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

Abstract

The 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.

Host resistance and influence of tuber surface on larval performance of potato tuberworm (Lepidoptera: Gelechiidae)

“…We also found evidence of post-larval invasion resistance ("cortex and Xesh resistance") similar to that reported earlier by Malakar-Kuenen and Tingey (2006) and Horgan et al (2007). Tuber resistance mediated by cortex and Xesh resistance mechanisms has the potential to provide useful supplemental defense against PTW losses in longer term potato storage.…”

“…While our Wndings indicate that intact tuber periderm provides similar levels of protection against PTW for both resistant and susceptible potato clones, the relative magnitude of periderm-mediated defense diminishes with tuber sprouting. Horgan et al (2007) reported similar Wndings in assays of tubers of the wild species, S. berthaultii and S. tarijense. Periderm appears to provide resistance in stored potato tubers against PTW prior to the loss of dormancy and the development of sprouts.…”

The Journey of the Potato Tuberworm Around the World

“…In contrast, the amount of information to improve potato genotypes against P. operculella is still lacking [225]. Cultivated potatoes have more than 100 tuber-bearing relatives native to the Andes of southern Peru; among them, Solanum chiquidenum L. and Solanum sandemanii L. for instance, which are highly resistant to P. operculella, damage in tubers [226]. The nutritional value of the host is an important resistance factor limiting normal growth and development of P. operculella [227].…”

The Potato Tuberworm: A Literature Review of Its Biology, Ecology, and Control

“…The evaluation of potato germplasm for resistance to potato tuberworm is valuable to developing integrated tuberworm management (Horgan et al 2007); however, no fully recognized resistance cultivar has been bred to date. Few attempts have been made to identify plant cultivars resistant to tuberworm (Foot 1976a;Raman and Palacios 1982;Musmeci et al 1997;Arnone et al 1998;Musmeci et al 2005).…”