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1. Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; 2. Bureau of Agriculture and Animal Husbandry of Hezhang, Bijie 553200, China

Supported by National Key Research and Development Plan (2016YFD-0100204-8); Special Project for Basic Science and Technology Work (2012FY110203); Special Project for Protection of Crop Germplasm Resources of Ministry of Agriculture (2016NWB037); the Agriculture Research System (CARS-24-A-01); the Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences (CAAS-ASTIP-IVFCAAS); Key Laboratory of Biology and Genetic Improvement of Horticultural Crops, Ministry of Agriculture.

1 Introduction

Chinese chives, a perennial herb belonging to Liliaceae, are one of China’s major onion and garlic vegetables and plays an important role in people’s diet. The cultivation areas of Chinese chives are very wide in China, and there is a certain area of Chinese chives in almost all provinces, cities and autonomous regions, and wild chives is almost distributed all over the country[1-2]. Chinese chives have wide uses and has health protection and therapeutic effects. It contains protein, fat, carbohydrates, cellulose, carotene, vitamin C and trace elements. It contains beneficial ingredients for human health and has the medical efficacy of body building and nourishment for vitality[3].

Guizhou Province has rich and diverse biological resources[4-5], where wild onion resources are distributed widely, and a large area of wild chives are distributed in Hezhang County[1]. It is reported that wild Chinese chive resources such asAlliumwallichiiKunth.,AlliumhookeriThwaites, andAlliumovalifoliumHand.-Mazz. are distributed in Hezhang County, Guizhou Province, of which a large area ofA.wallichiiKunth. is distributed in Jiucaiping Village to form magnificent natural landscape[6]. It has a very high value of research, protection and utilization. It is generally believed that wild chives have high nutritional value, a soft and delicious flavor, and a spicy taste; due to its original ecological growth environment, it is an organic vegetable mostly[7]. The investigation, collection and preservation of wildlife resources are of great importance to the enriching of genetic diversity of national crop genebanks and improvement of varieties[8-12].At present, the distribution and quality of wild Chinese chive resources in Hezhang County lack systematic investigation and analysis[3]. In this study, based on the systematic investigation of biological resources in Hezhang County in the early period[13], a special survey on the distribution of wild chives in Hezhang County was conducted, and its nutrition components were analyzed. The research results will provide important reference for the biological exploitation and utilization of wild Chinese chive resources.

2 Materials and methods

2.1InvestigationmethodsBased on general investigation and systematic investigation of resources, the obtained information was analyzed to determine a special investigation plan. In the special investigation, according to changes of actual situation, the plan should be adjusted by to further improve the investigation plan. An informal discussion should be conducted by Hezhang Meteorological Bureau and other departments to discuss and obtain related weather information of Jiucaiping. In August 2015,AlliumwallichiiKunth. growing in the main peak of Jiucaiping and connected vice peaks in Xingfa Township was investigated. Due to the large distribution area ofA.wallichiiKunth., samples were collected from three major distribution areas. To be consistent with the number of systematic survey in 2014, samples from each area were numbered 2014521130, 20141421101, and 2014521131 respectively. In each area, samples were collected from three sampling points, and 50 plants were collected at each sampling point.AlliumovalifoliumHand. -Mazz. (tentatively named) in Jiucaiping Village, Zhushi Township was surveyed, and the original habitat was investigated and recorded. Due to the small area ofA.ovalifoliumHand. -Mazz., in order not to destroy the original habitat, 30 plants were randomly picked at the distribution point, cataloged as one resource, and numbered 2014521135. The distribution ofA.hookeriThwaites (tentatively named) in Shuanglong Village, Zhijie Township were investigated and sampled, and it was mainly distributed along the riverside. It was cataloged as one resource and numbered 2014522106. One sampling point was chosen every 1 km along the riverside, and 50 plants were collected at each sampling point. All the excavated plants were pruned to cut off old leaves and mailed to the National Asexual and Perennial Vegetable Resource Plot to be planted. The commonAllaumtuberosumRottler ex Spreng. preserved in the National Vegetable Intermediate Bank was used as the control group (8A56). Three repetitions was randomly selected from each resource, and each repetition had five plants. These plants were used for the detection of main nutrition components and heavy metal content. At the same time, the leaves and scapes of plants ofA.wallichiiKunth. in the original habitats were collected to be used for the detection of main nutrition components and heavy metal content ofA.wallichiiKunth. 2014521131. For the detection of content of vitamin C, the commonA.tuberosumRottler ex Spreng. was used as the control group.

