Bph Resistance Genes Mapping And Candidate Gene Analysis Of Three Rice Varieties

Rice is the largest food crop in China,and brown planthopper(BPH)is one of the most important pests that cause rice crop loss.The most efficient and effective method to manage it was to explore resistance germplasm and to map the resistance genes.Here,three rice varieties ARC5984,570011,and CL48 were detected to be highly resistance to BPH,and the resistance genes were then mapped.Rice variety ARC5984 showed high resistance to BPH and had an average resistance score of 2.7 according to several times of seedling bulk test.One F2 population consisting of 230 families derived from 9311/ARC5984 was used to preliminarily map the resistance gene.Subsequently,it was located in a 6-cM region between RM5635 and RM5742 on chromosome 4,which had the maximum LOD of 59 and explained 72%of phenotypic variation.Next,based on the resistance score and genotype of the screened recombinants from BC1F2 and BC2F2,it was precisely mapped between markers BF3 and BF9 during which there was 46 kb in the genome of Nipponbare.Then,four candidate genes in the final region were analyzed with qRT-PCR,and found that Os04g35190 and Os04g35210 were significantly different between resistant and susceptible lines.Furthermore,sequencing results showed that the CDS of Os04g35210 from ARC5984 was the same as that of the cloned gene Bph6,but it was different for Os04G35190 between ARC5984 and 9311.In addition,less BPHs were observed on the pre-NILs and the resistance lines significantly restricted the BPH growth and development according to the host selection experiment,population growth rate(PGR),and survival rate tests.Finally,markers RM5635 and BF9 were successfully applied to the marker assisted selection(MAS),which should be beneficial for the BPH-resistance rice breeding.Rice variety 570011 was indicated to be highly resistance to BPH and had an average resistance score of 2.9.A total of 120 F2:3 lines derived from 9311/570011 and were applied to map the resistance gene.As a result,it was located one region harbored by 4m19.12 and 4m24.64 on chromosome 4.The candidate region was very close to Bph6 according to the markers information and reference genome of Nipponbare.Therefore,the candidate gene associated with Bph6 was sequenced and found that there were several SNP differences between the CDS.We speculated that the BPH resistance gene from 570011 was allelic to Bph6.As for rice variety CL48,it was also highly resistance to BPH and had a low resistance score(2.8).It was respectively crossed with KW and TP309 to obtain two F2 populations which were used to map the resistance gene.As a result,with analysis of the F2 population derived from KW/CL48,one major QTL was detected to be located between markers 11m16.89 and 11ml8.41 on chromosome 11,with the maximum LOD value of 22.5 and explained phenotype value of 78.4%.Based on the phenotypes of BPH body weight gain and honeydew secretion weight of F2 population derived from CL48/TP309,one major QTL was located between markers 11ml4.345 and 11m17.55,which was basically consistent with the location determined by using the population of KW/CL48.