SALT TOLERANCE STUDIES IN AMPHIDIPLOID SPECIES OF GENUS BRASSICA.

Abstract

Saline soils and brackish water are major deterrents to crop production, especially in arid and semi arid areas. A better knowledge of the performance of plants under such conditions may be helpful in identifying suitable species/ genotypes for improved yields. This research aimed at studying the response of some Brassica species at various growth stags (germination, early seedling and maturity) when exposed to different salinity levels. Ten locally adopted genotypes of amphidiploids species of Brassica (five each of Brassica napus and Brassica juncea) obtained from NIA & ARI Tandojam and NIFA Peshawar were used. The studies on germination were conducted in petri dishes which were placed in temperature controlled germinator with four salinity treatments (control, 10, 15 and 20dSm-1 NaCl). The genotypic response at early seedling stage was studied at 1.56, 6.0, 9.0 dSm-1 NaCl in beds filled with fine gravels in net house. These plants were also grown to maturity in a field where salinity ranged from 8.75 to18.88 dSm-1. Among the Brassica juncea genotypes, the genotype Toria selection and Agati sarheen had the best germination followed by NIFA raya & Sultan raya, whereas, the genotype P-78 was found highly sensitive during germination at 20 dSm-1 NaCl salinity level. Among the Brassica napus species, the genotype Wester was least affected by 20 dSm-1 NaCl salinity level, whereas Durr-e- NIFA and Abaseen-95 showed minimum germination. At early seedling stage Sultan raya and Agati sarheen in Brassica juncea, and Wester in Brassica napus performed better than other genotypes at 9 dSm-1 (NaCl) salinity level. It was also observed that the tolerant genotypes had higher K:Na ratio as compared to sensitive ones. In the field no growth was observed above15 dSm-1. Observation recorded in terms of plant height, number of branches plant-1, number of slique plant-1, slique length, grain wt plant-1, grain yield plot-1 and 100 grain wt., showed that among Brassica juncea genotypes, Agati sarheen had < 50% decrease under saline condition in all the growth parameters followed by Sultan raya having < 50% reduction in 7 growth parameters. Whereas, among the Brassica napus genotypes Wester and Abaseen-95 performed better, showing < 50% decrease in all the growth parameters under saline field conditions. The results obtained under natural saline field conditions are to great extent similar to the earlier findings obtained in green house studies. To improve the salt tolerance in Brassica genotypes, nitrogen and potassium were applied exogenously to some selected (tolerant and sensitive) genotypes alone or in various combinations @ 30 mM and 60 mM. Application of these growth promoting chemicals (GPC) improved plant growth under saline environments. Least reduction in different growth parameters was observed in T4 (NH4Cl @ 60 mM), followed by T2 (KCl @ 60 mM). Both these treatments showed comparatively higher increase in organic solutes (proline and glycine betaine) in plants. Sodium accumulation was also low, under T4 treatment followed by T2 treatment. On the basis of these results it can be concluded that application of higher dose of NH4Cl (60mM) and KCl (60 mM) proved suitable stretigies for alleviating the toxic effects of salinity in Brassica species.