Characterization of Infection and Colonization of Strawberry Crowns by Colletotrichum acutatum

Strawberry anthracnose, caused by Colletotrichum acutatum J.H. Simmonds, is one of the most important diseases of this crop in Huelva (southwestern Spain). Lesions can occur on all parts of the plant but anthracnose crown rot is specially severe leading to wilt and death of plants. In this work, the infection and colonization process of C. acutatum on strawberry plants was studied. 'Camarosa' strawberry plants (highly susceptible to C. acutatum) were inoculated by applying 100 mu l droplets of a conidia suspension of the fungus on crowns, on buds and between second and third stipules. Plants were evaluated for response over a 30 days period. The severity of disease, estimated as percentage of plants showing symptoms on aerial parts, and the amount of infected crown tissues were determined at 2, 5, 10, 15, 20, 25 and 30 days after inoculation. Depending on the inoculation site the severity of anthracnose crown rot varied between plants. Moreover, an ultrastructural study of infected plants exhibiting anthracnose crown rot was carried out by transmission electron microscopy. The colonization of the crown tissues by intracellular and intercellular hyphae in the cortex, medulla and vascular system was observed resulting in cell colapse and necrosis.