Association of promising germplasm exhibiting tolerance to psyllids, aphids, and zebra chip disease with foliar host chemistry

Authors: PRAGER, SEAN - University Of Saskatchewan; Wallis, Christopher; JONES, MICHELE - University Of California; Novy, Richard; TRUMBLE, JOHN - University Of California

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2017
Publication Date: 1/1/2018
Citation: Prager, S.M., Wallis, C.M., Jones, M., Novy, R.G., Trumble, J. 2018. Association of promising germplasm exhibiting tolerance to psyllids, aphids, and zebra chip disease with foliar host chemistry. Journal of Economic Entomology. 111:327-336.

Interpretive Summary: Zebra chip disease, caused by “Candidatus Liberibacter solanacearum” and spread by the potato psyllid Bactericera cockerelli, is a major threat to potato production worldwide. Long term, sustainable management requires the development of new potato cultivars that resist pathogen infection, insect vectors, or both. This study assessed the ability of promising breeding lines to resist psyllids and, for comparison, aphids. It also measured compound levels that could affect plant-insect interactions in the same breeding lines and compared observations with those in the commercial cultivar Atlantic. Although breeding lines possessed greater levels of alkaloids, phenolics, and terpenoids, all of which could negatively affect insect feeding, only insect reproduction was reduced in the breeding lines compared to the Atlantic controls. Regardless, reductions in insect vector reproduction when coupled with pathogen resistance will make such breeding lines useful in developing ZC-resistant cultivars.

Technical Abstract: Long term, sustainable management of zebra chip disease of potato, caused by “Candidatus Liberibacter solanacearum” (Lso) and vectored by potato psyllids (Bactericera cockerelli Sulc), will require development of new cultivars resistant or tolerant to infection and/or capable of reducing spread. The study examined the ability of five experimental breeding lines of potato for ability to affect potato psyllids and the ability to vector Lso. For comparison, the ability of these potato lines to resist aphids (green peach aphids, Myzus persicae Sulzer) also was examined. Due to the importance of host chemistry on plant-insect interactions, levels of the primary metabolites amino acids and sugars as well as the secondary metabolites polyphenolics, terpenoids, and alkaloids were compared between breeding lines and the susceptible commercial cultivar Atlantic. Findings about constitutive and psyllid-induced compound levels then were associated with observed changes in host susceptibility to psyllids or aphids. Psyllids oviposited less on the breeding lines A05379-211, PALB03016-3, and PALB03016-6 than Atlantic, but no significant effects of breeding lines on psyllid feeding or choice were observed. Aphids reproduced less on Etb-6-21-3 and PALB03016-6 than Atlantic. A05379-211 had greater sugar levels and post-psyllid amino acid levels than Atlantic. Total alkaloid and phenolic levels were greater in all breeding lines than Atlantic, but had no significant effect on insect resistance in this study. Total terpenoid levels were greater in PALB03016-3 and PALB03016-6 than Atlantic, which might explain, in part, the observed resistance to psyllid oviposition and aphid reproduction. Overall, these results determined increased levels of defensive compounds in the breeding lines of tested compounds could affect insect behaviors and host-insect interactions, albeit observed effects on the psyllids and aphids in this study were limited to reproduction.