| Cotton is the pillar industry in agriculture of Xinjiang, which was severely restricted by disease and pest. Tetranychus turkestani Vgorag et Nikolski is the dominant species in the spider mite population, experiments were conducted to study the damage degree in field of T. turkestani and its host preference on eighteen cotton varieties. On this basis, combing the population density and repellent, we determined the shape and the main biochemical composition of leaves and discussed the host- preference mechanisms of T. turkestani on different cotton varieties. The research results are as follows:1. Host- preference of T. turkestani on different cotton varietiesUsing the extent of damage in field and population density in laboratory as selective indicators, we determined the host- preference of T. turkestani on eighteen cotton varieties. The result showed that T. turkestani were not attracted evidently by Xinhai 21,Xinluzao 12,Xiluzao 22, Xinluzao 26, but attracted strongly by 297-5,Zhongmian 42,81-3.2. Comparison on repellent effects of T. turkestani to different cotton varietiesWe determined the repellent effects of T. turkestani to six cotton varieties in Petri dish; the results indicated that T. turkestani trend for most of the Biaoza A1 and 81-3 but trend for least of the Xinhai 21.3. The population parameter of T. turkestani on different cotton varietiesThe different cotton varieties had significant influence on the development and propagation of T. turkestani. The results indicated that the development duration of stages of T. turkestani in Xinhai 21, Xinluzao 12, and Xinluzao 26 with weak host preference was longer than that in 297-5, Zhongmian 42, 81-3 with strong host preference. Survival rate of development stages, trend index of population and the number of oviposition of T. turkestani in Xinhai 21, Xinluzao 12 and Xinluzao 26 was lower than that in 297-5, BiaozaA1 and 81-3.4. Relationship between host- preference of T. turkestani and external morphology of cottonThe result showed that the damage index had significant negative correlation with wax content (P=0.0089), significant positive correlation with water content (P=0.0092), some negative correlation with hair density (P=0.1594), but the correlation was not significant, i.e. Varieties with higher wax content and less water suffer less by mites, which determined the morphological non-preference mechanism of cotton varieties.5. Relationship between host- preference of T. turkestani and nutrient composition in cotton leavesHost- preference of T. turkestani had some negative correlation with the contents of soluble sugar, but the correlation was not significant (P=0.4994), evidently significant negative correlation with the amounts of chlorophyll (P=0.0243), i.e. Varieties with higher chlorophyll content suffer less by mites.6. Relationship between host- preference of T. turkestani and secondary compounds metabolism in cotton leavesThe host- preference of T. turkestani to different cotton varieties had evidently significant negative correlation with the amount of free gossypol (P=0.0244), flavonoids (P=0.0353) but positive correlation with tannin (P=0.0161), i.e. Varieties with higher the content of free gossypol, flavonoids and lower tannin suffer less by mites.T. turkestani seriously hampered the production and development of cotton in Xinjiang. The researches on the feeding selection of different cotton varieties and repellent effects can be the important scientific evidences for conducting sustainable Integrated Pest Management programme for T. turkestani. Key words : Cotton,Tetranychus turkestani Vgorag et Nikolski, Host- preference, Preference mechanism... |
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