2.2DetectionofmainnutritioncomponentsandheavymetalcontentThe three kinds of wild chives collected were planted in nutrient bowls. That is, 15 plants of each population ofA.wallichiiKunth. (2014521130, 2014521101, and 2014521131) were planted, while 15 plants ofA.ovalifoliumHand. -Mazz. (2014521135),A.hookeriThwaites (2014522106), andA.tuberosumRottler ex Spreng. (8A56) were also planted respectively. Five plants were as one repetition. After three months, all leaves of the plants were taken upward from the soil surface. The content of 17 hydrolyzed amino acids was detected by an automatic amino acid analyzer[14]. Vegetable Quality Supervision and Testing Center (Beijing), Ministry of Agriculture was entrusted with the detection of sugar, vitamin C, and heavy metals according to relevant national standards[15].

3 Results and analysis

3.1NaturegeographyandclimaticcharacteristicsofHezhangCountyHezhang County (104°10′28″-105°01′23″ E, 26°46′ 12″-27°28′18″ N) is located in the slope of the Wumeng Mountains (the transition zone of plateau in eastern Yunnan to mountains and hills in middle Guizhou) in the upper reaches of the Liuchong River in the north of the Wujiang River and the Sacha River in the south of the Wujiang River in the northwest of Guizhou Province. It borders on Bijie and Nayong in the east, Weining in the west, Liupanshui in the south, and Zhenxiong and Yiliang of Yunnan Province in the north. The county seat is 300 km away from the provincial capital Guiyang and 96 km away from the local administrative office.

The altitude of Hezhang County is high in the northwest, southwest and south and low in the northeast. In the county, mountains are high and slopes are steep; ridges and peaks rise one after another; ravines and gullies crisscross, and rivers are deep. In the county, the altitude of the highest peak Xiaojicaoping is 2 900.6 m, while the altitude of the lowest point the Shajie River is 1 230 m, and the average altitude was 1 996 m.

Hezhang County has a warm temperate cool climate with dry spring and wet summer, and it is a unique plateau mountain climate between the south temperate and middle temperate zones. Due to low latitudes, high altitudes, and complex topography, the following climatic features are formed: four seasons are not distinct; daily range of temperature is large, while monthly and annual range of temperature are small; wet and dry seasons are distinct, and water and heat are in the same season; lighting conditions are better, and solar radiation is higher, but the efficiency of light energy utilization is only 0.6%. Frost-free period is 206-255 d.

According to the weather statistics from 1981 to 2010, daily range of temperature was large, while annual range of temperature was small; annual average temperature was 13.56℃, and the maximum temperature was 37.1℃, while the minimum temperature was -6.5℃; annual average rainfall is 832.9 mm, and 55% of rainfall in a year concentrated from June to August; the number of annual average rainfall days was 174 d; annual average sunshine duration was 1 298.3 h.

3.2SpeciesandbasiccharacteristicsofwildchivesThree kinds of wild chives in Hezhang County were mainly investigated and sampled, includingA.wallichiiKunth.,A.ovalifoliumHand. -Mazz., andAlliumhookeriThwaites.

3.2.1Habitats and morphological characteristics ofAlliumwallichiiKunth. Among the three kinds of wild chives in Hezhang County, the area ofA.wallichiiKunth. was the largest, especially in Daweicaiping and its surrounding areas. It was distributed in four townships and towns ranging from Baiguo Town and Shuitangbao Township to Zhushi Township and Xingfa Township. Among these regions, the area and density ofA.wallichiiKunth. was the largest in areas around Dajiucaiping, Xingfa Township. The area was about 200 ha in core areas, while it was relatively small in other towns and townships, and the total area was around 667 ha. Xiaojiucaiping was the second core distribution area, and the area was 13.3 ha in core areas and about 33.3 ha in radiating zones. In the county,A.wallichiiKunth. was mainly distributed on sunny slopes of ridges at 2 500-2 800 m. The plants began to germinate around April each year. The flowering period of the groups was inconsistent, and flowering continued from July to October. The flowering period of each plant was about 10 d, and the flowers were available for viewing. The habitats and morphological characteristics ofA.wallichiiKunth. are shown in Fig.1.

