Napa cabbage

{{Short description|Subspecies of flowering plant}} {{Redirect-distinguish|Hakusai|Hokusai}} {{Use dmy dates|date=April 2017}} {{Infobox Cultivar | name = Napa cabbage | image = Napa cabbages.png | species = ''Brassica rapa'' | group = Pekinensis Group | origin = China, before the 15th century }} '''Napa cabbage''' (''Brassica rapa'' subsp. ''pekinensis,'' or ''Brassica rapa'' Pekinensis Group) is a type of Chinese cabbage originating near the Beijing region of China that is widely used in East Asian cuisine. Since the 20th century, it has also become a widespread crop in Europe, the Americas, and Australia. In much of the world, it is referred to as "Chinese cabbage".

== Names == {{Infobox Chinese | title = Regional names | pic = Chinese.cabbage-01.jpg | piccap = Napa cabbages | hide = no | name1 = Chinese name | c = {{linktext|大白菜}} | l = big white vegetable | p = dàbáicài | w = ta⁴-pai²-ts'ai⁴ | altname = Cantonese name | t2 = 紹菜 | y2 = siuh choi | j2 = siu⁶ coi³ | hangul = 배추 | rr = baechu | mr = paech'u | kanji = 白菜 | hiragana = はくさい | revhep = hakusai }}

The word "napa" in the name ''napa cabbage'' comes from colloquial and regional Japanese, where ''nappa'' ({{lang|ja|菜っ葉}}) refers to the leaves of any vegetable, especially when used as food.<ref>{{cite web |url= https://dictionary.cambridge.org/dictionary/english/napa-cabbage |title= napa cabbage |author= <!--Staff writer(s); no by-line.--> |date= |page= |issn= |doi= |pmid=|publisher= Cambridge Dictionary |volume=|issue=|access-date= 26 March 2026 }}</ref> The Japanese name for this specific variety of cabbage is ''hakusai'' ({{lang|ja|白菜}}), a Sino-Japanese reading of the Chinese name ''báicài'' ({{lang|zh|白菜}}), literally "white vegetable". The Korean name for napa cabbage, ''baechu'' ({{lang|ko|배추}}), is a nativized word from the Sino-Korean reading, {{Transliteration|ko|baekchae}}, of the same Chinese character sets. Today in Mandarin Chinese, napa cabbage is known as ''dàbáicài'' ({{lang|zh|大白菜}}), literally "big white vegetable", as opposed to the "small white vegetable" that is known in English as bok choy.

Outside of Asia, this vegetable is also referred to as '''Chinese cabbage''' or sometimes '''celery cabbage'''.<ref>{{cite web|title=Chi′nese cab′bage|url=http://www.thefreedictionary.com/celery+cabbage | access-date=20 January 2015}}</ref> It is also known as '''siu choy''' in Western Canada (Cantonese {{lang|yue|紹菜}}),<ref>{{cite web|title = Chinese Cabbage|url = http://chinesefood.about.com/od/vegetablesrecipes/ig/Chinese-Vegetables-Pictures/Chinese_Cabbage_Photo.htm|website = chinesefood.about.com|access-date = 20 January 2015|archive-date = 4 March 2016|archive-url = https://web.archive.org/web/20160304122533/http://chinesefood.about.com/od/vegetablesrecipes/ig/Chinese-Vegetables-Pictures/Chinese_Cabbage_Photo.htm|url-status = dead}}</ref> '''wombok''' in Australia<ref>{{cite web|url = https://en.wiktionary.org/wiki/wombok|title = Wombok|date = 7 April 2022}}</ref> and '''wong bok''' or '''won bok''' in New Zealand, all corruptions of ''wong ngaa baak'' (Cantonese {{lang|yue|黃芽白}}).<ref>{{cite web|url = http://www.cantonese.sheik.co.uk/dictionary/words/3958/|title = 黃芽白 (Wong4 ngaa4 baak6 &#124; ) : Napa cabbage; chinese cabbage - CantoDict}}</ref> In the United Kingdom this vegetable is known as '''Chinese leaf''' or '''winter cabbage''',<ref>{{Cite book|title=A Little Chinese Cookbook|author=Tan, Terry|page=51|publisher=Chronicle Books}}</ref> and in the Philippines as ''petsay'' (from Hokkien, {{lang|nan|白菜 (pe̍h-tshài)}}) or ''pechay baguio''.<ref name="AfableInc2004">{{cite book|last=Afable|first=Patricia O.|title=Japanese pioneers in the northern Philippine highlands: a centennial tribute, 1903-2003|url=https://books.google.com/books?id=hCJwAAAAMAAJ|year=2004|publisher=Filipino-Japanese Foundation of Northern Luzon, Inc.|isbn=978-971-92973-0-7|page=116}}</ref> Another name used in English is ''petsai'' or ''pe-tsai''.<ref name="prota">Toxopeus, H & Baas, J (2004) Brassica rapa L.. - In: Grubben, G.J.H. & Denton, O.A. (2004) Plant Resources of Tropical Africa 2. Vegetables. PROTA Foundation, Wageningen; Backhuys, Leiden; CTA, Wageningen. - p.146-151.</ref> In Ukrainian it is called ''{{lang|uk-Latn|pekins'ka kapusta}}'' ({{lang|uk|пекінська капуста}}), in Russian ''{{lang|ru-Latn|pekinskaya kapusta}}'' ({{lang|ru|пекинская капуста}}), and in Polish ''{{lang|pl|kapusta pekińska}}'', literally "Beijing cabbage".<ref>[http://em.shopargo.com/ogorod/kapusta/pekinka.htm Growing the Peking cabbage] (in Russian)</ref> In Sweden it is known as ''{{lang|sv|salladskål}}'' (salad cabbage) or sometimes ''{{lang|sv|kinakål}}'' (China cabbage).

