**5. Conclusions**

or genome editing including CRISPR/Cas9 is a broad category that offers an inexpensive, quick and easy technique to manipulate DNA and lessen the time and effort as compared to traditional breeding. Now-a-days, researchers are working on CRISPR/Cas9-edited versions to improve the different crops such as soybeans, rice, corn, canola and wheat with new traits like drought and flooding resistance and higher yields. Recently, various new plant breeding techniques such as zinc finger nuclease (ZFN) technology, acetate-mediated approach, oligonucleotide-directed mutagenesis (ODM), RNA-dependent DNA methylation (RdDM), cisgenesis, intragenesis, grafting (on GM rootstock) and reverse breeding allow the faster and

Agronomic practices can be mitigated the adverse effects of drought and flooding stresses by adopting various strategies. Seed priming is an effective and pragmatic technique to mitigate drought in which seeds are moderately hydrated. In this technique, germination rate, germination percentage and germination uniformity of primed seed increased [11, 203]. This approach has been useful to counteract the effects of drought stress in a range of crop species. Foliar application of plant growth regulators is another technique for improving growth against drought stress. Exogenously applied abscisic acid, uniconazole and brassinolide increased yields both under well-watered and drought conditions in soybean. Plant growth regulator treatments meaningfully increased water potential and chlorophyll contents under water stress conditions [204]. Traditional irrigation system causes >50% loss of irrigated water because of uncovered and unlined ditches. Therefore, a well-managed pipe system is required to avoid losses from traditional irrigation system as it can enhance the conveyance efficiency >90% [205]. Mulching involving covering of soil by using straw or plastic sheets, is another best strategy to retain moisture in soil. For instance, in China, soybean yield increased up to 23.4 and 50.6% by using mulching along with hole sowing and row sowing, respectively [206]. Several management practices have been tried to overcome completely or partially flooding injuries. Flooding induces nitrogen deficiencies resulting in a significant decrease in the uptake of nitrogen. As a result, yellowing of leaves occurred following 2–3 days of flooding. It has been reported that the application of nitrogen fertilizer i.e. polymer-coated urea (PCU) is effective to reduce nitrogen loss and recover flood damage in corn. It also helps to overcome oxygen deficiency in response to flooding stress preferentially [207]. Hypoxia also reduces the capacity of plant to absorb potassium (K). K plays a vital role in alleviating both biotic

ammonia [209], promoting photosynthesis which helps plant recovery and nutrient uptake. Foliar and soil applications oxygen-containing fertilizers lessen the drastic effects of flooding stress [210]. For example, under flooding, oxygen-containing fertilizers considerably retained

Under flooding stress, 1-aminocyclopropane-1-carboxylate (ACC) synthase enzyme along with several stress proteins were synthesized [212].The stressed plant consequently produces more ACC in their roots. In roots, ACC cannot be converted into ethylene due to insufficient oxygen. This ACC transferred from roots to shoots converting ACC to ethylene (sufficient oxygen environment) in shoots [213]. In soybean, phytohormone indole acetic acid (IAA)

ions are involved in detoxification of ammonium and

more efficient improvement of crop varieties.

50 Plant, Abiotic Stress and Responses to Climate Change

and abiotic stresses [208]. Indeed, K<sup>+</sup>

chlorophyll content and biomass in Italian basil [211].

**4.5. Agronomic practices to mitigate the effects of water stress**

Water stress has become major abiotic limitation factor on soybean production under warming climate. To combat drought and flooding stress, there is need to explore the resilient genetic resources and their utilization in breeding program. With the advancement in transcriptomics, proteomics, metabolomics, structural genomics and epigenetics, the production of soybean can be enhanced under water stress by integrating all disciplines. Recent advances in breeding system and agronomic practices will offer an opportunity for significant and predictable incremental improvements in soybean under water stress.
