Fruit trees and vegetables for arid and semi-arid areas in north-west China

Journal of Arid Environments (1986) 11, 3-16

Fruit trees and vegetables for arid and semi-arid areas in north-west China Wang Ming* & Sun Yun-wei*

Accepted 27 September 1985 According to our survey and investigations, we have found that there are many speciesof fruit trees and vegetables which grow very well in the arid and semiarid areas of north-west China. Most of them originated in China. The further development of these plants will play an important role in improving the ecological environment and the economic situation of the above regions. The main fruit trees and vegetables whichare adapted to the arid and semi-arid areas of north west China are as follows: (1) Fruit tree species: Ziziphus jujuba, Z. spinosus, Diospyros kaki, Diospyros oleifera, D. lotus; Elaegnus angustifolia, Amygdalus communis, Prunus armeniaca, P. davidiana, P. persica, Pyrus ussuriensis,P. bretschneideri, Punica granatum, Crataegus pinnatifida, Pistacia vera, Malus asiatica, M. prunifolia, M. sieversii, M. pumila, Cotoneaster spp., Vitis spp., etc. Other wild speciesare used for rootstocks of initial geneticstocks for breeding. (2) Cucurbits and vegetables: Cucumis melo, Cucurbita moschata, Hemerocallis spp., Lilium spp., Allium spp., Capsicum annuum var. longum, etc. The present paper gives a brief introduction to their values, usages and potential usages, as well as some of the special cultivation and propagating techniques.

Introduction

It has been estimated that 52.2 per cent of China is arid and semi-arid; much ofthis land lies in the north-west. This north western region includes five provinces and autonomous regions, i.e. Shaanxi, Gansu and Qinghai Provinces and the Ningxia Hui and Xinjiang Uighur Autonomous Regions, lying between 32° Nand 48° N and covering an area of 3,270,000 krrr', i.e. about one third of the total area of China. Of this, more than 96 per cent belongs to the arid and semi-arid regions, thus forming the largest of the major arid regions in China (see Fig. I). In the southern part is the famous Qinghai-Tibetan plateau, while the loess plateau lies to the east, the corridor of Gansu Province in the middle and the Xinjiang regions to the west, with their dry climate and more deserts. Since these regions are rich in natural resources, they are suitable for comprehensive development of agriculture, forestry, horticulture and livestock, as well as diversified economy. If we try to enhance the scientific research work, overcome the unfavourable factors and make rational use of the existing natural resources to the fullest extent, we shall contribute greatly towards developing the economy of the area. • Department of Horticulture, Northwestern College of Agriculture, Wugong, Shaanxi, China. 0140-1963/86/040003+ 14 $03.00/0

© 1986Academic Press Inc. (London) Limited

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Climate The different indices of dry and wet climates have been preliminarily determined by means of total rainfall, a major climatic factor in defining aridity and closely correlated with the vegetation. These are as follows: (a) arid, where the average annual rainfall is below 200 mm, (2) semi-arid, 200-450 mm, (3) semi-humid, 450-650 mm and (4) humid, 650 mm or more. Based on these indices, the geograpical boundaries of the arid and semi-arid areas can be preliminarily determined (Wang Qian, 1983). In accordance with the physical and agricultural conditions, dryness in particular, the north-west region may be divided into three zones (see Fig. 2) (Xiong Yunzhang, 1981).

Arid zone This zone has an area of more than 2' 3 million km 2 and comprises over 72 per cent of the five provinces and autonomous regions where most of the deserts and the famous Gobi occur. The climate is very dry, with an aridity index of above 2' 5, the maximum reaching 30'0. The average annual precipitation is below 200 mm with the minimum as low as c. 10 mm, decreasing gradually towards the west; in the Turfan Basin it is ony 4 mm. The average temperature in July is 20-28°C and in January -10- - 20°C.The annual frost-free period is 100-180 days. It is obvious that the climate in this zone is typically continental. Rivers all drain inland, fed by water from the thawing of snow and glaciers in the mountains.

Semi-arid zone This zone includes over 23 per cent of the total area of the arid north-west. The aridity index ranges from 1'25-2'5 with a gradual increase westwards. The annual precipitation in this zone is 200-450 mm on average, with a gradual decrease towards the west. The frost-free period is 120-200 days/year. This zone lies in the upper and middle reaches of the Huanghe River, in the western part of the Loess plateau; the rivers carry much sediment and soil erosion is uncontrolled.

Semi-humid and humid-zone This zone is located in the southern fringe of the region and occupies an area of less than 5 per cent of the total. Its aridity ranges from 1'0-1'5, with an annual precipitation of c. 500-800 mm, increasing gradually southwards. The frost-free period is more than 200 days/year.

Figure 1. Five provinces and autonomous regions in north-west China.

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Figure 2. Regional areas in the arid and semi-arid zones of north-west China.

