How are fruit tree germplasm resources distributed?

Plants with certain genetic material, which have utilization value for fruit tree production and breeding. Including the wild species of fruit trees, close relatives of wild species, varieties, cultivated species, semi-cultivated species, cultivars, strains and single plants. Fruit tree germplasm resources are the material basis necessary for further improvement of varieties. In order to increase the yield, improve the quality, expand the adaptability of fruit trees to the terroir, improve its resistance to natural disasters and pest resistance, and can adapt to processing and mechanized production, etc., the urgent need for a variety of germplasm. The richer the germplasm resources, the greater the predictability of breeding, the more likely it is that excellent new varieties will be produced (see Fruit Tree Breeding). Cultivated fruit trees have their origins in the wild, but they currently occupy only a very small part of the potential that can be exploited and utilized. The ultimate goal of the work on fruit tree germplasm resources is to make fruit plants better able to meet the evolving needs of mankind.

Nature's fruit tree germplasm resources are rich and diverse. Seed plants of more than 340 families, fruit trees account for more than 100 families. Some sections of the fruit tree species. For example, more than 20 genera of Rosaceae have more than 200 kinds of fruit trees, Rutaceae, myrtle, lacquer, mulberry, Sambucus, Vitis vinifera also have a lot of fruit trees. Certain genera provide a large number of fruit tree species, such as Citrus, Plum, Apple, Raspberry, Kiwi, Currant, etc.; while some families have only a few species, but economically important, such as Plantain, Bromeliad, Palm and so on. Nature's many wild fruit tree resources have yet to be further explored and developed (see Fruit Tree Classification).

Cultivated fruit trees have many varieties (see Cultivar). There are often thousands of varieties of major fruit tree species. There are more than 8,000 documented cultivars of both apples and grapes in the world. There are also around 600 European cherry varieties. Cultivated fruit trees are mostly propagated by grafting, and the rootstocks used are not limited to this rootstock, so the range of rootstock germplasm resources is also very wide. after the 1940s, with the fruit tree virus disease research, the discovery and utilization of fruit tree virus indicator plants. Now both fruit tree rootstocks and virus indicator plants have become part of fruit tree germplasm resources.

A brief history of research

Fruit trees are a natural resource for human survival in primitive societies. From the collection of wild fruits to the gradual domestication and cultivation of fruit trees, the utilization of fruit tree germplasm resources has a history of thousands of years. From "Er Ya", China in more than 2000 years ago, peach, plum, jujube, pear and other kinds of fruit trees have appeared some varieties. Fruit tree domestication and selection of history is the history of fruit tree germplasm resource discovery and utilization. In the process of people improving varieties, the germplasm resources used as breeding materials are usually referred to as the original breeding materials. With the development of mutation breeding, chromosome ploidy breeding, tissue culture and other fruit tree breeding techniques, the scope of the original material is also expanding. In the past, the collection and preservation of the original material of the place known as the variety nursery, mother garden or collectively referred to as the original material nursery, in fact, all belong to the fruit tree germplasm resources nursery; because the clear mention of the term germplasm resources is the 20th century after the 1960s.

Germplasm (germplasm) was originally a genetic term. It refers to the genetic material that determines hereditary traits and transmits genetic information to offspring. Germplasm of fruit trees refers to the material basis for the preservation and improved utilization of fruit tree plants. The main material that usually carries plant germplasm is seeds or various organs used for asexual reproduction, such as bulbs, plugs, scions, stem tips, etc. It can be a population, plant, or part of an organ or tissue, cell, or even chromosome and deoxyribonucleic acid fragments. Any original material used for variety improvement can be called germplasm resources.

Mankind in the process of development and production, the use of some of the plant germplasm resources, but also destroyed a considerable number of germplasm resources, resulting in a serious loss of germplasm. Even many germplasm resources that are not yet recognized and fully utilized by people have been in an endangered situation. Therefore, the exploration, collection and preservation of germplasm resources gradually became an international research work in the second half of the 20th century.

Germplasm Resources of Fruit Trees in China

China is the largest single center of origin of cultivated plants in the world. It also ranks first in the total number of plants that have provided usefulness to mankind. Fruit tree germplasm resources are especially rich. The number of species of apple, pear and plum in China is the highest in the world. Many citrus fruit trees are also native to China.

