cromar contains natural compounds named fructans, which are chains of oligosaccharides of fructose with an action based mainly on alleviating or minimising the effects of high temperatures on the denaturation of anthocyanins.
Fructans are a natural source of sugars which, thanks to their solubility and absorption, exert a number of beneficial effects:
- They increase the osmotic potential of cells and maintain their water content under conditions of high temperatures, thereby avoiding the enzymatic and thermal destruction of anthocyanins.
- As they reduce thermal stress, the photosynthetic rate is not reduced and the plant thus does not decrease its production of sugars.
- They contribute to increasing the cell’s sugar content and stimulate the activity of the PAL enzyme (phenylalanine ammonia-lyase) involved in the synthesis of anthocyanins.
- They inhibit the re-greening effect of gibberellins.
cromar achieves an increase in the coloured surface area of fruit and greater colour intensity, which makes it possible to harvest fruit in fewer harvesting passes, thus reducing crop load on trees at first harvest and favouring colouration of the remaining fruit.
This product is totally safe; its application does not pose any risks to the crop or the operator. It does not leave any residues.
crops, doses and time of application for cromar®
Crops, doses and time of application
Pome fruit trees, especially red apple varieties, e.g. Red Delicious and bicolour (Fuji, Gala, Annurca…) varieties
One application by foliar spray at the onset of ripening and another application 15 days later:
- When the day temperature is 20–32 °C, apply a dose of 250 grams per 100 litres of water (2.5 kg per ha).
- When the day temperature is above 32 °C, apply a dose of 300 grams per 100 litres of water (3 kg per ha).
how colour develops
The appearance of colour is associated with fruit ripening. Chloroplasts in fruit cells are “dismantled”, which destroys chlorophylls. This phenomenon unmasks other existing pigments, such as carotenoids (β-carotene, lycopene). In addition, ripening involves the de novo synthesis of flavonoid pigments located in the vacuole, the most abundant being anthocyans or anthocyanins.
Anthocyanins are synthesised through the phenylpropanoid pathway; their precursor is phenylalanine. The first enzyme to act on this precursor in this pathway is phenylalanine-ammonia-lyase (PAL). This pathway is regulated at a genetic level and is highly sensitive to abiotic factors, such as temperature, light or UV radiation and osmotic stress, and to hormone levels (gibberellins) or mineral elements, such as inorganic nitrogen.
stabilisation of anthocyanins
Anthocyanins are stabilised by glycosylation; they bind to sugar molecules by the action of the enzyme UDP-glucose flavonol 3-0-glucosyltransferase at the onset of ripening (colour change) and accumulate in the vacuoles of epidermal cells during fruit ripening. The sugar in anthocyanin molecules confers them solubility and stability.
anthocyanins = cyanidin (aglycone molecule) + sugar
The type and number of sugar molecules bound to the aglycone, the position of the bond and other factors play an important role in the colour and stability of anthocyanins. Another factor of stabilisation is copigmentation, which is the acetylation of sugars with colourless flavonoids.
Anthocyanins have a high antioxidant capacity and are synthesised as a means of protection against light stress or photostress, as part of the cell’s antioxidant system.
poor conditions for colour development
With poor light exposure and high temperatures, fruit colouration is POOR.
Anthocyans accumulate to protect the tissue from photostress when too much radiating energy is absorbed and cannot be used; that is why low light levels and high temperatures do not cause this type of stress and thus do not lead to the synthesis of anthocyanins.
High temperatures (but not too high) are necessary for an appropriate photosynthetic rate, optimum fruit development and correct ripening. However, temperatures above 32 °C cause the degradation of anthocyanins.
During hot weather, the photosynthetic activity of leaves decreases sharply during the day and, at night, carbohydrates are used rapidly for breathing, which is more intense as temperature rises. This leads to carbohydrates not or almost not being available for the synthesis of pigments.
Colouration in fruit with a low sugar content and high gibberellin content is POOR.
The presence of sugars is essential for anthocyanin formation. Fruits with good light exposure but a low sugar content are poorly coloured.
good conditions for colour development
With good light exposure and low temperatures, fruit colouration is GOOD.
Low temperatures contribute to colour formation as they directly reduce the activity of gibberellins, which increases PAL activity and therefore the synthesis of anthocyanins.
Temperature variations between day and night, combined with cool night temperatures (10–15 °C) in the period prior to harvest, are optimal conditions for good colouration, as they increase the synthesis of anthocyanins.
A decrease in the temperature, in addition to its influence on fruit development, contributes to the synthesis of anthocyanins, as it stimulates photosynthetic activity, thereby leading to an increased production of carbohydrates, which will be used for the synthesis of anthocyanins.
Colouration in fruit with a high sugar content but low gibberellin content is GOOD.
A certain sugar threshold value in the cell induces the expression of the genes involved in the synthesis of anthocyanins, while gibberellins inhibit these effects.
Trial with Fuji apples
Location: Lérida (Spain), year 2015
Two foliar applications of cromar were made at a dose of 3 g/l, the first at the beginning of colour change and the second 15 days later.
% of apples (% of coloured surface area)
The number of apples was measured in relation to the proportion of coloured surface area 30 days after the first application. Treatment with cromar achieved 25 % more apples with between 75 % and 100 % of coloured surface area with respect to the control group.
% of apples (colour intensity)
Peel colour intensity was also measured, and it was concluded that treatment with cromar achieved a higher percentage of apples with a shiny red colour, with a 44 % increase in comparison with the control group.
Trial with Gala apples
Two foliar applications of cromar were made at a dose of 2.5 g/l, the first at the beginning of colour change and the second 15 days later.
The proportion of coloured surface area was measured in 100 apples at harvest. In the sunny area, apples had 30 % more coloured surface area than those in the control group, while in the shaded area, apples had 44 % more coloured surface area than those in the control group.
% of coloured surface area (apples at second harvest)
% superficie de piel coloreada (frutos de segunda cosecha)