Colletotrichum acutatum: Causal Agent of Olive Anthracnose Isolation, Characterization, and Fungicide Susceptibility Screening in Punjab, Pakistan

Anthracnose of olive fruit caused by Colletotrichum acutatum was a severe epidemic disease in Pakistan that occurred in September 2020. The estimated disease incident was recorded as 59%. Anthracnose causes a significant reduction in yield and quality traits. Anthracnose has been found in several orchards. Agricultural practices, environmental factors, and disease aggressiveness vary between orchards. Therefore, we looked at spore size, cultural traits, morphological variation, growth pattern, and pathogenicity of different strains of C. acutatum from various orchards. Molecular and phylogenetic analysis confirmed the isolated strains as C. acutatum. In all, 15 C. acutatum isolates from olive orchards were tested for susceptibility to four commercial fungicides (P < 0.001). The examined isolates' in vitro fungicide sensitivity varied with fungicide concentration. The concentration at which conidial germination was hindered by 50% compared with the control values was observed for difenoconazole, tebuconazole, carbendazim, and cyprodinil, ranging from 0.12 to 2.69 g ml-1. Based on the findings of the fungal growth inhibition studies, carbendazim has been found to be the only fungicide that effectively reduces (P < 0.001) anthracnose caused by C. acutatum strains. Additionally, results revealed that preharvest site treatments of different fungicides greatly decreased anthracnose infections on olive fruit (70 to 90%), and postharvest site applications significantly reduced disease prevalence and severity (75 to 95%). The fungicide carbendazim significantly decreased pre- and postharvest anthracnose infection on olive cultivars. This study suggests that the latter compound might be used to control olive anthracnose in Pakistan while lowering environmental impact and fungicide resistance.