The effect of different vigour olive clones on growth, dry matter partitioning and gas exchange under water deficit

In the last decade, high-density olive planting systems have been developed to facilitate less costly mechanical harvesting and pruning by using straddle harvesters. High-density orchards allow faster production since the first crop of fruit starts a few years after planting. In high-density orchards the control of tree size is essential. It is possible to control the vigour and size of the tree by selecting suitable cultivars, by choosing rootstocks capable of controlling scion vigour and, finally, by applying deficit irrigation to reduce plant vegetative growth. Knowledge of tree water requirements is needed for precise irrigation scheduling. In this study, the dwarfing capacity of two Leccino clones, Leccino Dwarf (LD) showing low vigour, and Leccino Minerva (LM) highly vigorous, was investigated under two water regimens, well-watered (T100) and water deficit (T50). We analysed growth rates, dry matter production, gas exchanges and water relations of one-year-old plants of Leccino Dwarf (LD) and Leccino Minerva (LM), grown in pots in open fields. The two genotypes showed significant differences in vigour, demonstrated by measuring the trunk diameter, shoot length and leaf area; values were significantly lower in clone LD. Stem water potential, photosynthesis and stomatal conductance were similar in both genotypes under a well-watered regime; they decreased when subjected to water deficit with values significantly lower in LM clone during the summer months, indicating physiological differences among clones and that LD adapts better to water deficit.