Most areas of the arid north-west suffer to some extent from frequent disastrous droughts. With a 50-80 per cent drought frequency, droughts are liable to occur for several consecutive years. Despite the increased annual precipitation in the southern semihumid zone, there are often minor droughts within a 5-year interval, due to the uneven rainfall distribution. Consequently irrigation has become very important for agriculture in this region; without this, sustained cultivation would be impossible. The irrigated area consists of more than 80 per cent of the cultivated area, so that this zone is called 'the western irrigated agricultural zone'. The eastern part of the semi-arid zone belongs to 'the rainfed agricultural zone' where there are both rainfed and irrigated lands, with the emphasis on rainfed agriculture. The yield from these lands is very low and irregular, with the yield per unit being less than half that from irrigated lands. In the above arid and semi-arid regions, there are sufficient sources of sunlight and heat, especially in the south-west. The average total annual radiation is 190-200 kilocalorieszcm/. There are c. 3400 hours of sunshine/year. The rainfall is concentrated in July, August and September, it is dry in spring and winter. The annual precipitation varies from year to year. The large diurnal variation in temperature is suitable for the accumulation of plant organic matter. The sugar and vitamin contents are much higher; therefore, both the yield and quality of the tree fruits and cucurbit fruits from this region are much better than those from other regions where there is abundant rainfall or irrigation.

'China, mother of gardens' It is well known that the plant germ plasm resources of China are extremely rich and varied. The very brilliant Russian geneticist and plant breeder, N.!. Vavilov (1951) has indicated in his work 'The origin, variation, immunity and breeding of cultivated plants' that China represents the earliest and largest independent centre for the origin of world agriculture and important cultivated plants. There are many species of economic plants grown in north-west China, representing the varied nature of the arid and semi-arid environment. E. H. Wilson (1929) also described many species of Chinese fruits and vegetables and coined the phrase 'China, mother of gardens'. More than 200 species of fruit trees and important rootstocks originated in China. Numerous fruit tree germplasm resources were recorded in more than 50 ancient Chinese classics. Among the leading fruit tree species now grown in various countries of the world, over 60 species were derived from China. Some of them were spread to Iran via the Silk Road and then to Europe (Sun Yun-wei, Tu Shu et al. 1983). Vavilov (1951) has pointed out that 'China occupies first place in the wealth of fruit species of Pyrus, Malus and Prunus'. For instance there are 35 species ofthe genus Malus in the world, more than 20 of which originated in China, especially in the north-west; also, there are S4 species of the genus Actinidia in the world, 52 of which originated in China, again there are 25 species of

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Figure 3. A 200-year-old jujube, Ziziphusjujuba Mill., 'Jin jujube' in Shaanxi, China.

the genus Pyrus in the world and China possesses 14 of them, represented by c. 3500 varieties. There are also numerous species of wild fruit trees of economic value widely grown in north-west China, which are used either as cultivar rootstocks or for the purpose of dwarfing, cold hardiness and increasing resistance to drought, frost, salinity and diseases. Many of these wild fruits can be eaten fresh or processed and some may be used medicinally (Wang Ming, 1984).

Fruit trees The history of fruit trees grown in north-west China stretches back over 3000years. There are quite a few very old fruit trees distributed in different provinces of north and northwest China. For example, there are about a thousand maidenhair trees (Ginko biloba L.)