Note: A. Habitat; B. Plant; C. Scapes; D. Inflorescence.

Fig.1HabitatsandmorphologicalcharacteristicsofAlliumwallichiiKunth.

3.2.2Habitats and morphological characteristics ofAlliumovalifoliumHand. -Mazz. It was found thatA.ovalifoliumHand. -Mazz. was mainly distributed in steep cliff apertures with a slope of 80-90° at an altitude of about 2 800 m in Jiucaiping Village, Zhushi Township, Hezhang County, and the humus layer was deep here. The surface of the bulbs was between gray-brown and dark brown in color, showing a clear fiber network after aging. In the growth period, the leaves were oval and opposite, 7-15 cm in length, and 3-7 cm in width, and the apex was acuminate or nearly caudate. The habitats and morphological characteristics ofA.ovalifoliumHand. -Mazz. are shown in Fig.2.

Note: A. Habitat; B. Plant; C: Leaf; D. Inflorescence; E. Seeds.

Fig.2HabitatsandmorphologicalcharacteristicsofAlliumovalifoliumHand. -Mazz.

3.2.3Habitats and morphological characteristics ofAlliumhookeriThwaites. Seen from the results of this survey,A.hookeriThwaites was distributed in Shuanglong Village, Zhijie Township, Hezhang County, with an elevation of about 1 890 m. They were mainly distributed under the shade of trees along the river, and they continued along the stream until reaching Xiaojiucaiping.

Its leaves were similar to that ofA.wallichiiKunth., but there were big differences between them in terms of other morphological characteristics. The flowers were white, and the inflorescence was nearly spherical. The scapes were round, and the plant flavor was like onion. According to the investigation results of characters of 50 plants, the main characteristics were found as follows: the plant height was 30-72 cm; the leaves were 20-50 cm in length and 0.3-1.0 cm in width; the number of scapes was 1-2; the diameter of flower balls was 2-4 cm, and each ball had 11-50 florets. The habitats and morphological characteristics ofA.hookeriThwaites are shown in Fig.3.

Note: A. Habitat; B. Plant; C. Leaves; D. Inflorescence.

Fig.3HabitatsandmorphologicalcharacteristicsofAlliumhookeriThwaites

3.3Analysisofnutritioncomponents

3.3.1Content of hydrolyzed amino acids. According to Table 1, the content of 17 kinds of hydrolyzed amino acids in the three kinds of wild chives in Hezhang County was higher than that of the cultivated chives. Meanwhile, there were certain differences betweenA.wallichiiKunth. andA.ovalifoliumHand. -Mazz. in terms of content of amino acids. The total content of amino acids in the three populations ofA.wallichiiKunth. (2014521130, 2014521101 and 2014521131) was 20.2%, 22.47% and 19.86% respectively, averaging 20.84%. The total content of amino acids inA.ovalifoliumHand. -Mazz. (2014521135) andA.hookeriThwaites (2014522106) was 21.57% and 18.16% respectively. However, the total content of amino acids in the cultivated chives purchased on the market was low, only 10.27%. It showed that the content of amino acids inA.wallichiiKunth. andA.ovalifoliumHand. -Mazz. that grew at high altitudes on the mountains was higher than that ofA.hookeriThwaites that grew at low altitudes along the riverside. In general, the content of amino acids in the wild chives was higher than that of the cultivated chives.

Table1ContentofhydrolyzedaminoacidsinthewildchivesandcultivatedchivesinHezhangCounty

%

Note: Data in the table is average±standard error (the same as below).

