Analysis And Mapping Of Blast Resistance QTLs In Japonica Landrace Yangmaogu From Yunnan Province

Rice blast,caused by Magnaporthe oryzae?Hebert?Barr,is one of the main diseases in rice and exists in all rice-growing countries and regions.Development and utilization of resistant cultivars using traditional and modern breeding techniques is the most economic,environment-friendly and effective measure to control rice blast.However,due to the pathogenic variability of blast isolates,resistant cultivars often lose the resistance after release for 3⁵ years.Therefore,exploitation and identification of new resistant resources or broad-spectrum resistance genes is of great significance for breeding new resistance cultivars.The japonica landrace Yangmaogu?YMG?originated from Yunnan displays a broad-spectrum resistance to blast isolates,and the other landrace LTH is universally susceptible to blast isolates.In this study,a genetic linage map of the recombinant inbred lines?RIL?population(F_2:12)derived from the cross of YMG×LTH was constructed using 130 polymorphic simple sequence repeat?SSR?and intsertion and deletions?InDel?markers.The full length of the linage map is 1911.5 cM with an average interval of 14.7 c M.The RILs together with their two parents were inoculated with three different blast isolates,respectively by spraying inoculation method,and three resistant QTLs associated to lesion degrades were identified by using IciMapping software.The QTL qtl1-1 identified by isolate 99-26-2was located at 11 cM between markers i1-30.6 and i1-33.8 on the long arm of chromosome 1.The LOD value and additive effect of qtl1-1 was 4 and 0.47,respectively.It could explain 8.1%of phenotype variations.The QTLs qtl4-1 and qtl4-2 were both detected in the same region of chromosome 4 which is at 11 cM between markers rj4-2 and S4-2-1.For qtl4-1,the LOD value,additive effect and percentage of phenotypic variance explained were 18.6,0.94 and 32.2%.For qtl4-2,those values were 15.7,1.04and 27.0%.The QTL qtl1-1 identified by isolate 99-26-2 was located at 11 cM between markers i1-30.6and i1-33.8 on the long arm of chromosome 1.The qtl4-1 and qtl4-2 were newly found and adjacent in the same region.This result provided cues for identification of new resistant genes in YMG and improvement of cultivar using this resistant germplam.