FRUIT TREES AND VEGETABLES IN NORTH·WEST CHINA

which are 2000-3000 years old as well as jujube (Ziziphus jujuba Mill.) and sour jujube (Ziziphusjujuba var.spinosa Hu ex H. F. Chow) trees over 1000years old (Fig. 3) and are found in Shandong, Shaanxi and Shanxi Provinces respectively. There are also walnut trees (Juglans regia L.) of over 300 years old in Quinghai Province (see Fig. 4). Many pear trees that are 200-300 years old are still to be found growing in Gansu, Shaanxi, Shandong and Heibel Provinces respectively (see Fig. 5) and 200-300 years old persimmon trees (Diospyros kaki L.f.) are also found in Shaanxi Province. Fruit trees as old as these are rarely found elsewhere in the world (Sun Yun-wei, Tu Shu et al., 1983). The following is a list of fruit tree species which originated in China. Yellow River Valley and Northeast China: Akebia lobata Decne (A. trifoliata (Thunb.) Koidz.), Akebia quinata Decne, Elaeagnus angustifilia L., Castanea mollissima Bl., Chaenomeles sinensis (Thouin) 'Koehne, Corylus heterophylla Fisch. & Bess., Crataegus pinnatifida Bunge, Hovenia dulcis Thunb.,]uglans mandshurica Maxim., Malus asiatica Nakai, M. baccata (L.) Borkh., M. honanensis Rehd., M. hupehensis (Pamp.) Rehd., M. kansuensis (Batal.) Schneid., M. prunifolia (Willd.) Borkh., M. sieboldii (Regel) Rehd., M. sieversii (Ledeb.) Roem., M. transitoria (Batal.) Schneid., Pinus koraiensis Sieb. & Zucc., Prunus armeniaca L., P. davidiana (Carr.) Franchet, P. ferganensis (Kostina & Riab.) Kov. & Kostina,P. kansuensis Rehd.,P. mandshurica(Maxim.) Koehne,P. mira Koehne, P. 'persica (L.) Batsch, P. sibirica L., P. simonii Carr., P. tomentosa Thunb., P. ussuriensis Kovina & Kostina, Pyrus armeniacaefolis Yu, P. betulaefolia Bunge, P. bretschneideri Rehd., P. phaeocarpa Rehd., P. sinkiangensis Yu, P. ussuriensis Maxim., P. xerophila Yu, Vaccinium uliginosum L., V. oitis-idaea L., Vitis amurensis Rupr., Ziziphus jujuba Mill. var. jujuba and var. spinosus (Bunge) Hu ex H.F.Chow. Yangtze River Valley: Carya cathayensis Sarg., Castanea henryi Rehd. & Wilson, C. sequinii Dode, Citrus ichangensis Swingle, C. junos Siebold ex Tanaka, C. unshiu (Makina) Marcov., Diospyros kaki L.f., D. lotus L., D. oleifera Cheng, Elaeagnus multiflora Thunb., E. pungens Thunb., Eriobotrya japonica (Thunb.) Lindley, Fortunella crassifolia Swingle, F. margarita (Lour.) Swingle, Ginkgo biloba L., Myrica rubra (Lour.) Sieb. & Zucc., Photinia serrulata Lindley, Prunus mume Sieb. & Zucc., P. pseudocerasus Lindley, P. salicina Lindley, Poncirus trifoliata (L.) Raf., Pyrus calleryana Decne, P. pashia Buch.-Ham. ex D. Don, P. pyrifolia (Burm.f.) Nakai, P. serrulata Rehd., Rosa laeoigata Michx., Torreya grandis Fort. South China: Averhhoa carambola L., Canarium album(Lour.) Raeusch., Citrus aurantium L., C. grandis (L.) Osbeck, C. limonia Osbeck, C. medica L., C. medica L. var. sarcodactylis (Mooten) Swingle, C. reticulate Blanco, C. sinensis (L.) Osbeck, C. sunki Hort. ex Tanaka, Clausena lansium (Lour.) Skeels, Euphorbia longana Lam., Fortunella hindsii (Champ.) Swingle, F. japonica (Thunb.) Swingle, F. obovata Hort. ex Tanaka, Litchi chinensis Sonn., Malus sikkimensis (Wenz.) Koehne, Musa nana Lour., Pyllanthus emblica L., Rhadomyrtus tomentosa (Ait.) Haussk. In addition, there are some wild fruit tree taxa such as Rubus spp., Ribes spp., Sorbus spp., Cotoneaster spp., Akebia spp., Alaegnus spp., Vaccinium spp., Prunus tomentosa Thunb., Comus officinalis Sieb. & Zucc., Hippophae rhamnoides L., Xanthoceras sorb~folium Bunge, Schisandra chinensis (Turcz.) Baill., etc. in the mountain areasof China (Sun Yun-wei, 1983).

Some popular drought-resistant fruit trees The main drought-resistant fruit trees are jujubes (Chinese dates), persimmons, apricots, pomegranates, walnuts, almonds, peaches, plums, pears, apples, hawthorns, pistachios, and certain cultivated and wild species of Ziziphus, Diospyros, Prunus, Malus, Vitis, Elaegnus, Cotoneaster, etc. Of these, jujubes, persimmons and apricots are the most popular and important and cover extensive regions in the mountain areas or loess plateau

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Figure S. An old pear tree, Pyrus bretschneideri Rehd. grafted on to B. betulaefolia Bunge, over 380 years old. Shaanxi, China.

of north-west and north China. They are very easy to grow and manage; because of their excellent adaptability, especially for drought resistance, the local people call them 'iron fruit trees'. Such fruit trees can tap moisture deep down below the surface. The vertical root system of the jujube tree reaches to a depth of 13 m, persimmon (grafted on Diospyros lotus L.) to more than 9'1 m and apricot to 7'2 m (Xu Mingxian, 1983). Thus, in 1919, there was a terrible drought in Shaanxi Province, but neither the persimmon nor the jujube trees were affected. The fruits can be used not only as fresh food (for dessert), but can also be dried, preserved in sugar, made into jam, wine and vinegar as well as being used for medicine and other usages. The dried Chinese dates and persimmon fruits are rich in sugar and starch, so they can also be served as a substitute for cereal; for this reason, people usually called them food trees. Jujube, persimmon and apricot trees, etc. are also suitable for planting as shelter belts to protect farmland from wind and drifting sand, to conserve water and soil, to control natural calamities, to maintain the ecological balance, and regulate the climate and improve weather conditions. Interplanting fruit trees with cereal crops (wheat, corn, etc.) has proved to be beneficial in north and north-west China and has resulted in bumper crops of fruits and cereals (grain). For example, in Gaojiachuan brigade, Shenmu county, north-west Shaanxi, the farmers obtain 220 kg of grain/mu and 260 kg of dried jujube/mu in a total area of 1164/mu in this way (l mu = c. 0'17 acre = 0'067 ha). To sum up, these fruit tree species are really valuable economic plants and playa very important role in the development of agriculture and economy in the arid and semi-arid regions. The following is a brief introduction to the main fruit tree species which grow in these regions.

