Timing of fruit removal affects concurrent vegetative growth and subsequent return bloom and yield in olive (Olea europaea L.)
ABSTRACT Olive (Olea europaea) demonstrates a high tendency toward alternate fruit production, with significant negative consequences on the industry. Fruit load is one of the main cause-and-effect factors in the phenomenon of biennial bearing, often disrupting the balance between reproductive and vegetative processes. The objectives of the present study were to identify the time range during which heavy fruit load reversibly interrupts the reproductive processes of the following year. The linkage between timing of fruit removal, vegetative growth, return bloom, and fruit yield was studied. Complete fruit removal in cv. Coratina until about 120 days after full bloom (August 15) caused an immediate resumption of vegetative growth. The new shoots grew to twice the length of those on trees that underwent later fruit removal. Moreover, a full return bloom, corresponding with high subsequent yields, was obtained by early fruit removal, while poor or no bloom developed on late-defruited or control trees. Thus, the critical time to affect flowering and subsequent fruiting in the following year by fruit thinning occurs in olive trees even weeks after pit hardening—much later than previously suggested. Furthermore, the data indicate that flowering-site limitation, due to insufficient or immature vegetative growth during the On-year, is a primary factor inducing alternate bearing in olive.
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ABSTRACT: The olive tree (Olea europaea L.) is widely known for its strong tendency for alternate bearing, which severely affects the fruit yield from year to year. Microarray based gene expression analysis using RNA from olive samples (on-off years leaves and ripe-unripe fruits) are particularly useful to understand the molecular mechanisms influencing the periodicity in the olive tree. Thus, we carried out genome wide transcriptome analyses involving different organs and temporal stages of the olive tree using the NimbleGen Array containing 136,628 oligonucleotide probe sets. Cluster analyses of the genes showed that cDNAs originated from different organs could be sorted into separate groups. The nutritional control had a particularly remarkable impact on the alternate bearing of olive, as shown by the differential expression of transcripts under different temporal phases and organs. Additionally, hormonal control and flowering processes also played important roles in this phenomenon. Our analyses provide further insights into the transcript changes between "on year" and "off year" leaves along with the changes from unrpipe to ripe fruits, which shed light on the molecular mechanisms underlying the olive tree alternate bearing. These findings have important implications for the breeding and agriculture of the olive tree and other crops showing periodicity. To our knowledge, this is the first study reporting the development and use of an olive array to document the gene expression profiling associated with the alternate bearing in olive tree.PLoS ONE 02/2013; · 3.53 Impact Factor
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ABSTRACT: In drupe-type fruits, pit hardening, resulting from sclerification of the fruit endocarp, is widely used as a phenological marker for both physiological studies and orchard management. In spite of the importance of pit hardening for understanding fruit development processes and for agricultural practices, however, its quantification has remained obscure and precision has been lost with time and lax usage. In this study we used a mechanical device to measure the physical pressure required to break the olive pit in order to define the timing of pit hardening more precisely and to permit closer observation of its relationship to fruit and endocarp growth and development. Over four years we found that pit-hardening pressure increased following a sigmoid pattern, at first gradually but then with a large and rapid increment of change in a relatively short period of time. The rapid acceleration of hardening began at the time when pit longitudinal and transverse diameters attained their maximum size. That timing is consistent with the anatomical differentiation of the sclerified endocarp cells which can no longer expand nor divide. The results improve our knowledge of pit hardening and provide a more precise context for evaluating the metabolic costs, physiological interactions and genetic controls of stone fruit endocarp development. On a practical level, the association of the intensification of pit-breaking pressure with the cessation of pit expansion indicates that pit diameters can be useful morphological markers to identify the onset of this period.Annals of Applied Biology 01/2013; 163:200-208. · 2.15 Impact Factor