FIRST REPORT OF Botrytis cinerea CAUSING POSTHARVEST GRAY MOLD OF TEJOCOTE Crataegus mexicana FRUIT IN MEXICO
E.H. Nieto-López, L.A. Aguilar-Pérez, V. Ayala-Escobar, D. Nieto-Angel, R. Nieto-Angel, S. G. Leyva-Mir, J.M. Tovar-Pedraza
In Mexico, tejocote (Crataegus spp.) is grown commercially on a total area of more than 900 ha. During November and December 2013, fruits of Crataegus mexicana var. chapeado showing a gray and firm rot were collected in commercial markets in Puebla. Small pieces of decayed fruits were surface-disinfected for 1 min in a 2% sodium hypochlorite solution, rinsed in sterile distilled water, and plated onto potato dextrose agar (PDA). A fungus was isolated whose colonies were initially whitish but turned gray with age. Black and irregular sclerotia were formed after 14 days of incubation at 20°C. Conidiophores were erect, subhyaline and dichotomously branched, and bore unicellular, ovoid-ellipsoid, subhyaline conidia measuring 7.7-12.7x6.1-9.5 μm. Based on morphology, the fungus was identified as Botrytis cinerea. Genomic DNA was extracted and the internal transcribed spacer (ITS) region of rDNA was amplified using the universal primers ITS5 and ITS4 (White et al., 1990). PCR products were purified and sequenced. The resulting sequence of 496 bp was deposited in GenBank (accession No. KM594622). BLAST search showed 100% identity with B. cinerea sequences KF010847 and KJ476697. To confirm the pathogenicity of the fungus, 10 tejocote fruits were surface-disinfected with 80% ethanol. A conidial suspension (1x106 spores ml-1) was sprayed on the surface of non-wounded fruits. Control fruits were sprayed with sterile distilled water. Typical gray mold symptoms with gray sporulating lesions were observed only on inoculated fruits after eight days. Koch ́s postulates were fulfilled when the
pathogen was re-isolated from the diseased fruits. To our knowledge, this is the first report of B. cinerea causing postharvest fruit rot on tejocote in Mexico and worldwide.