Identification of saline tolerant rice hybrids for pokkali tract

Abstract

Various abiotic stresses causing a decline in global rice production are drought, salinity and chillness. Among these, salinity is the major factor that affects crop productivity. The traditional rice varieties grown under Pokkali area show remarkable tolerance to salinity and floods making it unique. However, the yield potential of these varieties is low. In India, out of ninety three rice hybrids developed, a few viz. DRRH 28, KRH 4, PSD 3, etc. were reported to have tolerance to salinity. Considering the potentials of hybrids, identification of salt tolerant hybrids suitable for Pokkali tract of Kerala is an urgent need of the hour. Hence, the study was designed to explore the adaptability of eight rice hybrids to the unique tract of Pokkali and evaluation of traits associated with salinity tolerance. The study comprised of two experiments, the first experiment was Laboratory screening for salinity tolerance and the second experiment was Field evaluation of rice hybrids in Pokkali tract. The laboratory screening was done following a completely randomised design and the genotypes were grown in Yoshida's solution and evaluated for various seedling characters. High shoot length, root length, high root CEC and high root and shoot proline content were seen in Vytilla-6 followed by Ezhome-2. Low root and shoot proline content were observed in IR-29 confirming its susceptibility to salinity. Among the hybrids, a high value for shoot length, root length, total number of roots, root CEC, root proline, shoot proline and survival per cent was observed in the hybrids CORH-3 and KRH-4. Vigour index was high in Sahyadri 4 followed by KRH-4 and low in MRP- 5401. Vytilla-6 and Ezhome-2 showed the high survival per cent while low survival per cent was noticed in Sahyadri 2 and MRP-5401. Vytilla-6 exhibited high chlorophyll content and RWC while low RWC was recorded in MRP-5401, Sahyadri- 2 and Sahyadri-4. Ca in root and shoot along with Na content in shoot were high in IR-29 while Vytilla-6 had low Ca and Na content. High Na in root was seen in Sahyadri 4 followed by Sahyadri 3. High amount of root Cl2 was recorded in Sahyadri-3, Sahyadri-1, Sahyadri-4, IR-29 and Sahyadri-2 while, the lowest amount of root and shoot Cl2 was in Vytilla-6. High amount of shoot Cl2 was seen in Ezhome-2 and IR-29. High amount of root and shoot SO4 content was seen in IR-29, Sahyadri-3, Sahyadri-4, Sahyadri-2 and Sahyadri-1. The lowest root and shoot SO4 content was recorded in Ezhome-2, followed by Vytilla-6. Low visual score of 3 was recorded in Vytilla-6 and Ezhome-2; a score of 5 was recorded for CORH-3, MRP-5401, TNAU RH-4 and KRH-4. Sahyadri-2, Sahyadri-3 and Sahyadri-4 were observed to have scored more than seven. Score 9 was noticed in Sahyadri-1 and IR-29, indicating that these genotypes are more susceptible to salinity. Visual score under salinity was found to be negatively correlated with shoot and root length, number of roots, vigour, proline content and RWC, while it was positively correlated with content of Ca, Na, Cl2, SO4 and K in the plant tissue. Field evaluation of rice hybrids in Pokkali tract was done during Kharif season of 2016-17, following a randomised block design. Days to fifty per cent flowering and maturity showed that all hybrids became early under salinity. Tall plants were observed in Vyttila-6 and Ezhome-2 and short plants in IR-29. High number of productive tillers was observed in CORH-3 and low in Sahyadri-2. Ezhome-2, IR-29 and Vyttila-6 had high number of spikelets per panicle while seed setting percentage and long panicles were observed in Ezhome-2. Spikelet sterility was high in Sahyadri-2 and low Ezhome-2. High 1000 grain weight was observed in Ezhome-2 and low in IR-29. Based on visual scoring Vyttila-6 was classified as highly tolerant and IR-29 as highly susceptible. Correlation studies indicated that grain yield per plant was positively correlated with productive tillers per plant and seed setting per cent, while it was found to be negatively correlated with sterility per cent. Visual scoring was negatively correlated with plant height, uppermost internodal length, days to maturity and seed setting per cent. The hybrid CORH-3 was found to be moderately tolerant based on visual scoring and it produced highest yield per plant indicating that this hybrid is better than saline tolerant traditional varieties.