Adaptation Responses to Early Drought Stress of West Africa Sorghum Varieties

Abstract

Sorghum is the fifth most important cereal crop world-wide and feeds millions of people in the Sahel. However, it often faces early-stage water deficit due to false onsets of rainy seasons resulting in production decrease. Therefore, developing early drought tolerant material becomes a necessity but requires a good knowledge of adaptation mechanisms, which remains to be elucidated. The present study aimed at assessing the effects of early drought stress on ten elite sorghum varieties tested over two years (2018–2019) at the National Agronomic Research Centre (CNRA) of Bambey (Senegal, West Africa). Two different water regimes (well-watered and drought stress) were applied during the dry season. Water stress was applied by withholding irrigation 25 days after sowing for one month, followed by optimal irrigation until maturity. Soil moisture measurements were performed and allowed to follow the level of stress (down to a fraction of transpirable soil water (FTSW) of 0.30 at the end of stress). An agro-physio-morphological monitoring was carried out during the experiment. Results showed highly significant effects of early drought stress in sorghum plants growth by decreasing leaf appearance, biomass, height but also yield set up. The combined analysis of variance revealed highly significant differences (p ≤ 0.01) between varieties in the different environments for most characters. Under water deficit, the variability was less strong on leaf appearance and plant height at the end of stress. The adaptation responses were related to the capacity of varieties to grow up fast and complete their cycle rather, increase the dead leaves weight, reduce photosynthesis rate, stomatal conductance, leaf transpiration and increase the roots length density. However, varieties V1, V2, V8 and V9 showed promising behavior under stress and could be suitable for further application in West Africa for sorghum breeding and farming.

Using UAV Borne, Multi-Spectral Imaging for the Field Phenotyping of Shoot Biomass, Leaf Area Index and Height of West African Sorghum Varieties under Two Contrasted Water Conditions

“…These varieties differ in terms of days to ma-turity (90 to 128 days for maturity), height (120 to 450 cm height), response to inputs (hy-brid vs. open pollinated varieties caudatum or guinea), and yield (2 to 4.5 t ha −1 ). These varieties are widely cultivated by the farmers due to their adaptability and agronomic characteristics [36][37][38][39].…”

Quantitative and population genomics suggest a broad role of staygreen loci in the drought adaptation of sorghum

“…One particular concern for offseason managed stress would be that differences in photoperiod regime relative to the TPE (i.e. the rainy season) could change in growth or developmental dynamics in a way that alters the drought response (Blum, 2010;Gano et al, 2021). However, the overall similarity of grain yield components in the rainy season (RF) and off-season experiments (Fig.…”

Sorghum Drought Tolerance is Associated with Deeper Root System and Decreased Transpiration Rate

“…At 0.3 FTSW, the photosynthetic rate and stomatal conductance were decreased by 70 and 81%, respectively, from the initial value [28]. Apart from this, Gano et al [5] reported that in sorghum, at 0.3 FTSW, the plants experienced drought stress as revealed by leaf rolling. Similarly, in this study, the plants at 0.4 FTSW on the 2 nd day showed leaf rolling symptoms.…”

“…The seedling and flowering stage drought tolerance of sorghum was associated with rooting depth, total length, and root conductivity [3][4][5]. Mace et al [6] showed a positive relationship between the root angle and drought tolerance of sorghum.…”