Alternate bearing in olive initiated by abiotic induction leading to biotic responses

Alternate bearing of olive trees is one of the most troublesome characteristics of this commodity, impacting its economy due to labor distribution, fruit and oil availability, oil mill capacity and marketing. The metabolic changes leading to alteration in fruit production are generally considered of direct genetic nature. In the present review, this approach is challenged, showing that all the biotic-metabolic changes in olive leading to ‘on’ and ‘off’ years are the results of initial abiotic effects on the trees. The nature of the metabolic changes induced by the abiotic regional and annual conditions described are, no doubt, genetically controlled but initiated only as a result of adverse environmental abiotic conditions such as seasonal temperatures, water stress, and soil nutrition conditions

Evaluation of the present information on the mechanisms leading to flower bud induction, evocation and differentiation in olea europaea

7 páginas, 1 figura, 2 tablas, 16 referencias.-- The "5th International Symposium on Olive Growing" will be held in Izmir, Turkey between 26 September- 2 October, 2004.-- Fué leído en el citado simposio por Shimon Lavee y por motivos desconocidos no figura en el libro de actas.The lack of regularity in reproductive organ development leading in many cases to severe alternate bearing is one of the major problems and drawbacks in today’s economy of the olive industry. Although a considerable amount of work has been devoted during the second half of the last century to this subject, our understanding of the metabolism leading to flower bud differentiation and ability to control alternate bearing is still limited. The genetic potential to induce flower buds is environmentally dependent. Temperature was found the most eminent environmental factor to affect the metabolism leading to flower bud induction. Specific but not yet clearly defined temperatures in early summer on one hand and relatively low winter temperature gradually fluctuating with warm ones in the winter are essential for inducing the metabolic pass-ways initiating the sequence of processes leading to the formation of flower buds. Changes in the RNA content of lateral buds expected to develop inflorescences in the spring was shown to occur already in the fall. Thus, some workers suggested that the low winter temperatures act as a dormancy breaking agent of pre differentiated buds. On the other hand, these same buds were shown to grow vegetative when induced without or with unsuitable winter temperature. This could be explained as dedifferentiation process however, no differentiated floral organs have been found in buds in the fall and no aborted secondary growing points in lateral buds have been found either. The presently available data indicate that neither summer-fall nor mid winter seasons could be individually responsible for flower bud initiation. The presently developing fruits on the trees were found to have a major affect on controlling the metabolism leading to reproductive development although they were shown to have no effect on the tree’s carboydrate level and only a minor one on the nitrogen balance. However, the protein composition of leaves on fruiting and non fruiting trees was found to be different with specific proteins developing in leaves of the fruiting trees and others on the non fruiting ones. Furthermore, chlorogenic acid, related to the cinnamic acid pass-way was found to accumulate in leaves of fruiting trees and to inhibit specifically winter differentiation. The messenger from the developing fruits to change the leaf metabolism is not yet entirely clear but believed to be specific gibberellins. Based on the present available data including the effect of harvest time on the following reproductive development and the amount of yield on vegetative growth, a two phase mechanism for reproductive bud development in the olive could be suggested. The initial developing bud of the olive is suggested to be indifferent. During the “off” year, when tha plant has normalized its situation after a heavy crop, the buds receive their initial induction to develop reproductive. Those buds which received their initial induction to differentiate reproductively will respond to the winter inductive conditions.Peer reviewe

The floral biology of the olive: effect of flower number, type and distribution on fruitset

10 pages, 1 figure, 5 tables, 15 references.The effect of flower number and distribution on the fruiting behavior of various olive cultivars was studied over a period of 10 years. The number of staminate flowers within each cultivar had no significant effect on fruitset. Pre-bloom removal of up to 50% of the flowers did not affect fruitset. Variation in prebloom flower-removal position resulted in similar fruitset per inflorescence, whether flowers were removed along the inflorescence axis or from the distal half of each inflorescence. Removal of half of the inflorescences resulted in doubling the fruit set on the remaining ones, except in cv. Koronaiki which normally sets more than one fruit on most of its inflorescences. The distal fruitful inflorescence set more than one fruit (mostly two) on 70–80% of the shoots of various cultivars. In cv. Santa Caterina a clear increase in fruitset per shoot was observed when 80% of the flowers per inflorescence were removed. In this cultivar the lateral flowers were significantly more fruitful than the king flower. This however, was not the case with cv. Manzanillo.Peer reviewe

