Growth Is Inversely Correlated with Yield Efficiency across Cultivars in Young Olive (Olea europaea L.) Trees

Abstract

Additional index words. modeling, yield efficiency, partitioning, harvest indexAbstract. The modern olive industry is increasingly interested in olive cultivars that start producing early and remain relatively small, because they are suitable for super highdensity orchards. Some cultivars are better suited to this than others but it is not clear why. Understanding the mechanisms that lead to early production and reduced canopy size is therefore important. The object of this study was to investigate whether differences in vigor across olive cultivars are related to earliness and abundance of bearing. We analyzed tree growth and productivity in young coetaneous trees of 12 olive cultivars, grown together in the same orchard. Trunk diameter increased over the observation period, reaching significantly different values across cultivars. Canopy volume also increased, reaching 2-fold differences between the minimum and the maximum values. Cumulative yield increased, reaching up to 3-fold differences. When the cumulative yield at the end of the experiment was plotted against the final trunk diameter, no correlation was found. A significant correlation was found when cumulative yield was plotted against the increment in trunk diameter during the observation period for which yield data were collected. This relationship improved (i.e., R 2 rose from 0.57 to 0.83) when yield efficiency [i.e., cumulative yield per unit of final trunk cross-sectional area (TCSA) or per unit of canopy volume] was used instead of yield. These results clearly showed that trees that produced proportionally more (i.e., higher yield efficiencies) grew less. We conclude that, in young olive trees, vigor is inversely related to early bearing efficiency, which differs significantly across cultivars. The results support the hypothesis that early and abundant bearing is a major factor in explaining differences in vigor across olive cultivars.The olive industry requires canopy reduction to allow super high-density orchards which permit earlier production and continuous mechanical harvesting (Rallo et al., 2007;Tous et al., 1999). This has stimulated much research into reduced vigor or even dwarf cultivars

Partitioning of Dry Matter into Fruit Explains Cultivar Differences in Vigor in Young Olive (Olea europaea L.) Trees

“…In a previous study (Rosati et al, 2017), we found that tree growth was inversely related to yield efficiency across 12 olive cultivars over a period of several years, thus including adult trees. In that article, causality was not proven, as no defruiting treatments were carried out.…”

“…Given the competition between crop and vegetative growth, we hypothesize that early bearing is implicated in the difference in vigor between such cultivars and more traditional ones that do not fruit until much older. In a previous study (Rosati et al, 2017), we found that tree growth, in terms of both tree diameter and canopy volume increments, was inversely related to tree yield across 12 cultivars in young olive trees. Similarly, Di Vaio et al, (2013) found that across 20 cultivars, the least vigorous tended to have greater early yields.…”

SILVOLIVE, a Germplasm Collection of Wild Subspecies With High Genetic Variability as a Source of Rootstocks and Resistance Genes for Olive Breeding

“…Convincing evidence has been provided that these traits are genetically encoded by the root portion of the grafted plant, playing the rootstock genotype essential roles in shaping variation of these traits in the scion (Warschefsky et al, 2016). In addition, rootstocks can also affect the branching pattern of the scion (Costes et al, 2010) and promote early and more abundant bearing in young olive trees (Rosati et al, 2017(Rosati et al, , 2018. On the one hand, we have verified that all subspecies can be grafted with commercial olive varieties, including cuspidata, which has the maximum genetic distance with europaea ( Supplementary Table S9).…”

Effects of cultivar, fruit presence and tree age on whole-plant dry matter partitioning in young olive trees

“…Recently, it has been found that deflowering resulted in strong increments in vegetative growth also in young olive trees, and that this eliminated differences in vigor (i.e. vegetative growth) between plants of the cultivar Arbequina (low vigor) and those of the cultivar Frantoio (high vigor), suggesting that cultivar differences in vigor may be explained in terms of different dry matter partitioning towards fruit (Rosati et al, 2017(Rosati et al, , 2018a. This demonstrated that competition for resources plays a major role in determining tree growth in young olive trees, suggesting that tree growth is source limited (Rosati et al, 2018b).…”