3.3.2Content of sugar and trace elements in the wild chives. According to Table 2, sugar content in leaves of the cultivated chives was the highest among the four kinds of wild chives, up to 24.10%. Sugar content in leaves of the three populations ofA.wallichiiKunth. (2014521130, 2014521101 and 2014521131) was 15.4%, 11.8% and 6.56% respectively. Sugar content in leaves ofA.ovalifoliumHand. -Mazz. (2014521135) andA.hookeriThwaites (2014522106) was 13.60% and 12.30% respectively. In general, sugar content in leaves of the wild chives was lower than that of the cultivated chives. Among the nine kinds of trace elements, the manganese, zinc and iron content ofA.ovalifoliumHand. -Mazz. were significantly higher than that of the other chives. The potassium, phosphorus, calcium, copper, selenium, and magnesium content of the wild chives was higher than or equal to that of the cultivated chives.

Table2ContentofsugarandtraceelementsinleavesofthewildchivesinHezhangCounty

WildchivesNo．Totalsugarcontent∥%Traceelementcontent∥mg/kgKPCaCuSeMgFeMnZnAlliumwallichiiKunth．201452113015．40±4．3457625．00±1242．527188．00±321．6423000．00±2000．4410．70±1．360．10±0．004950．00±58．99476．00±32．6796．10±｀3．18108．00±15．11201452110111．80±2．1353375．00±982．236538．00±201．1217375．00±1981．1211．60±0．980．156±0．014163．00±54．76634．00±44．56363．00±10．12104．00±13．5620145211316．56±0．9953875．00±687．565750．00±333．3218375．00±1564．329．19±1．000．07±0．015013．00±24．54469．00±21．67155．00±24．1292．30±12．67AlliumovalifoliumHand．?Mzt．201452113513．60±2．3242250．00±1782．156188．00±245．7825500．00±1232．3217．80±0．980．23±0．015775．00±67．78719．00±45．11488．00±13．21464．00±16．90AlliumhookeriThwaites201452210612．30±3．4561000．00±1613．46450．00±1213．1018625．00±1452．328．53±0．670．052±0．004625±32．24387．00±11．1196．30±5．4374．50±1．32AlliumtuberosumRott8A5624．10±1．1143000．00±978．218675．00±200．1217250．00±34．6815．60±0．110．22±0．005675．00±54．32548．00±9．9868．80±4．3567．00±1．23

Seen from Table 3, total sugar content in leaves and scapes ofA.wallichiiKunth. in the original habitats in Hezhang County was 16.67% and 29.07% respectively. The content of trace elements in leaves of the wild chives was higher than that of the scapes, and the content of potassium and calcium was higher than that of other trace elements.

Table3ContentofsugarandtraceelementsinleavesandscapesofAlliumwallichiiKunth.intheoriginalhabitatsinHezhangCounty

PartsTotalsugarcontent∥%Traceelementcontent∥mg/kgSeKPCaCuFeMgMnZnLeaves16．67±5．470．17±0．1748750．00±48750．007104．33±7104．3320458．33±20458．3313．98±13．98551．33±551．335358．33±5358．33217．70±217．70201．83±201．83Scapes29．07±1．480．15±0．0028375．00±992．166412．67±510．798083．67±883．1212．87±1．76104．60±18．112433．67±174．95151．67±3．06147．33±5．13

3.3.3Content of heavy metals in the wild chives. Under normal circumstances, metals with a specific gravity of more than 5 are called heavy metals. Heavy metals in vegetables mainly refer to metals with significant biological toxicity such as mercury, cadmium, lead, chromium, and arsenic. The terrain of Hezhang County is complex. According to local authorities, the local soil is rich in cadmium and other metals. Therefore, it is very necessary to detect the content of heavy metals in wild chives. According to theNationalFoodSafetyStandard:LimitsofContaminantsinFoodsissuedon June 1, 2013, cadmium content in the three species of wild chives significantly exceeded the national standard, and cadmium content inA.ovalifoliumHand. -Mazz. was significantly higher than that of other chives (Table 4). At the same time, arsenic, mercury, and lead content inA.ovalifoliumHand. -Mazz. also exceeded the limits.

