MORPHOLOGICAL AND ANATOMICAL DEVELOPMENT OF FRUITS OF TWO CULTIVARS OF OLIVE (OLEA EUROPAEA L.) GROWN UNDER IRRIGATED AND RAINFED CONDITIONS IN SOUTHWESTERN BUENOS AIRES PROVINCE

This study compared the fruit development of the olive cultivars ‘Arbequina’ and ‘Nevadillo’ grown under irrigated and rainfed conditions in the southwest of Buenos Aires province (38°50’21”S; 61°06’46”W). From fruit set to harvest, seven fruit sampling dates were selected, measuring fruit volume and mesocarp and endocarp transverse area (TA). Digital images of histological sections of the mesocarp were analyzed by counting cell number and cell TA. During the experimental period, rain accounted for 511 mm (rainfed). Water supplied by irrigation totalized 222 mm. The fruit growth dynamics based on the volume and the TAfruit in both cultivars fit to a double sigmoid function with two phases of rapid growth connected by a plateau between January and March. Throughout the study, plant water status, monitored by the RWC_leaf, was similar among water regimes. The TA_endocarp was similar between cultivars and water regimes. At final fruit volume, TA_fruit and TA_mesocarp showed significant differences between cultivars, being of 2.48 cm³, 165 mm² and 126 mm² in ‘Nevadillo’ and 1.36 cm³, 129 mm² and 93 mm² in ‘Arbequina’, respectively. Final TA_cell was similar in both cultivars averaging 6050 µm². The mesocarp cell number was higher in ‘Nevadillo’, which may explain its higher TAmesocarp. Fruits grown under rainfed had higher TA_fruit, TA_mesocarp, cell number and TA_cell than those grown under irrigation. Lower crop load in rainfed trees compared to irrigated ones could explain this last result.