== Origin == The first records of napa cabbage cultivation date back to the 15th century in the Yangtze River region in China. From China it later spread to Korea and Japan. Beginning in the 19th century with the Chinese diaspora, it was distributed to the rest of Asia, Europe, America as well as Australia. During the 19th century napa cabbage was first introduced to America from Europe and the supply of seed materials from Europe continued until World War I. After the blockade of the European seed supply, US government research institutes and the seed industry developed new seed stocks for vegetable crops. Oregon and California were the cabbage seed production areas during that time.<ref name= "Ramchiary">Genetics, Genomics and Breeding of Crop Plants (2011) N. Ramchiary, S. Park, X. P. Lim: Classical Breeding and Genetic Analysis of Vegetable Brassicas. Book 2. Clemson University, USA</ref> Today it is cultivated and eaten throughout the world.

Napa cabbage might have originated from natural hybridization between turnip (''Brassica rapa subsp. rapa'') and pak-choi (''Brassica rapa subsp. chinensis''). Artificial crosses between these two subspecies, as well as molecular data, strengthen this suggestion.<ref name="Sadowski">Sadowski, J., & Kole, C. (2011). Genetics, genomics and breeding of vegetable brassicas. Enfield: Science Publishers.</ref>

== Description == Napa cabbage is a cool season annual vegetable which grows best when the days are short and mild. The plant grows to an oblong shaped head consisting of tightly arranged crinkly, thick, light-green leaves with prominent white veins. Innermost layer leaves feature light yellow color.<ref>{{cite web|title=Napa cabbage nutrition facts|url=http://www.nutrition-and-you.com/napa-cabbage.html | access-date=20 January 2015}}</ref>

Napa cabbage belongs to the family Brassicaceae, commonly called the mustard or cabbage family. It is closely related to other species in its genus ''Brassica'', like broccoli, cauliflower, cabbage, and kale, as well as other cruciferous vegetables like arugula and wasabi.<ref>{{cite book|last1=Cartea|first1=M.E.|title=Genetics, Genomics and Breeding of Crop Plants|publisher=Clemson University|date=2011}}</ref><ref name= "Clemson">Genetics, Genomics and Breeding of Crop Plants (2011) Clemson University, USA Cartea M. E., Lema M., Francisco M, Velasco P.</ref> It is a different cultivar of the same species as bok choy and turnip.

