Inheritance of freezing stress in South African potato (Solanum tuberosum) germplasm

[摘要] English: a) Frost damage caused by freezing stress is a major problem for potato growers in some parts of South Africa. In this study two South African potato cultivars, Darius and BP1, were compared for yield loss due to freezing stress during the late vegetative, early reproductive and late reproductive growth stages. The cultivars were subjected to temperatures of -2°C and -4°C for three and six hours. Significant genotype x treatment interactions were observed for stem and leaf damage in both cultivars. Genotype x treatment interactions were also significant for yield and some of the yield components. The cultivars were shown to be the most sensitive to freezing stress during the early reproductive growth stage, followed by the late reproductive growth stage. BP1 was identified to be more sensitive to freezing stress in the early and late reproductive growth stages. Stem damage was positively associated with tuber number, whereas leaf damage correlated with tuber mass. b) Electrophoretic separations of proteins were done to study the polymorphisms as a result of freezing stress at -2°C and -4°C for three and six hours. The plants were treated during the late vegetative, early reproductive and late reproductive growth stages. The freezing treatments caused large variability in the protein profiles of Darius. Various new protein bands developed while others disappeared. Differences in the intensity of the bands were also recovered. A protein band of approximately 29/33 kDa developed consistently at -2°C treatment during the early reproductive growth stage. Plants subjected to -4°C for three and six hours developed protein bands of approximately 40/49 kDa during the three growth stages tested. c) In this study fourteen selected C1 progenies of a Caren x Bravo cross with the two parents were included, subjected to freezing temperatures of -4°C for four hours to study the heritability of potato yield under freezing stress conditions. The plants were treated during the early reproductive growth stage (the most sensitive growth stage). Freezing stress (-4°C) treatment during the early reproductive growth stage reduced potato yield, tuber diameter, tuber mass and number of tubers significantly. Significant genetic variability was found among offspring for leaf damage, yield, tuber diameter, tuber mass and number of tubers under freezing stress conditions. Tuber diameter (r=0.56), tuber mass (r=0.86) and number of tubers (r=0.75) were significantly correlated with yield for percentage damage caused by freezing stress. The freezing treatment had no significant effect on the correlation coefficients between potato yield and yield components. Relatively high broad sence heritabilities were recorded for potato yield (h2 =0.74) tuber diameter (h2=0.91), tuber mass (h2=0.87) and number of tubers (h2=0.79).

[发布机构] University of the Free State