Mapping Of Bacterial Leaf Streak Resistance Gene And Physiological And Biochemical Characteristics Of Response To Pathogenic Bacteria Infection In Rice

Rice is an important food crop,while disease is the main influencing factor that leads to a decline in rice yield and quality.Rice bacterial leaf streak(BLS),a rice disease caused by Xanthomonas oryzae pv.oryzicola(XooC),has become an important disease worldwide.The incidence of BLS is increasing year by year,and in severe cases,BLS can cause a 40-60%reduction in rice production.The most economical and effective way to control BLS is the cultivation and promotion of resistant varieties.The discovery of resistance genes is the key to breeding resistant varieties.However,only a few BLS resistance genes have been mappped at present,and the resistance genes that can be really applied to breeding practice are very limited.Moreover,BLS resistance mechanism is still unknown There are rare reports on changes in rice physiological and biochemical indexes such as endogenous hormones contents and enzyme activities after XooC infection.Therefore,further exploring BLS resistance gene and analyzing the physiological and biochemical characteristics of rice in response to XooC infection are of great significance for elucidating BLS resistance mechanism and cultivating BLS resistance varieties.In this study,a rice line HD 10 with high and stable resistance was used as the disease-resistant parent,and the sequenced variety 9311 was used as the susceptible parent.Through crossing and selfing,the F2 population was constructed for preliminary mapping BLS resistance gene.At the same time,the established rice BLS resistant and susceptible near isogenic lines were used as materials to analyze the physiological and biochemical characteristics of response to XooC infection in rice:the treatment groups were inoculated with XooC by pricking,while the control groups were inoculated with sterilized water.At 0h,24h,48h and 96h after inoculation,the rice leaves at the tillering stage were taken as samples to analyze the changes of salicylic acid(SA),jasmonic acid(JA),ethylene(ETH),gibberellin(GA),and zeatin(ZT)contents,and peroxidation Hydrogenase(CAT),malondialdehyde(MDA),phenylalanine ammonia lyase(PAL),peroxidase(POD),polyphenol oxidase(PPO),superoxide dismutase(SOD)activities.The results were as follows:1.By identifying BLS resistance of each individual plant in F2 population,the resistance of DH10 was controlled by quantitative trait loci(QTL).In order to screen the main effect QTL,the bulked segregated analysis method(BSA)was used,two SSR markers from 244 polymorphic markers between parents were found to have a linkage relationship with the resistant QTL,which were B03021 And B03045.These two markers are on chromosome 2 and located adjacent to each other.Then more polymorphic markers near these two markers were developed.Combining with the F2 population resistance phenotype and marker genotype,A main effect QTL was determined in this region,which located within 4cM distance between markers B03021 and B03029.This QTL cod explain 17.6%of phenotypic variation2.In both rice resistant and susceptible near isogenic lines,SA,ETH and ZT contents were no significant difference between the treatment and control groups,indicating that the changes in SA,ETH and ZT contents were not caused by XooC infection;After inoculation,JA content in the treatment group was significantly higher than that in the control;In the resistant near isogenic line,GA content in the treatment group decreased compared with the control;however in the susceptible near isogenic line,GA content in the treatment group increased compared with the control.It indicated that JA and GA might be related to the BLS resistanc.3.After XooC infection,the activities of CAT,PAL,POD,PPO and SOD in the resistant and susceptible near isogenic lines were increased,and the activities of these five enzymes in the resistant near isogenic lines were higher than those in the susceptible near isogenic lines,which indicated that the enhanced activity of these five enzymes might be helpful for improving BLS resistance.XooC infection led to MDA content decline in the resistant and susceptible near isogenic lines,and the MDA content in the resistant near isogenic lines was generally lower than that in the susceptible near isogenic lines,indicating that the accumulation of MDA content was negatively correlated with BLS resistance.