Evaluation of yield and quality attributes of barley cultivars with foliar spray of glycine betaine under lead toxicity

Lead (Pb) toxicity is a major environmental threat that severely affects growth and production of staple crops. Foliar applications of glycine betaine (GB) have been extensively studied for their ability to stimulate heavy metals (HMs) tolerance in plants. Despite that, no literature reports are available on the ameliorative behavior of GB application on barley cultivars under Pb stress. A pot experiment was conducted to assess the relative efficacy of exogenous GB (2 mM) supplementation on various morphological (spike length) yield (no. of spikelet spike−1, no. of grains spike−1, grain yield plant−1, and 1000 grain weight) and grain quality traits (carbohydrate and protein content) of two barley cultivars (BH946 BH959) under three levels of Pb stress treatments, viz. control, 15, 25, and 35 mM. Current research results revealed that Pb stress significantly (p < 0.05) decreased barley plants' yield traits and grain quality characteristics. More reduction was observed at the highest Pb stress, i.e., 35 mM. However, the foliar application of GB significantly (p < 0.05) mitigates the toxic effect of Pb stress and improves the yield traits, and ultimately, the grain yield per plant increases. Moreover, GB addition also enhances the quality of barley grain by improving the protein and carbohydrate content. The present research findings exhibit the ameliorative role of foliar-applied GB in enhancing the yield, and quality traits of barley cultivars might be attributed to modulating plant growth, photosynthetic activities, the antioxidant defense system, and diminished oxidative stress under Pb toxicity. According to the t-test results, both cultivars displayed the same trend under each stress and GB supplement. Therefore, only one cultivar can be considered for the experiment setup out of the two for further studies. In conclusion, GB at 2 mM concentrations successfully mitigates the toxic effect of Pb (up to 35 mM) and its implication might be recommended for crops suffering from Pb stress to improve their yield and quality traits.