Evaluation of Root Traits for Water Stress Tolerance in Rabi Sorghum Genotypes

Sorghum (Sorghum bicolor (L.) Moench) is one of the most important multipurpose cereal crops cultivated in tropical and subtropical regions of the world. Being a C crop plant, it plays an essential role in feed, food, and fodder security in dry land 4 agriculture (Chapke and Tonapi, 2019). India is the fifth largest producer of sorghum in the world with total production of 4.7 MTfrom its 4.8 million hectares of area (USDA, 2020). However the average yields of 1050 kg ha-1 is very low among the major sorghum producing countries. Among the sorghum producing state, Maharashtra is the leading state in sorghum production with the production of 2.15 MTfrom the area of 2.28 million hectares and the productivity of 941kg ha-1 during 2021-22 (ESM, 2022-23). Drought stress causes major losses in agricultural productivity every year (Ahluwalia et al., 2021). The early vegetative stage and reproductive stage (pre and post flowering) of sorghum are vulnerable to the effects of water deficit (Wani et al., 2013). In response to drought stress, plants undergo several physiological and morphological modifications like reduced transpiration and photosynthesis rate, osmotic adjustments, repressed root and shoot growth, overproduction of reactive oxygen species (ROS), modified stress signaling pathways, and senescence. These modifications can cause permanent injury to the plants (Ahluwalia et al., 2021). In order to acclimate to water shortage, plants adjust their growth and development to promote water absorption and reduce water loss (Zheng et al. 2016; Kim et al. 2020). Root response is of prime importance to crop productivity under drought stress. This is because the root size, architecture and distribution determine the ability of plants to access and uptake the water for proper physiological functioning of shoots (Taiwo et al., 2020; Henry 2013; Comas et al., 2013). Drought stress adapted plants are often characterized by deep and vigorous root systems. Water uptake capacity of roots can be estimated by root parameters including root biomass, root volume, primary root length, lateral root number, root depth, and root length distribution (Meng, 2018). Generally, under drought conditions, plants trigger several phenomena to generate more developed root systems and a higher root to shoot ratio. This is evidenced by a more pronounced restriction of shoot production than root production in plants underwater deficit (Zheng et al. 2016; Duet al. 2020). Sorghum grown in arid and semiarid parts of the tropics and subtropics are frequently prone to drought accompanied with water stress and high temperature stress in plants affecting various growth stages (Reddy et al., 2012). Therefore, the better water stress tolerant genotypes are desired in such a region to reduce the crop failure due to water deficit problem. The most drought tolerant and susceptible genotypes could be used in hybridization programmes to increase genetic variability and the selection criteria used underwater stress for drought tolerance in sorghum could be higher root length, shoot length with lower leaf water potential, osmotic potential, and turgor pressure (Bibi et al., 2012). Keeping inconsideration the above facts, an attempt has been made on different sorghum genotypes for water stress tolerance by studying and investigating the root architecture system of the sorghum genotypes.