Jujube (Ziziphus jujuba Mill.). Jujube is a special fruit product of China. It is seldom grown in other countries. North-west and north China are the principal producing areas, especially Shaanxi, Gansu, Shandong and Hebei Provinces. For instance, in Gansu Province there are about one million jujube trees; in Linze County alone they form 48'6 per cent of the total area of fruit trees and the income from jujube totals 82 per cent of total

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fruit products. Its output is 1600 tonnes per year and ranks first in the tree fruit production of this county. The history of jujube growing in China goes back over 3000 years. There are a number of very old jujube trees which are over one thousand years old. Jujube has always been very popular, not only for its fruits but also as a special tonic and as an ingredient in traditional Chinese medicine. A great quantity of dried and processed jujube is exported abroad every year. There are many different varieties in China, including some very famous ones, such as 'Jin Jujube' (Fig. 3), 'Linze Small Jujube', 'Ming shan Large Jujube', 'Honey Jujube', etc. The jujube fruit is very nutritious and contains a lot of sugar: 25-35 per cent (fresh fruit), 60-70 per cent (dried fruit); vitamin C: 400-600 mg/100 g (fresh fruit); vitamin D: 3000 mg/100 g (fresh fruit), plus minerals: Fe, P, Ca, etc. as well as various organic acids.

Sour jujube (Ziziphus jujuba Mill. var. spinosa Hu ex H.F .Chow). This is a very drought-

resistant species, originating in and restricted to China. Because of its drought-resistance it is widely grown, especially in the mountain areas of north-west and north China. It is usually a bush, but sometimes can be a vigorous tree. Some ancient sour jujube trees found in north and north-west China are about 1000 years old. The fruit is small and sour; it is rich in vitamin C (1000 mg/l00 g). It can be eaten fresh or the dried fruit can be ground to powder and used as a medicine to cure hypertension and stomach trouble (the type caused by insufficient gastric acid); the seeds are very useful in traditional Chinese medicine, as a sedative. It is widely used as stock for jujube propagation. The local people use the buds or shoots of jujube trees as scions for grafting onto wild sour jujube trees. This is a very successful and efficient way of developing jujube production rapidly and is practised throughout the whole of north and north-west China. For example, in Qingyang Prefecture, Gansu Province, farmers graft more than 100,000 jujube on to wild sour jujube trees each year.

Persimmon (Diospyros kaki L.f.) and related species. Thirteen species of Diospyros are native in China. The most important are persimmons (Diospyros kaki), of which there are about 500 varieties in our country; some of them are very valuable. Because of its strong adaptability, it is grown widely in China, especially in the arid and semi-arid areas. In Weibei plateau, one of the most important semi-arid regions in Shaanxi, a vast stand of several hundred-year-old persimmon trees thrive without watering and fertilizers. This emphasizes that persimmon is a truly drought-resistant species, as well as being one of the most popular fruit trees in north-west and north China. The fruit is very cheap in the domestic market, but very expensive in the international market. For example, in 1982, Shaanxi Province exported 15 tonnes offresh persimmon fruit to Hong Kong; the price was 18'5 per cent higher than that of 'Delicious' apples. Persimmon cake (dried persimmon fruit) is also a traditional export commodity, with about 2200 tonnes exported each year. There are a number of problems associated with persimmon production. There is difficulty of transport in the mountain areas and the primitiveness of the processing on the one hand, the extensive fruit output in the mountain areas on the other, with a considerable amount of the harvested fruit rotting and thus lost each year. Therefore, improvement of the transport conditions and processing equipent is of great importance. The most important wild Diospyros species are D. lotus L. and D. oleifera Cheng. Both are used as rootstocks for persimmon in north, north-west and east China, respectively. The latter, D. oleifera, is also used as a source of a lacquer, commonly known as 'persimmon lacquer' used in the painting of umbrellas. Apricot (Prunus armeniaca L., syn. Armeniaca vulgaris Lam.). In the dry mountainous area of the Yellow River valley, especially in north and north-west China, apricot is another popular and widely grown fruit tree. There are many good varieties developed in different provinces, some are suitable as desert fruit and others are used for artificially

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dried or sun dried apricots, preserved apricots and jam. In addition, the kernel is very useful medicinally. Huge quantities are exported every year. Besides the cultivated species, there are some wild species of apricot in China, such a: Prunus mandshurica (Maxim.) Koehne, P. sibirica L., P. holosericea, P. armeniaca L. vars. ansu Maxim and pendula jacq., etc. They are used for cold resistant rootstocks or as gene pools for breeding cold resistance into apricot.

