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Potato virus Y (PVY) has emerged as the main reason for potato seed lot rejections, seriously affecting seed potato production in the United States throughout the past 20 years. The dynamics of PVY strain abundance and composition in various potato growing areas of the United States has not been well documented or understood up to now. The objective of this study was to find out the prevalence of PVY strains in potato fields in the Pacific Northwest (PNW), including seed potato production systems in the State of Idaho and commercial potato fields in the Columbia Basin of Washington State between 2011 and 2021. Based on the testing of >10,000 foliar samples during Idaho seed certification winter grow-out evaluations of seed potato lots and seed lot trials in Washington State, a dramatic shift in the PVY strain composition was revealed in the PNW between 2011 and 2016. During this time period, the prevalence of the ordinary, PVY O strain in seed potato dropped 8- to 10-fold, concomitantly with the rise of recombinant strains PVY N-Wi and PVY NTNa , which together accounted for 98% of all PVY positives by 2021. In Idaho seed potato, PVY NTNa strain associated with the potato tuber necrotic ringspot disease (PTNRD) was found to increase threefold between 2011 and 2019, accounting for 24% of all PVY positives in 2019. Mild foliar symptoms induced by recombinant PVY strains may be partially responsible for the proliferation of PVY N-Wi and PVY NTNa in potato crops. A spike of another PTNRD-associated recombinant, PVY-NE11, was recorded in the PNW between 2012 and 2016, but after reaching a 7 to 10% level in 2012 to 2013 this recombinant disappeared from the PNW potato by 2019. Whole genome sequence analysis of the PVY-NE11 suggested this recombinant was introduced in the United States at least three times. The data on PVY strain abundance in the PNW potato crops suggest that virus management strategies must consider the current dominance of the two recombinant PVY strains, PVY N-Wi and PVY NTNa .

The potato psyllid, Bactericera cockerelli (Šulc), is a major pest of potato (Solanales: Solanaceae) as a vector of 'Candidatus Liberibacter solanacearum' (Lso). Bactericera cockerelli colonizes potato from noncrop host plants, yet we do not yet know which noncrop species are the primary sources of Lso-infected psyllids. The perennial weed, Physalis longifolia Nutt., is a high-quality host for B. cockerelli and Lso under laboratory conditions but has been overlooked in recent field studies as a source of Lso-infected psyllids. Our current study had four objectives: 1) determine whether P. longifolia is abundant in potato-growing regions of Washington and Idaho, 2) determine whether stands of P. longifolia harbor B. cockerelli and Lso, 3) identify the psyllid haplotypes occurring on P. longifolia, and 4) use molecular gut content analysis to infer which plant species the psyllids had previously fed upon prior to their capture from P. longifolia. Online herbaria and field searches revealed that P. longifolia is abundant in western Idaho and is present at low densities in the Columbia Basin of Washington. Over 200 psyllids were collected from P. longifolia stands in 2018 and 2019, confirming that B. cockerelli colonizes stands of this plant. Gut content analysis indicated that a proportion of B. cockerelli collected from P. longifolia had arrived there from potato. Confirmation that P. longifolia is abundant in certain potato-growing regions of the Pacific Northwest, and that B. cockerelli readily uses this plant, could improve models to predict the risk of future psyllid and Lso outbreaks., (Published by Oxford University Press on behalf of Entomological Society of America 2021.)

Bean common mosaic virus (BCMV) exists as a complex of strains classified by reactions to resistance genes found in common bean (Phaseolus vulgaris); seven BCMV pathotypes have been distinguished thus far, numbered I to VII. Virus genetic determinants involved in pathogenicity interactions with resistance genes have not yet been identified. Here, we describe the characterization of two novel field isolates of BCMV that helped to narrow down these genetic determinants interacting with specific P. vulgaris resistance factors. Based on a biological characterization on common bean differentials, both isolates were classified as belonging to pathotype VII, similar to control isolate US10, and both isolates exhibited the B serotype. The whole genome was sequenced for both isolates and found to be 98 to 99% identical to the BCMV isolate RU1 (pathotype VI), and a single name was retained: BCMV RU1-OR. To identify a genetic determinant of BCMV linked to the BCMV pathotype VII, the whole genome was also sequenced for two control isolates, US10 and RU1-P. Inspection of the nucleotide sequences for BCMV RU1-OR and US10 (both pathotype VII) and three closely related sequences of BCMV (RU1-P, RU1-D, and RU1-W, all pathotype VI) revealed that RU1-OR originated through a series of recombination events between US10 and an as-yet-unidentified BCMV parental genome, resulting in changes in virus pathology. The data obtained suggest that a fragment of the RU1-OR genome between positions 723 and 1,961 nucleotides that is common to US10 and RU1-OR in the P1-HC-Pro region of the BCMV genome may be responsible for the ability to overcome resistance in bean conferred by the bc-2(2) gene. This is the first report of a virus genetic determinant responsible for overcoming a specific BCMV resistance gene in common bean.