Regulation of salinity tolerance in Brassica juncea (L.) introgression lines: Osmoprotectants, antioxidative molecules and ionic content

Indian mustard [Brassica juncea (L.) Czern & Coss] is one of the most important oilseed crops worldwide yet drought and salinity stress significantly reduced its growth and yield. The research was carried out in order to test the effect of salinity on osmoprotectants (total soluble sugars, proline), antioxidant molecules (ascorbate, α-tocopherol) and ionic content from the dry sample of the leaves in introgression lines and varieties of Brassica juncea. Permanent saline plots are maintained in the field of soil sciences where different doses of sodium carbonate were given to maintain the relative sodium bicarbonate (RSC) to three levels. The results revealed the significant effect of salinity on biochemical attributes as well as on ionic content. Increase in total soluble sugars, proline, ascorbate, α-tocopherol and Na+ ion whereas rest of the ions Ca2+, Mg2+ and K+ decreased with increased salinity levels. Increased accumulation of Na+ increased the Na+/K+ ratio and decreased the K+/Na+. Significant finding among the introgression lines and varieties revealed low Na+ and high K+ correspondingly Na+/K+ low and K+/Na+ ratio. Decreased calcium and magnesium ion resulted in decline in chlorophyll content and membrane stability under saline conditions while decreased K+ concentration regulated the opening and closing of stomata thus hampering photosynthesis.