The leaves, which are the harvested organ, lay side by side densely, are lime green coloured with white leaf veins and have a smooth surface. The vegetable has an oval form and weighs {{cvt|1 to 3|kg}}.<ref>W. Franke (1976) Nutzpflanzenkunde. - Georg Thieme Verlag, Stuttgart, Germany</ref> The leaves are organized in basal rosettes. The flowers are yellow and have a typical Brassicaceae cross-linked arrangement, hence the name Crucifereae, which means “cross-bearing”. Because the plant is harvested in an earlier stage than flowering, normally the flowers are not visible on the field.{{Citation needed|date=May 2021}}

It develops similar to other head-forming leaf vegetables, such as cabbage and lettuce. The chronological stages on the BBCH-scale are germination, leaf formation, vegetative growth (head-forming), appearance of the sprout that bears the flowers, flowering, fruit development, seed ripening and senescence.<ref>Feller, C., Bleiholder, H., Buhr, L., Hack, H., Hess, M., Klose, R., et al. (1995). BBCH-Codierung der phänologischen Entwicklungsstadien von Blattgemüse (kopfbildend). In U. Meier, Entwicklungsstadien mono- und dikotyler Pflanzen: BBCH Monografie (S. 120). Biologische Bundesanstalt für Land und Forstwirtschaft.</ref>

== Uses == Napa cabbage is widely used in China, Japan, and Korea.<ref name="Lee2012">{{cite book|last=Lee|first=Cecilia Hae-Jin|title=Frommer's South Korea|url=https://books.google.com/books?id=VqQKke-MFbEC&pg=PA326|date=22 May 2012|publisher=John Wiley & Sons|isbn=978-1-118-33363-1|page=326}}</ref> Napa cabbage is used as a sign of prosperity in China,<ref name="Klein2012">{{cite book|last=Klein|first=Donna|title=The Chinese Vegan Kitchen: More Than 225 Meat-free, Egg-free, Dairy-free Dishes from the Culinary Regions of China|url=https://books.google.com/books?id=EKfkrESHgSgC&pg=PA30-IA54|date=4 December 2012|publisher=Penguin Group US|isbn=978-1-101-61361-0|page=30}}</ref> and often appears as a symbol in glass and porcelain figures. The Jadeite Cabbage sculpture of Taiwan's National Palace Museum is a carving of a napa cabbage variety. It is also found in North American and Australian cities after Asian immigrants settled in the regions.{{Citation needed|date=May 2021}}

=== Culinary === thumb|left|Napa cabbage and tofu soup {{nutritionalvalue | name=Chinese cabbage, raw| kJ=68 | protein=1.2 g | fat=0.2 g | carbs=3.2 g | fiber=1.2 g | sodium_mg=9 | calcium_mg=77 | iron_mg=0.31 | magnesium_mg=13 | vitC_mg=27 | source_usda=1 }}

Fermented Napa cabbage (suan cai/sauerkraut) is a traditional food in Northeast China.<ref name=":0">{{cite journal | vauthors = Yang X, Hu W, Xiu Z, Jiang A, Yang X, Saren G, Ji Y, Guan Y, Feng K | title = Effect of salt concentration on microbial communities, physicochemical properties and metabolite profile during spontaneous fermentation of Chinese northeast sauerkraut | journal = Journal of Applied Microbiology | volume = 129 | issue = 6 | pages = 1458–1471 | date = 17 July 2020 | pmid = 32677269 | pmc = 6723656 | doi = 10.1111/jam.14786 }}</ref>

In Korean cuisine, napa cabbage is the main ingredient of ''baechu-kimchi'', the most common type of kimchi, but is also eaten raw as a wrap for pork or oysters, dipped in gochujang.<ref name="Vongerichten2011">{{cite book|last=Vongerichten|first=Marja|title=The Kimchi Chronicles: Korean Cooking for an American Kitchen|url=https://books.google.com/books?id=IJqXfsmsc1YC&pg=PA37|date=2 August 2011|publisher=Rodale|isbn=978-1-60961-128-6|pages=37–42}}</ref> The outer, tougher leaves are used in soups. It can be used in stir-fry with other ingredients, such as tofu, mushroom and zucchini. It is also eaten with hot pot meals. Napa cabbage is particularly popular in South Korea's northern Gangwon Province.<ref name="Lee2012"/> In European, American and Australian kitchens, it is more common to eat it cooked or raw as salad.<ref>Michael Todt (1989) Untersuchungen zur Mikroflora des lagernden Chinakohls (Brassica pekinensis Rupr.). Dissertation, University Kiel, Germany</ref>

The vegetable is rich in vitamin C (26&nbsp;mg/100g) and has a fair amount of calcium (40&nbsp;mg/100g).<ref>Deutschen Forschungsanstalt für Lebensmittelchemie, 5. Auflage, (1994) Souci/Fachmann/Kraut.</ref> It tastes mildly aromatic.{{Citation needed|date=May 2021}}

