Study on the resistance components in ۳۳ commercial potato cultivars to Colorado potato beetle, Leptinotarsa decemlineata (Col.: Chrysomelidae)

Greenhouse and field experiments were conducted to evaluate the resistance components in ۳۳ potato commercial cultivars to Colorado potato beetle, Leptinotarsa decemlineata (Say) in ۲۰۰۸. In a field choice test, the numbers of attracted beetles to the cultivars was determined as antixenosis index. To evaluate the antibiosis, potato tubers were planted in pots under greenhouse conditions and on each pot, one sleeve cage was set up, in which ۱۵ first instar larvae were released and reared. The Larval weight after ۱۲ days of releasing, mortality percentages of larvae and pupae and the durations of developmental stages were analyzed as the antibiosis indices. To study the level of tolerance of cultivars, the infested and non infested plots were isolated and arranged based on a randomized complete block design in field. In infested plots, each plant was infested by ۴۰ medium larvae (second and early third instars) ۱۵ days prior to the blooming of plants. At the end of the season, defoliation and yield loss among infested plots were determined and compared to non infested plots for each cultivar. Significant differences were observed in all studied traits. The cultivars Cardinal, Carlita and Sinja showed antixenosis effects with the least numbers of attracted beetles, whereas cultivars Carlita, Sinja, Delikat, Aparet and Bridjet showed antibiosis effects in comparison to the others. The cultivars Santana, Satina, Nicola and Bridjet showed tolerance to damage of the pest. Using cluster analysis, UPGMA procedure was based on Euclidean distance and ۳۳ experimental cultivars were grouped in ۷ distance groups.