Nature Identification And Mapping Of Blast Resistance Gene During The Whole Duration In Rice

Rice is one of the most important crops in the world which is infected by all kinds of diseases in the whole growth duration.Rice blast is one of the most prevailing diseases worldwide.Practically,breeding for resistance cultivar have been proved to be one of the most effective and economical methods to control the rice blast.Two populations of recombinant inbred lines were employed to identify for their blast resistance and map the resistance genes by bulked segregate analysis(BSA).This study was carried out at three different developmental stages of rice,using natural infection over 2 years.The result was as follows.1.One RILs was derived from a cross between a resistant cultivar 194-3 and a susceptible cultivar Zhenshan 97B.The population showed a bimodal distribution for leaf blast at tillering stage,leaf blast at heading stage and neck blast at reaping stage on 2006 an 2007,suggesting the involvement of a major R gene R6 which was located in the region between two markers AP22 and RM19766 and near C5312 on chromosome 6.The major resistance gene was from the resistant cultivar 194-3.This gene was showed to resist against leaf blast and neck blast throughout the whole growing stages of rice under natural environment.2.The other RILs was derived from a cross between a resistant cultivar Erbaiyin-1 and Zhenshan 97B.The population showed a bimodal distribution for leaf blast at tillering stage,suggesting the involvement of a major R gene.This R gene was mapped on chromosome 6,nearly the marker AP22.The population showed normal distributions for leaf blast at heading stage.This result suggested that it was controlled by minor genes.The population showed deflective segregations for neck blast at reaping stage.3.The blast resistance gene R6 was introgressed into maintain lines and stelity lines by backcross breeding and marker-assisted selection.By now,we have got BC₂F₁ or BC₁F₁.Our results will be useful for the durable resistant breeding program by marker-assisted selection and gene cloning of the R6.