Common fig (Ficus carica L.) was introduced into Korea in the 1890s from Japan and planted in residential gardens for home consumption. Commercial cultivation of the tree did not begin until the 1990s (2). In early August 2012, several dozen unripened fig fruits, cv. Banane, were found damaged by fruit rot in an experimental plot of Jeollabuk-do Agricultural Research and Extension Services, Iksan City, South Korea (GPS coordinates 35°56′38.44″ N, 126°59′37.14″ E). Though infections recurred until late September, infection rates were as low as 1 to 5%. Early symptoms appeared as small, slightly sunken, water-soaked, and circular spots. Lesions increased in size, became more depressed, with a darkened central portion. The darkened areas contained blackish acervuli from which masses of salmon-colored conidia were released in moist weather. A semisoft decay resulted, sometimes causing premature fruit drop. No symptoms were found on leaves. Acervuli were circular to ellipsoid, 50 to 400 μm in diameter. Acervular setae were 2- to 3-septate, dark brown at the base, paler toward the apices, acicular, and up to 120 μm long. Conidia (n = 30) were long obclavate to oblong-elliptical, sometimes fusiform-elliptical, guttulate, hyaline, and 16 to 21 × 4 to 6 μm. These characters were consistent with the description of Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. (4). From an isolate (KACC46943, deposited in the Korean Agricultural Culture Collection), fungal DNA was extracted, and the complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1(5′-TCCGTAGGTGAACCTGCGG-3′)/ITS4(5′-TCCTCCGCTTATTGATATGC-3′) and sequenced. The resulting 606-bp sequence was deposited in GenBank (KC430919). The sequence showed 100% identity with sequences of C. gloeosporioides (e.g., JX669446, JQ936316, JQ753973). To confirm pathogenicity, inoculum was prepared by harvesting conidia from 3-week-old cultures on potato dextrose agar. A conidial suspension (3 × 105 conidia/ml) was sprayed onto 10 fruits wounded with a fine needle. Ten fruits sprayed with sterile water served as controls. Fruits were placed in moist chambers for 24 h and then kept in plastic containers (25°C and 60 to 80% RH). After 5 days, fruit rot symptoms, identical to those observed in the field, developed on the inoculated fruits, but never on controls. C. gloeosporioides was reisolated from the lesions of inoculated fruits. Anthracnose associated with C. gloeosporioides on common figs has been known from North America, Central America, South America, Australia, New Zealand, South Africa, and Turkey (1). In Korea, anthracnose fruit rot of common figs was recorded in 1928 under the name C. caricae F. Stevens & J.G. Hall, but without fulfillment of Koch's postulates (3). Subsequent to that time, there has been no published finding of the disease in Korea. C. caricae is regarded as synonymous with C. gloeosporioides (4). To our knowledge, this is the first confirmed report of anthracnose fruit rot of common figs caused by C. gloeosporioides in Korea. Anthracnose fruit rot of common figs may cause losses not only for fruit production but also for marketing.
References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, Retrieved January 24, 2013. (2) K. C. Ma et al. Res. Plant Dis. 14:107, 2008. (3) K. Nakata and S. Takimoto. Bull. Agric. Exp. Stat. Korea 15:1, 1928. (4) B. S. Weir et al. 2012. Stud. Mycol. 73:115, 2012.