First report of Colletotrichum acutatum and C. gloeosporioides causing anthracnose diseases on strawberry in Egypt

During the growing seasons of 2007 and 2008, typical anthracnose symptoms were observed in cultivated strawberry (Fragaria x ananassa) fields in Kalubia and Ismailia governorates, Egypt. Disease symptoms on immature and ripe fruits contained circular, sunken, and dark-coloured lesions (1-12 mm) bearing salmon-coloured masses of conidia (Fig. 1), with lesions also appearing in necrotic petioles and stolons (Freeman & Katan, 1997). A representative Colletotrichum acutatum culture (isolate 4), from infected fruit (cv. Yael), possessed hyaline, cylindrical conidia attenuated at both ends, measuring 12.6 (11.8-15.4) x 4.1 (3.3-5.1) µm (Gunnell & Gubler, 1992). Additional symptoms of wilted plants resembled those of anthracnose crown rot caused by C. gloeosporioides (Freeman et al., 2002). A representative C. gloeosporioides culture (isolate 1), isolated from necrotic roots (cv. Tamar), possessed hyaline, oblong conidia with obtuse ends, measuring 15.5 (14.3-17.3) x 4.5 (4.3-5.0) µm (Gunnell & Gubler, 1992).

Symptoms typical to those observed in the field were obtained three weeks after inoculation on two-month-old potted strawberry transplants (six replicate plants each for isolate 1 and isolate 4), sprayed with conidial suspensions (10⁶ conidia/ml) and maintained in a moist chamber for 48 h at 25°C. Water-inoculated plants remained healthy. Re-isolations were made from infected fruit, petioles, stolons and crowns, verifying the causal agents of disease.

Species-specific PCR amplification was conducted on the two representative Colletotrichum isolates. The identities of the pathogens were confirmed as C. gloeosporioides (isolate 1) resulting in a single amplified DNA fragment of 450 bp using primers ITS4 and CgInt; and C. acutatum (isolate4) with an amplified product of 490 bp using primers ITS4 and CaInt2 (Freeman et al., 2002) (Fig. 2). This is the first reliable and accurate report, based on molecular identification, of Colletotrichum acutatum and C. gloeosporioides causing anthracnose on strawberry in Egypt , although a record on occurrence of strawberry anthracnose was published previously in a local journal (Khafagi, 2006).