The price of fruit is largely determined by quality factors whose appreciation is at the mercy of customer’s whims. For the fresh fruit market flavor and appearance are still basic determinants for the acceptance of the fruit and the popularity of the cultivars. In addition, the importance of fruit size as a parameter of quality has increased markedly in recent times. This is reflected in the changes in the legal regulations which have risen recently in minimum diameter to accept a fruit as marketable in the European markets. Further, the consumer’s preference for big fruit determines huge differences in market price to a point that the income from the smaller, albeit marketable, fruit is often lower than the actual costs of production and commercialization. Fruit size has become as important as total yield in the determination of the profitability of the citrus plantations. This applies not only to the small-fruited mandarins but also to species of a larger fruit size such as lemons, oranges and grapefruits.
Fruit size is affected by many factors and for a given cultivar may range between wide limits. In a survey carried-out with more than 500 trees of the Navelate sweet orange it was found that the mean fruit weight ranged from 280 g (a very large fruit) to less than 125 g (Guardiola, 1988). Some of the factors affecting fruit size are beyond the control of the grower (climate effects) or may not be manipulated (soil type and rootstock). On the other hand, fruit size is inversely related to fruit number and crop load, but this effect accounts for less than 500% f the total variability in size. Flower number, a physiological parameter which may be manipulated, and several cultural practices -pruning, girdling, fertilization and irrigation-, have marked effects on fruit size. However, in many cases a premium is obtained increasing fruit size beyond the limit which may be obtained through the optimization of these parameters. The application of synthetic Auxins is performed to achieve this goal.
Click here to download the full article.
Source:
Jose L. Guardiola
Valencia. Spain