| Wheat powdery mildew,caused by Blumeria graminis f.sp.tritici(Bgt),is one of the major diseases in wheat production areas in China,cultivating and planting of disease-resistant varieties is one of the most effective,economic and safe measures for preventing and controlling wheat powdery mildew.Gene postulation based on gene for genehypothesis can analyze a large number of varieties or high-quality germplasms for disease resistance in a relatively short period,and the results can provide a basis for breeding and variety use for disease resistance.In this thesis,the resistance of 36 wheat varieties or lines were tested in the greenhouse,and its genes for powdery mildew resistance were analyzed The results are as follows:The disease resistance spectrum of wheat Variety ’RC17’ was basically the same with the powdery mildew resistance gene Pm4 c,and it was speculated that ’RC17’ carried Pm4 c,just as the same,variety ’Changjiang8866’ was presumed to possibly contain the powdery mildew resistance gene Pm17.The four cultivars of ’Mianzhaimai 1101*’,’cau17’,’cau29’ and ’N382’were only susceptible to some strains with Pm4 b,therefore,it was assumed that they also contained other powdery mildew resistance genes besides Pm4b;Four varieties showed resistancend other three varieties showed susceptibile to all 24 Bgt stains;23 varieties(lines)differed from all 48 known genes tested in disease resistance spectrum,it is speculated that these varieties(lines)may contained other powdery mildew resistance genes other than those tested.Chlorophyll fluorescence imaging is a technique for rapid and noninvasive detection of plant photosynthesis,which has been gradually applied in plant disease stress researches.To investigate the feasibility of applying this technique in wheat powdery mildew monitoring,chlorophyll fluorescence measurements were performed on detached wheat leaf segments,one-leaf wheat seedlings and two-leaf wheat seedlings inoculated indoors with six different concentrations(including non-inoculated control)of spores of B.graminis f.sp.tritici,and the images and data derived from Fv/Fm,NPQ,Chlidx,and RGB parameters were analyzed in this thesis,and the results were as follows:The comparison of the images of four parameters,Fv/Fm,NPQ,Chlidx and RGB,treated with different inoculum concentrations of pathogen spores revealed that the images could more visually reflected the degree of infestation or incidence of powdery mildew in wheat.The changes of Fv/Fm values with inoculum concentration were not obvious at the 3rd day after pathogen inoculation,but at the 5th day after inoculation,the Fv/Fm values showed a decreasing trend with increasing inoculum concentrations;and the results also showed that the chlorophyll fluorescence parameters Fv/Fm values were different from different pathogen spore inoculum concentrations,and the overall Fv/Fm values of wheat seedlings or detached leaf segments in the uninoculated control treatment were different.The overall Fv/Fm values of wheat seedlings or detached leaf segments in the uninoculated control treatment were significantly higher than those of the inoculated treatment,and the Fv/Fm values of the treatment with the highest inoculum concentration(5 μg/ml)were significantly lower than those of other treatments in the same period.Further analyses of the correlation between the severity of wheat powdery mildew disease and chlorophyll fluorescence parameters revealed that there was a highly significant negative correlations between Fv/Fm or Chlidx and the disease severity.Basd on these resuls,the disease severity estimation models of both Fv/Fm and Chlidx were established,and The comparison of the fitting of the models revealed that the RMSE or R2 of the Fv/Fm-based and Chlidx-based disease estimation models for detached wheat leaf segments,one-leafed wheat seedlings and two-leafed wheat seedlings,respectively,were relatively close.Therefore,both chlorophyll fluorescence parameters,i.e.,Fv/Fm or Chlidx,can be used to monitor and estimate the degree of powdery mildew disease occurrence in seedling wheat. |
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