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Effects of Potato-Psyllid-Vectored ‘Candidatus Liberibacter solanacearum’ Infection on Potato Leaf and Stem Physiology

First and third authors: United States Department of Agriculture–Agricultural Research Service, San Joaquin Valley Agricultural Sciences Center, Crop Diseases, Pests and Genetics Research Unit, 9611 S. Riverbend Ave, Parlier, CA 93648; second author: Department of Plant, Soil, and Entomological Sciences, University of Idaho Aberdeen Research and Extension Center, Aberdeen 83210; and fourth, fifth, and sixth authors: Texas A&M AgriLife Research, 6500 Amarillo Blvd. W., Amarillo 79106.

The bacterium ‘Candidatus Liberibacter solanacearum’ is associated with zebra chip disease (ZC), a threat to potato production in North America and New Zealand. It is vectored by potato psyllids. Previous studies observed that ‘Ca. L. solanacearum’ infection causes potato tubers to undergo ZC-symptom-associated shifts in physiology, such as increased levels of amino acids, sugars, and phenolics. However, little is known about how ‘Ca. L. solanacearum’ infections caused by psyllid vector feeding may affect metabolism in potato foliage and stems. This study compared metabolism in potato plants fed upon by ‘Ca. L. solanacearum’-positive psyllids with potato plants not exposed to psyllids. Foliar levels of asparagine, aspartic acid, glutamine, fructose, glucose, sucrose, a ferulic acid derivative, and quinic acid were lower in ‘Ca. L. solanacearum’-inoculated than noninfected plants. However, foliar levels of proline, serine, four phenolic compounds, and most terpenoids were greater in ‘Ca. L. solanacearum’-inoculated than noninfected plants. Upper stem levels of asparagine and aspartic acid, upper and lower stem levels of ellagitannins and most monoterpenoids, and lower stem level of sesquiterpenoids were greater in ‘Ca. L. solanacearum’-inoculated than noninfected plants. These results suggest that many defense-related terpenoid compounds might increase in plants which had psyllids inoculate ‘Ca. L. solanacearum’. This could impact progression and spread of ZC.

Additional keyword: carbohydrates.