In Vitro Selection Of Mutants To Wilt Disease Resistant And Studies On Their Resistance Mechanisms In Strawberry

A co-cultivation technique system was developed for in vitro selection of mutants, in which crude toxins extracted from Fusarium oxysporum Schl. f.sp. fragariae were used as selection factor. The physiological and biochemical property of regenerated mutants and their parents were determined.1. The proper regeneration system of strawberry by leaf explants was established. The effects of carbon pressure, hormones and AgNO3 on callus regeneration from leaves of strawberry were investigated. The opyimal condition of callus regeneration is MS+maltose 20g/L+TDZ 3mg/L+ AgNO31 mg/L. The quality of callus induced by BA is worse than that induced by TDZ.2. The toxins had toxic sffects on plants and buds of strawberry. The toxins can cause the similar symptom with that caused by Fusarium oxysporum f. sp . The death rate of buds increased as the concentration of toxins increased gradually. Inhibitory toxicity dose of 15%(v%) caused 50% of sengena buds wilted, and 10%(v%) caused 50% of others buds wilted.3. The resistance of mutants resistant to Fusarium. oxysporum f.sp fragaria toxin could be improved as the concentration of toxins increased gradually and cultivate times. The survival rate of buds was improved during the cultivation. The differentiation of buds of mutant cultivated by toxin was not as well as CK, but it was better than wild type. The treatment of toxin reduced the index of wild type strawberry, sucn as height of plant, length of root and dry weight, and the index of mutant was highter than that of wild type. The result of resistance identification indicated that the resistant levels of strawberry mutant resistant to the disease were increased compared with their parents.4. Two variants were further analyzed by RAPDs, RAPD primers generated different profiles compared to their control plants.5. The plants of mutant and wild type were treated with Fusarium oxysporum Schl. f.sp. fragariae. The dynamic activities of protective enzymes in root of regenerated mutants and their parents inoculated by Fusarium oxysporum Schl. f.sp. fragariae were determined. The result indicated that the dynamic activities of protective enzymes in root of regenerated mutants enhanced. The variance of SOD, CAT and POD have the similar tendedcy. Thay increased at the beginning, and then delined after the regenerated and their parents were treated with the fungus. The activities of SOD, CAT and POD in root of regenerated mutants was highter than that of wild type. The protective enzymes in root of regenerated mutant and wild type did not change without treated with Fusarium oxysporum Schl. f.sp. fragariae. The MDA of regenerated mutants and wild type increased after treated with pathogrn and the growth of mutant was highter than that of wild type. The root activity of plants treated with pathogrn wes declined as the time flies, and that of mutant was highter than that of wild type. The change of root electrolyte leakage was opposite to root activity. It dereased after treated with pathogrn. The protective enzymes in root of regenerated mutant and wild type did not change without treated with Fusarium oxysporum Schl. f.sp.