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The study entitled ‘Physiological characterization of thermo-sensitive genic male sterility in rice (Oryza sativa L.)’ was carried out at College of Agriculture, Vellayani during 2014-16. The main objective of the study was to develop thermo-sensitive genic male sterile line in red rice background and its physiological and phenological characterization. The TGMS line from International Rice Research Institute (IRRI), EC720903 and red rice varieties, Uma and Jyothi were used in this experiment. TGMS plants become male sterile at high temperature and male fertile at low temperature. Seed multiplication was done at Regional Agricultural Research Station (RARS), Ambalavayal where the temperature is low. The work was done in three experiments.
Experiment I. Development and evaluation of male sterile F2 plants. The TGMS line as well as Uma and Jyothi were grown in pots for hybridization. First flowering, 50% flowering, crossing and maturity dates were noted and F1 seeds were obtained. F2 seeds were collected pollen and spikelet sterility were recorded. The TGMS line was found to be a suitable female parent as it exhibited synchronous flowering and had 100% sterility with pollen free anthers at Vellayani conditions.
Experiment II. Physiological and phenological characterization of thermo-sensitive male sterile line. F2 seeds developed were used for this experiment. Seeds were sown at monthly interval and the critical sterility point was identified. Pollen sterility and spikelet sterility of F2 plants were monitored. Those plants which were sterile at Vellayani were taken to Ambalavayal for confirming the TGMS character in ratoon crop. The TGMS seeds were multiplied at RARS Ambalavayal where the season suitable for seed multiplication was noted. From these plants more than 200 red seeds were collected. The F2 plants exhibited similar flowering duration as that of the TGMS parents. The sterile plants were showing sterility characters similar to that of the female parent (TGMS) with pollen free anthers and100% spikelet sterility.
From the temperature data of Vellayani, critical sterility point (CSP) was found to be 26.10 C above which the TGMS plants showed complete sterility. The total free amino acid content in F2 plants was higher in sterile plants than in fertile. The weather data from Amblavayal clearly indicates the reliability for seed multiplication at Ambalavayal where the mean temperature is always less than 250 C.
Experiment III. Samples were collected from sterility inducing and fertility inducing conditions, simultaneously and analysed for various biochemical parameters like chlorophyll, total free amino acids, proline, phenolic compounds, Superoxidedismutase (SOD), Malondialdehyde (MDA), ascorbate content, auxin, and total soluble proteins. Chlorophyll was found to be higher in sterile plants than in fertile plants. Total free amino acids, proline, phenolic compounds, SOD, MDA, ascorbate content, auxin, and total soluble proteins were higher in sterile plants.
The study revealed that CSP of the TGMS line under study is 26.10 C. It can be used as a reliable female parent in rice breeding programme. TGMS red rice under Jyothi background was developed. The presence of higher amount of MDA, SOD, ascorbate, phenol etc. in sterile plants clearly indicates a higher level of oxidative stress experienced by TGMS plants under sterility inducing condition which may be leading to the expression of sterility.