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Practical tips for the prevention of cracking of sweet cherries
Cracking of cherries or division into parts
In the South are cultivated the more tolerant varieties such as Lapins, Sweet HART, Kordia and Regina, the latter is the most strongest of all varieties, economic importance at present. However, to achieve high-quality expertspeople fruit, it is necessary to organize the defense of production, in particular, to organize a superficial cover. The physiology affects the quality of the fruit and can, in some seasons, to lead to complete loss of the crop.
To better understand the phenomenon of cracking, it is necessary to know the phase of development of the fetus. The first phase is characterized by rapid growth. The second coincides with the cell differentiation, the duration of which depends on the variety (early or late). The latter provides for further growth of the fetus, and includes approximately ten to twenty days to Mature. The period of greatest sensitivity to cracking occurs at the time of dyeing and the transition to ripening in the presence of moisture or heavy rains.
Studies conducted to determine the mechanisms responsible for
The results of these studies, the main reason is the absorption of water through the epidermis of the fruit ( "microfractures"). Furthermore, the absorption of water through root canal, can lead to segmentation of the fruit, when the rains come after long periods of drought.
Water absorption through the cuticle of the fruit by osmosis may cause only slight superficial damage to the epidermis. In contrast, the increase in cell volume affects the peripheral histological elements, such as the mesocarp and the pericarp, which can lead to tearing if you exceed the limits of elasticity.
These fruits with thin-walled cells represent the greatest degree of manifestation of the phenomenon being more evident in the apical region of the fruit where the outer layer of the cuticle is absent. Damage in sweet cherry fruits can be divided into three categories:
A) the Legs (present in a region located on the side of a dark substance)
C) Apical
C) the Backrest can have very serious injuries that can go into the pulp.
Damage belonging to the first two categories are manifested in the fruit before the color change. These injuries may heal, if they occur at the time of the color change, while when fully ripe, the tissue is unable to respond and the damage would heal. On the other hand, damage on fruits, ensure access and dissemination of pathogenic micro-organisms such as Monilia, Gray mold, and R. nigricans.
Factors affecting cracking
A) Factors of environment and cultivation
• Climate and soil conditions
• Rootstock
• Method of stringing
• Planting density
C) Varietal susceptibility
• Ability to spread on the epidermis
• The thickness and permeability of the cuticle
• Stomatal density
D) Fruiting and yield characteristics
• Productivity
• The size of the fetus
• The integrity of the pulp
• The state of ripeness
• Concentration of sugar in the juice
The most susceptible varieties
| Category cracking | Grade |
| Susceptibility to more than 40% | New Old Garnett, Sam, Silvia |
| Sensitivity 20% 40% | Celeste, Bing, Lambert, Leith Maria |
| The susceptibility of less than 10% 20% | The Summit, Van, Amberst |
| Moderate resistance to 10% | Lapins, Sweet HART |
| Increased resistance | Kordia, Regina |
Fruit cracking occurs due to a number of chemical factors (e.g., composition of the wax cuticle), morphology (cuticular fractures), physiology (e.g., polarization metabolic pathways related to fractures, cherries) in addition, the relative humidity, the influence of growth regulators of plants, as nutrients and water regime of the trees. High potassium has a relationship with the increase in the cracking of the fruit. In order to avoid cracking or minimize, you need to know these factors and their interaction. Currently, there are a number of technical strategies to reduce incidence.
System for the prevention of cracking of sweet cherry
Physico-mechanical system
Research conducted abroad and at the national level, have proved the effectiveness of the cover film to prevent cracking of cherries. As a rule, the structures consist of concrete or wood poles. The support surface is covered with a transparent plastic film or other material, characterized by a different spectrum of light transmission, as in the case of bright materials that allow you to absorb infrared radiation and lower the temperature during peak heat, allowing, in turn, improve fruit quality, among other aspects. Woven fabrics of synthetic fibres are fixed by means of plastic fasteners, and incorporate a steel or metal mounting bushings. The shelter is set along the projection of the garden with an approximate height of 5 metres, is fixed in order to avoid the effect of "sail" caused by the wind. In southern Chile, there are zones characterized by strong winds coming from the South, in the period of development and ripening. For the above reasons, it is imperative that the design had very good fixation or anchoring to avoid falling off. Distance of each section of the cover is aligned on the distance between two consecutive stanchions. A drawback of woven fabrics of synthetic fiber is its high cost, the requirement to have a large number of workers; maloustoichiv or ineffective in very windy areas and where the environment has extreme conditions (foothill areas), where the protection system may be damaged. In particular, damage can be subjected to the support structure and the covering fabric, mainly due to climatic phenomena, such as increased wind and snow load.