Peaches (Prunus persica (L.) Batsch.) and related wild species. North-west China is also a very rich source of peach germplasm. Some of the cultivated and wild species originated in this area. There are about 800 peach varieties in China, including some very famous and rare varieties found in the Shaanxi and Gansu Provinces for example, an extremely late maturing variety called 'winter peach' which is grown in Mei County, Shaanxi. It is an old variety which has been described in ancient Chinese literature as far back as 200-300 Be. Its fruits ripen in winter (from November to December), but the fruit is rather small, so it is used as the male parent for crossing with other good varieties (such as 'Si-nung Honey Peach', 'Fei City Peach', etc.) to develop several new late maturing varieties, combining larger fruit with good quality. Prunus kansuensis Rehd. is a wild species found only in the Gansu and Shaanxi Provinces. It has been used as a parent for drought-resistance, hardiness, resistance to green peach aphid (Myzus persicae Sulzer) and the peach nematode; it has also been used as a resistant rootstock for peach trees. In previous studies, Prunus kansuensis was found to be a valuable source of resistance germplasm and has been used by certain foreign countries, e.g. the United States and the Soviet Union in their peach-breeding programmes for the above-mentioned traits and from which they have developed several new peach varieties. The other important local wild species are Prunus mira Kohene, P. ferganensis (Kostina & Rjab.) Kov. & Kostina,P. davidiana(Carr.) Franch., andP. persicavar. densa Makino. The latter has an unusual dwarf stock and is an extremely useful source of germplasm for dwarfing in peach breeding. Almond (Amygdalus L.). There are two species, six varieties and about SO cultivars of almond grown in the Xinjiang autonomous region. They areA. commuis L. (also known as Prunus communis (L.)) vars communis, fragilis (Borkh.) Bronh., dulcis DC., amara DC., persicoides Ser., microcarpa Dierb. and A. ledebouriana Schlecht. Walnut (Juglans regia L.) and related wild species. The walnut originated in Iran, Asia Minor and the Xinjiang autonomous region of China. It was introduced into Shaanxi Province during the Han Dynasty (138-136 BC). It exhibits drought-resistant characteristics in Xinjiang and Shaanxi, and is widely distributed in the mountain areas (Chang Chao, 1962). The walnut tree in China displays a rich and diversified germplasm resource. Here, we only intend to briefly introduce a very important and valuable walnut variety grown in Fufeng County, Shaanxi Province called 'Genian Walnut'. This variety begins to come into flower and set fruit in the second or third year after sowing (Fig. 6); flowering and setting fruit in the common walnut varieties is much later, usually 8-10 years after sowing. Because fruit of the walnut is rich in oil (67-70 per cent), protein (12-27 per cent) and vitamins, it has become one of the principal traditional export crops in north-west China. The income from external trade in this crop is of great significance for improving the living standards within certain mountain areas. Besides the cultivated walnut varieties, there are a number of related wild species of Juglans which originated in, or are grown in different regions of China. They areJuglans fallax Dode, J. cathayensis Dode, J. sigil/ata Dode, J. mandshurica Maxim. and J. hopeiensis Hu (a hybrid ofJ. regia x Carya sp.).

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Figure 6. A two yearold seedling of an earlymaturingvariety of walnut,Juglans regia L. grown in Fufeng County, Shaanxi, China. It flowers and sets fruit in the secondor third year after sowing.

Cucurbits and other important vegetable crops Most cucurbit and vegetable crops require sufficient water; only a few are to some degree drought-resistant. Among the crops grown in north-west China are muskmelons, (Cucumis Melo L.), Cucurbita moschata (Duchesne ex Lam.) Duchesne & Poir., Hemerocallis spp. Lilium spp., Allium spp., Dioscorea opposite Thunb. (syn. D. batatas Decne), hot pepper (Capsicum annuum L. var. longum (DC.) Bailey). This article will concentrate on muskmelons, Hemerocallis spp., Lilium spp. and Allium spp.

Melon (Cucumis melo L.). Southwest Asia is believed to be the region of origin of the muskmelon, C. melo subsp. melo Li, while the Chinese or oriental melon, C. melo subsp. orientalis Li, originated in south China. In 1972, G. Ch. Wang et al. found a wild melon species in Ningyang County, Shandong Province, which was named Cucumis bisexualis Lu & Wang. In 1959, Wu Mingzhu found a wild melon in Shanshan County, Xinjiang, and in 1981, a farmer again found a wild melon in Tuokesun County, Xinjiang. The main charactristics of this species are as follows: vigorous growth, with average length of main vine 240 em, a leaf shape similar to the common cultivated muskmelon, inflorescence monocious, multiflowered, very prolific fruit setting with an average of about 50 fruits/plant. Fruit weight is 60 g and the flesh is thin, sour, bitter, puckery and slightly sweet in flavour; solid content 4'8-7 per cent, seed rather small, (8'1 g/1000 seeds); the chromosome number is 2n = 24, the same as for Cucumis melo; compatability and fruit setting are both very fine in self-fertile and cross-fertile with C. melo (Lin Depei, 1983). Although the existence of the above wild melon species is proven, some consider the evidence is not enough to show that Xinjiang is also one of the native habitats of the muskmelon, because the wild species was only found in the vicinity of where people live, despite the fact that no other related species or subspecies of melon have been found there. Xinjiang and Gansu are the most important areas for melon production. In Xinjiang, muskmelons are grown on a large scale both north and south of the Tianshan mountain

