Cotton (Gossypium spp.) is a major source of natural fiber and an important cash crop. The cotton growth habit and architecture determine its productivity and influence management strategies for commercial production. The GATA transcription factors (TFs) control various developmental processes in plants, such as flower, bract and embryo development, and petal differentiation. As stable transformation is still a bottleneck in many plant species, TRV-VIGS was used to manipulate gene expression in different plants, including Gossypium hirsutum L. In this study, we undertook the TRV-based VIGS to functionally characterize two candidate genes, Gohir.D05G103700 and Gohir.D12G153600, identified through expression QTL analysis for five floral induction and meristem identity genes using the upland cotton mini-core collection. Virus-induced silencing of the Gohir.D05G103700 gene resulted in up to a 1.4-fold reduction in the transcript level in two inoculated plants, G3 and G4, and Gohir.D12G153600 gene resulted in up to a 2.3-fold reduction in transcript level in a single inoculated plant P05 relative to the mock-treated plant. The TRV2-Gohir.D05G103700-inoculated plants G3 and G4 also exhibited loss of the supernumerary (fourth) floral bract in the squares, whereas the TRV2-Gohir.D12G153600-inoculated plants did not show any observable phenotypic change relative to the mock-treated plants. Altogether, this study suggested that TRV-VIGS can be used to characterize genes in cotton relatively rapidly, and the cotton Gohir.D05G103700 gene is a positive regulator of the indeterminate growth habit in cotton, which could be manipulated to obtain a cotton plant with architecture best suited for the cultivation area.

Cotton (Gossypium spp.) is the primary source of natural textile fiber in the U.S. and a major crop in the Southeastern U.S. Despite constant efforts to increase the cotton fiber yield, the yield gain has stagnated. Therefore, we undertook a novel approach to improve the cotton fiber yield by altering its growth habit from perennial to annual. In this effort, we identified genotypes with high-expression alleles of five floral induction and meristem identity genes (FT, SOC1, FUL, LFY, and AP1) from an Upland cotton mini-core collection and crossed them in various combinations to develop cotton lines with annual growth habit, optimal flowering time, and enhanced productivity. To facilitate the characterization of genotypes with the desired combinations of stacked alleles, we identified molecular markers associated with the gene expression traits via genome-wide association analysis using a 63 K SNP Array. Over 14,500 SNPs showed polymorphism and were used for association analysis. A total of 396 markers showed associations with expression traits. Of these 396 markers, 159 were mapped to genes, 50 to untranslated regions, and 187 to random genomic regions. Biased genomic distribution of associated markers was observed where more trait-associated markers mapped to the cotton D sub-genome. Many quantitative trait loci coincided at specific genomic regions. This observation has implications as these traits could be bred together. The analysis also allowed the identification of candidate regulators of the expression patterns of these floral induction and meristem identity genes whose functions will be validated.

Soybean is the primary oilseed crop in the United States, with significant industrial value. Understanding the molecular mechanisms of heat stress tolerance in soybean plants is critical for developing stress-resistant cultivars. Current knowledge about the role of fatty acid desaturases (FADs) in modulating membrane fluidity under abiotic stress prompted this investigation into the impact of mutations in the FAD genes on seed germination from heat-stressed plants. In soybean plants, exposure to heat stress during anthesis is known to significantly reduce seed germination. In silico expression analysis indicated high expression levels of the soybean FAD2 and FAD3 genes in the leaves. Therefore, a detailed expression analysis of these genes was conducted using qRT-PCR from leaf tissue. Generally, downregulation of these genes was observed in the mutants; however, two genes, FAD3A and FAD2-3, showed a more than 2-fold increase in expression in six out of ten mutants under heat stress. This upregulation was particularly pronounced (7-fold) in the mutant S17CR-170. Correlation analysis revealed a positive correlation (up to 0.48) between the expression level of FAD3A, FAD3B, FAD3C, and FAD2-3 and the decline in germination from heat-stressed plants. This suggests these FAD genes may act as negative regulators of germination under heat stress conditions.

