PhD

The project entitled “Marker assisted transfer of thermosensitive genic male sterility to high yielding red kernelled varieties of rice (Oryza sativa L.)” was conducted in the Department of Plant Physiology, College of Agriculture, Vellayani during 2011 to 2014. The main objectives were to develop molecular markers associated with TGMS gene and to transfer TGMS character to red rice background. For the present investigation, two TGMS lines were imported from International Rice Research Institute (IRRI) namely, TGMS1 and TGMS2which are from two different TGMS sources ID24 and IR32364 respectively.
The TGMS lines along with two popular red rice varieties of Kerala, Uma and Jyothi were sown on monthly intervals for their initial phenological study. The critical sterility temperature and period of TGMS lines were characterised in the field using tracking method. The activity of antioxidant enzymes plays an important level in causing sterility in rice pollen grains, though the reason behind male sterility is unknown.
Morphological, agronomic and floral traits were studied during the specific crop growth stage and were recorded as per the standard evaluation systems given by IRRI. Phenological, floral and morpho-agronomic characterisation of TGMS lines revealed that the line TGMS1 performed better with short stature, early maturity, more productive tillers, wider glume opening, higher panicle and stigma exertion, more filled grains and longer panicles. Stages of panicle development were determined by various methods viz., physical method, morphological index method and tracking method. The results have shown that TGMS1 is a better candidate for Kerala condition with critical sterility period of 15-22 days before heading and the sterility inducing average temperature of 27.25 o C.
For hybridisation, TGMS1 plants were grown under sterility inducing condition and they were crossed with a popular red rice variety, Uma to produce F1. The F1 s were then selfed to get F2 population. A gene specific primer was designed for the red pericarp colour (Rc) which can be used as a background selection marker. Fifty F2 plants were used for marker analysis. Microsatellite analysis was done to find out the SSR markers polymorphic to the tms gene. DNA was isolated from the 50 F2 plants and performed PCR using 45 SSR markers. Capillary electrophoresis was done for the allele sizing of PCR products. Among 45 SSR markers used, three primers RM 3351, RM23 and RM31 could differentiate Uma, Jyothi andTGMS1, TGMS2. A set of twenty one primers were able to distinguish TGMS1 and Uma. The F2 plants sterile as per the TGMS markers were found to be sterile under sterility inducing condition. Under low temperature their fertility was transformed indicating the presence of tms gene.
Linkage analysis using MAPMAKER version 3.0, seven linkage groups and a few unlinked primers were found. A segregation ratio of 2.57:1 was obtained between fertile and sterile lines. This ratio explains the monogenic nature of tms gene.Among 20 polymorphic markers, six (RM23, RM31, RM3351, RM 212, RM258 and RM244) were found significant. These on further analysis using χ 2-test revealed the possible association between the sterility phenotype and marker.
From the present study, the sterility tms gene got successfully transferred into 14 sterile F2 plants and RM31, RM23, RM3351, RM212, RM244 and RM258 can be used for the evaluation of TGMS1 X Uma hybrids and their F2s.