EFFECTS OF STORAGE ENVIRONMENT AND DURATION ON IMPERMEABLE SEED COAT IN SOYBEAN

Seed of commercially grown soybean [Glycine max (L.) Men.] cultivars have a highly permeable, or normal, seed coat (NSC) that allows them to imbibe water rapidly, sprout, and emerge uniformly when sown. The quality of such seed may decline, however, if they experience high temperature and humidity in the field before harvest or during storage. A possible solution is to use cultivars having an impermeable seed coat (ISC) characteristic. A study was conducted at Stoneville, Mississippi, using held-grown seed of Forrest and Sharkey (NSC cultivars) and D86-4565 and D87-4647 (ISC Lines) to evaluate the effect of storage environment and duration on impermeability and germination. Storage environments were: (1) a ventilated shed subject to prevailing temperature and humidity; (2) a cold room having a constant temperature of 10 degrees C; (3) an indoor laboratory with temperatures ranging from 21 to 27 degrees C; and (4) a standard freezer with a constant temperature of -2 degrees C. Germination and impermeability measurements were made at 1.5, 8, 15, and 20 months after harvest. Impermeability of seed of the ISC lines did not change significantly and germination of unscarified seed of all cultivars and lines was not appreciably affected by storage in the latter three environments. After storage in the shed, germination of Forrest and Sharkey declined from 96 to 12% and from 93 to 21% after 20 months, respectively, while germination of seed of the ISC lines that had been stored in the shed and then scarified had only declined from 96 to 78% (D87-4647) and from 98 to 75% (D86-4565). These results are evidence that the ISC character can maintain viability of soybean seed during long periods of storage under natural conditions of temperature and humidity.