ARS | Publication request: Resistance of potato germplasm to the potato tuberworm (Lepidoptera: Gelechiidae)

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 2009
Publication Date: July 30, 2009
Citation: Rondon, S.I., Hane, D., Brown, C.R., Vales, M.I., Dogramaci, M. 2009. Resistance of potato germplasm to the potato tuberworm (Lepidoptera: Gelechiidae). Journal of Economic Entomology. J. Econ. Entomol. 102:1649-1653.

Interpretive Summary: Potatoes are very costly to grow because they are preyed upon by numerous pests. Potato tuberworm is a new pest in the Pacific Northwest. It invades field as a small nondescript brown moth. Larvae mine the stems causing relatively little damage. Toward the end of the season, the adult moths leave the foliage and enter the soil cracks until they find tubers, wher they then lay eggs. Upon hatching the larvae burrow into the tubers, immediately destroying the value of the tubers for any kind of use. Although expertly timed insecticide applications are being used to control the tuberworm, any increase in resistance to tuber damage would be a welcome addition to the management tools. The researchers in this study harvested tubers of diverse breeding materials and laid them out in the field for several weeks at the end of the season. The tuberworm pressure was quite high. In addition they placed newly harvested tubers in screened containers and manually placed eggs on the tubers. They found that there were significant differences natural genetic resistance to tuber damage that matched in the field and in containerized exposures. However, no level of natural resistance reached extreme resistance. The highest level of resistance would still alow for at least one larval penetration, a degree of damage considered unacceptable by the industry. Included in the tests was a single transgenic clone that expressed the Bacillus thuringensis gene CryIAa, which encodes a toxin effective against tuberworm. This clone did show zero damage in the field and in containers. As it is unacceptable in the marketplace at the present time, this is not a feasible solution in the United States and Canada. The natural resistance may be sufficient when combined with insecticides applied near the end of the growing season, or when combined with tillage practices that seal the soil and discourage descent of moths to the depth where tubers are found in the soil.

Technical Abstract: The evaluation of potato accessions for resistance to potato tuberworm Phthorimaea operculella (Zeller) is a valuable component of integrated pest management; however, few attempts have been made to identify natural genetic tuber resistance to tuberworm on potato germplasm. The objective of this study was to screen potato accessions with potential tuberworm resistance for tuber resistance under laboratory and field conditions. Experiments were conducted over a 2-year period at the Hermiston Agricultural Research and Extension Center, Oregon. Out of one hundred twenty five accessions that were tested in 2006, thirteen accessions were selected in 2007. These accessions were: A0008TE, A97066LB, NY123, PA00N10-5, PA99N2-1, PA99N82-4, Paciencia, Q174-2, Russet Burbank, Rubi, Ranger Russet, SpuntaG2, and T88-4. Tuber resistance of potato accessions was determined based on the number of live larvae and the number of mines per tuber. Tubers of Spunta G2 were resistant to tuberworm damage. All other accessions tested in this study, including Russet Burbank and Ranger Russet, showed some level of susceptibility to tuberworm under pressure of the pest in the field and laboratory experiments. Incorporation of resistance to tuber penetration by larvae together with appropriate cultural practices including limitation of exposure time of tubers in the field may provide the best management option in the future if appropriate resistance genes are found.