Physiological Maturity and Vigor in Production of ‘Florida Staysweet’ Shrunken‐2 Sweet Corn Seed

Abstract

Shrunken‐2 (sh‐2) sweet corn (Zea mays L.) exhibits relatively poor germination and seedling vigor. Early harvest is sometimes advocated for avoidance of seedborne fungi. Our objectives included studying the effect of maturity on seed vigor, defining physiological maturity, and optimizing vigor testing. Six crops of ‘Florida Stay sweet’ seed were produced in 1987 and 1988 and harvested 22 to 90 days after silking (DAS). Maximum kernel dry weight was obtained 43 to 47 DAS except for very late (mid‐June) plantings, which required 48 and 66 DAS. Decline in kernel moisture content was linear. Unreated seed, harvested 72 to 75 DAS from mid‐April plantings. produced an 80% stand in the field the following year. Harvest at maximum dry weight (43 to 47 DAS) produced final stands of 20% of lower. Delaying planting of the seed crop until mid‐May resulted in a decrease of maximum attainable field emergence to 50% in 1987 but not in 1988. Delaying planting until mid‐June lowered maximum attained field emergence to 30% in 1987 and 40% in 1988. laboratory germination test maxima preceded field emergence maxima by 12 to 26 d. Black layer formation preceded low vigor resulting from immaturity. The soil cold test, accelarated aging, and mean leachate conductance (ASA 610) were more highly correlated wiht final stand (median r = 0.87, 0.85, and ‐0.88, respectively) than was rolled‐towel germination (median r = 0.71). In conclusion, early harvest (45 to 60 DAS) resulted in seed with high germination and low vigor. Leaving the crop in the field as long as 80 to 90 DAS resulted in consistent production of relatively high vigor seed, as long as the crop was not planted very late (mid‐June).