MSc

Measures to improve abiotic stress tolerance in plants is gaining importance due to raised concerns on climate change and food security issues all over the world. Though different methodologies for combating abiotic stress like conventional breeding and molecular breeding have been in existence, they are often limited by time and biosafety concerns respectively. Chemical priming is a cost-effective approach in managing abiotic stress. It is reported that use of chemicals, both synthetic and natural, prior to stress events can enhance tolerance to abiotic stresses such as salinity and drought. Application of chemical agents externally can impart a minor stress which will help to generate stress signals that can lead to certain biological changes resulting in increased stress tolerance in later stages of the crop. Rice is a crop badly affected by salinity. Use of chemicals such as beta amino butyric acid (BABA), sodium nitroprusside and calcium chloride as seed primers to improve salinity tolerance may turn promising. With this objective a study was formulated with three experiments. The experiments were screening rice varieties for salinity tolerance, effect of seed priming on germination of rice varieties under salt stress condition and field trial to assess the effect of priming in rice fields with saline water intrusion. The First experiment was a lab study to screen three rice varieties namely Jyothi, Uma and Vytilla-10 at five salinity levels i.e., non-saline, 3 dS/m, 6 dS/m, 9 dS/m and 12 dS/m. Based on the results it was concluded that at 16 DAS with salinity level of 6 dS/m variety Vytilla-10 was highly tolerant (score 1). Variety Jyothi was found susceptible at 6 dS/m (score 7) whereas variety Uma was moderately tolerant (with score 5). At 21 DAS, varieties Uma and Vytilla-10 were found to be susceptible at salinity levels of 6 and 9 dS/m respectively with a score of 7.
Objective of second experiment was to assess whether chemical priming could improve salinity threshold of the three varieties. The design used was two factorial CRD with three replications. The treatments were four priming chemicals and two salinity levels. Based on the results of the first experiment, threshold salinity level for Jyothi, Uma and Vtyilla-10 were estimated. Jyothi and Uma were susceptible at 6 dS/m, while Vytilla-10 was susceptible at 9 dS/m. Therefore, in second experiment variety Jyothi, salinity levels of 6 dS/m and 9 dS/m, for variety Uma salinity levels of 6 dS/m and 9 dS/m and for Vytilla-10 salinity levels 9 dS/m and 12 dS/m were taken. Each variety was primed using three chemicals, namely beta amino butyric acid (BABA 1 Mm/L), sodium nitroprusside (SNP,100 μM) and calcium chloride (CaCl2, 2%), water priming was included as control. The efficacy of each priming chemical was analyzed based on germination percentage, growth parameters and visual salt injury symptoms. Priming seeds with calcium chloride was found to influence both the growth parameters and salinity tolerance of seedlings. Based on the results of second experiment, a field trial was undertaken to assess the efficacy of priming chemicals as seed primers and as foliar spray. An experiment was laid out at Rice Research Station, Vytilla in factorial RBD with three replications. The treatments were three priming chemicals namely beta amino butyric acid (BABA), sodium nitroprusside (SNP) and calcium chloride (CaCl2), with water priming as control and three foliar sprays at weekly intervals, fortnightly intervals and weekly water spray. Rice variety Vytilla-10 was used for the study. The seedlings were transplanted to main field and foliar spraying of priming chemicals was done at weekly intervals at 30, 37 and 45 DAS, fortnightly intervals at 30, 45 and 60 DAS as well as weekly water spray. Calcium chloride seed priming was found effective in increasing plant height at 60 DAT, leaf area index, number of panicles, percentage of filled grains, thousand grain weight, yield, proline content in leaf and chlorophyll content (at 60 DAT). Most of the growth and yield parameters were influenced by weekly spray of calcium chloride. More tillers/m2 was observed in seedlings primed using SNP and weekly foliar spraying of SNP was effective in increasing tillering. Total chlorophyll content was found to increase with SNP seed priming and foliar spraying of SNP at fortnightly intervals was found most effective at 60
DAT to increase chlorophyll content. Grain filling was found to increase with BABA seed
priming and weekly foliar spray of the same chemical was highly effective.
Priming rice seeds with 2 % calcium chloride and foliar spraying of calcium
chloride at 2 % on a weekly basis was found to be a reliable method to combat salinity
stress and for improving growth, yield and yield attributes of rice.