1, the disease during storage and the law of occurrence

1.1 Fungal Diseases Existing studies have shown that all pathogens that damage grapes during storage are fungi. The growth of bacteria is limited due to the pH of grape berry in the range of 2.9 to 4.0. Pathogens that damage grapes during low temperature storage include: Boltyclem Pets, Penicillias pp., Allemaria spp. , Cladosprium Sp. and Stemphylium sp., etc. The pathogenic bacteria in the grape during storage and transportation at room temperature are mainly Rhizopusstolorifer (Ehrenb.: Fr.) Vuill.

1.1.1 Gray mold Botrytis cinerea is the most harmful during storage. The fruit is susceptible to the disease in the field. It develops at low temperature (0～8°C), and can grow and reproduce at -5°C, and the grape resists it. weak. The pathogenic bacteria invade the stratum corneum and epidermis through the wound, and the onset is rapid, causing the fruit depressions to shrink, the peels easily broken, a large number of ash or yellow mycelium and spores accumulate on the skin, the internal chemical composition changes significantly, tannins and certain Aromatic substances are destroyed, causing the fruit to lose its commercial value.

1.1.2 Penicillium wilt Penicillium is infested from the wound and natural cracks of the fruit during cold storage at 0 to 10°C, and it spreads deep into the flesh tissue. The rotten berries have a very musty smell. But it does not infect healthy fruits.

1.1.3 Alternaria rot disease grapes infected by Alternaria alternata, the incidence of disease in the 0 ~ 2 °C conditions, the incidence of the site in the fruit stems, fruit stems and fruit side, resulting in fruit stems shrinking, fruit shattering . Mycobacterium tuberculosis is susceptible to fruit and fruit stems and occurs at low temperature storage. Rhizopus and black mold occur in the hot season.

1.1.4 Branches of fungal rot The sites of infecting D. cinerea are mainly stems of fruit stems and stalks, and the fruit is not susceptible to disease. The onset of symptoms is similar to that of Alternaria syringae, and the onset of disease occurs when other pathogenic bacteria are inhibited at 0-2°C. The bacteria can also grow at a temperature of -8°C, but it grows fastest at 24°C and stops growing above 34°C. Uninjured grapes are easily infected by wounds.

1.1.5 Soft rot Rhizopus has a high pathogenicity rate. Only 24 to 48 hours after infection, the infected parts are mainly fruits. After the hyphae invaded the fruit, the infested area was first immersed in water-like patches, and then the fluid flowed, rotted, the peel peeled off, and infected the healthy tissues at the speed. Because the pathogenic bacteria cannot grow at -0.5°C to 0°C, the storage fruits can be stored for several days under high temperature and this disease can occur. The diseased fruit grows with gray bacilli.

1.2 Physiological diseases

1.2.1 Cracking If the humidity is too high during storage, some varieties will produce cracks. Due to different species, their symptoms are also different. Some are longitudinally split from the bottom of the fruit pedicle; some are split from the top of the fruit and occur on the stigma. After the berries have cracked, some will have an outflow of juice, which will be quickly infested by various molds, causing the entire fruit and ear to spoil.

1.2.2 Freeze-damaged berries differ in their sugar content in different freezing points. Varieties with low sugar content are more likely to reach freezing point, suffer from freezing injury, poor appearance of grapes damaged by frost, fruit wilting, severe brown, fleshy soft rot, and Juice oozes out.

1.2.3 SO2 Damage When the concentration exceeds a certain standard, the fruit will produce bleaching, the red variety will turn light red, the white variety will turn gray, and then it will turn brown. The fruit wound and the part of the fruit pedicle show symptoms first and then spread to the entire fruit. In severe cases, the whole ear, including the spikes, is bleached. Damaged grapes turn brown when exposed to high temperatures after leaving the storehouse. They have a very strong taste of sulfur and lose their value.

1.2.4 Ammonia Harmony The refrigeration system of a cold storage is a closed system. Common ammonia is used as a refrigerant. If the pipes are not closed tightly or there is a problem, the missing ammonia will cause damage to the grapes. The red grapes will turn blue and the green grapes It will turn light blue and it will also make the grape stems dark blue or black. Prolonged exposure to high concentrations of ammonia will kill tissue cells, causing the grapes not to return to their normal appearance and gradually turning brown.

2. Prevention of diseases during storage

2.1 Reasonable cultivation and management Reasonable cultivation techniques are conducive to the accumulation of sugar in grape berry, which is the premise to enhance the storage of fruits. Organic fertilizer and potash fertilizer should be added, and the use of nitrogen fertilizer should be strictly controlled in the later period. Water should be stopped within half a month before harvesting, and reasonable loads should be used to strengthen comprehensive prevention and control of pests and diseases. In addition, pre-harvest calcium injection can increase the calcium content in the fruit, maintain the hardness of the fruit, enhance the fruit's storability, and improve the fruit's ability to resist decay. The calcium content of berries is a factor that determines the storage stability.

2.2 Appropriate harvesting and avoiding bruising The grape fruit is a non-respiratory leap. The post-harvest carbohydrate content is reduced due to respiration and directly affects the storage quality and storage period of the grape fruit. The biochemical indicators of proper fruit harvesting are: sugar content of about 18%) 0.6% to 0.8% of leg content, sugar to acid ratio of 20 to 35:1, ratio of total pectin to soluble pectin 2.7 to 2.8:1 , Should be appropriate late mining, increase fruit sugar content, reduce moisture content, improve quality, and make fruit stems and peels of protective tissue integrity, enhanced toughness.

2.3 Sterilization, storage and antibacterial treatment before storage

SO2 is the best agent for storage sterilization. The concentration of SO2 should be mastered, and the tolerance of SO2 in different species is different. It is necessary to determine the appropriate concentration in advance through experiments. Sulfur treatment is generally carried out at 20g of sulfur powder per cubic meter. In addition, sec-butylamine, peracetic acid, and the like can also be used. During the storage period, measures such as low temperature, gas regulation, radiation sterilization and chemical sterilization are adopted to create an environment that is not conducive to the growth of pathogens, improve the storage of grapes, and extend the storage period to achieve the purpose of preservation.

2.4 Regularly inspect the refrigeration system to see if there is ammonia leakage. If it is necessary to open the warehouse as soon as possible to change the air and spray water to clean the air, SO2 and ammonia can also be introduced. The SO2 concentration must not exceed 1%.

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