Evaluation Of Drought Resistance Of White Clover And Correlation Analysis Of SSR Molecular Markers

Drought has always been considered as one of the most important factors which restricted the global agriculture.The cultivation of drought-resistant plant varieties is an effective way to deal with drought.Molecular marker association analysis is an effective method to understand the relationship between phenotypic variation and genetic polymorphism,it has become an important tool in molecular breeding.Photosynthesis is one of the most sensitive indexes for plants to respond to drought stress.Therefore,it is an effective way to explore and select drought resistant materials by studying the photosynthetic characteristics under drought stress and its correlation analysis with molecular markers.Here,the photosynthetic response characteristics and drought resistance ability of 77 white clover materials from different sources were evaluated by analyzing and comparing the main photosynthetic indexes under simulated drought stress.Additionally,the correlation analysis was carried out between the results of SSR molecular markers and photosynthetic indexes of drought,and the molecular markers related to drought resistance were also screened.The main conclusions of the study are as follows:1.The net photosynthetic rate(PN),stomatal conductance(GS),intercellular CO2concentration(CI)and transpiration rate(Tr)of white clover were significantly decreased under drought stress(P<0.01).In the four photosynthetic indexes,Gs decreased the most,and the stress treatment group decreased by 66.3% compared with the control group.The changes of Ci were the least,and the stress treatment was 31.7%lower than the control group.There were significant differences in Pn,Gs,Ci and Tr among the all tested materials after drought stress.Taking PN as an example,the decrease range of 77 materials was 4.3% to 89.4%.2.The comprehensive evaluation of drought resistance based on 4 photosynthetic indexes showed that 77 materials had significant difference in drought resistance.The materials of HZMCY932,HYZMC623 and HZMC1235 had high comprehensive drought resistance coefficient and strong drought resistance,but Bai 01044,Bai 01176 and Bai 01232 were extremely sensitive to drought stress and the drought tolerance were poorly.The 77 materials were divided into five categories: drought sensitive type,drought sensitive type,middle resistant type,drought resistant type and extremely drought resistant type.3.By using structure 2.3.4 software,the materials were divided into three subclasses.Through GLM and MLM models,52 molecular markers were detected to associated with drought-resistance photosynthetic index,and 86 markers were significantly correlated(P?0.05).The number of SSR loci simultaneously detected by the two models was 47,and totally 4 significant correlations(P?0.05).Among them,21 SSR markers were significantly correlated with 2 or more relative photosynthetic indices.For example,gtrs370,gtrs613 and gtrs931 were associated with four photosynthetic indexes at the same time.