Studies On Resistance Mechanism Of Cotton Varieties To The Cotton Aphid, Aphis Gossypii Glover

Amounts of the winged aphids of the cotton aphid, Aphis gossypii Glover landing on cotton plants were surveyed and parameters of growth development were determined on 8 cotton varieties including Xuzhoul42, E'mian No.6, JimianlO, E'mianl247, Dezimian4313, Acalal517, Liaomian7109, SGK kangchongmian in order to research both non-preference and antibiosis of them to the aphid in laboratory. Moreover, resistance mechanism was studied on the basis of the morphological characteristics, contents of soluble sugar and contents of free amino acid of the cotton varieties. The principal results of this paper are as follows.1. There was obvious difference in preference of the winged aphids to cotton varieties. Aphids weren't attracted evidently by Xuzhou 142 and E'mian No.6, however attracted strongly by Acalal517, Liaomian7109 and SGK kangchongmian.2. There was significant difference in development periods of the aphid on the different cotton varieties. The development periods on the Xuzhoul42 and E'mian No.6 were longer than that of on the Acalal517, Liaomian7109 and SGK kangchongmian.3. The result showed that the population amounts of the aphid on the Xuzhou 142 and E'mian No.6 were lower than those of on the Acalal517, Liaomian7109 and SGK kangchongmian; The amounts of aphid on different varieties all increased with the growth of cotton in the investigation period, however, the amounts of the aphid increased more quickly on the Acalal517, Liaomian7109 and SGK kangchongmian.4. The regression models about non-preference indexes of the aphid in relation to pubescence density, content of epidermis wax, thickness of epidermal cell, soluble sugar and free amino acids of cotton varieties were built. The content of epidermis wax was a principal factor influencing on non-preference. Both pubescence density and soluble sugar were negatively related to non-preference, while the free amino acids and thickness of epidermal cell positively.5. There was significant difference in the content of tannins and the activity ofPeroxidase (POD ) , Polyphenol oxidase ( PPO ), Phenylalanine ammonia ( PAL ) between normal seedlings and damaged seedlings. But, differences in the content of tannins and the activity of POD, PPO, PAL among normal seedlings were not evident.6. The regression models about resistance indexes of cotton varieties hi relation to contents of free amino acids were built by applying the main component analysis and interrelation analysis. The contents of amino acids Tyr were positively related to resistance in five-leaf stage of cotton, while Asp negatively; the contents of amino acids Pro,Tyr were positively related to resistance in the boll stage of cotton.