Screening Of Vertivcillium Wilt Resistant On Gossypium Hirsutum Races And The Pilot Study Of Resistance Mechanism

Gossypium hirsutum L.race as known as semiwild cotton originated in the Americas, Mexico. It is a wild material that not cultivation domesticated. Gossypium hirsutum L. race which has good disease-resistance and stress resistance is an important genetic resources for cotton breeding. Verticillium wilt is a world cotton major diseases, which seriously hindered the development of cotton production. So far, the materials of cotton Verticillium wilt resistance are very lack. Therefore, we have to find new germ plasm resources about resistance to Verticillum wilt. It is the necessary way for breeding of Verticillium wilt resistant cultivars. In present study, we screened the materials which existed resistance or tolerance to Verticillium wilt from 220 accessions of all seven races of Gossypium hirsutum. We chose 8 accessions, from which 4 existed resistance and 4 susceptible, respectively, to analysis the resistance mechanism of Verticillium wilt. The main results were as follows:1. We screened out 18 materials which existed resistance and included 1 higher resistance . 30 maretials were screened out as tolerance. There are 16 G.hirsutum races latifolium, 1 G.hirsutum races yucatanese and 1 G.hirsutum races punctatum in resistance. Tolerance materials include 28 G.hirsutum races latifolium,1 G.hirsutum races punctatum and 1 G.hirsutum races marie-galante. We chose 8 resistance materials to make disease nursery appraisal and found that 5 materials were consistent with the greenhouse appraisal result, but 3 materials were changed to tolerance.2. We studied the Verticillium dahliae expand speed in the stem of Gossypium hirsutum L.race using acupuncture inoculation and found that the Verticillium dahliae expand speed was lower in resistant materials than in susceptible materials. The result supported the organizational structure resistance theory , and also proved the resistance to spread in disease-resistant materials.3. Determination the affinity in the roots of coton materials and Verticillium dahliae spores, we found that the affinity between disease-resistant materials'roots and Verticillium dahliae was low ,but susceptible ones reversed. The results showed that the resistance to infection in disease-resistant materials.4. The studies about saccharide in root exudates showed that the kinds of saccharide in root exudates were same in resistant accessions and susceptible ones ,but the saccharide contents in root exudates from resistant accessions were obviously less than those from susceptible accessions. It could be considered that the saccharide contents in root exudates were related to diseasse resistance, more saccharide contents, higer diseasse resistance.5. The studies about amino acid in root exudates showed that the amino acid contents in root exudates from resistant accessions were obviously less than those from susceptible accessions. The kinds of amino acid in root exudates from resistant accessions were clearly less than those from susceptible ones and, very interestingly, arginine existed peculiarly in resistant semiwild cotton. Generally speaking, more amino acid contents and kinds, higer diseasse resistance.6. We studied the hypha growth and spore germination under the influence of root exudates. Results showed the root exudates from resistant accessions restrained the hypha growth and spore germination but the exudates from susceptible ones reversed.7. We compared Gossypium hirsutum L.race with upland cotton and found that the resistance mechanism of Verticillium wilt was same. We concluded that the resistance mechanism of Verticillium wilt was not related to the kinds of cotton materials, but was related to the diseasse resistance.