Corn seed germination and vigor following freezing during seed development

The potential for an early autumn frost to reduce corn (Zea mays L.) seed quality is a concern for seed producers. This study evaluated the effect of freezing rate, freezing temperature (-6, -11 degrees C and duration (4,6 h), ear attachment, and endosperm composition on seed germination and vigor (accelerated aging [AA] and cold test) during seed development and maturation of six corn hybrids in 1998, 1999, and 2000. Severe reductions in seed germination and vigor occurred for the most immature seeds frozen at > 400 g kg(-1) seed moisture content (SMC). The effect was reduced as seed developed for all hybrids resulting in a linear increase in germination and vigor to maximum levels at <= 300 g kg(-1) seed moisture, which was slightly after physiological maturity (PM, maximum dry seed weight). The effect of freezing on seed germination and vigor was the same when (i) ears were frozen attached or detached from the plant; (ii) ears were exposed to different freezing rates; or (iii) seeds with sugary and starchy endosperm were frozen. The degree of freezing injury at a given temperature and duration of freezing was similar across four F, hybrids, but seed from one F-2 hybrid was injured slightly less at a given moisture content. Thus, the stage of seed development must be considered by seed companies before making harvesting decisions when facing a potential predicted freezing event. Our results suggest that a seed producer will have higher germination and vigor if they harvest immature seeds (<= 400 g kg(-1) SMC) before the freezing event instead of after they are exposed to freezing temperatures.