Susceptibility to Bactrocera oleae of advanced selections from a cross-breeding program

Abstract: In the last years, the need for more suitable cultivars promoted the development of olivebreeding programs in the main olive-producing countries based in intraspecific cross-breedingbetween cultivars of known merit aiming at combining the good qualities of the genitors in some ofthe genotypes of the progenies. Pest and disease resistance are usually cited among the breedingobjectives in these programs. However, despite the economic importance of olive fruit fly in theMediterranean basin, there are not reports about the susceptibility of new genotypes to this parasite.The selections evaluated in this work come from the crosses between ‘Arbequina’ and ‘Picual’ olivecultivars carried out in 1997. Initial, middle and end of the ripening period were recorded accordingto the ripening index of fruits based on colour changes of peel and pulp. Samples of 50 fruitscollected at the end of the ripening period were used for determining fruit characters (size, moistureand oil content) and the total infestation percentage by fruit fly. Significant differences betweengenotypes were obtained for all the evaluated traits. The percentage of infestation varied from 6.5 to58.4% between selections with five genotypes showing percentage of infestation lower than 15%(including ‘Arbequina’) and three of them higher than 20% (including ‘Picual’). A positivecorrelation was found between infestation and ripening dates (mainly initial ripening date) and fruitsize but not with fruit moisture or oil content. The most susceptible genotypes showed both largefruit size (>3.5g) and late ripening (initial ripening time in October). On the contrary, smaller fruitsize, earlier ripening or both were associated with much lower percentages of infestation.