Sorghum bicolor salt-sensitive genotype grown in saline soil benefitted the eBL seed-priming treatment

Soil salinization is a phenomenon increasing and spreading worldwide and continuously damaging ecosystems and reducing yield of crop, mainly in the major cereals. Thus, it is crucial to identify salt-tolerant crops and/or technologies able to improve salt tolerance in sensitive ones, without harming the ecosystem. This is necessary to ensure food availability for the increasing world population in the changing environment. Sorghum bicolor, being a salt-tolerant crop, represents a staple food in many arid and semi-arid regions of the world, thus it is a good candidate for this study, although differences among genotypes were found (2). Brassinosteroids (BRs) are a class of steroidal hormones well known for their role in plant development and tolerance to different stresses, including salt-stress. Brassinosteroids could be exogenously applied, also as seed-priming, to improve salt resistance in crops with minimum impact to the environment (1). In this study the effects of salt stress and of the seed priming treatment with the 24-epibrassinolide, a BR active precursor, were evaluated on two sorghum genotypes, Bianca, a salt-tolerant genotype, and Tonkawa, a salt-sensitive one. The aim was to evaluate if the seed-priming could mitigate the negative effect of the salt-stress in plant cultured in pots. The results obtained from 40-days-old plants in vegetative phase evidenced the efficiency of eBL treatment in enhancing the photosynthetic activity and in mitigating the negative salt effects on the leaf anatomy in the salt-sensitive genotype. Gas exchange analyses showed a significant increase in the net photosynthetic rate and a decrease in the intercellular CO2 content, leading to a higher carboxylation efficiency in plants grown in saline soil with the pre-treatment with eBL in comparison to the salt treatment alone. Shoot morphological analyses showed that the priming treatment was beneficial for Tonkawa’s parameters under saline soil conditions. Histological analyses highlighted more differences among treatments in Tonkawa, with respect to Bianca, especially between plants treated only with salt and those pre-treated with the hormone. Altogether, the results show that seed priming, with a specific eBL concentration, can increase salt-tolerance in the salt-sensitive genotype.