China's native temperate fruit tree resources are: white pear, pear, autumn pear, pear, pear, rowan, Xifutang fruit, sand fruit, thuja, peach, plum, apricot, plum, cherry, cherry, hawthorn, papaya, mountain grapes, thorn grapes, kiwi, ginkgo, hazelnut, chestnut, jujube, hickory, botrytis cephalotaxus, fruit pine and so on. Subtropical and tropical fruit trees include: sweet orange, mandarin orange, tangerine, orange, kumquat, huangpi, hedgehog, persimmon, juniper berries, loquat, yangmei, lychee, longan, olive and so on. Plus yet to be domesticated fruit tree relatives, wild species, rootstock resources and so on are more.

China's fruit tree germplasm resources for the world fruit tree production and variety improvement has made a lot of contributions. Such as peaches, apricots, sweet oranges have been cultivated around the world, Wenzhou mandarin orange and Chinese kiwi were widely cultivated in Japan and New Zealand. Chestnut for the United States and Europe chestnut disease-resistant breeding; sand pear, autumn pear, DuPi for the Western pear fire blight breeding: zinnia, autumn pear and mountain grapes, respectively, for apples, pears and grapes, cold-resistant breeding: Hovenia as citrus, cold-resistant rootstocks, and so on, have provided extremely valuable germplasm resources.

Ancient Chinese people not only domesticated the region's wild plants into cultivated fruit trees, but also in the very early beginning of the introduction of many fruit trees from around the world. Such as grapes, walnuts in the Han Dynasty has been introduced to China, and later introduced more species. Native to China and the introduction of fruit trees, in the complex natural conditions through long-term cultivation selection, the formation of many ecological types and local varieties. The cultivated varieties of pear alone are estimated to be about 3,000 or more. Persimmon varieties are more than 800, more than 500 varieties of jujube, and there are many excellent varieties of various types of fruit trees that have long been famous. Such as Laiyang Chip Pear, Ding County duck pear, Feicheng Buddha peach, Huaxian large apricot, Tongxiang bright plum, Yiwu jujube, Zhanhuang jujube, Xinzheng gray jujube, Leling Jinshi jujube, Xinjiang paper walnuts, Hebei Grindstone persimmons, Guangdong's Hanging Green, Gui taste, sticky rice cake lychee, Fujian's Pumingan, Fukou eye, Wulongling Longan, Zhejiang and Jiangsu, the soft branch of the White Sand, according to the species of loquat, as well as citrus in the Xinhui oranges, orange, orange, Jiao Kankan, Wenzhou mandarin orange, Ponkan mandarin orange, Nanfeng honey orange, Shatian pomelo and so on.

China's fruit tree resource census since the 1950s has initially organized a variety of fruit tree cultivars. In the local varieties also continue to discover a lot of rare and valuable varieties, many of which are productive, high-quality, many times the fruit, spike fruiting, no nucleus or nucleus degradation and other valuable germplasm resources. Also found one after another in the past not enough attention to the wild fruit tree resources. Such as the Ili River in Xinjiang, along the Kung Nai Si River, there are large areas of wild apple forest; Qionglai Mountain area in Sichuan, Danba, Luding, Huili and other places there are large areas of wild Begonia species, plum, cherry, etc.; Guangdong, Guangxi, Hainan mountainous areas of the wild Lychee forest: wild longan forest in southwestern Yunnan; Huaihua, Hubei, Daocheng County, there is a wild citrus grove: Yunnan has also discovered a new species of Citrus grandifolia Orange subgenus -- Red River orange and Citrus sinensis, the new species of Citrus Grandiflora, the new species of Citrus grandiflora, the new species of Citrus Grandis. -Red River orange and a new type of citron; only in the southwest region found kiwifruit species and varieties have been nearly a hundred. The discovery of these fruit tree germplasm resources is of great significance to the development and utilization of fruit trees and further understanding of the origins of the domestication and cultivation of fruit trees.

