Cercospora leaf spot of olive in Uruguay

Abstract

Cercospora Leaf Spot (CLS) of olive is an important fungal disease in Uruguay, causing severe early defoliation. Fungal isolates were obtained from olive leaves with typical CLS symptoms from Uruguayan orchards. The isolates were identified based on phenotypic characteristics and DNA sequence analyses. Infection processes under field conditions were characterized. Phylogenetic analyses confirmed that Pseudocercospora cladosporioides is the causal agent of CLS in Uruguay. Three colony morphologies were observed for isolates growing on potato dextrose agar. Mean conidium length ranged from 65.7 to 101.8 µm, and widths from 4.3 to 5.0 µm. Mean optimum growth temperature was 21.5°C (range 19.2 to 24.8°C). Under field conditions, initial CLS symptoms on leaves were observed 5 months after inoculation of cv. Arbequina plants, confirming the disease’s lengthy incubation period. This study shows that CLS as one of the most prevalent and destructive olive diseases in Uruguay, and emphasizes the importance of further research to develop efficient management of this disease.