Articles
Characterization of pomegranate diseases in the Southeast US
Article number
1254_39
Pages
263 – 268
Language
English
Abstract
A survey of pomegranate (Punica granatum L.) diseases in the Southeast United States was conducted from 2014 to 2016. Symptomatic leaves, stems, pedicels, buds, flowers, and fruits were collected, surface-disinfected with 1% chlorine for 1 min, and placed on V8 juice agar amended with rifampicin (0.01 mg L‑1) and ampicillin (0.25 mg L‑1). Fungal species were identified based on morphological and molecular characterization.
The rDNA internal transcribed spacer (ITS) region, translation elongation factor 1-α (EF-1α), and β-tubulin genes were sequenced.
Sequences were compared to those in NCBI database to confirm pathogen identity based on sequence identity.
Fungal isolates were inoculated on pomegranate leaves and fruits to determine pathogenicity.
Nine fungal species including two species of Colletotrichum, Neofusicoccum parvum, Pilidiella granati, Lasiodiplodia theobromae, Alternaria sp., Nigrospora sphaerica, Corynespora casiicola, and a unique species belonging to the order Diaporthales were pathogenic on leaves.
The two Colletotrichum species, N. parvum, P. granati, L. theobromae, and the Diaporthales species were also highly pathogenic on fruit.
Housekeeping gene and ITS sequences derived from the Diaporthales species exhibited low similarity to sequences in the NCBI database, suggesting that the isolates recovered from pomegranate may represent a new fungal species.
Based on the frequency of isolation, Colletotrichum was identified as a prevalent pathogen of pomegranate in the Southeast US. Multigene phylogenetic analyses of the two Colletotrichum species showed that isolates grouped within the C. acutatum and C. gloeosporioides complexes, with more than 75% belonging to the latter group.
Pathogenicity assays demonstrated that representative isolates from the C. acutatum species-complex were more aggressive than isolates from the C. gloeosporioides-species complex when inoculated on detached pomegranate fruit.
Results from the survey show the importance of certain fungal pathogens on pomegranate in the Southeast US and will be used to develop effective disease management strategies to improve pomegranate production.
The rDNA internal transcribed spacer (ITS) region, translation elongation factor 1-α (EF-1α), and β-tubulin genes were sequenced.
Sequences were compared to those in NCBI database to confirm pathogen identity based on sequence identity.
Fungal isolates were inoculated on pomegranate leaves and fruits to determine pathogenicity.
Nine fungal species including two species of Colletotrichum, Neofusicoccum parvum, Pilidiella granati, Lasiodiplodia theobromae, Alternaria sp., Nigrospora sphaerica, Corynespora casiicola, and a unique species belonging to the order Diaporthales were pathogenic on leaves.
The two Colletotrichum species, N. parvum, P. granati, L. theobromae, and the Diaporthales species were also highly pathogenic on fruit.
Housekeeping gene and ITS sequences derived from the Diaporthales species exhibited low similarity to sequences in the NCBI database, suggesting that the isolates recovered from pomegranate may represent a new fungal species.
Based on the frequency of isolation, Colletotrichum was identified as a prevalent pathogen of pomegranate in the Southeast US. Multigene phylogenetic analyses of the two Colletotrichum species showed that isolates grouped within the C. acutatum and C. gloeosporioides complexes, with more than 75% belonging to the latter group.
Pathogenicity assays demonstrated that representative isolates from the C. acutatum species-complex were more aggressive than isolates from the C. gloeosporioides-species complex when inoculated on detached pomegranate fruit.
Results from the survey show the importance of certain fungal pathogens on pomegranate in the Southeast US and will be used to develop effective disease management strategies to improve pomegranate production.
Authors
K.V. Xavier, A.N. KC, Z. Deng, W. Castle, N. Peres, W. Lovett, G.E. Vallad
Keywords
Punica granatum, Florida, pathogenicity, fruit rot, leaf spot
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