Color of fruits and leaves of Portuguese olive cultivars (cvs. Cobrançosa, Madural and Verdeal Transmontana) and their relation to Bactrocera oleae (Rossi) (Diptera: Tephritidae) oviposition preference

Abstract: In the present work the influence of physical factors, namely color of olives and leaves and their possible relation to olive fly oviposition preference was studied. For this reason fruits and leaves from cvs. Cobrançosa (less susceptible), Madural (intermediate susceptibility), and Verdeal Transmontana (high susceptibility) were collected during olives maturation and color was measured with a colorimeter. Maturation index and infestation levels were also measured. Olives from cv. Verdeal Transmontana were the most susceptible (24.5% infestation) followed by cvs Madural (17.5%) and Cobrançosa (8.5%) (data from olives harvest, 1st week of November). Olives from cv. Cobrançosa reported a faster maturation process with a maturation index (MI) of 3.0 at the end of the study while cvs. Madural and Verdeal Transmontana reported respectively 2.0 and 0.9. In leaves, color of lower surface revealed no important differences among cultivars, but it was observed a significant higher luminosity (L* values) of upper surface in cv. Verdeal Transmontana. This observation was also observed in fruits. Olives from the three cultivars at the same MI report significant difference of L*, mainly in cv. Verdeal Transmontana. With the advance of maturation L* values decreased significantly in cv. Cobrançosa and Madural, while in cv. Verdeal Transmontana L* values increased during maturation. By a principal component analysis is possible to verify that olives and leaves color can distinguish olive cultivars, a fact that could intervene in the oviposition preference of olive fly. The luminosity verified in both leaves and olives from cv. Verdeal Transmontana is a crucial factor in the oviposition preference of olive fly. This aspect allied to the slower maturation stage of cv. Verdeal Transmontana and turns this cultivar susceptible for longer periods comparatively to cvs. Madural and Verdeal Transmontana.