Expression Profiling of Rice for Salt-responsive Genes Using qRT-PCR and Its Morphological, Physiological and Biochemical Evaluation
S. D. Gunjal *
Plant Biotechnology Centre, College of Agriculture, Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli, Maharashtra, India.
S. V. Sawardekar
Plant Biotechnology Centre, College of Agriculture, Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli, Maharashtra, India.
S. S. Sawant
Plant Biotechnology Centre, College of Agriculture, Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli, Maharashtra, India.
T. J. Bedse
Department of Soil Science and Agricultural Chemistry, College of Agriculture Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli, Maharashtra, India.
V. G. Kelkar
Plant Biotechnology Centre, College of Agriculture, Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli, Maharashtra, India.
V. Shrikaran
Plant Biotechnology Centre, College of Agriculture, Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli, Maharashtra, India.
P. L. Shriname
Plant Biotechnology Centre, College of Agriculture, Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli, Maharashtra, India.
S. M. Suryawanshi
Plant Biotechnology Centre, College of Agriculture, Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli, Maharashtra, India.
*Author to whom correspondence should be addressed.
Abstract
Soil salinity is a major constraint on rice productivity in coastal tracts such as the Konkan region of Maharashtra, India, where locally grown varieties remain poorly characterised in terms of their molecular and physiological responses to salt stress. This study examined the expression of two candidate negative regulators of salt tolerance, OsSIDP301 and OsbHLH024, together with the morphological, physiological and biochemical responses of four rice genotypes: the salt-tolerant landrace Pokkali, the salt-sensitive check Karjat-184 and two regionally important test varieties, Karjat-4 and Ratnagiri-8, under four levels of induced salinity (0, 4, 6 and 8 deciSiemens per metre). Seedlings were raised hydroponically in Yoshida nutrient solution, and gene expression was quantified by quantitative real-time polymerase chain reaction using the comparative threshold-cycle method, alongside evaluation of germination percentage, seedling water status, chlorophyll content, proline content, glycine betaine content and peroxidase activity. Both candidate genes were progressively suppressed in Pokkali and progressively induced in Karjat-184 with increasing salinity, whereas the two test varieties showed intermediate, genotype-specific patterns that broadly paralleled their physiological performance. Pokkali consistently retained the highest germination, water content, chlorophyll content and osmolyte accumulation and showed the strongest antioxidant enzyme induction, whereas Karjat-184 showed the weakest response across nearly every parameter measured. Ratnagiri-8 and Karjat-4 differed mainly in the physiological traits on which each relied more heavily under stress. These findings validate the negative regulatory roles of both candidate genes in an indica genetic background and identify them as promising molecular markers for advancing salinity-tolerance breeding in regionally important rice varieties of the Konkan coast.
Keywords: Rice, salinity stress, salt tolerance, qRT-PCR, gene expression, OsSIDP301, OsbHLH024, Pokkali, physiological response, osmolyte accumulation, peroxidase activity