STUDIES ON THE INFLUENCE OF PHOTOPERIOD AND TEMPERATURE ON FLORAL TRAITS IN BUCKWHEAT (FAGOPYRUM-ESCULENTUM MOENCH) UNDER CONTROLLED STRESS CONDITIONS

Floral traits of three Japanese and one European buckwheat varieties were studied in a phytotron under three photoperiods (short-day 10/14 h, long-day 14/10 h, extreme long-day 18/6 h) and two thermoperiods (25/20, and 15-degrees-C constant temperature). The Japanese varieties showed a strong delay in flowering under prolonged day length, whereas one European variety reacted almost day-neutral. Also affected by the photoperiod were the number of flower clusters as well as their sizes. A constant low temperature of 15-degrees-C led to a strong delay in flowering under short- and long-day in all the varieties tested. In particular, the Japanese varieties were sensitive to temperature, developing more flower clusters under high temperature. Futhermore the experiments revealed complex genotype/photoperiod/thermoperiod interactions. The study, conducted to investigate the causes of low seed-set observed in buckwheat, offered some suggestions for new breeding strategies. Insensitive genotypes, showing less sensitivity to photoperiod as well as to thermoperiod, should be included in further buckwheat improvement.