Screening Methodology for Resistance to Field Weathering of Soybean Seed1

Abstract

Soybean [Glycine max (L.) Merr.] seeds may lose vigor prior to harvest, especially when grown in humid, tropical environments. This study compared three seed weathering treatments to identify soybean genotypes with resistance to field weathering of seed. Thirty‐five genotypes were planted in replicated trials on three dates and subjected to 1) field weathering (seeds were harvested 3 weeks after physiological maturity), 2) incubator weathering (pods at physiological maturity were detached from the plant and kept at 30°C and 90 to 95% relative humidity for 10 days), and 3) wet‐bag weathering (plants at physiological maturity were placed in wet burlap bags for 10 days). Under the wet‐bag treatment, extreme seed deterioration of nearly all genotypes tended to mask their differences in resistance. Incubator weathering was more consistent across experiments than field weathering. Mean seedling emergence scores varied less among experiments for incubator weathering (30, 28, and 22%) than for field weathering (78, 46, and 54%). The genotype ✕ planting date interaction accounted for 7 and 29% of the total sums of squares for incubator and field‐weathering, respectively, indicating that incubator weathering minimized environmental effects that would confound comparisons among genotypes of different maturity. The percentage of hard seed after 1 h of soaking ranged from 0 to 64% and was correlated (r = 0.73, P < 0.01) with seedling emergence following incubator weathering. Large‐seeded genotypes were generally susceptible to seed weathering and deterioration in storage. Some small‐seeded genotypes were resistant; others were susceptible. Black‐seeded genotypes were more resistant to incubator weathering than yellow‐seeded genotypes. Genotypes with a high percentage of seedling emergence following incubator weathering also had high seedling emergence after ambient storage. Genotypes identified as having resistance to weathering of seed and to deterioration in storage were: INDO 153, INDO 131, INDO 243, INDO 226, INDO 255, ‘Fort Lamy’, ‘Lee A’, INDO 173A, and ‘Biloxi 3’.