Comparative in Vivo and In Vitro Studies on Growth Bioregulatory Role of Thiourea in Improving Salt Tolerance of Hybrid Maize

Abstract

This research project was undertaken to see the sights in the bioregulatory mode of action of thiourea in improving salinity stress tolerance in maize. For this purpose, the studies were conducted both in vivo and in vitro. Seeds of (six) marketable maize hybrids (P1543, 34N43, 31P41, DK6789, 33M15, 32B33) were used to accomplish the objectives of improving salinity tolerance in both systems. For in vivo studies, the experiments were conducted in two seasons (autumn and spring) in pots. Salinity treatment applied in both the systems was 120 mM developed with sodium chloride to find out the comparative responses of the hybrids. Based on growth responses, hybrid 33M15 was found to be highly salt tolerant while DK6789 was highly salt sensitive. Both these hybrids were used in selecting an appropriate level of thiourea out of a range from 0 to 2400 μM (at an increment of 200 μM). For both the hybrids, based on growth attributes, 400 μM level was the most optimal in enhancing growth parameters, and was therefore selected for use at both in vivo and in vitro level experiments. For in vivo experiment, the data revealed that applied salinity was damaging to growth, gas exchange, oxidative stress, antioxidants, osmoprotectants and nutrients characteristics of both the hybrids (DK6789 being more affected) while autumn season was more adverse than spring. Medium supplementation of thiourea was almost equally effective in both the seasons in improving the salinity tolerance of the hybrids during in vitro studies while the behavior of 33M15 was more profound towards the callusing, shooting and rooting and regeneration ability. Overall the results suggested that the medium supplementation of thiourea can effectively improve the salinity tolerance of maize by producing physiological and biochemical changes at the cellular level together with the parameters measured in the lab/pot experiments. The studies can be extended both at the molecular level to find out the patterns of gene expression, and in the field to explore the real benefits that the farmers can accrue using the approach employed in the control conditions.