Molecular Genetics Studies Of Cotton Aphid, Aphis Gossypii Glover(homotera:aphididae) On Population Differentiation And Artificial Induction Of Sexuales

Cotton aphid, Aphis gossypii (GlovcrXHemiptera:Aphididae) is one of the most important pests to various plants,and also an efficient vector of several plant viruses. The powerful hetergeny for population differentiation and genetic variation strength its adaptability to variable ecosystems, and also are the intra-factor for its outbreak. Therefore, it is the core for IMP research. This study combined the population ecology with molecular biology. Two multilocus genetic markers(RAPD- PCR and SPSR-PCR) as well as two genetic diversity index(gene diversity index and polymorphic rate of loci) and various statistical analysis were used to detect and analyse the population differentations of A. gossypii related to hosts and seasons. Moreover the sexuales of this species was induced successtlilly under laboratory condition. The result showed that DNA polymorphisms was increasing with the population gradations. The DNA diversity among different clones of A. ss)pii from same host or seasonal population was lower than that of the different host or seasonal populations. The results of RAPD-PCR showed that the genetic differentiation among different host populations were only at population level but had not achieved the subspecies level. Moreover based on the analysis of Nei genetic distance(D), it was assumed that the population sources on cotton and melon might come mainly from hibiscus and pomegraniate instead of Chinses prickly ash. The analysis of SPSR-PCR showed that the differentiation among three overwinter host populations were at low levels , but in high level differentiation appeared between populations from overwinter hosts and from summer hosts. The fundatrix of A. gossii might consist of two body-color forms, i.e. unchangeable yellow form and changeable green form. The former always keep yellow both in fi.indatrix and its parthenogenetic offsprings under nature environment, but the latter, green fiindatrix could produce both green and yellow offsprings. The body-color variation in A. gos.sypii was closely related with temperature and nutrition. But a detailed study may need to explain interaction between genetic basis and environmental factors in this variation. The genetic differentiation among different body-color populations from different seasons was only at population level, instead of subspecies level. The dwarf form population was the mixture of two body-color forms, but transformed mainly from the green fiindatrix. Field observation revealed that sexual phase in annual life cycle of A. gossypii usually began at late autumn, and only sustained for 2 to 3 weeks. One male was able to mate with several females. The PCR technique with 3 microsatellite primers was used to analyse the DNA polymorphism in seven forms (Sexupara, Sexual female, Male, fundatrix, Apterous and Mate Virginogenia) of A. gossypii. The results sh~wed that there were significant differences between sexual forms and parthenogenetic forms of cotton aphid with characteristic bands appeared. There were closely genetic relationship among sexupara, sexual female and male, this may suggest that the mother of sexual female also be the mother of male. Compared with virginogeniae, genetic relationship between fundatrix and the first generation of virginogeniae (apterous) produced by fundatrix (apterous) were more closer than the virginogeniae after the 2 nd generation. Under lab...