Abstract
Drought has become a major threat to food security, because it affects crop growth and development. Drought tolerance is an important quantitative trait, which is regulated by hundreds of genes in crop plants. In recent decades, scientists have made considerable progress to uncover the genetic and molecular mechanisms of drought tolerance, especially in model plants. This review summarizes the evaluation criteria for drought tolerance, methods for gene mining, characterization of genes related to drought tolerance, and explores the approaches to enhance crop drought tolerance. Collectively, this review illustrates the application prospect of these genes in improving the drought tolerance breeding of crop plants.
Highlights
With population growth and climate change, food security has become a major global challenge
Sahar et al compared 24 indices and found strong positive correlations between the grain yield and nine indices, such as the mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI), mean relative performance (MRP), relative efficiency index (REI), modified stress tolerance indices 1 and 2 (MSTIk), harmonic mean of yield (HM), and relative decrease in yield (RDY), which can be used for selecting drought tolerant and high-yield genotypes [13]
Most transgenic plants with drought tolerance phenotypes were based on the overexpression of genes using constitutive promoters, such as actin, CaMV35S, and ubiquitin
Summary
With population growth and climate change, food security has become a major global challenge. Crop production is being impacted by increasing abiotic stresses. Drought is one of the most severe abiotic stresses on crop production, and its impact depends on its timing, duration, and intensity, caused by insufficient rainfall and/or altered precipitation patterns. It is urgent to accelerate the genetic improvement of crop drought tolerance by using desirable genes through the application of new biotechnological tools. In the history of crop breeding, conventional techniques such as cross, backcross, artificial mutagenesis, pedigree selection, and recurrent selection have played an important role in the genetic improvement of drought tolerance. Conventional breeding mainly relies on phenotypic selection in the field; it is greatly affected by the environmental conditions and requires many years of identification and evaluation, resulting in highly labor-intensive, time-consuming, and low efficiency. In the present review, the evaluation criteria of crop drought tolerance were reviewed, followed by mining approaches of drought tolerance genes and methods to improve the drought tolerance of crops
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