Delineating eco-physiological traits linked to salt tolerance and fruit yield in pomegranate

Salt stress can suppress pomegranate growth and yield to varying degrees, reflecting the need for developing salt tolerant cultivars. We studied the effects of salinity stress [soil salinity 6.0-7.75 dS/m; irrigation water salinity -4.0 dS/m] on growth, eco-physiological relations, and fruit yield and quality in 15 genotypes of pomegranate comprising 13 soft- and hard-seeded ecotypes and two commercial cultivars ('Ganesh' and 'Bhagwa'). There were contrasting differences (p<0.05) between the soft- and hard-seeded types for several traits; the former were distinctly more productive, had thinner fruit peels, higher 100-aril weight and more juice content than the latter. Such differences were likely due to Na+exclusion, resulting in far lower leaf Na+/K+ and Na+/Ca2+ ratios in softthan in hard-seeded types. Analysis of Variance revealed highly significant (p<0.001) differences amongst the genotypes for all the traits; fruit weight, aril weight and juice content were particularly highly variable, reflecting the scope for further selection. Higher levels of leaf K+, Ca2+ and Mg2+ relative to Na+ and Cl- implied the ability of the tested pomegranate genotypes to overcome salt-induced nutritional deficiencies. Correlation analysis revealed that proline accumulation was likely due to excess Na+, rather than for osmotic adjustment. Strong Na+ and Cl- exclusion capacities in some of the tested genotypes may facilitate their use as parents for developing the salt excluder rootstocks. Lower malondialdehyde and hydrogen peroxide levels, better leaf chlorophyll, higher leaf water potential and reduced uptake of Na+and Cl-were identified as the major traits underlying salt tolerance and higher fruit yield in genotypes 'Raj-4' and 'Ajm-3'.