• When auxins are applied early, in the white button state, it can positively influence the retention of fruit set and the development process, reducing fruit drop and ensuring production.
• This is due to antagonism with abscisic acid (ABA), which is the phytohormone of senescence.
• For its part, according to local research, the use of gibberellins (AG3) as essential for the size gain in the final stage of fruit formation prior to harvest.

Auxins, cytokinins and gibberellins are the most important phytohormones that function as growth regulators in cherry trees. When choosing to use these regulators, it must be a priority to ensure the balance of the plants in terms of technical/cultural management to maintain an adequate level of reserves, optimal vegetative development, load regulation according to the potential of the orchard and maintain perfect management. water according to the demands of the crop according to each phenological stage.

After the cherry harvest, it is a priority to focus on the nutritional recovery of the plant, its nutrient extraction is a fundamental task to maximize its productive potential. Given the physiology of fruit formation in sweet cherry and considering the rapidity of its phenological progress from full bloom to harvest, it is suggested to pay maximum attention to be successful.

“The development of the cherry fruit is very fast, we even find varieties with a shorter cycle with 45 days from full blossom to harvest (DDPF). This course is known as the “perfect run,” where every slip can diminish your full potential. Already in the season, the nutritional programs, both foliar and soil, are a base to be able to maximize the development of the fruit and foliage and thus achieve its maximum potential. These programs must be adjusted to the specific characteristics of each variety/rootstock combination, since in practice there are clear differences in demand for different nutrients and some special needs.”said Carlos Tapia, Avium director.

As a complementary aspect to nutritional programs, the use of growth regulators (Plant Grow Regulator; PGR) is required, which are part of specific actions to enhance the formation of fruits in the different phases of their development. Where its use must go hand in hand with an appropriate balance of the orchard in different areas (reserves, load regulation and water management).

The constant work of growth regulators such as auxins, cytokinins and gibberellins, are managed during three different phenological stages of the plant, which are cell division, stone hardening and cell elongation.

Stage one of the formation of the cherry tree, goes from flowering to the hardening of the stone and corresponds to cell division. It is the moment in which the cells that constitute the fruit are generated and their division is fundamental.

During this time the use of auxins has a direct action with the active growth of tissues of reproductive and vegetative organs, and the synthesis in plants is in charge of the juvenile meristems of both shoots, flowers and fruits. However, its action is secondary and never more important than cytokinins and gibberellins.

Various investigations have determined that in addition to what was mentioned above, the action of auxins has been related to fruit retention once the flowers have been fertilized due to antagonism with abscisic acid (ABA), which is the phytohormone of senescence.

“A type of synthetic auxin such as 2.4 DP has shown that, in early applications in cherry trees, in the white button state, it can positively influence the retention of fruit set and in the development process, decreasing at the end of the process fruit drop and ensuring production. It should be clarified that auxins do not have a direct effect enhancing fruit set, but rather work as abscission inhibitors of already formed fruits and not as fertilization and subsequent fruit set enhancers.Tapia added.

Cytokinins.

The phytohormones that are most linked to the cell division process are cytokinins, which, depending on the variety, could extend up to 25-30 days after full flower (DDPF). Although there is scientific evidence that it could already start from the exposed bouquet prior to the white button stage.

Over time, different sources of natural cytokinins have been used through foliar applications from full flower, especially using zeatins, beatins, among others, with positive effects on the increase in fruit size in stage I of cell division and that would be inducers of own cytokinins generated by plants. Information released last season on the use of Thiodiazuron at a concentration of 10 ppm applied between 5-7 DDPF showed clear results in increasing the weight and diameter of fruits and an improvement in the proportion of fruit in sizes larger than 28 mm. (Super Jumbo) compared to a control. In turn, it showed favorable results in dry matter of fruits, durofel, and without negative effects in color of cover, soluble solids and fruit condition in postharvest. In any case, this type of synthetic cytokinins should not replace the applications of natural cytokinins since they would be a complement as precursors of the action of the plants’ own synthesis. It is important to remember that the cell division period is the most important in the formation of the fruit and it will be at this stage where a strong base of dry matter is formed, concentration of soluble solids that will be very important when evaluating the condition and quality of the fruit. .

Giberelinas.

During cell elongation, the phytohormone that is most related to general management at this stage of cherry production is gibberellin. Its mode of action is mainly based on enhancing the cell elongation process in already formed fruits, specifically from the beginning of stage III of fruit development, recognized in practice from the color change from green to yellow, commonly known as “straw” color. ”. It must be taken into account that the great endogenous contribution of gibberellins is provided by the seed of the fruit itself.

“It is recognized that the application of gibberellic acid (AG3) has a positive and direct effect on the increase in fruit size when it is incorporated into the leaves in the cell elongation stage. The doses, based on a known concentration (ppm) will depend, in turn, on the cultivar in terms of its susceptibility to cracking, the complexity of having an adequate cover color and the state of charge, since it has been widely studied that the AG applications3 and its effect on fruit size could play against fruit splitting (greater caliber, more splitting) not only due to the effects of rain, a disordered color development and the genetic capacity of each cultivar to provide good fruit size. of natural form” added the expert.AG’s applications3In addition, it generates positive effects on the reduction of epidermal defects in the fruit such as pitting, bruising and roughness. However, in recent Chilean studies it has been shown that high concentrations of gibberellic acid could have an unfavorable effect on the stability of the pedicel tissue, responding with anticipated dehydration, which is an important quality defect at destination.