First report of Diplodia seriata causing fruit rot of loquat in Pakistan
Loquat (Eriobotrya japonica Lindl.) is achieving significant importance in Pakistan and 98% Pakistani commercial loquat plantations are located in Punjab (31.0° N, 72.0° E) and Khyber Paktoon Khawa (34.0° N, 71.32° E). During the survey of loquat orchards, 6 to 13 mm irregular brownish dry spots were observed on loquat fruits. The fruits were incubated at 22 °C for two weeks and spots turned to black or dark brown. Surface of symptomatic fruits was disinfected with cholrox and planted them in Czapek Dox Agar. Dark gray mycelium was observed on both side of plate surface at 26 °C. Aseptate brown conidia with the apex broadly rounded and the base rounded or truncate, and 22 × 10 μm (n = 49) in size were observed. Molecular identification of Diplodia seriata was performed with the primers ITS1 and ITS4 and nucleotide BLAST analysis of PAK20, PAK21 and PAK33 (GenBank Accession No. KR822800, KR822801 and KU052580) showed 99% to 100% identity with D. seriata (KJ463386 and KT447249). Four mm fungal mycelial plug (one plug per fruit; n = 9) of PAK20, PAK21 and PAK33 was transferred to skin wounds on superficially disinfected loquats whereas wounded but not inoculated fruit were used as controls. The experiment was repeated thrice and fruits were incubated 7 to 21 days at 20 °C. Nineteen to 98 mm lesions were observed on inoculated fruits and no lesion was recorded on controls. The fungus was re-isolated from inoculated fruits and compared with mother cultures. D. seriata is a broadly spread pathogen causing blight, cankers, dieback and fruit rots in vines and many fruit trees (Bobev et al. 2008; Choudhury et al. 2014; González-Domínguez et al. 2014; Kim et al. 2016). To our knowledge, this is the first report of D. seriata causing loquat fruit rot in Pakistan.
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