== Cultivation == Napa cabbage can be cultivated in many different areas of the world, the main area of diversification represents Asia.<ref name="Clemson" /> Napa cabbage is an annual plant that reaches the generative period in the first year. It must be consumed in its vegetative period, so there is a challenge in cultivation not to reach the stadium of flowering. The stadium of flowering can be initiated by cold temperatures or the length of the day. Napa cabbage reproduces mainly by allogamy.<ref name="Buschbaum"/> Napa cabbage produces more leaves, bigger leaves and a higher biomass under long day conditions than under short day conditions.<ref>Nerlich, K., Pfennig, J., Kleemann, G., Feike, T., Graeff, S., Claupein, W., et al. (2009). Beschreibung von Wachstum und Entwicklung bei Chinakohl (Brassica rapa L. var. pekinensis) in Abhängigkeit von Temperatur und Tageslänge - Basisdaten zur Modellierung mit DSSAT. 45. Gartenbauwissenschaftliche Tagung, (S. 158). Humboldt-Universität zu Berlin.</ref>

=== Soil requirements === Napa cabbage requires deeply loosened medium heavy soil. There must not be any compaction due to plowing. The crop achieves particularly high yields on sandy loam. Extremely sandy or claylike soils are not suitable.<ref name="Buschbaum">Buschbaum, H., & Heinen, B. (1978). Chinakohl. Bonn: Rheinischer Landwirtschafts-Verlag.</ref> The crop prefers a pH range from 6.0 to 6.2, a high organic matter content and good moisture holding capacity of the soil. Lower pH or droughty soil can lead to calcium or magnesium deficiency and internal quality defects.<ref name="Cook">Cook, W. P., & Smith, P. (February 1996). Oriental Cabbage Production. Hort. Leaflet 68, S. 1-4</ref>

=== Climate requirements === Napa cabbage needs much water during the whole growth period.<ref name="Baggaley">Baggaley, A., Barter, G., Caldon, H., Rosenfeld, R. L., Ruch, P., Vowles, D., et al. (2011). RHS Good fruit & veg guide. London: Dorling Kindersley Limited.</ref> Often an irrigation system is needed, especially for August and September.<ref name="Buschbaum"/> The required amount of water depends on the stage of crop growth, weather conditions, and soil type. The most critical stage after establishment is when the head is forming. Inadequate water at this time will result in reduced uptake of calcium. This condition causes dead leaf tips within the head which makes it unmarketable. During head formation, {{convert|1|to|1+1/2|in|mm|abbr=on|order=flip|round=5}} of water per week is needed to maintain sustained growth rates.<ref name="Cook"/>

Temperature requirements are low. Temperatures below {{cvt|0|C}} are tolerated for short time periods; persistent frosts below {{cvt|-5|C}} are not endured.<ref name="Buschbaum"/> Too low temperature can induce premature bolting. The plants perform best under temperatures between {{cvt|13|and|21|C}}, depending on the cultivar.<ref name="Rimmer">Rimmer, R. S., Shattuck, V. I., & Buchwaldt, L. (2007). Compendium of Brassica Diseases. St. Paul: American Phytopathological Society.</ref>

=== Seedbed requirements & sowing === Napa cabbage has very small seeds with a thousand kernel weight of about 2.5 to 2.8&nbsp;g. For professional cultivation it is recommended to use disinfected seeds to prevent onset diseases. With the single-grain sowing technique, about 400 to 500&nbsp;g of seeds per hectare is required; with the normal sowing technique, about 1&nbsp;kg per hectare. If the normal sowing technique is used, the seedlings must be thinned out after two to four weeks. The seeds should be deposited {{cvt|1 to 2|cm}} deep, with a row width of {{cvt|40 to 45|cm}} and {{cvt|25 to 30|cm}} distance between the seeds.{{Citation needed|date=May 2021}}

The seedlings can be grown in the greenhouse and then transplanted into the field after two to three weeks. Earlier harvest can be achieved with this method. Seventy thousand to 80,000 seedlings per hectare are required.<ref name="Buschbaum"/><ref name="Baggaley"/> The transplanting method is normally used for the spring crop and the seeding technique for the fall crop.<ref name="Rimmer"/>

