IDENTIFICATION OF LOW GRAIN SHATTERING QTLS IN RICE USING BACKCROSS INBRED LINES OF MTU1010

Abstract

Rice is an important food crop in Asia and is predominant in India. Rice crop is affected by biotic or abiotic stresses which culminate in yield loss. Grain shattering is physiological problem among the several stresses in rice. Some rice varieties which are improved through breeding still have problems like grain shattering. The mega variety MTU 1010 has several desirable traits but having high grain shattering has been a major drawback. Therefore identification of QTLs for low grain shattering is important for improving MTU 1010 with marker assisted breeding programmes. Eighty four backcross inbred lines in BC2F8 generation were developed from the cross MTU1010/JGL17004. The parental polymorphism survey was carried out with 626 SSR markers. Out of these, 88 markers were polymorphic between the parents. The population was subjected to genotyping with the eighty eight polymorphic markers. The genotyping data was used in QTL ICImapping Version 4.2 to generate a linkage map which covered 2381cM. The IM and ICIM analysis detected 29 and 22 QTLs respectively at a LOD threshold of 2.0. The epistatic analysis detected 453 epistatic QTLs. Four novel QTLs viz., qSh-2-1, qSh-2-2, qSh-3-1 and qSh-10-1 for shattering were detected in both ICIM and IM. These four QTLs were also co-localized with 24 epistatic QTLs. Among the four QTLs identified in the present study, qSh-3-1 on chromosome 3 is far away from the QTLs reported earlier while, the QTL qSh-2-2 might be nearer to the gene (OsGRF4) for moderate grain shattering identified in earlier studies. But till date, none of the QTLs were identified for low grain shattering on chromosome 10. The current study also identified some major QTLs viz., qPHt-3-1 , qDFF-6-1, qPL-8-1, qUFG-2-1, qSF-2-1 and qTW-6-1 with high phenotypic variance. The BILs with low grain shattering can be utilized for further confirmation studies and the regions with QTLs for low grain shattering can be analyzed more precisely. So that they can be introgressed into the varieties with high grain shattering.