A review of drought-stress responsive genes and their applications for drought stress tolerance in cassava (Manihot esculenta Crantz)

Climate change intensifies drought stress which limits a plant’s full genetic yield potential. Plants navigate drought stress via diverse mechanisms including drought avoidance, tolerance or resistance. The tropical root crop cassava is no exception. The crop’s inherent tolerance to drought stress classifies it as a climate smart root crop for use in mitigating the negative effects of climate change. Indeed, this has been linked with the crop’s sustainable yield that provides food security to food-vulnerable populations in drought prone regions of the world. Although tolerance to water deficit is genotype-dependent, cassava adapts to drought stress by deploying multiple responses at morphological, physiological and molecular levels. This review details expression patterns of genes and associated signaling pathways under antioxidants, reactive oxygen species, aquaporins, mitogen-activated protein kinases, calcium ion (Ca+) sensors, potassium ion (K+) transporters, glutaredoxins and late embryogenesis abundant proteins in cassava plants subjected to varied drought stress treatment. The review further provides a summary of key genes within the various signaling pathways that could be candidates for application in molecular marker development, genetic engineering and CRISPR/Cas9 genome editing for rapid introgression of drought tolerance traits in cassava genotypes. Full exploitation of these genes and omics’ techniques for improved cassava performance under drought and other abiotic stresses, could ensure sustainable food and nutrition security under changing climatic conditions.