PLANT GROWTH REGULATORS AND ELECTRIC CURRENT BREAK TUBER DORMANCY BY MODULATING ANTIOXIDANT ACTIVITIES OFPOTATO

Abstract

Potato (Solanum tuberosum L.) is an important food crop in Pakistan and produced twice or more in a year. Its tubers undergo a certain period of dormancy after the harvest and are incapable to sprout which can limit their usage as seed for the next season. Therefore, this study was planned to break the tuber dormancy using plant growth regulators and electric current. For this purpose, three experiments were conducted from April 2015 to July 2016 with the objectives: i) to screen out genotypes based on their dormancy duration and ii) to assess the effects of two dormancy breaking methods on seed tuber dormancy breakage, hydrogen peroxide contents and antioxidative activities at one and three week storage. The first experiment comprised of 22 equal number of white and red skin potato genotypes. Mean dormancy ranged from 36 to 85 days in these genotypes, including FD51-5 and PRI Red in short-term dormancy group; Sante and FD73-49 in medium-term dormancy group and FD69-1 and FD8-1 in long-term dormancy group. The secondexperiment consisted of above screened genotypes and three levels of benzyl aminopurine (30, 60 and 90 mgL-1) and gibberellic acid(10, 20 and 30 mgL-1). The solution of 60 mgL-1benzyl aminopurine significantly reduced the dormancy duration in all genotypes but did not have a significant effect on the sprout outgrowth. While, 20 mgL-1GA3produced maximum sprout length with non-significant effect on dormancy duration. The genotype × PGR interaction was more pronounced in short and medium-term dormancy genotypes than in long-term dormancy genotypes. The third experiment also consisted of above six genotypes with five levels of electric current (0, 20, 40, 60 and 80 volt). The use of electric current was most effective at 80 volt for shortening tuber dormancy and inducing sprout length. Hydrogen peroxidecontents, superoxide dismutase and ascorbate peroxidase activities after treatment with plant growth regulators and electric current increased with dormancy progression. In contrast, catalase and peroxidase activities decreased. Our results indicate that enhanced antioxidative activity is closely associated with the effect of applied treatments, storage period, genotypes and genotype × storage period. Nevertheless, further research should be continued to evaluate the combined effect of BAP and GA3on dormancy termination.