External potassium (K+) application improves salinity tolerance by promoting Na+-exclusion, K+-accumulation and osmotic adjustment in contrasting peanut cultivars

• External K+ application improves plant water status and overall physiology in peanut under salt stress.
• The tolerant and sensitive cultivar showed differential response of K+ application on salinity tolerance.
• Comparatively better response of supplementary K+ application was observed in salt-sensitive cv. TG 37A.
• The tolerant cv. GG 2 relied more on organic solute accumulation and showed lesser Na+ uptake as tolerance strategy.

Achieving salt-tolerance is highly desirable in today's agricultural context. Apart from developing salt-tolerant cultivars, possibility lies with management options, which can improve crop yield and have significant impact on crop physiology as well. Thus present study was aimed to evaluate the ameliorative role of potassium (K+) in salinity tolerance of peanut. A field experiment was conducted using two differentially salt-responsive cultivars and three levels of salinity treatment (control, 2.0 dS m−1, 4.0 dS m−1) along with two levels (with and without) of potassium fertilizer (0 and 30 kg K2O ha−1). Salinity treatment incurred significant changes in overall physiology in two peanut cultivars, though the responses varied between the tolerant and the susceptible one. External K+ application resulted in improved salinity tolerance in terms of plant water status, biomass produced under stress, osmotic adjustment and better ionic balance. Tolerant cv. GG 2 showed better salt tolerance by excluding Na+ from uptake and lesser accumulation in leaf tissue and relied more on organic osmolyte for osmotic adjustment. On the contrary, susceptible cv. TG 37A allowed more Na+ to accumulate in the leaf tissue and relied more on inorganic solute for osmotic adjustment under saline condition, hence showed more susceptibility to salinity stress. Application of K+ resulted in nullifying the negative effect of salinity stress with slightly better response in the susceptible cultivar (TG 37A). The present study identified Na+-exclusion as a key strategy for salt-tolerance in tolerant cv. GG 2 and also showed the ameliorating role of K+ in salt-tolerance with varying degree of response amongst tolerant and susceptible cultivars.

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