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 4 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.

Fruit pit hardening: Physical measurement during olive fruit growth

Orchard experiments were carried out in Botswana with the objective of evaluating the effect of 2,4-dichlorophenoxyacetic acid (2,4-D) on reducing premature fruit drop. Different concentration levels of the 2,4-D (8, 16 and 20 mg/L were applied exogenously to mature fruit trees of sweet orange (Citrus sinensis L.) in the 2004/2005 season. In the 2005/2006 season the 2,4-D treatments ranged from 20 to 40 mg/L concentration. There appeared a general increase in fruit drop for the month of October in all treatments but a decrease in fruit drop was observed in the fruit trees with 16 and 20 mg/L 2,4-D concentration, that is, from November through February; with the latter showing the least number of fruits that dropped throughout the execution of the experiments. The application of 20 mg/L 2,4-D significantly reduced fruit drop by more than 50% but higher concentration levels of the plant growth regulator significantly increased fruit drop. It was also evident that, small sized fruits were more susceptible to fruit drop than larger fruits. These findings suggested that, 2,4-D can be an effective tool to control fruit drop by enhancing retention, as well as improving the quality of navel oranges under dry climatic conditions.

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The influence of exogenously applied 2,4- dichlorophenoxyacetic acid on fruit drop and quality of navel oranges (Citrus sinensis L.)

SummaryPeaches and nectarines belong to a self-pollinating species and therefore tend to set a large number of small fruit. Chemical-thinning is not efficient in stone fruit. Consequently hand-thinning of fruitlets has become the commercial practice, although it is very expensive and not efficient at this stage. Over five consecutive years (2003 – 2007), application of 25 mg l−1 GA3 to the basal part of shoots during flower bud induction (60 d after full bloom ) reduced flowering of ‘Snow-Queen’, ‘Queen-Giant’, and ‘Arctic Mist’ nectarines, and ‘Scarlet-Snow’ peach in the following season. As a result, the time spent on hand-thinning was reduced by ca. 50%, and the yields of large fruit increased approx. two-to-three fold. Ripening of ‘Queen-Giant’ nectarine fruit was delayed slightly, and the incidence of internal breakdown following storage was reduced. Since the effect of the GA3 treatment lasted for only 1 year, it is suggested that it should be applied annually.

GA3 inhibits flowering, reduces hand-thinning, and increases fruit size in peach and nectarine

Two plant growth regulators (PGRs), one auxin analog i.e. triclopyr and one cytokinin i.e. forchlorfenuron were applied on two apricot cultivars (“Nafsika” and “Niovi”) during the early stages after fruit set (cytokinin) and at the beginning of pit hardening (auxin). The two PGRs were applied either alone or in combination, each at the time indicated above. The fruit growth rate along with fruit physiological, organoleptic and phytochemical characteristics was assessed during two successive years. In all treatments where auxin was included, the growth rate of the fruits was significantly enhanced. Fruit weight increased significantly with auxin (by 30% in “Niovi” and 34% in “Nafsika”), as well as the diameter in chicks and suture line along with fruit length, without altering fruit shape, as confirmed by fruit shape index and sphericity calculations. Although the concentration of carbohydrates was not significantly different among treatments, the overall carbohydrate content of the fruit was significantly enhanced by auxin application. Total phenolic compounds as well as individual phenolic ones and antioxidant capacity of the fruit were not influenced by PGRs application. Cytokinin did not enhance fruit quality parameters, while at the same time retarded maturation, as the fruits retained the green color, firmness was quite high as were also the total organic acids and titratable acidity. The present findings support even further the use of auxin as the PGR of choice for stone fruits and especially for apricot, while cytokinin do not seem to be able to improve fruit quality characteristics.

Auxin (triclopyr) and cytokinin (forchlorfenuron) differentially affect fruit physiological, organoleptic and phytochemical properties of two apricot cultivars

Quality is the major factor which is perceived by the consumer. In stone fruits, quality criteria can be judged by appearance, colour, size, fragrance and their internal composition such as sugars, phenolics, specific gravity, total solids and other biochemical constitutes. Stone fruits are considered as a rich basket of phytonutrients. There are numerous factors which determine quality of the fruits. Orchard factors like orchard soil, microclimate, quality of irrigation water, application of nutrients, rootstock, canopy management, pollination and use of hormones are more prominent which influence overall quality and acceptance by the consumer. The reason being they regulate different catabolic and anabolic processes which lead to further improvement in quality characteristics. Climatic conditions affect from its cultivation to harvest. High temperature leads to injury, whereas frost also caused damage to cells. Fruit size and colour development in temperate stone fruits are highly variable and dependent upon temperature. Mineral nutrition determines various levels of photosynthates, sugars, acids and other compounds. Deficiency of these leads to various physiological disorders. Suitable rootstocks control accumulation of nutrients and water from the soil and also influence vigour of the tree. Some salt-resistant rootstock improves fruit quality in mango, peach and ber. Similarly, training and pruning are major aspect in temperate stone fruits. Hormones play an important role in governing various metabolic processes and enzymes. They create resistance against various diseases and stresses. Therefore, combination of these orchard factors not only influences the quality but also alters the shelf life. This chapter will be discussing about various orchard factors which influence quality and food value of stone fruits.

Orchard Factors Affecting Postharvest Quality of Stone Fruits

SummaryThe only commercial apricot cultivar grown in Israel, ‘Canino’, produces relatively small fruit. Over three consecutive years (2003–2005), application of 25 – 50 mg l–1 2,4-dichlorophenoxypropionic acid [2,4-DP; as its butoxyethyl ester (PowerTM)], 15 mg l–1 3,5,6-trichloro-2-pyridyloxyacetic acid [3,5,6-TPA; as the free acid (Maxim®)], or 25 – 40 mg l–1 2,4-dichlorophenoxyacetic acid (2,4-D) plus 30-50 mg l–1 naphthaleneacetic acid (NAA; 0.3% – 0.5% AmigoTM), at the beginning of pit-hardening, when the widest diameter of the fruit was 25 mm, caused appreciable and significant increases in fruit size and total yield. Anatomical studies revealed that the main effect of these synthetic auxins was via direct stimulation of fruit cell enlargement. None of the above auxins had any negative effect on fruit quality, either at harvest or after 1 month of storage at 0°C, or on return yield in the following year. Two other synthetic auxins formulations: 2,4-D (HadranolTM) and 2,4-dichlorophenoxypropionic aci...

Ben-Arie Ruth

Papers

The effect of synthetic auxins on fruit development, quality and final fruit size in ‘Canino’ apricot (Prunus armeniaca L.)