Screening Cultivars Of Resistant To Rust And The Resistant Mechanism To Rust Of Adzuki Bean

Adzuki bean rust,caused by the Uromyces vignae,is one of the most serious diseases on adzuki bean production.Selection and rational use resistant varieties was the safest and most efficient way in controlling adzuki bean rust.However,information about the adzuki bean accessions resistance against rust was limited.Moreover,main cultivars used currently were not resistant to rust resulting in no available resistant varieties for adzuki bean production.In present study,the resistance of 85 accessions were evaluated by artificial inoculation with Uromyces vignae urediospore suspensions.Subsequently,in order to understanding the resistance mechanism,the infection process of Uromyces vignae on different resistant cultivars were observed and the activity of catalase,superoxide dismutase,peroxidase,polyphenol oxidase and resistance related genes expression were also conducted.The main results are as follows:1.Resistance of 85 adzuki bean germplasm resources against rust were evaluated by artificial inoculation method.A total of 2 immune cultivars,16 high resistance cultivars,10 medial resistant cultivars,26 medial susceptible cultivars and 31 high susceptible cultivars.Compared with susceptible cultivars,the main performances of the rust resistance were 2-3 days delayed in symptomatic and sporulation and generate low density of uredia.2.Differences of the infection process on resistant and susceptible varieties were investigated using fluorescence microscopy.On the susceptible cultivar,the urediospore can germinate and form appressorium at 6 h after inoculation(hai),then the substomata vesicle and haustorial mother cells were observed at 24 hai.Subsequently,intracellular haustoria were formed at 48 hai,8 days after inoculation(dai)the uredia formed on the leaf surface could be observed.Comparing with the susceptible cultivar,formation of the appressorium was significantly delayed and the ratio of germination and penetration were decreased.In the resistant cultivar,the cell wall adjacent to the fungal hyphae were deposited to prevent fungal hyphae spread accompany with time delayed of the uredia generation.The results indicated that the resistant cultivar mainly depends upon uredospore germination,penetration and spreading inhibition.3.The relationship between the changes of defensive enzyme activity and the disease resistance was studied by using physiological and biochemical techniques.The results showed that thedisease resistance and susceptible varieties interacted with adzuki bean rust,the activity of CAT,POD,SOD and PPO in leaves increased in different degrees.In the resistant and susceptible cultivars,CAT and POD activity reached the first peak at 48 h after inoculation,respectively.In resistant cultivar,12 h after inoculation,SOD activity in leaves was 25.9% lower than susceptible cultivars,However,48 h after inoculation,the SOD activity of the resistant cultivars was higher than that of susceptible varieties;The activity of PPO in the resistant and susceptible cultivars began to increase at 12 h after inoculation,and the PPO activity in the leaves of the resistant cultivars was always higher than that of susceptible varieties.The results showed that CAT,POD,SOD and PPO activities were positively correlated with disease resistance.4.The expression of chitinase(CHI)gene and ?-1,3-glucanase(GLU)gene in different resistant cultivar was studied by qRT-PCR.The results showed that the resistant cultivar were inoculated with rust 24 h after inoculation,CHI gene was up-regulated,and reached the maximum at 48 h after inoculation,at this time the relative expression of 24.5 times the control treatment.In susceptible varieties,The expression level of CHI gene was up-regulated at 12 h after inoculation,after the expression began to decline,and no significant change compared with the control;The relative expression of GLU gene in the resistant cultivar did not change significantly within 0-48 h after inoculation,120 h after inoculation significantly increased,and at this time the expression reached a peak,up 7.1 times.The relative expression of GLU gene in susceptible cultivar was similar to that of resistant cultivar,however,the expression level of GLU gene in susceptible cultivar was lower than that in resistant cultivar.These results show that CHI gene and GLU gene are closely related to the cultivar of rust resistance.