Yield performance and stress responses of sorghum

Abstract

Climate change has emerged as one of the most important global environment issues. Rising CO2 and temperature, changing rainfall patterns, and an increase in the frequency and duration of heat stress and water stress are all effects of climate change. Sorghum being a C4 plant with increased photosynthetic efficiency and abiotic stress tolerance, is a key crop in semi-arid tropical regions. Assessing the impact of climate change on sorghum productivity is crucial for addressing future food security challenges. This PhD project aimed to assess yield performance, response to water and heat stress in sorghum. In the first part of the project (chapter 2), twenty grain sorghum varieties were evaluated for the yield performance and variations in plant and leaf morphology. In the second part (Chapter 3), four sorghum genotypes including two grain sorghum (Sorghum bicolor ‘Farfara’ and Sorghum sudenense) and two wild sorghum (Sorghum bulbosum and Sorghum macrospermum) genotypes were grown focusing on studying the responses of these genotypes under water stress and heat stress conditions. In the third part (chapter 4), a large population of sorghum genotypes with different aquaporin alleles were grown to study the link between stomatal anatomy and kinetics and their relationship with water use efficiency under water stress. The first experiment was carried out in field conditions at College of Agriculture, Vellayani, Kerala, India. The second and third experiments were carried out in potted plants grown in the glasshouse at Hawkesbury Institute for the Environment, Western Sydney University, Australia. The first experiment revealed significant variations in growth and yield attributes among different sorghum varieties at various stages of development. CSV 17 performed exceptionally well across a variety of measures. It showed significantly higher grain yield, early flowering, and a shorter time to maturity, and higher harvest index compared to other varieties. CSV 20 demonstrated impressive economic performance, with the highest net returns per hectare and a remarkable benefit-cost ratio due to its significantly higher stover yield. In terms of leaf area index (LAI) and leaf area duration (LAD) variety CSV36 performed better. In second experiment S. bicolor ‘Farfara’ exceled in maintaining high intrinsic water use efficiency (iWUE) and quantum yield of photosystem II (ΦPSII) under water stress, while S. bulbosum excelled by maintaining carbon assimilation rate (An) and stomatal conductance (gs). In third experiment we observed a large variation in stomatal kinetics and their related dynamic water use efficiency and only stomatal opening speed (kopen) was found to be affected by water stress among other stomatal traits. The results of this research will provide valuable data for breeding programs focused on creating new sorghum varieties