Cotton (Gossypium spp.) is a major source of natural fiber and an important cash crop. The cotton growth habit and architecture determine its productivity and influence management strategies for commercial production. The GATA transcription factors (TFs) control various developmental processes in plants, such as flower, bract and embryo development, and petal differentiation. As stable transformation is still a bottleneck in many plant species, TRV-VIGS was used to manipulate gene expression in different plants, including Gossypium hirsutum L. In this study, we undertook the TRV-based VIGS to functionally characterize two candidate genes, Gohir.D05G103700 and Gohir.D12G153600, identified through the expression QTL analysis for five floral induction and meristem identity genes using the upland cotton mini-core collection. Virus-induced silencing of the Gohir.D05G103700 gene resulted in up to a 1.4-fold reduction in the transcript level in two inoculated plants, G3 and G4, and Gohir.D12G153600 gene resulted in up to a 2.3-fold reduction in transcript level in a single inoculated plant P05 relative to the mock-treated plant. The TRV2-Gohir.D05G103700 inoculated plants precisely G3 and G4 also exhibited loss of the supernumerary (fourth) floral bract in the squares, whereas the TRV2-Gohir.D12G153600 inoculated plants did not show any observable phenotypic change relative to the mock-treated plants. Altogether, this study suggested that TRV-VIGS can be used to characterize genes in cotton relatively rapidly and the cotton Gohir.D05G103700 gene is a positive regulator of the indeterminate growth habit in cotton, which could be manipulated to obtain a cotton plant with architecture best suited for the cultivation area.

Cotton is an economically important crop. However, the yield gain in cotton has stagnated over the years, probably due to its narrow genetic base. The introgression of beneficial variations through conventional and molecular approaches has helped broaden its genetic base to some extent. The growth habit of cotton is one of the crucial factors that determine crop maturation time, yield, and management. This study used 44 diverse upland cotton genotypes to develop high-yielding cotton germplasm with reduced regrowth after defoliation and early maturity by altering its growth habit from perennial to somewhat annual. We selected eight top-scoring genotypes based on the gene expression analysis of five floral induction and meristem identity genes (FT, SOC1, LFY, FUL, and AP1) and used them to make a total of 587 genetic crosses in 30 different combinations of these genotypes. High-performance progeny lines were selected based on the phenotypic data on plant height, flower and boll numbers per plant, boll opening date, floral clustering, and regrowth after defoliation as surrogates of annual growth habit, collected over four years (2019 to 2022). Of the selected lines, 8×5-B3, 8×5-B4, 9×5-C1, 8×9-E2, 8×9-E3, and 39×5-H1 showed early maturity, and 20×37-K1, 20×37-K2, and 20×37-D1 showed clustered flowering, reduced regrowth, high quality of fiber, and high lint yield. In 2022, 15 advanced lines (F₈/F₇) from seven cross combinations were selected and sent for an increase to a Costa Rica winter nursery to be used in advanced testing and for release as germplasm lines. In addition to these breeding lines, we developed molecular resources to breed for reduced regrowth after defoliation and improved yield by converting eight expression-trait-associated SNP markers we identified earlier into a user-friendly allele-specific PCR-based assay and tested them on eight parental genotypes and an F₂ population.

Soybean is the primary oilseed crop in the United States, with significant industrial value. Understanding the molecular mechanisms of heat stress tolerance in soybean is critical for developing stress-resistant cultivars. Current knowledge about the role of fatty acid desaturases (FADs) in modulating membrane fluidity under abiotic stress prompted this investigation into the impact of mutations in the FAD genes on seed germination from heat-stressed plants. In soybean, exposure to heat stress during anthesis is known to significantly reduce seed germination. In silico expression analysis indicated high levels of expression of the soybean FAD2 and FAD3 genes in leaves. Therefore, a detailed expression analysis of these genes was conducted using qRT-PCR from leaf tissue. Generally, downregulation of these genes was observed in the mutants; however, two genes, FAD3A and FAD2-3, showed a more than 2-fold increase in expression in six out of ten mutants under heat stress. This upregulation was particularly pronounced (7-fold) in mutant S17CR-170. Correlation analysis revealed a positive correlation (0.5) between the expression level of FAD3A, FAD3B, FAD3C, and FAD2-3 and the decline in germination from heat-stressed plants. This suggests these FAD genes may act as negative regulators of germination under heat stress conditions.