GENETIC-CONTROL OF LOW-TEMPERATURE TOLERANCE IN GERMINATION OF THE COMMON BEAN (PHASEOLUS-VULGARIS L)

Cultivars tolerant to low temperature during the germination and emerg ence stages and carriers of the grain quality standards demanded by co nsumers are needed to increase the success of irrigated common bean in Southern Minas Gerais State. To study the genetic mechanisms controll ing these traits and assess the possibility of generating the desirabl e materials, a diallel cross involving ten cultivars including introdu ctions and pure lines from the breeding program of ESAL was carried ou t. Speed of germination of the F-2 generation from the crosses was ass essed under laboratory conditions at 12 degrees C. The diallel analysi s 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 germ ination 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 obs erved either for germination percentage or germination speed. The pare nts 'A-488', 'Small White' and 'Rio Vermelho' showed the greatest gene ral combining ability. Additive genetic effects predominated for both traits. Our results suggest that cold tolerance can be bred successful ly into commercially acceptable cultivars.