Temperature and photoperiod affected time of flowering in ‘Red Kidney’ and ‘Great Northern UI 1’ varieties of dry beans. ‘Great Northern-1’ was delayed in flowering under 18-hr photoperiod and the low temperature of 60°F night and 70° day. However, at higher temperatures it flowered normally under all photoperiods. ‘Red Kidney’ on the other hand was delayed under 18-hr photoperiod and high temperatures, above 85° day and night temperatures 70° or higher. It was relatively insensitive to photoperiod under the low temperature, and under the medium temperature of 70° night and 80° day.
Studies of the flowering response of parental and hybrid populations under 18-hr photoperiod and the high, medium and low temperature conditions indicated that ‘Red Kidney’ and ‘Great Northern-1’ differ by 2 major temperature-sensitive genes. ‘Red Kidney’ has a dominant gene Ht which causes delayed flowering at temperatures above 85° and long photoperiod while ‘Great Northern-1’ has a dominant gene Lt which causes delayed flowering at temperatures below 75° and long photoperiod. The F1Htht Ltlt is delayed at all temperatures under long photoperiod.
Anatomical studies indicated that flower initiation had occurred under all photoperiod and temperature conditions but further development of floral primordia into flowers was delayed or completely inhibited under the conditions responsible for delay.