symptom
Grape coloring takes 20 to 30 days from the beginning of berry coloring to full maturity. Some varieties accumulate pigment in the cortex, and the chlorophyll of white varieties decomposes in large quantities, showing yellowish white transparency or producing fruit powder, and the seed coat gradually changes color. The sugar content of the berries increases rapidly, and the acidity and tannins decrease.
Etiology
Research on the regulation of grape fruit coloring by plant growth regulators suggests that the level of endogenous ABA (abscisic acid) is a signal to start grape fruit entering the initial ripening period, and the decrease in the level of endogenous hormone auxin (IAA) in fruit is the root cause of grape coloring .
Both the increase of ABA level and the decrease of IAA level in the later stage of fruit development can stimulate the plant to produce ethylene, thereby enhancing the activity of phenylalanine ammonia lyase (PAL) and the permeability of the cell membrane, promoting the movement of sugar into the cell, and affecting the production of anthocyanins. The synthesis and accumulation may have a direct effect.
The use of plant growth regulators GA (gibberellin) and CTK (cytokinin) in the early stage of fruit development can mediate the levels of endogenous ABA and IAA in the later stage of fruit development, thereby controlling coloring. Applying exogenous GA and CTK in the late stage can inhibit the degradation of chlorophyll in the fruit and delay the synthesis of anthocyanins.
The study also found that ABA and ethylene can enhance the gene expression of flavonoid 3,5-glycoside conversion enzyme (UFGT), the control point of anthocyanin biosynthesis in grape peel, and increase the synthesis of chlorophyllase. There are experiments in Japan that manganese deficiency in grapes can also cause poor coloring.
Prevention method
(1) At the initial stage of coloring of 10% of the Kyoho grape fruit, soak the ears with 250 mg/L S abscisin fermented by fungi containing 1% of abscisic acid (ABA), which can improve the coloring index of the grapes, and turn the color blocks early when ripe, and the pulp No softening, no ear drop. Red Globe grapes can also be treated with 50-100 mg/L of abscisic acid (ABA) compound with an effective content of 1.25%, which can effectively improve the coloring of the grapes, and the peels will start to change color after 7 days of use.
(2) Spray 500-1000 times liquid of 5% uniconazole wettable powder on grape ears about 20 days and 10 days before grape fruit ripening, which can significantly promote the formation of anthocyanins in the pericarp, promote fruit coloring, and increase fruit weight by 5 %, improve fruit quality.
(3) Advocate the use of accelerator control agent PBO. PBO can make the grapes have strong fertilization function, high fruit setting rate, good coloring, basically no fruit cracking, fruit expansion, single fruit weight increase, fruit size uniformity, and prevent yield reduction by 10% to 25%.
