Improving heat stress tolerance in late planted spring maize by using different exogenous elicitors

Recent global warming has increased the risk of heat stress which may adversely affect crop productivity worldwide. Higher temperature during reproductive stage is one of major constraint that adversely affects grain filling and seed setting in spring maize (Zea mays L.) The purpose of this study was to evaluate the potential of different elicitors (salicylic acid, CaCl2, Moringa oleifera Lam. leaf extract) to improve yield performance of heat stressed spring maize. Seed priming techniques (hydropriming, osmopriming, organic priming and hormonal priming) were used to investigate the impact of exogenous elicitors on physiological, biochemical and yield-related attributes of late planted spring maize. Results revealed that higher temperature at maturity caused membrane leakage, reduced photosynthetic pigments and net assimilation rate which ultimately led to decreased grain yield. However, exogenous elicitors improved emergence characteristics and triggered early seedling development, and exhibited significantly higher seedling chlorophyll contents than control plants. Among elicitors, salicylic acid (SA) exhibited significantly higher photosynthetic pigment (17%), membrane stability index (26%), relative water content (16%), crop growth rate (13%), net assimilation rate (29%), grain yield (27%), biological yield (14%), harvest index (9%) and grain protein (28%) as compared to control in late planted spring maize. The multivariate analysis also indicate that physio-biochemical traits were more pronounced in hormonal priming with SA as compared to other exogenous elicitors. In conclusion, application of exogenous elicitors like SA is most effective and easy approach that may help to improve crop performance with increased grain yield and quality in late planted spring maize that prone to high temperature.

Keywords
Global warming; heat stress; maize; Moringa oleifera; priming techniques; salicylic acid.