REPRODUCTIVE DEVELOPMENT OF 8 WHEAT CULTIVARS AND A TRITICALE AS INFLUENCED BY SOWING DATE

Vernalization generally is required for adaptation of winter cereals to temperate climates and is basic to breeding and selection of new cultivars. The objective of this study was to assess the reproductive development of eight winter-sown wheat (Triticum aestivum L.) cultivars and a triticale (x Triticosecale Wittmack) as related to vernalization and heat accumulation using sequential sowing dates at four environments. The study was conducted at Gainesville, FL (29-degrees 38' N lat); Quincy, FL (30-degrees 36' N lat); and Griffin, GA (33-degrees 15' N lat), in 1987-1988 and was repeated at Gainesville in 1988-1989. Seed of cultivars were sown in field plots, beginning about 15 December and continued biweekly through 1 March. Cold and heat units were computed from Class AB weather-station air temperatures logged daily. Spring-type wheat cultivars Florida 301, Florida 303, and Owens and Beagle 82 triticale developed spike primordia after almost-equal-to 2 mo and headed in 100 to 120 d, irrespective of vernalization. Intermediate winter cultivars Florida 302, Hunter, and Phoenix had not initiated spikes by almost-equal-to 3 mo, and headed only if sown on or before 15 February. In contrast to this response in 1987-1998, Hunter headed irrespective of sowing dates at Gainesville in 1988-1989. Cultivars Coker 983 and Caldwell required vernalization, and headed only if sown by December in the warmer year (1988-1989) or if sown in December or January in the colder year (1987-1988). We conclude that spring-type wheat cultivars and triticale reproduce normally without vernalization, and are adapted to a broad range of latitudes and sowing dates in southern USA. Winter-type cultivars require vernalization and should be seeded in early winter at lower latitudes.