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The impacts on soybean seed quality from shifting to using earlier soybean planting dates (PDs) and earlier‐maturing varieties in the southeastern United States are not well understood. The objective of this study was to determine the impact of diverse PDs and maturity groups (MGs) on soybean protein content, oil content, seed damage, and purple seed stain. Studies were installed across seven North Carolina locations in 2019 and 2020 to determine the impact of PD (mid‐March through mid‐July) and MG (2–7) on seed quality. Protein content declined as planting was delayed for the early MGs (2–5) but was stable across PD for the later MGs (6–7). It was observed that early‐maturing varieties (MG ≤5) had a lower protein content than the later‐maturing varieties (MGs 6–7). The oil content was greater in the early MGs (MGs 2–4) compared with the later MGs (MGs 5–7), with oil content and protein content having an inverse relationship. Seed damage was greatest when planting before late April with early MGs (MGs 2–4). Less purple seed stain was found in MGs 5–7 compared with the earlier MGs across all PDs. Further research is needed to understand how to minimize seed damage and purple seed stain as producers consider shifting to an earlier production system for the associated yield benefits in North Carolina and across the southeastern United States. Core Ideas: Early‐maturing varieties had a lower protein content than later‐maturing varieties.Protein content was consistent across planting date for later‐maturing varieties.Seed damage was greatest when planting before late April with early MGs (2‐4).Purple seed stain was lower in MGs 5‐7 compared with the earlier MGs across all planting dates. [ABSTRACT FROM AUTHOR]

Soybean [Glycine max (L.) Merr.] seed quality has declined in the mid-southern United States due to the shift to soybeans that mature during mid August through September as opposed to October to November, which was common in the past. This decline was shown to be related to increased temperatures during seed maturation, increased levels of Phomopsis seed decay (PSD), and potentially maturity per se. In this study, the effects of maturity and Phomopsis longicolla Hobbs, the cause of PSD, on seed quality were evaluated in a field trial of two sets of near-isogenic soybean lines ('Clark' and 'Harosoy'), where the maturity of each line within a set varied. No effects of maturity on germination, accelerated aging germination (AA), or hardseededness were detected. Phomopsis longicolla level had a significant negative effect on germination in both isoline sets. Year had a significant effect on germination in both isoline sets. In addition, year and P. longicolla level had a significant negative effect on AA for the Clark set, and only year had an effect on AA in the Harosoy set. Phomopsis longicolla level, not maturity, was the most significant factor in seed germination and vigor. Therefore, there continues to be a great need to develop varieties of soybeans with resistance to P. longicolla and high germinability when seed are produced in conditions of high humidity and high temperatures. [ABSTRACT FROM AUTHOR]

Soybean mosaic virus (SMV) is one of the most important viral diseases, causing drastic reductions in seed yield and quality. Seven SMV strains, G1 through G7, have been identified, and three resistance loci, Rsv1, Rsv3, and Rsv4, have been reported in the United States. The objectives of this study were to evaluate the reactions of a set of modern soybean [Glycine max (L.) Merr.] cultivars to SMV and to deduce which previously reported genes were involved in resistance. A total of 303 cultivars currently grown in the mid-southern United States were screened in the greenhouse with six SMV strains (G1, G2, G3, G5, G6, and G7). The results demonstrated that 189 cultivars were susceptible to all six SMV strains. Three cultivars were resistant to G1, G2, G3, G5, and G6 but developed stem-tip necrosis after infection with G7, so these were presumed to carry the Rsv1 allele. Sixty-six cultivars were resistant to G1 through G3 but susceptible to G5 through G7 and presumably carry Rsv1-y. One cultivar was resistant to G1 through G3 but necrotic to G5 through G7 and may carry Rsv1-k. Two cultivars probably carry Rsv1-t because they were resistant to G1, G2, G5, and G6 but necrotic to G3 and G7, and another two cultivars may carry Rsv1-n because they were necrotic to G1, G2, G5, and G6 but susceptible to G2 and G7. Four cultivars were susceptible to G1 through G3 but resistant to G5 through G7, and therefore they may carry Rsv3. Two cultivars were resistant to all six SMV strains, and therefore they may carry Rsv4, Rsv1-h, or two-gene combinations. There were 34 cultivars exhibiting unique SMV reaction patterns that may carry novel genes or alleles, including 23 cultivars that may carry novel alleles at the Rsv1 locus and 11 that may carry novel alleles at the Rsv3 locus. The results from this study can be used by breeders to choose resistant cultivars as parents in soybean breeding programs and by producers to select resistant cultivars in areas where SMV is a disease of concern for soybean production. [ABSTRACT FROM AUTHOR]