Dr. P. VENKATA RAMANA RAOV. S. SAMPATH2024-05-012024-05-012024-05-01D6555https://krishikosh.egranth.ac.in/handle/1/5810208530Rice is one of the major crops cultivated in Asia and is staple food in India. Grain shattering causes significant yield loss in MTU 1010, a mega rice variety cultivated in Andhra Pradesh and other states of India. The present investigation was aimed to identify QTLs for low grain shattering in backcross inbred lines (BC2F8 generation) developed from the cross between MTU1010 (high grain shattering variety) and JGL17004 (low grain shattering variety). Phenotyping for low grain shattering and yield traits was carried out in the BILs. The phenotypic data was collected for ten traits viz., score for grain shattering (Sh), plant height (PHt), days to fifty percent flowering (DFF), number of ear bearing tillers per plant (EBT), panicle length (PL), number of filled grains per panicle (FG), number of unfilled grains per panicle (UFG), spikelet fertility (SF), grain yield per plant (GYPP) and test weight (TW). Score for shattering was estimated and categorized as low, medium and high (Low - <5%, Medium- 5 to 10%, and High- >10%). Proper methods were followed to record and compute yield traits. Out of 84 BILs 54 BILs showed low grain shattering, 20 BILs showed moderate shattering and 10 BILs showed high shattering. Recurrent parent recorded high grain shattering than the donor parent. For yield traits BILs recorded higher values than the parents. The BILs 55 and 53 recorded a low shattering of 1.52% and 0.34 % respectively with a high grain yield per plant (35.7 g and 33.8 g respectively). The data recorded from phenotyping was subjected to ANOVA using augmented RBD. The genetic parameters were also computed for the phenotypic data. The results showed that the data was significant among BILs for most of the traits. Some of the traits showed higher values for genetic parameters like GCV and PCV (Sh, FG, UFG, and GYPP). Heritability was high for shattering and yield traits. The parental polymorphism survey was carried out with 626 SSR markers. Out of these, 88 markers were polymorphic (14.05%) between the parents. The population was subjected to genotyping with the eighty eight polymorphic markers. xiv 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.EnglishThesis