ARS | Publication request: Quantification of Cylindrocarpon in roots of almond and peach trees from orchards affected by Prunus replant disease

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2011
Publication Date: August 15, 2011
Repository URL: http://www.apsnet.org/meetings/Documents/2011_Meeting_Abstracts/a11ma83.htm
Citation: Bhat, R.G., Schmidt, L.S., Browne, G.T. 2011. Quantification of Cylindrocarpon in roots of almond and peach trees from orchards affected by Prunus replant disease. Phytopathology. 101:S15.

Technical Abstract: Prunus replant disease (PRD) is a poorly understood soilborne complex that suppresses replanted almond and peach orchards in California. Using culture-dependent and culture-independent approaches, we found Cylindrocarpon (Cyl) macrodidymum among microorganisms associated with PRD. We developed a qPCR assay to further examine the Cyl-PRD association; a selective primer pair that amplified a 374 bp rDNA fragment from C. macrodidymum was coupled with a specific hydrolysis probe. The assay was validated using genomic DNA from the target and >70 non-target microorganisms and rootstocks. The lower detection limit was 100 fg Cyl DNA per 25µl. The assay was used with root samples from replicate healthy and PRD-affected almond and peach trees (in fumigated and non-fumigated plots, respectively) in five California orchards. All orchards were planted in winter and expressed PRD symptoms (tree stunting, wilting) the following summer. Root samples were collected on 1 to 5 dates per orchard from Apr.-Sep. the year trees were planted. In orchards 1-3, Cyl levels were significantly greater in PRD-affected than in healthy roots on some dates (7 of 11 total), but in orchards 4 and 5 (1 date each) Cyl levels were near the lower detection limit and did not differ in relation to PRD incidence. We conclude that Cyl concentration in roots is positively associated with PRD in at least some orchards, but the relationship may be time-sensitive, requiring a sampling time course for detection.