MOLECULAR REGULATION OF DROUGHT STRESS TOLERANCE IN SYMBIOTIC PULSES PRODUCED UNDER DROUGHT STRESS
Peas and chickpeas are the most common varieties of pulses, the leguminous crops whose nutrient-reach grains are used to nourish the world's growing population. However, due to global climate change, abiotic stresses such as drought, high temperature and salinity are increasingly hindering crop health, yield and global food security. Increasing demands for food increases the importance and urgency of understanding how microbiomes may be exploited to increase crop yields and reduce losses caused by abiotic stress. In recent two decades, modern agricultural microbiology science is applying novel approaches to overcoming abiotic stresses. Yet, there are very few detailed studies highlighting the impacts of plant-associated endophytes on plant health and development when exposed to extreme drought. In this study, a few selected fungal strains of Penicillium sp. SMCD 2206, and Paraconiothyrium sp. SMCD 2210, and bacterial strain of Streptomyces sp. SMCD 2215 endosymbionts were tested for their capacity to promote plant growth and reduce oxidative damage in tested plants grown under drought stress. A transfer of the stress tolerance from first (F1) to second (F2) generation was also tested. The study findings showed that under drought chickpea and pea F2 seeds produced from F1 inoculated (E+) with endophytes (SMCD 2206, SMCD 2210, and SMCD 2215) have high germination and better root and shoot growth compared to non-inoculated (E−) plants. Furthermore, the reactive oxygen species (ROS) level was assessed in chickpea and pea F2 seeds and found that the fungal endophytes SMCD 2206, SMCD 2210, and SMCD 2215 reduced the oxidative damage under drought conditions in F2 generation seeds produced from F1 plants inoculated (E+) with these endophytes. The assessment of the impact of fungal endophytes on antioxidant gene expression found that endosymbionts downregulate antioxidant gene expression (proline, superoxide dismutase (SOD), manganese superoxide dismutase (MnSOD), dehydrin), indicating the significance of endophytes in stress tolerance. In addition, the quality of seeds in regard to protein content is also improved by fungal endophytes. Furthermore, the relationship between ROS level and seed germination was investigated, and found that an inverse relationship exists. Overall, the endophytic symbionts SMCD 2206, SMCD 2210, and SMCD 2215 improve germination and plant growth, while reducing oxidative damage in second generation chickpea and pea seeds under drought conditions. In addition, the endophytes pass on the stress tolerance to next generation; however, the mechanism of action remains obscure. In conclusion, endosymbionts have the potential to increase agricultural production under adverse environmental conditions. However, additional research at the molecular level is vital to understand the stress tolerance and inheritance mechanisms, and field/natural conditions are imperative to confirm the applicability of endophytes.
Drought, 2nd generation (F2), Endophyte, Stress tolerance
Master of Science (M.Sc.)
Food and Bioproduct Sciences