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ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Crop Diseases, Pests and Genetics Research » Research » Publications at this Location » Publication #387518

Research Project: Characterization and Management of Citrus Pathogens Transmitted by Phloem-Feeding Insect Vectors

Location: Crop Diseases, Pests and Genetics Research

Title: Evaluation of reliable sampling tissue and seasonality for consistent detection of CLas by qPCR

item HAJERI, SUBHAS - Central California Tristeza Eradication Agency
item KUMAGAI, LUCI - California Department Of Food And Agriculture
item Yokomi, Raymond - Ray

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/13/2021
Publication Date: 10/6/2021
Citation: Hajeri, S., Kumagai, L., Yokomi, R.K. 2021. Evaluation of reliable sampling tissue and seasonality for consistent detection of CLas by qPCR. California Citrus Conference. Citrus Research Board.

Interpretive Summary:

Technical Abstract: Early detection and prompt response are key factors in the eradication or suppression of HLB. qPCR is the regulatory method for CLas detection. However, due to lack of visible symptoms, low titer and uneven distribution of CLas in a tree, selecting the best sample for lab testing is a major hurdle for early detection. Overall goal is to identify the most reliable tissue to sample, matched with its ideal season for consistent detection of CLas. We monitored the presence and relative titer of CLas from mature leaves, new flush, fruit peduncle/bark and feeder roots. A variety of trees from within and outside HLB quarantine zones were utilized for the study. These included known CLas-positives, inconclusive CLas-positive, and ‘exposed’ but unconfirmed for CLas infection status. Two important data were considered for analysis of results: 1) titer (based median Ct value) and 2) reliability of a tissue (based on positive trees identified by a specific tissue type). CLas is unevenly distributed in citrus. Irrespective of seasons, bark of fruit peduncle showed higher titer than other tissues tested. Feeder roots had relatively lower titer in all seasons tested. Fruit peduncle was more reliable tissue followed by feeder roots for CLas testing in the fall and winter months. However, feeder roots were more reliable tissue followed by fruit peduncle in the spring and summer months. This research was supported by CRB 5300-204.