Unraveling the Genetic Architecture of Two Complex, Stomata-Related Drought-Responsive Traits by High-Throughput Physiological Phenotyping and GWAS in Cowpea (Vigna. Unguiculata L. Walp)

Abstract

Drought is one of the most devasting and frequent abiotic stresses in agriculture. While many morphological, biochemical and physiological indicators are being used to quantify plant drought responses, stomatal control, and hence the transpiration and photosynthesis regulation through it, is of particular importance in marking the plant capacity of balancing stress response and yield. Due to the difficulties in simultaneous, large-scale measurement of stomatal traits such as sensitivity and speed of stomatal closure under progressive soil drought, forward genetic mapping of these important behaviors has long been unavailable. The recent emerging phenomic technologies offer solutions to identify the water relations of whole plant and assay the stomatal regulation in a dynamic process at the population level. Here, we report high-throughput physiological phenotyping of water relations of 106 cowpea accessions under progressive drought stress, which, in combination of genome-wide association study (GWAS), enables genetic mapping of the complex, stomata-related drought responsive traits “critical soil water content” (θcri) and “slope of transpiration rate declining” (KTr). The 106 accessions showed large variations in θcri and KTr, indicating that they had broad spectrum of stomatal control in response to soil water deficit, which may confer them different levels of drought tolerance. Univariate GWAS identified six and fourteen significant SNPs associated with θcri and KTr, respectively. The detected SNPs distributed in nine chromosomes and accounted for 8.7–21% of the phenotypic variation, suggesting that both stomatal sensitivity to soil drought and the speed of stomatal closure to completion were controlled by multiple genes with moderate effects. Multivariate GWAS detected ten more significant SNPs in addition to confirming eight of the twenty SNPs as detected by univariate GWAS. Integrated, a final set of 30 significant SNPs associated with stomatal closure were reported. Taken together, our work, by combining phenomics and genetics, enables forward genetic mapping of the genetic architecture of stomatal traits related to drought tolerance, which not only provides a basis for molecular breeding of drought resistant cultivars of cowpea, but offers a new methodology to explore the genetic determinants of water budgeting in crops under stressful conditions in the phenomics era.

Ebb-and-Flow Subirrigation Improves Seedling Growth and Root Morphology of Tomato by Influencing Root-Softening Enzymes and Transcript Profiling of Related Genes

“…Chlorophyll content is an important parameter reflecting the photosynthetic capacity of crops [73,74]. Net photosynthetic rate (Pn) reflects the plant photosynthetic capacity [75] and stomatal conductance (Gs) is closely related to plant stress resistance [76]. The water content of soil or substrate is closely related to plant photosynthesis [77,78].…”

Identification of Genomic Regions Associated with Fusarium Wilt Resistance in Cowpea

“…SNPs with the threshold of logarithm of odds (LOD) ≥ 2.5 were defined as significant SNPs. According to the cowpea linkage disequilibrium (LD) decay distance (350 kb) [18], the two significant SNPs within a same LD decay block were considered to represent the same QTL.…”

“…GWAS has been widely used in crops such as rice, corn, soybean and watermelon [16]. In cowpea, using the GWAS based on the Cowpea iSelect Consortium Array (Illumina, Inc., San Diego, CA, USA) containing 51,128 SNP markers, Xu et al (2017) [6] identified 72 SNPs associated with pod length, Lo et al (2018) [17] identified 17 SNPs for grain size and Wu et al (2021) [18] identified 30 SNPs loci for cowpea drought tolerance. The objective of this study was to screen the FW resistant accessions in Chinese cowpea germplasms and identified the genes/QTLs conferring FW resistance.…”

Editorial: Improvement for Quality and Safety Traits in Horticultural Plants

“…For example, non-destructive plant imaging combined with destructive leaf sampling allowed deep analysis of salt resistance (Berger et al, 2012 ). By employing non-destructive physiology-based phenomics assay, drought responses such as stomatal closure of tomato, cowpea and pepper were precisely and continuously phenotyped (Berger et al, 2010 ; Xu et al, 2015 ; Halperin et al, 2017 ; Dalal et al, 2019 ; Wu et al, 2021 ). Even though the phenomics characterization of quality and safety traits in horticultural crops has still been rare to date, a wave of phenomics-based technological revolution on phenotyping of these traits is expected to come soon in the near future.…”