Genetic control of low temperature tolerance in germination of the common bean (Phaseolus vulgaris L.)

Cultivars tolerant to low temperature during the germination and emergence stages and carriers of the grain quality standards demanded by consumers are needed to increase the success of irrigated common bean in Southern Minas Gerais State. To study the genetic mechanisms controlling these traits and assess the possibility of generating the desirable materials, a diallel cross involving ten cultivars including introductions and pure lines from the breeding program of ESAL was carried out. Speed of germination of the F sub(2) generation from the crosses was assessed under laboratory conditions at 12 degree C. The diallel analysis was carried out using Griffing's method IV (1956) and predictions of the cross potential were made by the methodology developed by Jinks & Pooni (1986). The results indicated that the parents differed in germination speed at low temperatures with 'Small White', 'A-488' and 'Rio Vermelho' being the most tolerant and 'Carioca', 'ESAL 609' and 'ESAL 591' the most sensitive. No effect of the reciprocal crosses was observed either for germination percentage or germination speed. The parents 'A-488', 'Small White' and 'Rio Vermelho' showed the greatest general combining ability. Additive genetic effects predominated for both traits. Our results suggest that cold tolerance can be bred successfully into commercially acceptable cultivars.