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range. The total area of melon cultivation is about 25,000 mu (mu = 0.067 ha); the total yield is about 200,000 tonnes per year. It is the major melon producing area in China. Because of the very long history (about 3000 years) of melon growing in Xinjiang and Gansu, these regions are one of the most important melon germplasm centres in the world. Investigators have found tremendous variations in the melons. The characteristics of the different varieties vary greatly in both exterior and interior appearances and in qualities such as drought resistance, heat and cold tolerance, early maturing, yield, size of fruit, length of storage, etc. (Ma Keqi, 1983). Of the 214 varieties of melon grown in Xinjiang, 105 are native (49'06 per cent). Approximately 95 per cent of the melons grown for commercial production are native varieties. The most famous and popular varieties are called 'Hami melons' (C. melo var. saccharinus Naud.). They are well known world-wide. As a matter of fact, the so called 'Hami melon' is not a single variety, but a very complicated group of melon varieties growing in Xinjiang. It includes many different varieties such as 'Mijigan', 'Kekouchi', 'Kalakekouchi', etc. Because the weather is warm, sunny and extremely dry (the total precipitation is only 4 mm/year in Tulufan, Xinjiang), high temperatures prevail for long periods during the summer. Thus, it is a very suitable climate for melon growing. The sugar content of melons here is much higher than that of other regions. Some Hami melon varieties ('Kalakekouchi', 'Jingeda') are extra large, weighing up to 20-25 kg each. Some also have very good keeping qualities, lasting over six months. Hami melon is highly regarded both at home and abroad. The dried flesh of Hami melon is also a very famous speciality; in Gansu Province, some people grind the dry flesh into melon powder for food. In Gansu Province there are also a great number of native melon varieties, such as 'Golden bar', 'White bar', 'Iron rind', 'White rind', 'Early yellow rind', 'jintasi', 'Golden frog', 'Tipsy melon', etc. In the mid-1940s, an American variety of melon, 'Honey Dew' was introduced to Gansu and then to Xingiang and other dry areas. It grew very well and has rapidly become one of the most widely grown melon varieties in Gansu province. The quality and yield has been improved following a long period of cultivation and selection by growers and breeders in Gansu. Now, Honey Dew melon is among the very valuable crops grown for foreign trade.

Day lily (HemerocalIis spp.). There are 14 species of Hemerocallis, 11 of which grow or originated in China. Several species of Hemerocallis can be used as a special kind of vegetable, of which H. citrina Baroni, Lanzhou Lily, is the most important (Fig. 7); others

Figure 7. The Lanzhou Lily, Hemerocallis citrina Baroni, growing in Gansu Province, China.

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are H. fulva (L.) L., H. minor Mill., H. lilo-asphodelus L. (syn. H. fiaoa L.), etc. Many different species or varieties of Hemerocallis are widely grown in China. Shaanxi and Gansu are the most famous producing areas in the north-west region. For example, in Dali County, Shaanxi Province, there are about 200,000 kg of dried day lily produced each year, 65,000 kg of which are for export. Day lily is a perennial and once planted it can be harvested over a period of 12 years. Because it has a very strong root system, it is both drought- and cold resistant, and tolerant to exposed sites. Thus, it is very suitable for the arid and semi-arid regions, especially for the loess plateau of Shaanxi and Gansu Provinces. It is a very useful plant for soil and water conservation, as well as for the beautification of the environment. Its large flower buds are rich in nutrients and vitamins, (See Table 1), and have a very good flavour, so that the flower buds (especially the dried ones) are a very popular delicacy in China. Dried day lily is easy to store and transport. It is also a traditional export commodity of Shaanxi and Gansu Provinces. The fleshy root can also be used for food or for making wine; the leaf can be used for forage or as a raw material to produce artificial cotton gunnysack and rope. The development of day lily production has a great potential and significance in the arid and semi-arid regions. In order to develop day lily production more quickly, plant tissue culture techniques have been used to accelerate its multiplication. Some Chinese researchers (Zhou, 1980; Lu, 1981) have successfully tissue cultured the day lily using MS medium supplemented with hormones. At present, the problems of production are the low yield per unit area (the average yield is only 90 kg/mu) and the primitive processing techniques. These should be improved as soon as possible. The germplasm resources of the genera Allium and Lilium in Xinjiang and Tibet is very rich and varied. Xinjiang is the centre of origin for many species of Allium;according to the recent survey, there are 63 species grown in Xinjiang, 99% of them are wild. These plants are widespread in grassy marshland and wilderness, especially around the mountain area and prairie of Tianshan and Altai mountain, indicating that these species have a high adaptability and drought resistance. The Allium species originating from or growing in Xinjiang are as follows (Lin Depei, 1983). (1) Wild species, Allium altaicum (2n = 16), A. decipiens Fisch. ex Roemer & Schult. (2n = 16), A. fetissovii Regel (2n = 16), A. /lavidum Ledeb., A. galanthum Kar. & Kir. (2n = 16), A. lineare L. (2n = 16), A. oreoprasum Schrenk (2n = 16), A. pallasii Murr. (2n = 16),A. ramosum L. (syn. A. odorum L.) (2n = 16, 32),A. schoenoprasum L. (2n = 16, 32), A. sinkiangense Wang & Y. C. Tang. Table 1. Nutrient content offresh and dried day lily compared with tomato and cabbage Nutrients (mg) Carotene (mg) Thiamine (mg) Riboflavin (mg) Nicotinic acid (mg) Absorbic acid (mg) Ca (mg) P(mg) Fe (mg) Protein (mg) Fat (mg) Sugar (mg)

