Effect of hydrogen peroxide and thiourea on dormancy breaking of microtubers and field-grown tubers of potato.

Abstract

Potato (Solanum tuberosum L.) microtubers or field-grown tubers have a dormant apical bud (also called tuber dormancy). They do not readily sprout even if environmental conditions are favorable, including optimum temperature and humidity. The objective of this study was to evaluate the involvement of hydrogen peroxide (by direct or indirect application of thiourea, a catalase inhibitor) in dormancy release and sprouting of potato microtubers and tubers was evaluated using two complementary experiments. First, the kinetics of the sprouting (percentage of sprouted microtubers with time) was examined on microtubers planted in peat and cultivated in a glasshouse after exogenous application of different concentrations of hydrogen peroxide (20, 40 and 60 mM) and thiourea (250, 50 0 and 750 mM). Second, the sprouting kinetics was examined on field-grown tubers during storage, after application of hydrogen peroxide (20, 40, 60 and 80 mM) and thiourea (250, 500, 750 and 1000 mM). Their sprouting capacity was also evaluated. Then, kinetics of field emergence of treated and sprouted tubers was examined after planting them in a field. Direct application of hydrogen peroxide or application of catalase inhibition through thiourea application on the release of dormancy promote sprouting on potato microtubers and field-grown tubers. Results showed that hydrogen peroxide (20 mM) caused rapid and synchronous sprouting of microtubers; while higher concentrations (40 and 60 mM), caused asynchronous sprouting. Thiourea at a concentration of 250 mM was the most effective in reducing the dormancy period and increasing the number of sprouted microtubers. In field experiment, sprouting was optimal when tubers were treated with 60 mM of hydrogen peroxide; whereas at a lower concentration, sprouting was less stimulated. In addition, tubers treated with 250 mM thiourea had maximum sprouting and better sprouting  capacity. It is clear that both substances affect hormonal regulation and antioxidant enzymes, leading to dormancy release in both: microtubers and tubers.

Keywords: Antioxidant enzymes, potato, Solanum tuberosum, thiourea