Development Of Functional Marker Of Pi2 And Applied In Rice Blast Resistance MAS

The three major diseases of rice cause serious reduction in rice production every year,which the mainly disease is blast.Host resistance improvement using marker-assisted selection(MAS)is considered to be the most economic and effective way to overcome rice blast.In this study,an allele mining strategy was used to find variation of the Pi2 gene among different rice varieties,the main results as following:(?)In some varieties,there was an out-of-frame deletion of 3 base-pairs(bp)at the1543-1545 site of the Pi2 gene.Deletion of these 3 bp causes the loss of cysteine-arginine and their replacement with glycine in the protein product.As a consequence,the predicted protein structure was changed,especially in the LRR region which is important to plant blast resistance.Plants with the deletion allele showed poor rice blast resistance compared with those without the deletion variant.Haplotype analysis showed that the deletion of these 3 bp was common only in indica rice,and the rice varieties with 3 bp deletion perform poor rice blast resistance,which indicates that the deletion allele variant of Pi2 occurred recently and was artificially selected.(?)We developed a functional molecular marker Pi2-1,spanning base pairs 1543-1545 of the Pi2 gene.A single band with a length of 62 bps was amplified from the resistant cultivar by the Pi2-1 marker;two bands were amplified from susceptible cultivars,one band was amplified from the LOC-Os06g17920 genome,the fragment length is 62 bps,and the another is the amplification production of the Pi2 genome.Since there were 3 base deletions,the fragment length was only 59 bps.Pi2-1 is a functional molecular marker of rice blast resistance gene Pi2.In the identification of rice blast resistance molecular markers,this functional molecular marker was used for amplification,followed by marker genotype identification.Any amplification of a single band of 62 bps indicated that there is no base deletion and Pi2 gene function is normal,with rice blast resistance phenotype.The amplification of two fragment bands(62bps and 59bps)indicated that the Pi2 gene in this species was missing 3 bases,the gene function was abnormal,and rice blast resistance was poor.Therefore,using Pi2-1,it is possible to quickly and efficiently distinguish between rice varieties with good rice blast resistance and with poor resistance.(?)Using Pi2-1 applied in MAS breeding,effectively improve rice blast resistance of Wenxiang-1,which was susceptible to rice blast.The test results show that,the selection efficiency of Pi2-1 was as high as 90%,and MAS-364? MAS-365? MAS-395 and MAS-403 were selected using the marker Pi2-1,which with excellent agronomic traits and have certain resistances to rice blast.