| Verticillium wilt is one of the serious diseases in most cotton-growing areas of the world and can result in great economic losses in cotton production. Development of cotton resistant cultivars can provide an effective and economical method for controlling verticillium wilt. Thorough understanding of the expression mechanism of cotton responding to verticillium wilt is significant to cotton resistance breeding. One hundred and eight cultivars, bred in China since 1950's, were used to analyze the reaction of verticillium wilt resistance and the effects of different resistant genotypes on yield and fiber quality. The relationship was analyzed between progenitor gene of resistant cultivars and verticillium wilt resistance. The statistics for verticillium wilt symptoms in main stem and on leaves and segregation ratio of the resistance genes in F2 population from resistant variety × susceptible variety crosses were conducted in this study. The influence of host resistance to its isolate was investigated based on ISSR makers and phenotypes. Gene expression of resistance response was examined in Gossypium barbadense Pima90-53 induced by verticillium dahliae with cDNA-AFLP. The main results were as follows:1. The resistance reaction of verticillium wilt of cotton was studied using factor analysis. The disease development was controlled by four principal factors. More variances could be explained by the first principal factor (F1) and second principal factor (F2). F1 and F2 factors were related to the disease indices from July 26 to August 5 and from August 20 to September 4, respectively. One hundred and eight varieties (lines) were classified into 4 groups based on 4 factors loading. Varieties of type â… with high resistance in the prior stage and rapid disease development in the late stage with low yield and fiber quality. Varieties of type â…¡ with high resistance in the prior and late stages provided high yield. Varieties of type â…¢ expressed low disease index in the prior stage and rapid development in the middle stage, their yield was higher than yield of type â…£. Varieties of type â…£ with low resistance provided low yield. The above results showed that the disease resistance of some stagecould not represent the disease resistance of the varieties.2. The analysis of relationships among verticillium wilt, yield and yield component indicated that the disease index was negatively correlation with yield and the impact of verticillium wilt on yield was due to boll number per plant decreasing. Verticillium wilt had little influence on yield and yield component at the early flowering stage, but had big influence at the first occurrence peak of verticillium wilt. The impacts of Verticillium wilt on uniformity and micronaire of fiber were more severe than on the length and elongation, and the least was on fiber strength. The relationship between the ratio of different disease grade and yield component was analyzed using partial correlation analysis methods. The results indicated that yield and yield component negatively correlated with the ratios of grade 0 or grade 4, but positively with ratio of grade I. The correlation between the ratios of grade 2 or grade 3 and yield altered from early to late stage. The relationship between fiber quality and the ratios of different disease grades showed similar results to that of yield.3. The pedigrees of 52 cultivars and the effect of different germplasm on disease resistance of cultivars to verticillium wilt were analyzed. The results indicated that Deltapine and Stonville descents contributed to most of the varieties, followed by Foster. The cultivars with more Stoneville germplasm expressed high resistance to verticillium wilt. However, the cultivars with King germplasm and a little of Stonville germplasm or with Foster germplasm possessed low resistance to verticillium wilt.4. Verticillium wilt symptoms in main stem and on leaves were analyzed using F2 plants from three crosses between resistant and susceptible varieties (Han208xPima90-53, Zhong8xPima90-53and Jimian20> |
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