First Report of Curvularia lunata Causing Fruit Rot of Tomato (Lycopersicum escztlentum) in Pakistan.

In April 2015, fruit rot of tomato (Lycopersicum esculentum) was observed during a survey of tomato plants (cv. Roma) growing in tunnels at the University of the Punjab, Lahore, Pakistan. The incidence of affected fruits was estimated as 70%. The symptoms included 1-to 2-cm water-soaked lesions on the tomato fruit which progressed into light-brown to black lesions that enlarged gradually (3 to 4 cm). In advanced stages, the lesions became sunken, leathery, dark, and covered with fungal fruitifications. Yellowish-green symptomatic tomato fruits were collected for pathogen isolation. Diseased fruit tissues (3 mm × 3 mm) were cut from lesion edges, surface sterilized in 1% sodium hypochlorite 3 to 4 min, and rinsed with sterile distilled water. The infected tissues were embedded in potato dextrose agar (PDA) and incubated at 27°C (16-h light and 8-h dark cycle) for 5 days. Colonies of the fungus on PDA were fast-growing, brownish, and cottony. Conidiophores were straight to flexuous, multiseptate, usually simple but sometimes branched, brown, and bearing spores apically. Conidia (porospores) were 3 to 5 celled, more or less fusiform, clavate, 26 to 28 µm long, 8 to 10 µm wide, and slightly curved at the third cell from the base, which was larger than the others. Basal and apical cells were pale or subhyaline, intermediate cells were brown, and the third cell from the base was usually darker. The pathogen was identified as Curvularia lunata (Wakk.) Boedijin based on its colony and morphological characteristics (Ellis 1971). DNA was extracted using the CTAB method (Doyle and Doyle 1987). The internal transcribed spacer region of extracted DNA was amplified by PCR primers ITS1 and ITS4 (White et al. 1990). The PCR product was purified, sequenced, and BLAST analyses were used to compare sequences with those in GenBank. The resulting sequence was 525 bp long and was 100% identical with multiple sequences of C. lunata in GenBank. A sequence from a representative isolate was submitted to GenBank (Accession No. LN879926). A representative isolate also was submitted to the First Fungal Culture Bank of Pakistan (FCBP Isolate No. 1404). Pathogenicity tests were conducted according to the techniques described by Okigbo et al. (2009). Healthy tomato (cv. Roma) fruit were surface sterilized. A 5-mm cork borer was used to remove a disc from the fruit and was replaced with an agar disc colonized by C. lunata. Negative controls were inoculated with sterile PDA. Three tomatoes were placed in a sterile polyethene bag for each treatment and stored at 27°C (16 h light and 8 h dark cycle). Each treatment was replicated three times. After three days, all tomato fruits showed symptoms of water soaked lesions with a slightly brownish appearance on the inoculated areas. The pathogen was reisolated and identified as C. lunata. Noninoculated control fruits showed no symptoms of rot. This is the first report of C. lunata causing fruit rot on tomato in Pakistan. The previous reports of C. lunata on other crop plants in Pakistan and its wide host range together suggest potential for this fungus to be a pathogen on a range of plant species. © 2016, American Phytopathological Society. All rights reserved.