Commercial production area and yield of sweet persimmon (Diospyros kaki L.) in Spain has doubled in the last 10 years to more than 5,000 ha and 50,000 tons, respectively, mainly because of the high quality and consumer demand for the Valencian autochthonous cultivar ‘Rojo Brillante’ in European markets. In a recent survey of decay on ‘Rojo Brillante’ persimmons stored in commercial packinghouses, fruit were found with disease symptoms of firm brown to dark brown round spots scattered on the fruit cheeks. Isolation of the potential causal agent (isolate IVIA QCV-2) was performed by disinfecting the surface of symptomatic fruit with alcohol, aseptically cutting pieces of infected peel tissue, and then plating them onto potato dextrose agar (PDA). The fungus grew fast, covering the entire plate surface (9 mm diameter) after 7 to 10 days of incubation at 25°C with cottony grayish mycelium that darkened with time. Masses of salmon-colored conidia were apparent in the center of some colonies. Conidia were one-celled, hyaline, aseptate, ovoid to oblong with rounded or obtuse ends, and 11.5 to 15.5 × 3.0 to 6.5 μm (n = 50). The identification of Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. [synonym: Vermicularia gloeosporioides Penz.; teleomorph: Glomerella cingulata (Stoneman) Spauld. & H. Schrenk] was performed at the Instituto Valenciano de Microbiología (IVAMI, Bétera, Valencia, Spain) by macro and micro morphological observations and confirmed with the amplification and subsequent sequencing of the ribosomal DNA regions 5.8S-ITS2-28S, using the primers ITS3 and ITS4 (4). A representative nucleotide sequence was deposited in GenBank (Accession No. KC113600) and a BLAST search showed 99% identity with the strain C1254.3 of C. gloeosporioides (JX010153) (3). To fulfill Koch's postulates, selected healthy ‘Rojo Brillante’ persimmons were surface sterilized by dipping them for 2 min in a 0.5% sodium hypochlorite aqueous solution and thoroughly rinsing with fresh water. Mycelial plugs (5-mm diameter) from the edge of 7-day old colonies of isolate IVIA QCV-2 grown on PDA at 25°C were aseptically transferred to skin wounds (one plug per fruit). Wounded but not inoculated fruit were used as controls. Persimmons were placed in three humid chambers that each contained four fruit and incubated at 20°C for up to 21 days. The experiment was repeated twice. While inoculated persimmons developed anthracnose disease in all cases and C. gloeosporioides was consistently reisolated from these fruit, no decay was observed on control fruit. To our knowledge, this is the first report of C. gloeosporioides causing postharvest persimmon fruit rot in Spain. Persimmon anthracnose caused by this pathogen is well known in Asian countries such as China and Korea (1). This disease was also reported in Brazil (2).
References: (1) J. H. Lee et al. Plant Pathol. J. 20:247, 2004. (2) M. A. S. Mendes et al. Fungos em Plants no Brasil. Embrapa-SPI/Embrapa-Cenargen, Brasilia, Brazil, 1998. (3) B. S. Weir et al. Stud. Mycol. 73:115, 2012. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press Inc., San Diego, CA, 1990.