Table4ContentofheavymetalsinleavesofwildchivesinHezhangCounty

mg/kg

According to Table 5, mercury, cadmium, and lead content in leaves and scapes ofA.wallichiiKunth. in the original habitats in Hezhang County exceeded the limits. Meanwhile, the content of the four heavy metals in samples from the original habitats was higher than that of samples transplanted in Beijing. Mercury content in scapes ofA.wallichiiKunth. in the original habitats was so low that it was not detected.

Table 5 Content of heavy metals in leaves and scapes ofAlliumwallichii Kunth. in the original habitats in Hezhang County mg/kg

3.3.4Content of vitamin C. The content of vitamin C in leaves and scapes ofA.wallichiiKunth. in the original habitats in Hezhang County was detected and compared with that of the cultivated chives. The content of vitamin C in leaves of the cultivated chives was only 21.3 mg/100 g, while the content of vitamin C in leaves and scapes ofA.wallichiiKunth. was 94.1 and 65.1 mg/100 g respectively.

4 Discussions

4.1StrengtheningthecollectionandconservationofwildchiveresourcesisofgreatsignificanceWild chives are native to China and have abundant local breed resources and wild chive resources[12]. However, with the popularization and application of new varieties of chives, many local cultivars have been eliminated from the market. Since people’s outdoor activities become increasingly frequent and they dig for wild resources, some wild chive germplasm resources are on the verge of extinction. Although 270 chive germplasm resources have been conserved in the National Vegetable Germplasm Resource Bank, few wild chive resources have been collected and preserved, accounting for less than 1%. Guizhou Province is an important distribution area of wild onion resources, and a large area of wild chives are distributed in Hezhang County in particular. The collection, preservation and protection of wild resources and local farm varieties of chives are of great significance.

4.2WildchivesinHezhangCountyarepreciousresourcesfortheimprovementofchivesinqualityIn this study, the content of major nutrition components such as amino acids, trace elements, and vitamin C in wild chives in Hezhang County was higher than that of the cultivated chives, indicating that wild chive resources had great development and utilization value in the improvement of nutritional quality of chive resources. However, sugar content in the wild chives was lower than that of the cultivated chives, so that the taste of the wild chives is worse than that of the cultivated chives. In the original habitats, sugar content in the scapes ofA.wallichiiKunth. Was obviously higher than that of the leaves, so local ethnic minorities prefer eating the scapes of chives. In the development and utilization of resources, sugar content can be further increased by means of screening and genetic transformation, thereby increasing the taste and quality of wild chives.

4.3ContentofheavymetalsinwildchivesinHezhangCountyisaproblemworthyofattentionThere are many sources of heavy metals in vegetables, such as the direct discharge of a large number of wastewater containing heavy metals from mining metal smelting and electroplating industry, and use of phosphate fertilizers. In this study, lead and cadmium content in wild chives in Hezhang County were high, which may be related to the presence of cadmium and lead in the local mountains. At the same time, cadmium and lead content in leaves ofA.wallichiiKunth. from the original habitats were higher than that of the chives transplanted in Beijing, indicating that the residue of cadmium and lead in the wild chives gradually decreased after years of cultivation. It is worth mentioning that the samples of wild chives were collected from the remote mountainous areas of Hezhang County, but the cultivated chives of local residential areas were not collected and tested, so the results did not represent the content of heavy metals in wild chives under local cultivation conditions. From the content of heavy metals in wild chives by the riverside near residential areas, it can be found that the closer the sampling points were to the residential areas, the lower the content of heavy metals was. Therefore, due to the fact that the the residential areas were far away from the mountains, the content of heavy metals in the cultivated chives detected by professional organizations should be as the criterion.

4.4TheidentificationandclassificationofwildchivesinHezhangCountyneedstobestrengthenedfurtherThe three species of wild chives found by this study were named based on local knowledge, namelyAlliumwallichiiKunth.,AlliumramosumL., andAlliumovalifoliumHand. -Mazz. However, their biological identification still requires experts to further study it by means of biological features, physiology, and molecular markers. With the help of experts from the Institute of Botany, the Chinese Academy of Sciences, it is believed that the species known asAlliumramosumL. should beAlliumhookeriThwaites. The exact botanical location ofAlliumovalifoliumHand. -Mazz. needs detailed identification, and experts believe that it may be a new species near Allium victorialis L.

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