ESWARA REDDY, N.P.ARPITHA SHANKAR, BANDI2018-08-142018-08-142017http://krishikosh.egranth.ac.in/handle/1/5810064272D5523Due to global warming and quickening industrialization environment is changing day by day and heat stress has become a major challenge for sustained production of rice. Rice is highly sensitive to heat stress during all growth stages, which will reduce the yield and create great losses. Production levels are decreasing gradually due to high temperature conditions. Hence, the present investigation was carried out to identify rice genotypes which can withstand high temperature conditions by employing Selective Line Genotyping approach. A set of 74 genotypes were tested for heat tolerance under laboratory conditions employing Temperature Induction Response (TIR) technique with three temperature conditions viz. Control at room temperature, Sub-lethal gradual exposure to 38˚C -55˚C range and Lethal at 55˚C. Based on survival percentage (SP), relative root length, and relative shoot length measured under sub-lethal conditions over control, 14 genotypes were selected each under tolerant and sensitive classes. The genotypes under tolerant class fell between 80-100% survivability. Of 14 tolerant genotypes, two genotypes viz. FR13A and Swarna Sub1A showed 100% survivability and were highly out performed to check genotypes in relative root length (62.53% and 47.56%, respectively) and shoot length (106.20% and 40.74%, respectively), in comparison to known tolerant genotypes. Next to survival percentage, root length plays an important role for selecting genotypes. In our study Maximum root length fell in the range of 4.8 cm - 10.74 cm and maximum RRL was observed for BPT1235 (82.54%). Also when it comes to shoot length, highest shoot length was recorded in BPT1235 which is about 11.75cm. Based on the survival percentage (SP), RRL and RSL of genotypes, a total of 14 genotypes under each class viz. heat tolerant and heat sensitive classes were selected and used for molecular studies employing selective line genotyping approach (SLG). Under selective line genotyping approach, the selected tolerant and sensitive sets were genotyped with 51 SSR and genic markers. Out of all the 51 markers which were genotyped, the markers RM17270, RM16216, RM5687 and TTC/TTM gave polymorphic alleles, whereas 92% the markers couldn’t distinguish tolerant set from sensitive and as well among reported tolerant genotypes (N22, Dular and Nipponbare). In our study, the alleles generated by different polymorphic markers were not clearly distinguished the tolerant set from sensitive set of genotypes. Among the reported genotypes also the allele sizes were varied except for the marker TTC/TTM, as they are from different sub groups of rice. N22 and Dular comes under Aus group, whereas Nipponbare comes under japonica group. From the experiment, we have concluded that both heat stress tolerant genotypes FR13A and SwarnaSub1A can be used as donor sources for heat tolerance because these genotypes proved themselves to be good performers under sublethal conditions, also their amplification pattern with well reported loci RM17270 is similar to checks Dular and Nipponbare. Although, the other three markers are not much informative in the current study, to distinguish the tolerant group from sensitive group, they are reported to be linked to heat tolerance by different research groups. Thus, our study has unveiled valuable markers (regions) and genotypes in developing alternative donor sources in indica rice, rather original aus and japonica group, where they originally identified, to use them in heat tolerance breeding programmes for better yields. Put together the involvement of small set of phenotyping panel and use of extremely core set of genotyping panel for SLG that generated most relevant association of potent markers along with identified donors comparable to QTL mapping results. Further, the diverse allele pattern exhibited by genotypes alike large association panel, additional knowhow of the degree of association of a locus makes the SLG technique to be challenged as greatly powerful.en-USnullThesis