Highlights of strategies adapted by two Pennisetum glaucum (L.) R. Br. races in a simulated drought stress experiment

Abstract Pearl millet (Pennisetum glaucum) is an important staple food crop in Asia and Africa. The most severe abiotic stress that hinders growth and development of crop is Drought. Four genotypes of P. glaucum were grown for 4 weeks in a greenhouse facility with the aim to identify several physiological responses observed after 12 days of drought stress and transcriptional profiling related to drought tolerance. Distinct parameters like relative water content (RWC), water use efficiency (WUE), stomata quantification (SI%), electron transport rate (ETR), photochemical (qP) and non-photochemical quenching (qNP) were measured under simulated drought condition for the selected four genotypes. The genotypes were grouped into two pearl millet races viz., nigritarum and globosum. Genotype 1P35451 of the nigritarum race showed augmentation in dry weight (DW) and tolerance index (TI) under the condition of decreased soil water due to transpiration. It exhibited a remarkable ability for recovery of leaf after an imposed drought condition in RWC, WUE and SI. Also, the transcriptional expression of CBF, RubSc and PIP 2;3 genes indicated that they were quick to respond to drought. CBF gene has proven to be useful for evaluating the ability to withstand drought in both races. RubSc and PIP2:3 displayed a pronounced increase in their expression level in nigritarum race. However, the drought tolerant genotype 1P13013 of globosum functioned in stomatal movement which is well linked with the expression of the Nicotinamide Adenine Dinucleotide Phosphate (NADP) enzyme. Therefore, the results indicate that mRNA expression of genes in both races under drought stress provides information on their ability to resist drought and could supply valuable molecular information for drought-tolerant elite breeding programs in the future.