Day lily (fresh)

1'17 0'19 0'13

1'1

33

73 69

Day lily (dried)

Cabbage

0'37 0'03

0'02 0'04 0'04

3'44

0'36 0'14 4'1

o

463

173

1'4

16'5

11.6

60'1

2'9 0'5

Tomato (red)

14'1 0'4

Source: Institute of Health, Chinese Academy of Medical Science

0'02

0'6

8 8 24

0'8 0'8

0'3 2'2

0'3 38 32

24

0'3 1'1 0'2

3'4

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W. MING & S. YUN-WEI

(2) Cultivated species, Allium cepa L. (2n = 16), A. fistulosum L. (2n = 16), A. sativum L. (2n = 16,32, one of the most popular vegetables grown widely in China), A. tuberosum Rottl, ex Spreng. (2n = 32). The list of Allium and Lilium originating from or growing in Tibet are as follows (most of them are wild species) (Du Wufeng & Zhang Baoxi, 1982). Allium ascalonicum L., A. astrosanguineum Schrenk, A. changduense J. M. Xu, A. chrysantum Regel, A. fasciculatum Rendle, A. hookeri Thwaites, A. macranthum Baker, A. prattii C. H. Wright, A. przewalskianum Regel, A. pelyrhizum Turcz. ex Regel (syn. A. subangulatum Regel), A. tanguticum Regel, A. tuberosum Rotti. ex Sprengel, Lilium brownii F. E. Brown ex Miellez, L. lancifolium Thunb. Many species of Lilium originated in China. Lilies are drought-resistant plants, very

suitable for arid and semi-arid regions. They grow very well, especially in Gansu Province. The species in Tibet can grow very luxuriantly, e.g. L. brownii is a wild lily, with quite a large bulb which can weigh as much as 235 g. The main species used as a vegetable are L. trigrinum Ker-Gaul.; others are L. auratum Lindley, L. brownii var. viridulum Baker (syn. var. colchasteri (van Houtte) Wilson ex EIwes), L. concolor Salisb., L. leichtlinii Hack.f. var. maximowiczii Baker. The fresh lily scales can be used as a vegetable---either fried or for making a sweet soup and other sweet foods. Dried lily scales are also a very famous local speciality of Gansu province, both at home and abroad. Lilies are drought-resistant plants, very suitable for arid and semi-arid regions. They grow very well, especially in Gansu Province. Normally, lilies are propagated vegetatively by division of the bulbs, a slow process. Some Chinese researchers use plant tissue culture techniques to speed up the multiplication process. Yang Zenghai & Wang juying (1982) adopted the small scale segments (0'5 em) from different varieties such as Yichang, Yunnan, Quin Ling and Lanzhou lilies as explants and cultured them on MS medium with ZT 0'5 mg/I, IBA 0'05 mg/I, or BA 0'5-1'0 mg/a, NAA 0'5 mg/a respectively. The calluses ofYichang lily formed one month from innoculation; 6 weeks later adventitious buds formed through the calluses and produced small bulbs. The Lanzhou lily on MS medium with Ba 1'0 mg/a, N AA O· 5 mg/I can induce plantlets after 2 months culture in vitro.

Gravel-sand mulching in north-west C!hina The gravel-sand mulched fields, known locally as 'sand fields', were created by the farmers in Gansu province about 300 years ago. Nearly 86,000 ha of such fields are distributed between 35°and 38°Nand 103°and 105° E on the loess plateau; nearly 80,000 ha or 93% of them are in Gansu province. The fields are covered by a 5-16 em layer of water conserving mulch, made up of a mixture of different-sized pebbles, gravel and sands taken from river alluvium or glacial deposits. These fields are tilled and fertilized by means of special farm tools and implements to prevent the mixing ofsoil and mulch so that the benefits of the mulch can be maintained for as long as possible. This mulch is used mainly on the non-irrigated fields known as 'dry and fields', but some irrigated fields are also mulched in this way and are referred to as 'irrigated sand fields'. The dry sand fields receive a much thicker mulch than the irrigated sand fields and therefore can last for 30-40 years. The crops in the dry sand fields consist of spring wheat and other cereals, legumes, vegetables and especially melons (Fig. 8). The crop yields of the gravel-sand fields are two to three times greater than from unmulched fields. The mulch is partly removed during sowing and manuring and restored immediately afterwards. When 25% by weight of the sand mulch has mixed with the underlying soil, its function will almost entirely diminish. The old mulch should then be

