Freeze drying, also known as lyophilisation or cryodesiccation, is a low temperature dehydration process[1] that involves freezing the product, lowering pressure, then removing the ice by sublimation.[2] This is in contrast to dehydration by most conventional methods that evaporate water using heat.[3]
Freeze drying results in a high quality product because of the low temperature used in processing.[1] The original shape of the product is maintained and quality of the rehydrated product is excellent.[4] Primary applications of freeze drying include biological (e.g., bacteria and yeasts), biomedical (e.g., surgical transplants), food processing (e.g., coffee) and preservation.[1]
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Citrus yellow shoot Citrus yellow shoot Alias ​​Yellow Tip? Injury symptoms? The yellow tip of the diseased tree and mottled leaves are typical symptoms of Huanglong disease. At the time of onset, there were few or a few shoots of yellow leaves on the green canopy, showing distinct yellow shoots. This yellow tip often appears at the top and periphery of the crown. Along with it, the lower branches of the diseased shoots and other branches of the crown are successively developed. The disease can occur throughout the year, with the most incidence occurring in summer and autumn shoots, followed by spring shoots. When the summer and autumn shoots are onset, the shoots that are drawn are often turned green without turning green shoots into yellow shoots, and the leaves are uniformly yellowed or show yellow spots. The onset of spring shoots is when the spring shoots newly harvested in the year turn green normally. As the spring shoots grow old, the leaves begin to fade from the veins and gradually expand to form mottled yellow. Yellow leaves forming yellow tips can be divided into three types: 1. Uniform yellow leaves. In the initial stages of the diseased trees and the occurrence of summer and autumn shoots, many trees appeared, and the leaves showed a uniform pale yellow-green color, and the symptoms persisted on the branches for a short period of time. Therefore, it is harder to see in the field.
?? 2. mottled type yellowing leaves. The leaves showed uneven patches of yellow and green phases. The shape and size of the plaques were indeterminate. From the veins near the base, it is particularly prone to yellowing from the bases of the midribs and the vicinity of the apices of the lateral veins (ie, the chloroplasts), gradually expanding the formation of yellow-green mottles, and finally allowing the yellowish-green yellowing of the entire leaves. This kind of leaf is easier to find in spring, summer and autumn shoots, and in the early and middle and late diseased trees.
?? 3. Deficiency-type yellowing leaves. Also known as mosaic, this type of leaf veins and leaf veins are green and veins yellow. Similar to the lack of trace elements such as zinc, manganese and iron, the leaves appear in the diseased trees in the middle and late stages.
?? The above three types, because the mottled type of yellow leaves can be found in various tip and early, middle and late disease trees, the symptoms are obvious, it is often used as a basis for the diagnosis of Huanglong disease trees. In addition to the symptoms of leaf yellowing, the diseased tree also has fallen leaves. From time to time, the tip shoots are short and weak, and the leaves are small. In some species, the midvein enlarges and protrudes, and the local wood is plugged and cracked. Diseased trees are sparsely populated, with many dry branches and short plants. The diseased trees bloom early and are numerous. The petals are shorter, thicker, lighter, yellowish, and dull. The flowers on the twigs are often clustered into groups, which are called flower balls in Guangdong. The fruit setting rate is low, the fruit size is small, the deformity (such as variable length or fruit shape is skewed), some varieties (such as Fu orange, October orange, etc.) become orange-red early in the vicinity of the fruit pedicle, and the color is not uniform. Fujian is commonly called red nose fruit. . The roots of the diseased trees were normal at the initial stage and rotted at the later stage. Decay begins with fibrous roots and gradually rots to large roots. The xylem becomes dark and the root bark falls off.
Distribution area: Fujian, Guangdong, Guangxi, three provinces, Yunnan, Sichuan, Hunan, Jiangxi, Zhejiang Huanglong disease pathogen? Huanglong disease difficult to cultivate bacteria, the candidate was named Liberobacter asiaticus. The spread of Huanglongbing? Huanglongbing can be grafted and propagated? The breeding of seedlings with disease trees scion, and the spread of disease scions and diseased seedlings is the main way of the disease spread long distance. In the field, Huanglong disease is transmitted by Diaphorina citri Kuwayama. Citrus grandiflora occurs 8-10 generations a year in South China. Adults pass winter. If grafted and bred on diseased trees, the seedlings raised are generally diseased. Long-distance transmission of Huanglong's disease relies on the transport of sick scions or diseased seedlings. The three signs indicate that the seeds may also spread. The natural propagation medium in the field is the citrus hibiscus. The citrus hibiscus sucks the sap and then transfers it to the tree for smoking. The circumstance of the pathogen in the lice is about 20 days to 1 month, and the minimum is 2 days. Instar larvae and adults older than 3 years can spread.
?? Prevention and treatment methods?? Drug control can reduce the symptoms of Huanglong disease, but can not be eradicated, must implement comprehensive prevention.
1. Find new methods and resistant materials to breed resistant citrus rootstocks and scion varieties.
?? 2. Strengthen the detection and control of citrus hibiscus, cut off the transmission route, is an important part of the prevention of Huanglong disease epidemic. The application of yellow plywood can not only monitor hibiscus, study its biology and ecology, but also can study the growth and decay of natural enemies of citrus hibiscus, supplemented with the trapping of citrus hibiscus host plant, harrington, and the results will be improved. Better, adults and nymphs can catch it. The basic elimination is achieved by monitoring the strict control of citrus rafts.
??3. Strictly implement the quarantine system. The scion and seedlings in the ward are prohibited from flowing into new areas and disease-free areas. The new district will use disease-free seedlings and scion, on the unknown seedlings, regardless of their quality and asymptomatic performance. It should be burned in accordance with the phytosanitary regulations. ?? 4, the establishment of disease-free nurseries, the cultivation of disease-free seedlings. According to the pathogenic characteristics and transmission characteristics of the disease. The disease-free nursery is best selected in non-endemic areas where there are no citrus rafts, such as in the ward, must have isolation conditions, that is, the distance around the nursery should be more than 5 kilometers from the citrus plant, natural conditions (such as mountainous areas, Forest area) is better blocked. Before the construction of the garden, the hosts of the sporadic citrus plants such as the citrus trees of the nearby citrus trees should be removed.