Survey Reveals a Broad Range of Fungal Pathogens and an Oomycete on Peonies in the United States

Abstract

Peonies, Paeonia lactiflora and hybrids, are popular ornamental plants grown in landscapes and as cut flowers. As with many ornamental plants, the information on the etiology of peony diseases is incomplete with varying amounts of detailed descriptive material; sometimes validation of Koch’s postulates is also lacking. In a survey to identify the range of diseases of peony in the United States, samples were obtained from 12 states. Fungal and oomycete plant pathogens recovered from symptomatic, diseased tissue were identified by morphology and BLAST identification of the internal transcribed spacer, glyceraldehyde 3-phosphate dehydrogenase, the 28s large subunit, and/or cytochrome c oxidase subunit 1 gene nucleotide sequences for representative isolates. Ten fungal or oomycete genera were identified, and Koch’s postulates were confirmed for selected plant pathogens found during this survey. New disease reports are generated for several states, including five genera never previously reported on peonies in the United States: a Botryosphaeria sp., multiple Colletotrichum spp., Mycocentrospora acerina, a Phoma sp., and Pilidium concavum. The information gained from this survey will provide plant disease diagnosticians and growers a more comprehensive resource for understanding the regional prevalence of peony diseases and subsequently making better disease management decisions.

First Report of Botrytis Mold Caused by Botrytis cinerea on Peonies (Paeonia lactiflora Pall.)

“…These species were B. cinerea, B. paeoniae, and a novel species called B. euroamericana (Garfinkel et al, 2017). Speciation of Botrytis isolates has continued to diversify (Garfinkel and Chastagner, 2019). Indeed, in a study on 178 isolates with pathogenicity in peonies from the Pacific Northwest in the United States, 15% were not assigned by molecular phylogeny to known species (Garfinkel and Chastagner, 2019).…”

“…Speciation of Botrytis isolates has continued to diversify (Garfinkel and Chastagner, 2019). Indeed, in a study on 178 isolates with pathogenicity in peonies from the Pacific Northwest in the United States, 15% were not assigned by molecular phylogeny to known species (Garfinkel and Chastagner, 2019). In a comparison of peony isolates from Washington and Oregon to those from Alaska, different patterns in the dominant species were observed with isolates identified as B. cinerea comprising 29% and 40%, respectively (Garfinkel and Chastagner, 2019).…”

“…The morphological characteristics of colonies of PBC-2, when grown on PDA under dark conditions, was within the wide variability observed in Botrytis sp. (Ellis and Waller, 1974;Garfinkel and Chastagner, 2019). Variation in morphology is extreme in these species, as illustrated by the appearance of different colonies 30 undefined species in the characterization study of Garfinkel et al (2017).…”

“…Because colony morphology, the extent of sporulation, temperature effects, and sclerotia formation are highly variable traits in the Botrytis genus (Garfinkel and Chastagner, 2019), sequences of selected genes were obtained. Initially, sequences were analyzed from the internal transcribed spacer (ITS) region, the large 28S subunit rRNA, and the translation elongation factor 1-alpha (tef1) from isolate PBC-2 (Raja et al, 2017;White et al, 1990).…”

“…2A-C). Each of these iso- lates is associated with gray mold disease on peonies in the United States (Garfinkel and Chastagner, 2019;Garpinkel et al, 2017). Determining whether the outbreak of gray mold in the Korean peonies was caused by a single species requires the sequencing of additional purified cultures.…”