FRUIT TREES AND VEGETABLES IN NORTH-WEST CHINA

15

Figure 8. Gravel-sand mulching techniqueused in the arid regions of NorthwestChinato conserve moisture. removed and replaced by a new mulch (Niu Pu & Zhai Yunzhi, 1981). In recent years, a plastic film over the gravel-sand mulched fields has achieved good results. Conclusions The drought-resistant economic plants are the basic resources for developing rainfed agriculture and raising the economy of the arid and semi-arid areas of China. Therefore, a complete survey, collection, evaluation, preservation and utilization of the above-mention germplasm resources in north-west China is of strategical importance in these areas. It is suggested that further investigations and research on such economic plants should be carried out in order to improve the production of the previously mentioned fruits, curcurbits and vegetables. It is necessary to emphasize that we must pay greater attention to the conservation of rare, endangered or slowly-reproducing cultivated species as well as the more valuable wild species and assist in the multiplication of desirable genotypes. It may be possible to propagatesome ofthem using special techniques, such as plant tissue culture, in order to increase their importance in commercial production, while others may serve as initial gene stocks for plant breeding. In addition, the selection of the existing economic species adapted to dryness, the breeding of new varieties with improved drought resistance, the acclimatization of wild species as well as the introduction of useful species from other areas of China and abroad should also be included in the research programme. We believe that the rich and varied plant germplasm resources of China are not only of value to our motherland, but also to the whole world. For this reason, it is important to develop and strengthen international co-operation, to engage in further exchange of materials, technical information and experiences, and to carry out co-operative research in this field. We feel sure that from the research and experience gained, China could make a valuable contribution to the development of rainfed agriculture elsewhere in the world.

16

W. MING & S. YUN·WEI

References Chang Chao (1962). Fruit tree resources of Xinjiang. Acta Horticulturalia, 1: 129-136. Du Wufeng & Zhang Baoxi (1982). A survey of vegetable germplasm resources in Tibet. Annual Report of Scientific Research, Institute of Vegetable Research, Chinese Academy of Agriculture Science. Lin Depei (1983). The germplasm resources of Allium genus in Xinjiang, China. (Unpublished). Lin Depei (1983). Study on the wild melon in Xinjiang. (Unpublished). Lu, T. L. (1981). Study on Day Lily tissue culture. Plant Physiology Newsletter No.6. Ma Keqi (1983). Growing andBreeding of Melon. Beijing, China: Agriculture Press. Meyer, F. N. (1916). China, a Fruitful Field for Plant Exploration. In: 1915 Yearbook of the United States Department of Agriculture, pp. 205-224. Ni Pu & Zhai Yunzhi (1981). The gravel-sand mulched fields in the arid regions of northwest China, 1981, Agricultural Newsletter for Arid andSemiarid Areas (Northwestern College of Agriculture, Wugong), 1: 8. Porterfield, W. M. (1937). Chinese Vegetable Foods in New York. Journal ofthe New York Botanical Garden, 38: 254-257. Sun Yun-wei, Tu Shu & Yao Kun-de (1983). History of FruitCulture andResources of FruitTrees in China. Shanghai, China: Shanghai Science and Technique Press, 146. Vavilov, N. I. (1951). The origin, variation, immunity and breeding of cultivated plants (trans. from the Russian by K. S. Chester). Chronica Botanica, 13: 1-366. Wang Ming (1984). Brief on the concept of germplasm and the origin, history and present status of vegetable germplasm in China. FAO Fellow's Thesis for academic study in 1981-1982. Department of Horticulture, Cook College, Rutgers University, N.J., USA. Wang Qian (1983). Distribution of the arid and semiarid areas in China and their major climatic characteristics. Agricultural Research in the Arid Areas. (Northwestern College of Agriculture, Wugong), 1: 9-24. Wilson, E. H. (1929). C hina-Mother of Gardens. Boston, Massachusetts: The Stratford Company. 418 pp. Xiong Yunzhang (1981). Irrigation in arid and semiarid regions in northwest China. Agricultural Newsletter forArid andSemiarid Areas (Northwestern College of Agriculture, Wugong), 12: 1-4. Xu Mingxian (1983). On the role of fruit trees in the development of agriculture of the arid areas.

Selected Works of Science and Technique Reports of RainfedAgriculture in China, 326-330.

Yang Zenhai & Wang [uying (1982). In vitro of scale culture of lily (Lilium spp.). Northwestern Collegeof Agriculture, Wugong. Northwestern College of Agriculture, Wugong. (Unpublished). Zhou, P. H. (1980). Preliminary study on tissue culture of Day Lily (Hemerocallis L.). Journal of Hunan Agricultural College, 4: 47-49.