=== Fertilization, field management === The nutrient removal of napa cabbage is high:<ref name="Buschbaum"/>

* 150–200&nbsp;kg N per hectare * 80–120&nbsp;kg P₂O₅ per hectare * 180–250&nbsp;kg K₂O per hectare * 110–150&nbsp;kg Ca per hectare * 20–40&nbsp;kg Mg per hectare

Fertilizer recommendations are in the range of the nutrient removal.<ref name="Buschbaum"/><ref name="Baggaley"/><ref>Ackermann, I., Funk, M., Hintze, C., Joachimi, A., Potzkai, G., Rieger, W., et al. (1993). Feldgemüsebau : Buschbohnen, Chinakohl, Dicke Bohnen, Erbsen, Einlegegurken, Grünkohl, Knollensellerie, Kohlrabi, Kopfkohl, Kopfsalat, Möhren, Porree, Rote Beete, Schälgurken, Spargel, Spinat, Zwiebeln . Münster-Hiltrup: Landwirtschaftsverlag.</ref> Organic fertilizer must be applied before sowing due to the short cultivation time of napa cabbage and the slow availability of organic fertilizers. Synthetic N fertilizer should be applied in three equal doses. The last application must happen before two thirds of the cultivation time is over to avoid quality losses during storage.{{Citation needed|date=May 2021}}

Weeds should be controlled mechanically or chemically.<ref name="Buschbaum"/>

=== Harvest, storage and yield === [[File:Tonghai Xian - Gaoda Daizu Yizu Xiang - P1360659.JPG|thumb|Harvested napa cabbage being loaded on a truck in Tonghai County, Yunnan]]thumb|Napa cabbage sold in Japan Napa cabbage can be harvested 8–12 weeks after sowing. The harvest work is mostly done by hand. The plant is cut {{cvt|2.5|cm|0}} above the ground. It is usual to harvest several times per field to achieve consistent cabbage quality. Cabbages will keep in good condition for three to four months in cool stores at {{cvt|0-1|C}} and 85 to 90 percent relative humidity.<ref name="Buschbaum"/> Napa cabbage achieves a yield of 4 to 5&nbsp;kg/m².<ref name="Clemson" />

=== Breeding === ''Brassica rapa'' species are diploid and have 10 chromosomes. A challenge for breeding of napa cabbage is the variable self-incompatibility. The self-incompatibility activity was reported to change by temperature and humidity. In vitro pollination with 98% relative humidity proved to be the most reliable as compared to greenhouse pollination.{{Citation needed|date=May 2021}}

A lot of work has already been done on breeding of napa cabbage. In the 21st century, 880 varieties of Napa cabbage were registered by the Korea Seed and Variety Service.<ref name="Sadowski" />

Breeding of napa cabbage was started by the Korean government research station of horticultural demonstration in 1906 to overcome starvation. As napa cabbage and radish are the main vegetables for kimchi, research focused on increasing yield. The most important person for this process was Dr. Woo Jang-choon who bred hybrid cultivars with self-incompatibility and contributed to commercial breeding by developing valuable materials and educating students. The main purpose of the hybrid cultivar was high yield and year-round production of napa cabbage after 1960.<ref name="Sadowski" />

To enable year round production of napa cabbage, it has to be modified to tolerate high and low temperatures. Normally, sowing in the late summer and harvesting in late autumn can produce high quality vegetables. As an example, a summer cultivar called “Nae-Seo-beak-ro” was developed 1973 by a commercial seed company. It tolerates high temperatures, could endure high humidity in the monsoon, and showed resistance to viral disease, soft rot and downy mildew. The low temperature in early spring reduces the quality of the vegetable and it cannot be used for kimchi. In the 1970s the developing of winter cultivars started. The majority of new cultivars could not endure the cold winter conditions and disappeared. The cultivar “Dong-Pung” (meaning “east wind”) was developed in 1992 and showed a high resistance to cold temperature. It is mostly used in Korea, where fresh napa cabbage is nowadays cultivated year round.<ref name="Ramchiary" />

