Submitted to: Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2010
Publication Date: 5/2/2011
Citation: Yang, X., Malik, N.S., Perez, J.L., Liu, T. 2011. Impact of potato psyllid (Hemiptera: Triozide) feeding on free amino acid composition in potato. Insect Science. 18(6):663-670. Interpretive Summary: The potato psyllid has recently become an important insect pest on many solanaceous crops in the United States, Mexico, Central America, and New Zealand. This piercing-sucking insect possesses the potential to be the most devastating pest in potato industry due to the transmission of a bacterial pathogen which can cause the severe potato disorder named Zebra Chip (ZC). The phloem amino acid compositions could render plant resistance to insect pests especially the piercing-sucking type insect pests that perhaps feed on phloem material. It is interesting to note that the changes in amino acid profiles brought about by the feeding of one insect could affect the feeding or attack by other insects. For example; potato beetles fed on plants damaged by potato leafhoppers showed reduced growth and survival. Perhaps the specific changes in amino acids brought by on set of insect may be responsible for deterring other insects to feed because of their preference for certain amino acid balance. Therefore, it is important to study the changes in free amino acid profile of the host plant as affected by specific insects for evaluation of food value of the host plant products as well as to develop efficient management practices. Therefore, in this study, changes in the levels of free amino acids in leaves and tubers of potato plant were studied in response to potato-psyllid infestations. Our results indicate psyllid attack on potato leaves produce direct effects on changes in free amino acids from specific feeding behavior of insects and it also produces indirect effects that result from responses of the plant to stresses and injury. Changes in free amino acid pools in potato tuber are, perhaps, greatly affected by the bacterial pathogen introduced by psyllids, but other factors such as transportation of amino acids from infected leaves and altered metabolism in the tuber all play a part. Additional studies would be required to see how some of these changes could be managed to improve crop productivity through manipulation of management practices.
Technical Abstract: Foliage feeding impacts of potato psyllid (Bactericera cockerelli) on the free amino acids (FAAs) composition in potato leaf and tuber were determined under the greenhouse conditions. The free amino acids in plant extracts were separated by HPLC, and in both leaf and tuber samples, at least, 17 FAAs were detected. The psyllid feeding significantly changed the levels of several FAAs in both leaf and tuber samples. Leucine concentration increased 1.5-fold while serine and proline levels increased 2-fold and 3-fold, respectively after the feeding. On the other hand, the concentrations of glutamic acid, aspartic acid, and lyscine were significantly reduced by 42.0, 52.1, and 27.5%, respectively, after psyllid feeding. There were also significant changes in the levels of FAAS in the zebra chip infected tubers compared with the healthy tubers; i.e., levels of six of the FAAs increased, and levels of nine of the FAAs decreased after psyllid feeding. The results from our study indicate that potato psyllid cause major changes in free amino acid composition of plant tissue, and this change in plant metabolism may contribute to the plant stress (as indicated by increased levels of proline) and hence aiding in the development of plant diseases such as zebra chip disease.