World fruit tree germplasm resources

Fruit tree germplasm resources around the world have their own characteristics. Southeast Asia's native fruit trees are mainly bananas, coconuts, pineapples, breadfruit, olives, mangosteen persimmons, etc.; India mainly busy fruit, citrus, popcorn, etc.; Central Asia, European grapes, walnuts, lentils, pistachios, pears, apples, etc.: West Asia has figs, pomegranates, European grapes, lentils, European chestnuts, pistachios, quince, walnuts, pears, apples, etc.: Mediterranean region, olive oil, guillotines, and some plum fruit trees: Europe, the European fruit tree domestication and cultivation origin is of great significance. In the Mediterranean region, there are olive, guillotine and some plum fruit trees: in the Euro-Siberian region, there are pears, western cherries, raspberries, currants, etc.; in North America, there are American grapes, American plums, raspberries, strawberries, hickory, etc.; in Central and South America, there are papaya, avocado, cashews, hickory, heartnut, guava, lychee, cactus, pineapple, Chilean strawberries, cherry picker and brazil nut, etc. The above mentioned fruit trees have been introduced to other countries. The above fruit trees have been introduced elsewhere, and some of them have become of worldwide importance (see Origins of Cultivated Fruit Trees).

The areas where fruit trees originated in cultivation are rich in germplasm, but are not necessarily the centers of their present-day production. Due to human production activities, especially fruit trees in the world introduction, exchange, germplasm utilization and the rapid development of varietal improvement, and now the main origin of many fruit trees has been far from their place of origin, such as bananas originating in Southeast Asia, now the world's center of gravity of production in Latin America: originating in the Brazilian pineapple, the center of production in Hawaii: originating in Asia, citrus, and now the main origin of the United States, Japan, Spain, and Italy. These fruit trees have formed new centers of secondary origin in many places, and are also the richest sources of cultivated varieties. In order to develop fruit trees, from the cultivation of the origin of the center or the secondary center of the introduction of seed is certainly important, sometimes explore the region's fruit tree germplasm resources can solve the problem. Such as the United States economic cultivation of most of the fruit trees introduced from other regions, at first did not attach great importance to the original local germplasm resources. Because of the terroir adaptation problems, in the introduction of European grapes and European plum repeatedly failed, and then turned to the American system of grapes and plum germplasm resources for domestication and improvement, have achieved remarkable results.

In addition to cultivated species, the wild species of fruit tree rootstock resources are also very important. They play a great role in disease resistance, insect resistance and expanding terroir adaptability, and some of them have restrained serious disasters. For example, in the 1870s, grape phylloxera seriously threatened the French grape industry, and later used several species of grapes from the Americas, such as Vitis rupestris Scheele, as insect-resistant rootstocks before solving the problem of this devastating pest. As for the breeding of apple aphid-resistant rootstocks, the aphid-resistant variety Northern Spy was utilized. Other fruit trees such as dwarfing rootstocks, cold-resistant rootstock search, and even a variety of fruit tree varieties, the germplasm resources provided around the world, the development of fruit trees have played a positive role in the cause.

