|RASHED, ARASH - University Of Idaho|
|OLSEN, NORA - University Of Idaho|
|PAETZOLD, LI - Texas A&M University|
|WOODELL, LYNN - University Of Idaho|
|RASHIDI, MAHNAZ - University Of Idaho|
|WORKNEH, FEKEDE - Texas A&M University|
|RUSH, CHARLES - Texas A&M University|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/13/2017
Publication Date: 9/25/2017
Citation: Rashed, A., Olsen, N., Wallis, C.M., Paetzold, L., Woodell, L., Rashidi, M., Workneh, F., Rush, C. 2017. Postharvest development of ‘Candidatus Liberibacter solanacearum’ in late-season infected potato tubers under commercial storage conditions. Plant Disease. 102(3):561-568. https://doi.org/10.1094/PDIS-05-17-0619-RE.
Interpretive Summary: Tubers infected with ‘Candidatus Liberibacter solanacearum’ (Lso), the causal agent of zebra chip disease, just prior to harvest appear asymptomatic but may develop undesirable zebra chip disease symptoms while in storage. This study characterized tuber Lso titers, frying quality, and associated changes in tuber phenolic chemistry when potato plants were inoculated with Lso 4, 10, or 14 days before harvest. In all cases, as storage time increased infected tubers exhibited greater Lso titers and associated phenolic accumulation. Plants inoculated with Lso 10 or 14 days before harvest had decreased tuber frying quality at the end of the storage period, whereas plants inoculated 4 days before harvest had no such reductions in quality. These results suggest that greater screening for Lso in tubers prior to placement in storage is needed, and confirm recommendations to control psyllid vectors up to at least a week before harvest.
Technical Abstract: Zebra Chip (ZC) disease has been a challenge to the potato industry in the Americas for close to two decades. ZC is associated with the vector-borne plant pathogen ‘Candidatus Liberibacter solanacearum’ (Lso), which is transmitted by the potato psyllid Bactericera cockerelli (Hem., Triozidae). Following the relatively recent emergence of ZC in major potato growing areas of the U.S. Pacific Northwest (PNW), in 2011, research questions were raised to address Lso development, and its impact on potato quality, under conditions resembling those of the PNW agro-ecosystem and cultural practices. The present study was designed to evaluate effects of late-season Lso infections on post-harvest quality, with particular emphasis on the storage process. Using infective potato psyllids, potato plants were inoculated in field cages 14, 10 and 4 days before harvest. Tubers were sampled at harvest and throughout different stages of storage to evaluate changes in Lso titer, and also changes in concentration of the phenolic compounds known to be associated with enzymatic browning of the tuber. In all treatments Lso continued to increase in titers within infected tubers after harvest. Although Lso was detected in all treatments, the impact of Lso infection on tuber quality remained negligible in plants infected 4 days before harvest compared to tubers from plants inoculated earlier. Minimizing post-harvest tuber handling prior to marketing would help to reduce disease development and its potential impact on tuber quality. Further studies are needed to understand the impact of other cultural practices, including vine-kill, on Lso-tuber interactions. Based on the current results, psyllid management is recommended until at least one week before vine-kill.