Genetic studies on cold tolerance in snap bean (Pltaseolus vulgaris L.) [electronic resource].

Includes references.

Crosses between snap bean cultivars, i.e., Paulista, Oxyra and Bronco (tolerant to cold) and Primera, Samantha and Giza-6 (susceptible to cold) were made to study the inheritance and nature of cold tolerance and some related characters. Cold tolerance, Earliness and total green pod yield per plant were found to be inherited quantitatively. Partial dominance were detected for high cold tolerance, high number of days calculated from sowing date to the first flower bud anthesis and high total green pod yield per plant over low levels of these characters. The estimates of broad sense heritability ranged from 47.59% to 82.470/0, 47.000/0 to 63.46% and 58.678/0 to 60.95%, while those of the narrow sense heritability ranged from 39.44% to 58.01%,9.73% to 38.05% and 24.90 to 40.27% for cold tolerance, earliness and total green pod yield per plant, respectively. The minimum number of effective gene pairs controlling cold tolerance, earliness and total green pod yield per plant ranged from I to 4, I to 4 and I to 5 gene pairs, respectively. There were highly significant differences between parents, FI, F2, Bel and B~ populations of the crosses Paulista x Samantha and Oxyra x Giza-6 in photosynthetic pigments (chlorophyll a, b and total carotenoides) and sugars content (reducing, non-reducing and total). The cultivar Oxyra. which was tolerant to low temperature, had the highest contents of photosynthetic pigments and sugars, while the cultivar Giza-6, which was susceptible to low temperature, had the lowest content. Cold tolerance was positively correlated with each of number of days from planting date to the first flower bud anthesis, number of branches per plant, number of pods per plant, fruit set percentage and total green pod yield per plant in the F2 populations of all crosses, and with each of reducing, non-reducing and total sugars, chlorophyll a, b and total carotenoides in the F2 populations of the crosses Paulista x Samantha and Oxyra x Giza-6. .In the crosses Paolista x Primera and Bronco x Giza-6, number of days from planting date to the first flower bud anthesis, number of branches per plant, number of pods per plant, fruit set percentage, and total green pod yield per plant were found to have a significant combined effect on cold tolerance. Moreover, in the crosses Paulista x Samantha and Oxyra x Giza-6, the combined effect of number of days from planting date to the first flower bud anthesis, number of branches per plant, number of pods per plant, fruit set percentage, total green pod yield per plant, total sugars and chlorphyll a was significantly correlated with cold tolerance.

Summary in Arabic.

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