Biennial bearing in olive (Olea europaea)

Alternate bearing is a wide spread phenomenon in many fruit tree species and causes severe labor, marketing and thus economical problems. The domestic olive (Olea europaea) is genetically highly alternating in fruit production. The expression of alternate bearing in olives involves a wide range of changesin activation and repression of endogenous metabolic pathways. The degree of alternate bearing is highly dependent on the environmental conditions and might be very different in accordance with the climate in each growing region. The objective of this work was to present the main endogenous and environmental factors and their interactions that lead to alternate bearing and to review approaches with which alternate bearing is reduced

Evaluation of the present information on the mechanisms leading to flower bud induction, evocation and differentiation in olea europaea

6 páginas, 1 figura, 2 tablas, 16 referencias.-- Trabajo presentado al VI International Symposium on Olive Growing, celebrado del 9-13 de septiembre 2008, en Évora, Portugal.Environmental factors such as suitable light and thermal conditions are essential for the reproductive development of olive buds. However, the tree and its buds have to be in a suitable responsive physiological state in order to respond. Furthermore sufficient well developed buds from the previous season with a good nutritive balance, capable to differentiate are required on the tree. In the present paper, we are demonstrating the changes in the nutritional state of the tree developing in ON and OFF years affecting the responsiveness of the buds and level of vegetative growth to the environmental conditions. After a heavy crop a nutrient dilution occurred and vegetative growth is inhibited. Thus, a following growing season is required to regain a good nutrient balance for generating vegetative growth with sufficient buds responsive to environmental differentiation stimuli for the initiation of the next ON year.Peer reviewe

Evaluation of salt tolerance of in vitro-grown grapevine rootstock varieties

6 pages, 5 figures, 3 tables, 32 references.The response of 11 grapevine rootstock varieties to increasing salt concentrations (0, 50, 85, 120, 155 mMNaCI) was studied under in vitro and growth chamber conditions. The effect of salinity on the mortality of explants was compared with that of plantlets grown under growth chamber conditions and with data in literature on rootstock resistance under field conditions. In addition, in vitro stem elongation, bud number, and rooting ability were related to salinity. The rootstock varieties can be divided into sensitive (41 B, R.Lot, 110 R, 140 R and 161-49), moderately tolerant (13.5 and Ramsey) and tolerant (196-17, CH-1, CH-2 and Superior). Measurements ofthe water and nutrient contents of plantlets indicate that increasing salt concentrations decreased the hydration of aerial parts and roots of all plants; however, the decrease of hydration was smaller in salt tolerant varieties. Increasing salt concentrations significantly reduced the K content and, to a smaller extent, the P and Ca contents. With and without salt treatments the levels of K and P were lower in sensitive plants. Na and Cl accumulated to a higher extent in tolerant plants. The tolerance to NaCl of in vitro-grown rootstocks seems to be due to their capacity to accumulate salt, to increase K concentration in the tissue and to maintain a high water content. Our results indicate that salt tolerance of grapevine varieties may be tested under growth chamber conditions and using in vitro explants.Peer reviewe

The floral biology of the olive II. The effect of inflorescence load and distribution per shoot on fruit set and load

12 pages, 1 figure, 6 tables, 16 references.The effect of inflorescence number and distribution along the shoot on the level of fruit-set was studied using `ON' year olive trees with a high level of floral differentiation. Reduced levels and different inflorescence distribution patterns were created artificially by hand inflorescence thinning. In most cases, removal of up to 50% of the inflorescences had either no effect on the total amount of fruit load per shoot or increased it significantly. Thus, the percentage of fruit set increased with the reduction in inflorescence number due to both, a higher percentage of fruitful inflorescences and higher numbers of fruits per inflorescence. Inflorescences on the distal half of cv. Barnea shoots were less fruitful than on the proximal half. With cv. Manzanillo no such difference was found. Single inflorescence distribution significantly raised the level of both, the fruit load and fruit set compared with distribution of the inflorescences along the shoot in pairs, although the amount of this increase varied with the different thinning levels. The actual percent of fruit set on a flower number basis increased in parallel with the reduction of their number in response to inflorescence thinning.Peer reviewe