1, 2006,March 18, 2007,July 16, 2007 and November 20, 2007, we studies the quantity and populative structure of solid minitype invertebrates as well as number of microorganisms in three different kinds of cotton fields at an old cotton farm in China Cotton Institution of Agricultural Scientific Academy (Anyang, Henan Province) in which one has always planted traditional non-transgenic cotton, one has planted transgenic insect-resistance cotton for six years and another planted for eleven years. Meanwhile, it also studies the effect of root exudates of transgenic insect-resistence cotton on the growth of Fusariun oxysporum and Verticillium dahliae Kleb, and also analyses the kinds and quantity of saccharide and amino acid in root exudates. The reslult shows that:1. Among above three cotton fields, change rules of various microbial population number is consistent, while change rules of different microbial population differs in growth period. Compared with conventional cotton filed, there is no notable effect on the number of bacteria, fungi, denitrifying bacteria and Nitrobacteria after planting transgenic insect-resistance cotton for six and eleven years. However, transgenic insect-resisitance cottons have disadvantage effect on the number of aerobic azotobacter due to long planting years.2. Compared with traditional cotton, there is no notable effect of transgenic insect-resistance cotton on the number of soil invertebrates, predominance groups, diversity index, but seen from the curves, it has no consistent regularity in soil invertebrate Simpson index, Shannon-wiener diversity index and homogeneity index in the three cotton fields. However, the Shannon-wiener diversity index and homogeneity index in the 6th transgenic resistant-pest cotton and 11th transgenic resistant-pest cotton was higher than that in the conventional cotton in most times of one year.3. Compared with parent conventional cotton, this two kinds of transgenic insect-resistance cotton have less resistance on Fusariun oxysporum and Verticillium dahliae Kleb in some degrees, with their root exudates promoting spore germination and the growth of hypase.4. It has a distinct difference in kinds and content of saccharine and amino acid between transgenic insect-resistance cotton and parent conventional cotton. Total saccharide content in cotton root exudates is in positive correlation with its disease index of Fusariun oxysporum and Verticillium dahliae Kleb, while amino acid contents is rarely in correlation with disease index of Fusariun oxysporum and Verticillium dahliae Kleb, but in a close correlation with the kinds of some amino acid.