Towards Developing Drought-smart Soybeans

Abstract

Drought is one of the significant abiotic stresses threatening crop production worldwide. Soybean is a major legume crop with immense economic significance, but its production is highly dependent on optimum rainfall or abundant irrigation. Also, in dry periods, it may require supplemental irrigation for drought-susceptible soybean varieties. The effects of drought stress on soybean including osmotic adjustments, growth morphology and yield loss have been well studied. In addition, drought-resistant soybean cultivars have been investigated for revealing the mechanisms of tolerance and survival. Advanced high-throughput technologies have yielded remarkable phenotypic and genetic information for producing drought-tolerant soybean cultivars, either through molecular breeding or transgenic approaches. Further, transcriptomics and functional genomics have led to the characterisation of new genes or gene families controlling drought response. Interestingly, genetically modified drought-smart soybeans are just beginning to be released for field applications cultivation. In this review, we focus on breeding and genetic engineering approaches that have successfully led to the development of drought-tolerant soybeans for commercial use.

Soybean resilience to drought is supported by partial recovery of photosynthetic traits

“…Owing to the expedited climate change, many scholars and breeders are pursuing identifying and screening diverse soybean cultivars to document traits backing to select drought-tolerant cultivars ( Wang et al., 2018 ; Yan et al., 2020 ; Arab et al., 2022 ). They claimed that the plant functional traits, which are potentially linked to drought tolerance, may ensure recovery and resilience to drought under unpredictable climate change ( Arya et al., 2021 ). Theoretically, plant functional traits, namely morphological and physiological traits, can track environmental changes and reflect the adaptive strategy of the crop to changing climate conditions ( Wijewardana et al., 2018 ; Zhuang et al., 2020 ; Monteoliva et al., 2021 ).…”

“…They tested the cultivars mostly through a scenario called cumulative drought stress, which simulates a condition of low frequent precipitation during the season ( Elsalahy et al., 2020 ; Gao et al., 2020 ; Saleem et al., 2022 ). Based on the findings, the researchers claimed that drought-tolerant cultivars are a promising candidate for building resilient crop production systems ( Arya et al., 2021 ; Guzzo et al., 2021 ; Monteoliva et al., 2021 ; Arab et al., 2022 ). Whereas, within an agriculture context, the change in rainfall pattern can cause episodic drought, which is a prolonged period of no precipitation that is projected to occur more frequently in the future ( Hari et al., 2020 ).…”

Evolving role of synthetic cytokinin 6-benzyl adenine for drought stress tolerance in soybean (Glycine max L. Merr.)

“…According to Le Roux et al (2019), wheat plants transformed with a vector expression of Arabidopsis thaliana cysteine protease inhibitor (OVERLYTOLERANT TO SALT-1, OTS1) showed enhanced stress tolerance and delayed tissue senescence compared to other lines of this species that only contained SUMO proteases. In soybean, drought negatively influences the various parameters shown in Table 1, in addition to causing significant changes in the shoot and root morphology, reduction of cortical tissue in stems, and causes a decrease in the number and size of flowers, fruit pods, and seeds (Du et al, 2020;Arya et al, 2021). Apart from these diminished vegetative and reproductive growth, soybeans also show serious inhibitions on the formation of cell protuberance containing nitrogenfixing Gram-negative bacteria in the roots, discussed later in this paper.…”

“…Low water content in the cells causes leaves to wilt and drop (Wang et al, 2022), have a negative impact on plant's architecture by affecting stem elongation, branching and subsequently blossoming as well as fruit production (Du et al, 2020;Arya et al, 2021). All of these growth effects appears to be modulated or regulated by cytokinins as illustrated later in Figure 5.…”

Identification of effective Rhizobium isolate(s) for efficient symbiosis with soybean under moisture stress conditions

“…Further, the drought stress affects the performance of soybean, which must be clarified for minimizing the threat of climate change to global food security. The effects of moisture are significant on soybean germination, plant respiration, chlorophyll content, leghemoglobin, proline, flowering, gene expression, seed development, and seed quality (Moloi et al, 2021;Arya et al, 2021). Nonetheless, there are only a few reports on the effects of drought stress exerted on root morphology safety (Pantalone et al, 1996).…”