Susceptibility of Olive Cultivars and Selections to <i>Colletotrichum</i> Species Causing Anthracnose in Spain

Anthracnose, the most critical fruit disease affecting olive crops, necessitates the evaluation of the susceptibility of traditional and new varieties. In Spain and Portugal, anthracnose is caused by several <i>Colletotrichum</i> species, with <i>C. godetiae</i> and <i>C. nymphaeae</i> being dominant and <i>C. acutatum</i> and <i>C. fioriniae</i> being secondary. This study explores the susceptibility of fruits from an F₁ progeny resulting from a cross between 'Picual' (resistant) and 'Arbequina' (moderately susceptible) cultivars to <i>C. godetiae</i>. While most genotypes showed resistance levels comparable to their parents, seven showed a 50% reduction in disease severity compared with 'Picual.' The normal distribution of genotypes' response to the pathogen suggests a complex resistance mechanism. Furthermore, we assessed the susceptibility of four traditional cultivars, two new cultivars ('Sikitita-2' and 'Martina'), and five advanced selections (pre-commercial genotypes) to <i>C. godetiae</i> and <i>C. nymphaeae</i>. Despite the significant interaction between the olive genotype and <i>Colletotrichum</i> species in this experiment, the new cultivars and advanced selections were classified as susceptible or moderately susceptible against both species. A subsequent analysis of the interaction between 'Picual' (resistant) and 'Hojiblanca' (susceptible) fruits with the four mentioned <i>Colletotrichum</i> species revealed significant differences among cultivars but no interaction between genotype and pathogen species. <i>Colletotrichum</i> species were categorized as follows: (i) <i>C. godetiae</i> and <i>C. nymphaeae</i> as highly virulent, (ii) <i>C. acutatum</i> as moderately virulent, and (iii) <i>C. fioriniae</i> as weakly virulent. Finally, <i>C. nymphaeae</i> exhibited an enhanced ability to infect and develop acervuli in olive leaves, potentially serving as an inoculum source for this species. The absence of a correlation between leaf and fruit susceptibilities to the pathogen suggests differences in resistance mechanisms. In conclusion, this study provides valuable insights into the complex interactions between olive genotype and <i>Colletotrichum</i> species, essential for cultivar selection and understanding the disease cycle.