Inheritance and Morphological Traits of a Phytochrome‐controlled Single Gene in Bean¹

Three bean ( Phaseolus vulgaris L.) lines that changed from indeterminate non‐climbing bush to indeterminate climbing, with control by the red/far‐red light ratio, were crossed with a line which remained an indeterminate non‐climbing bush under all red/far‐red ratios. The climbing trait was found to be controlled by one major gene based on segregation data in F 2 and backcross progeny from crosses to both parents. Red light stimulated the activity of this dominant allele and far‐red light retarded it. As climbing occurred, internode elongation was greater in climbing than non‐climbing plants. Genetic control of flowering sensitivity to long‐day photoperiod was independent of the gene for climbing vs. non‐climbing growth habits. It was concluded that flowering and climbing are two genetically independent phytochrome‐controlled responses.