PREDICTION OF SWEET CORN PHENOLOGY IN SUBTROPICAL ENVIRONMENTS

Limited information on phenology of sweet corn (Zea mays L.) grown in subtropical regions is available to processors wishing to manage harve st scheduling. This study was conducted to investigate developmental c haracteristics of both standard sugary (su) and mutant endosperm sugar y enhancer (se), and shrunken-2 (sh2) sweet corn in subtropical Austra lia. Field experiments were conducted at three locations with numerous times of planting so that a broad range of environments were encounte red. Models of daily rate of development for the period sowing to kern el maturity (720 g kg-1 moisture) were derived by an iterative optimiz ation procedure. Development rate was related to mean daily temperatur e and photoperoid. Temperature was the most important factor affecting rate of development. The temperature response was best described by a broken linear function. Various photoperiod functions fitted as multi pliers to the temperature response did not improve goodness-of-fit. Cu ltivars were classified into three maturity groups based on analysis o f covariance. Developmental characteristics appeared independent of ge netic background as the response of the three sh, cultivars was not si gnificantly different from a tropical su type, and the se cultivar 'Sw eet Champion' did not differ significantly from the majority of su typ es. Only su cultivar 'Terrific' differed significantly from both of th ese groups. Base temperatures (range from 5.4-6.4-degrees-C) were lowe r than the value traditionally quoted for sweet corn (10-degrees-C). O ptimum rates of development occurred at temperatures ranging from 30.8 to 33.8-degrees-C. The models accurately predict the duration of sowi ng to maturity and were shown to be a practical tool for harvest date prediction of both standard and mutant endosperm sweet corn in subtrop ical environments.