ABSTRACT
Cercospora leaf blight (CLB), caused by Cercospora cf. flagellaris, C. kikuchii, and C. cf. sigesbeckiae, is a significant soybean [Glycine max (L.) Merr.] disease in regions with hot and humid conditions causing yield loss in the United States and Canada. There is limited information regarding resistant soybean cultivars, and there have been marginal efforts to identify the genomic regions underlying resistance to CLB. A Genome-Wide Association Study was conducted using a diverse panel of 460 soybean accessions from maturity groups III to VII to identify the genomic regions associated to the CLB disease. These accessions were evaluated for CLB in different regions of the southeastern United States over 3 years. In total, the study identified 99 Single Nucleotide Polymorphism (SNPs) associated with the disease severity and 85 SNPs associated with disease incidence. Across multiple environments, 47 disease severity SNPs and 23 incidence SNPs were common. Candidate genes within 10 kb of these SNPs were involved in biotic and abiotic stress pathways. This information will contribute to the development of resistant soybean germplasm. Further research is warranted to study the effect of pyramiding desirable genomic regions and investigate the role of identified genes in soybean CLB resistance.
ABSTRACT
Edamame is a food-grade soybean [Glycine max (L.) Merr.] that is harvested immature between the R6 and R7 reproductive stages. To be labeled as a premium product, the edamame market demands large pod size and intense green color. A staggered harvest season is critical for the commercial industry to post-harvest process the crop in a timely manner. Currently, there is little information to assist in predicting the optimum time to harvest edamame when the pods are at their collective largest size and greenest color. The objectives of this study were to assess the impact of cultivar, planting date, and harvest date on edamame color, pod weight, and a newly minted Edamame Harvest Quality Index combining both aforementioned factors. And to predict edamame harvest quality based on phenological stages, thermal units, and planting dates. We observed that pod color and weight depended on the cultivar, planting date, and harvest date combination. Our results also indicated that edamame quality is increased with delayed planting dates and that quality was dependent on harvest date with a quadratic negative response to delaying harvest. Maximum quality depended on cultivar and planting and harvest dates, but it remained stable for an interval of 18-27 days around the peak. Finally, we observed that the number of days between R1 and harvest was consistently identified as a key factor driving edamame quality by both stepwise regression and neural network analysis. These research results will help define a planting and harvest strategy for edamame production in Arkansas and the United States Mid-South.
ABSTRACT
Purple seed stain (PSS), caused by Cercospora kikuchii, is a prevalent soybean disease that causes latent seed infection, seed decay, purple seed discoloration, and overall quality deterioration. The objective of this research was to screen soybean accessions from the United States Department of Agriculture germplasm collection for resistance to PSS. In total, 123 plant introductions (PI) from 28 different countries, representing maturity groups (MG) III, IV, and V, were screened. Incidence of Cercospora leaf blight (% CLB), visual PSS (% PSS), and seed infected by C. kikuchii (% C. kikuchii) in harvested seed were determined. In 2007, % C. kikuchii was 2 to 51% for MG III, 2 to 35% for MG IV, and 0 to 33% for MG V. In 2008, % C. kikuchii was 0 to 45% for MG III, 1 to 71% for MG IV, and 0 to 15% for MG V. In total, four and ten PI from MG III and IV, respectively, were identified as resistant to PSS in both years. Highly positive correlations were found for inoculated versus noninoculated treatments and for % PSS versus % C. kikuchii infection. The PSS-resistant PI identified in this study will be valuable to breeders in developing resistant cultivars.
ABSTRACT
Natto is a popular soyfood in Japan, and the U.S. is the largest supplier of natto soybeans. However, information on natto seed chemical and sensory properties is very limited. The objectives of this study were to evaluate differences of seed chemical and sensory properties among natto types and determine heritability and correlation. A total of 15 small-seeded natto genotypes (three superior, nine moderate and three inferior) were evaluated for protein, oil, calcium, manganese, boron and sugar content and processed into a natto product to evaluate appearance, stickiness, flavor, texture and shelf-life. The superior natto group had a higher sugar content but lower protein plus oil, calcium, manganese and boron content than other two groups. Most seed quality traits exhibited high heritability. The natto sensory preference was positively correlated with sucrose and oil content, but negatively correlated with seed hardness, protein, protein plus oil, calcium, manganese, and boron contents. Selecting soybean lines with low protein, protein plus oil, calcium, manganese, and boron content while with high sucrose will be an effective approach for soybean breeding for natto production.