There are stationary and mobile sealing of the structure. The first option, after
However, this system is more expensive in comparison with stationary, as it requires high labor costs. In any case, it is desirable to use light-stabilized ukryvnoy system, as it will lead to economic benefits in the future.
Among the most common covering system for growing sweet cherries are the following types:
A) Polytunnel: constructed of steel arches with a height of four meters, c lateral support, and is covered with a film for the shelter of the trees.
In) Grid: design involves the use of concrete or wooden stands from 5 to 6 meters tall. Metal or plastic straps used to support cloth.
C) Tunnel: hothouse design, usually used to grow vegetables in southern Chile. The tunnel is composed of metal arches, with a height of approximately three meters. When using this covering system, the system forming the crowns of the trees must be Y, a V-shaped or columnar, with the aim of efficient use of space. This system, in addition, prevents cracking, allows to regulate the microclimate, growth and productivity of the garden. It was found that the use of tunnels allows you to modulate the time of harvest, maintaining high quality for export markets. The tunnel is better suited for areas with high wind load during growth and ripening.
The use of shelters film significantly reduces cracking of cherries. However,fabric made of synthetic fibers can cause a rise in temperature and relative humidity, in particular in the upper part of the tree, reducing fruit quality during harvest, influencing the fruit cracking, and on such factors of fruit quality, such as hardness, color and sugar content. Vysheozvuchennoy depends on the type of fabric used for shelter, grade (combination of rootstocks), control gear, shelter, and especially from ventilation in the top to drain excess moisture.
For special climatic conditions of southern Chile, you must perform research to determine project type of structures that will be mounted shelters, tunnels and materials (such as textiles) and their effect on yield and fruit quality. Foreign studies conducted with different plastic materials (physical characteristics) already show their influence on the ripening process of the cherries and on the qualitative characteristics, as previously mentioned.
Other physical and mechanical systems, used to prevent cracking of helicopters and air nozzles to remove water from the fruit. This technology, however, has increased the cost and the results are not effective.
Chemical system
A mechanism based on the formation of the outer film is able to balance osmotic
This fact helps to create greater coherence between the cells. In addition, it prevents the disintegration of the fruit by inhibiting the action of enzyme polygalacturonase responsible for the degradation pectate.
Calcium salts may enhance the structure of the cell walls, to enhance the mechanical strength of tissues and reduce water absorption rate. Foliar application of calcium is applied directly on the surface of the fruit, as translocation from leaves to fruits is limited. Calcium can easily be washed during heavy rains, especially in southern Chile. In order to reduce the leaching of calcium, experimental tests were carried out using automated systems on the crowns of trees able to activate the use of calcium chloride (CaCl2) on the apical parts of the plant simultaneously with the rain. The automated system was deemed successful. However, for technical and economic reasons (high cost of equipment) is not a solution to the problem on a large scale. The use of copper salts has shown good results in reducing the cracking of cherries, but the toxicity of the treatments does not recommend their use.
Foliar application of silicon (sodium silicate) has reduced the percentage of cracking of sweet cherry, extraordinary climatic conditions of southern Chile. However, when planting less tolerant varieties, and in conditions of heavy rainfall (>22 mm), fruiting occurs in 30-60% of the fruit. This indicates that currently the only effective technology available to prevent the generation of cracking is the use of nets or covering materials.
INIA Chile,
Translation: Rasul Telibekov, Club SAP
