Investigating the Pearl Millet ( Pennisetum glaucum ) as a Climate-Smart Drought-Tolerant Crop under Jordanian Arid Environments

To investigate drought tolerance under arid conditions, eleven pearl millet breeds (HHVBC tall B6; IP13150; IP19586; IP19612; IP22269; IP6110; IP7704; MC94C2; P. millet icms7709; Sudan-pop I; Sudan-pop III) were tested under arid water-scarce climatic conditions. A field randomized complete block design experiment with three replicates per year was conducted at the Deir-Alla Regional Agriculture Research center in the middle Ghor within the Jordan Valley from 2010 to 2020. The plant-deficit irrigation was maintained at 80% based on the crop water requirements using a time-domain reflectometer. The plant morphological characteristics, forage production, seed formation, and water-use efficiency (WUE) were monitored for ten years for two case scenarios: seed and forage production. The individual and combined drought indices of the precipitation, temperature, and vegetation were calculated and correlated with the millet morphological and yield parameters. Climate change analyses show significant impacts, reaching a 1 mm/year reduction in precipitation and a 0.04 mm/year increase in air temperature, which causes the study area to be more prone to drought events. Along with the proven increase in the drought intensity over time, the millet breeds showed significant drought-tolerance capacities under arid, drought-prone conditions by adjusting their system to tolerate salt, heat, and water stresses. For the seed production scenario, the WUE ranged from 27 to 57.3 kg/ha·mm, and from 7.1 to 14.9 kg/ha·mm for fresh and dry conditions, respectively. The IP13150 millet breed showed the highest capacity to tolerate the drought of Jordan’s environment, and it is thus recommended as a good substitute under water-scarcity situations, with an average production of 17.7 ton/ha. For the vegetative production scenario, the WUE ranged from 32.03 to 64.82 kg/ha·mm for the fresh biomass and from 10.8 to 24.6 kg/ha·mm for the dry biomass. Based on the WUEs and vegetative production results, the IP19586, IP22269, IP19612, IP7704, and HHVBC tall B6 millet breeds are recommended as forage support due to their phenological characteristics, which tolerate drought and heat conditions. In contrast to the vegetation drought index, both the precipitation and temperature drought indices show strong correlations (above r > 0.6) with the plant growth factors and a moderate correlation (0.3 < r < 0.6) with the yield factors. Both precipitation and temperature indices are capable of explaining the variations among millet breeds, especially as related to millets’ morpho-physiological characteristics.