Contents of germplasm resources

①Investigation and collection. In the past, most of the investigation is limited to the description of morphology and fruit characteristics, the economic characteristics such as cold resistance, drought resistance, disease and insect resistance, dwarfing potential, absorption and accumulation of mineral elements and other investigations are not yet sufficient. The investigation of fruit tree germplasm resources in China, on the basis of census in various places, had published some national and local fruit tree species list, fruit tree atlas and fruit tree journal, but comprehensively organize and analyze and appraise still need further work. In the resource survey at the same time, a wide range of collection, finishing work. For cultivated varieties generally more to take the way of collection. Collection of grafted seedlings, scions or plugs. Sometimes seeds are also collected for rootstock species. When collecting wild species, it is important to consider the diversity within a species, and to take a wide sample in order to retain the variability. Cultivars produced through modern breeding routes have some characteristics that meet the needs of cultivation, and while valuable for production, are of much less significance in terms of preserving a wider range of genes. More attention is now being paid to the survey, collection, evaluation and preservation of original fruit germplasm, including local varieties and wild species. Introductions are still an effective way for most countries to enrich their varietal resources. With the establishment of a worldwide germplasm bank, a systematic collection of fruit tree germplasm resources has been initiated, with emphasis on registering, numbering and studying them for exchange (see Germplasm collection). ② Preservation. The collection and preservation of germplasm is to provide a broader material basis for breeding. Cultivation of new and old varieties, local varieties, close relatives of wild species and potential utilization of wild species are the object of preservation. There are various methods of conservation, and in the late 1950s, the United States established a system of long-term conservation of crop germplasm resources by seed. Subsequently, many countries have also set up germplasm repositories, which have become more permanent centers for the conservation of germplasm resources. The use of low-temperature preservation of dry seeds is today the main method of preserving crop germplasm such as grains and vegetables. However, fruit trees, especially the asexual lines of cultivated varieties, cannot be preserved from seed. Moreover, the seeds of fruit trees such as citrus, chestnut, persimmon, loquat, lychee and longan are not resistant to drying. So in addition to some wild fruit trees and rootstocks with species, can not use this method. Currently mainly planted plants to save fruit tree germplasm resources. As for the use of low temperature, drying, vacuum and other conditions for a longer period of time to preserve pollen and nutrient organs, has also been explored in research. With the progress of tissue culture technology, in which low-temperature and ultra-low-temperature storage of stem tip cultures provides a promising method for preserving fruit tree asexual germplasm. Initial success has been achieved in strawberries, grapes on a few fruit trees. The United States has been from the 1970s, has established 12 fruit tree asexual germplasm library, division of labor to save all kinds of fruit tree germplasm. China has been categorized according to fruit trees were set up around the country in the national fruit tree germplasm resource nursery. Germplasm bank's main task is to carry out the exploration of germplasm materials, collection, quarantine and processing, the identification of the collected materials, preliminary valuation and proliferation, storage, record file, and exchange of information with the relevant units, exchange or distribution of germplasm materials and so on (see germplasm resources preservation). ③ Research and utilization. Effective preservation of fruit tree germplasm resources and in-depth research, has been an important feature of modern fruit tree breeding, by the international community attaches great importance to, has been widely tested the use of modern technology on all types of fruit tree germplasm for accurate and rapid trait identification. China 1985 ~ 1990, the organization of the country's 14 fruit tree germplasm preservation unit of collaborative research on apple, pear, peach, plum, apricot, grapes, strawberry, citrus, pineapple, longan, litchi and other 17 types of cultivated fruit trees and some of the wild fruit tree germplasm resources for agronomic traits, productivity traits, quality traits, storage traits, processing traits, chromosome ploidy, isozymes, as well as resistance to cold, drought, Salt, disease and insect resistance were evaluated and identified. The results will provide a basis for the direct utilization of germplasm resources or cross-breeding of fruit trees. At present, the research on fruit tree germplasm resources mainly focuses on the problems of fruit tree nursery planting and preservation, and researches on simple and easy, low-cost and effective methods. The cell mass of date palm is frozen to liquid nitrogen temperature, and after thawing and thawing, with the help of culture medium containing hormones, it has been able to cultivate into a complete plant. This research, if further improved, will hopefully provide a more ideal method of preserving asexual germplasm. Current research has focused on the effects of low temperature on cell viability and ultrastructure, and changes in growth patterns, in order to study the physiology of cell injury and its results when subjected to low temperatures. The most fundamental aspect of the technology is to explore the optimal conditions for cryo-storage, the most suitable freezing and thawing rate, the type and concentration of cryoprotectant and the type of culture. The utilization of fruit tree germplasm resources has been successively developed and added to the ranks of cultivated fruit trees in the 20th century, such as lingonberry, kiwi, sea buckthorn, and so on. In China, in the development and utilization of germplasm resources of wild fruit trees, mountain grapes, kiwifruit, sea buckthorn, prickly pear, lingonberry, etc. have been researched and gradually applied to production. In terms of rootstocks, a number of dwarfing rootstocks for apple, peach, plum, citrus and other cultivated fruit trees have been selected and bred from wild and semi-wild fruit trees such as Hubei Begonia, Henan Begonia, Sikkim Begonia, Zumi Begonia, oxalis, bur-cherry, mountain cherry, Hovenia, etc. respectively.

Fruit table

See Fruiting branch.