Biochemical and Molecular Basis of Varietal Difference in Plant Salt Tolerance.

World agriculture is facing a lot of challenges like producing 70% more food for an additional 2.3 billion people by 2050. However, the productivity of crops is not increasing in parallel with the food demand. The lower productivity is attributable to various abiotic stresses, of which increased soil salinity is one of the foremost causes. The negative effect of salinity is caused by Na+ and Cl- ions producing the critical conditions for plant survival. The obvious outcome of salinity includes membrane damage, nutrient imbalance, altered levels of growth regulators, enzymatic inhibition and improper metabolic functions, including photosynthesis which ultimately leads to plant demise. Crops vary significantly in their threshold limits of salt tolerance. A well-focused approach combining the molecular, physiological, biochemical and metabolic aspects of salt tolerance is essential to alleviate the drastic effects of salinity and develop salt-tolerant crop varieties. The exploitation of genetic differences of available germplasm has the greatest significance, because it helps to identify the genotypes performing well even under saline conditions. Screening of crops for tolerance can strengthen the breeding programs by identifying genotypes with high salt tolerance and yield potential. This strategy involves comparative investigation of various morphological, physiological, biochemical, enzymatic and ionic responses, together with the study of differential expression pattern of genes/proteins concerned with salt tolerance at different developmental stages under salt stress in salt-sensitive and salt-tolerant cultivars. If the response is greater in the salt-tolerant line, it suggests a role in stress tolerance. Many pitfalls are associated with such approach, i.e., climatic variation, varied physiochemical properties of soil and amount of precipitation, which reduces the effectiveness of screening under field conditions. Even then, such studies can readily identify the salt-tolerant genotype, leading to the identification of novel genes or markers contributing towards salt tolerance, when overexpressed in the susceptible cultivars. The tolerant genotypes, thus screened can be recommended for cultivation in marginal saltaffected areas. This review focuses on the biochemical and molecular basis of varietal differences in salt tolerance among the cultivars of various plant species.

Carbohydrate content and antioxidative potential of the seed of three edible indica rice (Oryza sativa L.) cultivars.

Rice (Oryza sativa L.) grains or seeds are known to lose much of their nutrient and antioxidant contents, following polishing. The current study was undertaken to evaluate and compare the carbohydrate content and antioxidant parameters in the unpolished and polished seeds of three edible indica rice cultivars, namely Swarna (SW), the most popular indica rice cultivar in India and aromatic or scented cultivars Gobindobhog (GB) and Pusa Basmati (PB). While both the sucrose and starch content was the maximum in PB seeds (both unpolished and polished), the amylose content was the highest in SW polished seeds. SW polished seeds were superior as compared to GB and PB cultivars in terms of total antioxidant capacity, DPPH radical scavenging and Fe(II) chelation potential, as well as the highest lipoxygenase (LOX) inhibition or H2O2 scavenging potential, probably due to the maximum accumulation of total phenolics and flavonoids, the two important antioxidants. The reducing power ability was, however, identical in both SW and GB polished seeds. The PB polished seeds were more potent in superoxide and hydroxyl scavenging, whereas GB in nitric oxide (NO) scavenging. The common observation noted after polishing of seeds was the reduction in the level of carbohydrates and antioxidant potential, though the extent of reduction varied in the three cultivars. The only exception was GB, where there was no alteration in NO scavenging potential even after polishing. Our study showed the better performance of SW polished seeds with respect to higher amylose content and majority of the tested parameters governing antioxidant capacity and radical scavenging potential, thus highlighting the greater dietary significance of SW over the other two cultivars.

Analysis of comparative efficiencies of different transformation methods of E. coli using two common plasmid vectors.

The efficiencies of different transformation methods of E. coli DH5α strain, induced by several cations like Mg2+, Mn2+, Rb+ and especially Ca2+, with or without polyethylene glycol (PEG) and dimethyl sulfoxide (DMSO) were compared using the two commonly used plasmid vectors pCAMBIA1201 and pBI121. The widely used calcium chloride (CaCl2) method appeared to be the most efficient procedure, while rubidium chloride (RbCl) method was the least effective. The improvements in the classical CaCl2 method were found to further augment the transformation efficiency (TR)E for both the vectors like repeated alternate cycles of heat shock, followed by immediate cold, at least up to the third cycle; replacement of the heat shock step by a single microwave pulse and even more by double microwave treatment and administration of combined heat shock-microwave treatments. The pre-treatment of CaCl2-competent cells with 5% (v/v) ethanol, accompanied by single heat shock also triggered the (TR)E, which was further enhanced, when combined heat shock-microwave was applied. The minor alterations or improved approaches in CaCl2 method suggested in the present study may thus find use in more efficient E. coli transformation.