Periderm‐ and cortex‐based resistance to tuber‐feeding Phthorimaea operculella in two wild potato species

Abstract

AbstractThe trichome‐bearing wild potatoes Solanum berthaultii (Hawkes) and Solanum tarijense (Hawkes) (Solanaceae) have noted resistance to leaf‐feeding insect herbivores; however, little is known about their resistance to tuber‐feeding herbivores. This study evaluates resistance in tubers of these two species to attack by the potato tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae). Tubers from a range of accessions were presented to recently emerged neonate tuber moth larvae. Resistance to neonates varied between accessions and was generally higher in accessions of S. tarijense. The contribution to observed resistance of periderm vs. cortex factors was assessed by perforating tuber periderm in paired‐tuber experiments. Across species and accessions, an average of 62% of resistance was attributed to periderm‐related factors. All larvae entered tubers through the eyes. Unidentified cortex‐related factors affected larval development time and pupal weight. Sprouting compromised resistance by reducing the protective value of the periderm. The degree of sprouting also decreased larval development times and increased pupal weights in one of two accessions examined. These results demonstrate the potential of S. berthaultii and S. tarijense as sources of tuber‐resistance and identify accessions of both species with notably high periderm‐based protection. Levels of periderm resistance were not correlated to levels of cortex resistance and represent an independent resistance source compatible with the food value of crop potato.