Reaction of Ten Commercial Potato Cultivars to Wireworms and Influence of Type and Amount of Tuber's Sugars on Infestation Rate

During 2001-2003, in an experiment, ten commercial potato cultivars Diamond, Aula, Agria, Concord, Marfona, Ajax, Desire, Santana, Picasso and Kozima were planted in a randomized complete block design with three replications. The experiment was conducted in a wireworm infested field, in Shahr-e-Kord region. Wireworm specimens in this region were collected by pheromone traps and determined. Common cultural practices, without insecticide use, were applied during the experiment. At harvest time, percentage of wireworm infested tubers were determined by counting number of tubers with more than 2mm feeding holes. Ten medium sized unattacked tubers were also randomly selected and amount of sucrose, glucose and fructose were assessed in them using HPLC. Data were analyzed and means were compared using Duncan’s test. Linear correlation were observed between infestation percentage and amount of different sugars, as well as sugar sum. Results showed significant differences among cultivars for infestation percentage, as well as for amount of glucose and fructose and sugar sum, at levels of 0.01, 0.05, 0.01 and 0.05, respectively. Ajax and Agria, having the highest and lowest infestation percentages, showed significant difference with other cultivars and arranged in separate groups. Comparison of cultivars for sugar showed that these two cultivars had the highest and lowest amount of each sugar and sugar sum. For sucrose, no significant difference was found among cultivars, while for glucose and fructose Ajax and Agria significantly differed from other cultivars and arranged, in separate groups. Correlation coefficients between infestation percentage and amount of sucrose,glucose, fructose and sugar sum were significant at levels of 0.05, 0.01, 0.01 and 0.01, respectively. It seems that sugar amount of tubers influences percentage of infestation, and effects of glucose and fructose are greater than sucrose.