Identification Of Resistance To Scab By Fusarium Crude Toxin And Induction And Screen Of Scab-resistant Mutants In Wheat

Fusarium head blight(FHB) of wheat also known as wheat head scab causes severe production losses worldwide,especially in warm and humid environment.It also affects grain quality and induces toxicological problems in humans and animals.The incidences of FHB have increased in recent years,due to climate warming and changes in farming systems.The cultivation of genetically resistant cultivars is the most cost-effective method to control the disease,and the accurate,rapid identification and creation of new sources of scab-resistant varieties are of great significance to improve the breeding efficiency.These experiments were done:identifing wheat scab-resistance methods by fusaurium crude toxin were studied with wheat cultivars of various scab resistance;Anti-scab mutants were screened by inoculating Fusarium graminearum in the field after dry wheat seeds treated by ⁶⁰Co-γ-rays and Ar⁺ ion beam had been sowed,and differences between mutants and original species were detected with SSR markers;the study of inducing and screening anti-scab mutants by cell engineering on fusarium toxin media was made with immature embryos from the cultivars treated by ⁶⁰Co-γ-rays.The results are showed as follows:1.Four methods of toxin treatment were compared.The results showed that the method treating the seeds of cultivars which had the same radicle emergence could be used in the identification of resistance to scab in wheat cultivars because it excluded the effect of difference in seed vigor.The inhibition rates in root weight,root length,seedling weight and seedling length were closely related to scab-resistance of wheat cultivars,the cultivars with higher scab-resistance were inhibited little.2.The same length etiolated coleoptiles were treated by 0.5%and 2%crude toxin. The results showed that the inhibition rate of etiolated coleoptiles could be used in the identification of resistance to scab in wheat cultivars because it excluded the effect of difference in seed vigor.The inhibition rates of cultivars with different scab-resistance are significant different,the results of identification were consistent with those in the field,the cultivars with higher scab-resistance were inhibited more slightly.3.Toxin treatment changed the permeability of the root cells,SOD and POD activity and the content of MDA in seedling,isoenzyme electrophoresises of SOD,POD and CAT confirmed the toxin treatment changed the types and expression of isozymes.There were significant differences in the permeability of the root cells among different cultivars treated by 35%crude toxin,obviously,the cultivars with strong resistance were of small cell permeability.The incremental ratios of SOD activities were positive correlated with scab-resistance of cultivars,and the incremental ratios of POD activities and the contents of MDA was negatively correlated with scab-resistance of cultivars.These physiological and biochemical indicators are closely related to scab-resistance of cultivars,can be used in scab-resistant identification.4.Two anti-scab mutants from Wanmai19 and Fenghua8903 were found by screening M₂ and M₃ populations inoculated Fusarium graminearum in the field after dry wheat seeds treated by ⁶⁰Co-γ-rays and Ar⁺ ion beam and sowed.There were no significant differences between the mutant from Wanmai19 and its original cultivar in the characters of agronomy and quality,but effective spike rate and grain hardness were significantly different between the mutant from Fenghua8903 and its original cultivar.5.Differences between mutants and their original cultivars were detected with SSR markers.The results showed that the mutation of the mutant from Wanmai19 occurred in Xgwm261,Xgwm493,Xwmc41 and Xgwm212,the four gene mutation sites located at 2D, 3B,5A and 5D;the mutation of the mutant from Fenghua8903 in Xgwm493,Xbarc164, Xgwm161,Xgwm312,Xgwm156 and Xgwm427,located at 3B,2A,5A and 6A.6.In the study of inducing and screening anti-scab mutants by cell engineering on fusarium toxin media with immature embryos from the cultivars treated by 60 Co-γ-rays, 17 anti-toxin individual plants have been gotten.After inoculated Fusarium graminearum in the field,7 in17 were found significantly better in scab-resistance than their original cultivars,and further identification should be done by inoculation and SSR markers in the future generations.