In the 1970s, one seed company developed the rose-shape heading variety while other seed companies focused on the semi-folded heading type. As a result of continuous breeding in the commercial seed companies and the government research stations, farmers could now select what they wanted from among various high quality hybrids of Chinese cabbage.<ref name="Sadowski" /> The fall season cultivar 'Yuki', with white ribs and tight leaf folding, gained the RHS's Award of Garden Merit (AGM) in 2003.<ref name= "RHSveg" >{{cite web |url=https://www.rhs.org.uk/Plants/207958/i-Brassica-rapa-i-(Pekinensis-Group)-Yuki/Details |title=Brassica rapa (Pekinensis Group) 'Yuki' |author=<!--Not stated--> |date=November 2018 |publisher=Royal Horticultural Society |access-date=23 November 2019 }}</ref>

In 1988, the first cultivar with yellow inner leaf was introduced. This trait has prevailed until today.<ref name="Sadowski" />

A very important breeding aim is to get varieties with resistance to pests and diseases. There exist varieties with resistance to turnip mosaic virus but as mentioned above, there exist numerous other diseases. There have been attempts to breed varieties with clubroot resistance or powdery mildew resistance but the varieties failed due to bad leaf texture traits or broken resistances.<ref name="Sadowski" />

== Pests and diseases ==

=== Gomasho === ''Gomasho'' (ゴマ症),<ref name="au-dpird-burt">{{cite journal |last1=Burt |first1=John |last2=Phillips |first2=Dennis |last3=Gatter |first3=David |title=Growing chinese cabbage in Western Australia |journal=Bulletins of Department of Primary Industries and Regional Development |date=June 2006 |issue=4673 |url=https://library.dpird.wa.gov.au/cgi/viewcontent.cgi?article=1159&context=bulletins |access-date=6 February 2025 |publisher=Department of Primary Industries and Regional Development |format=pdf |issn=1833-7244|page=20}}</ref><ref name="jshs-matsumoto">{{cite journal |last1=Matsumoto |first1=Mieko |title=Studies on the Occurrence of Goma-sho of Chinese Cabbage and its Prevention |journal=Journal of the Japanese Society for Horticultural Science |date=1988 |volume=57 |issue=2 |pages=206–214 |doi=10.2503/jjshs.57.206 |url=https://www.jstage.jst.go.jp/article/jjshs1925/57/2/57_2_206/_pdf |access-date=6 February 2025|doi-access=free }}</ref> also known as ''pepper spots'', is a cosmetic defect affecting leaves' surfaces, primarily the outer ones. It takes a form of spots appearing on the white parts of a leaf, with clearly defined edges, usually elongated, up to 2&nbsp;mm in size. The color ranges from brown to black. A spot is formed through a collapse of cell walls and may be invisible during harvest and packing, only becoming apparent after storing in cold.<ref name="flo-simmone">{{cite web |last1=Simonne |first1=Eric |last2=Brecht |first2=Jeff |last3=Guodong |first3=Liu |last4=Ozores-Hampton |first4=Monica |title=HS1101/HS352: Pepper Spot ("Gomasho") on Napa Cabbage |url=https://edis.ifas.ufl.edu/publication/HS352 |website=Ask IFAS - Powered by EDIS |publisher=University of Florida |access-date=6 February 2025 |language=en}}</ref><ref name="au-dpird-burt"/>

No pathogen is known to cause ''pepper spots'' and affected leaves are safe to eat.<ref name="flo-simmone"/> The formation of ''gomasho'' has been linked to high nitrogen levels in fertilizers.<ref name="ashs-warner">{{cite journal |last1=Warner |first1=John |last2=Cerkauskas |first2=Ray |last3=Zhang |first3=Tiequan |last4=Xiuming |first4=Hao |title=Response of Chinese Cabbage Cultivars to Petiole Spotting and Bacterial Soft Rot |journal=HortTechnology |issue=January–March 2003 |pages=190–195 |url=https://journals.ashs.org/downloadpdf/view/journals/horttech/13/1/article-p190.pdf |access-date=6 February 2025 |publisher=American Society for Horticultural Science }}</ref> The defect has to be differentiated from fungal diseases and soil fragments.

=== Fungal diseases === ''Alternaria'' diseases are caused by the organisms ''Alternaria brassicae'', ''Alternaria brassicicola'' and ''Alternaria japonica''. Their English names are black spot (not to be confused with midrib 'pepper spots' which are physiological in origin and often result from improper storage), pod spot, gray leaf spot, dark leaf spot or ''Alternaria'' blight. The symptoms can be seen on all aboveground plant parts as dark spots. The infected plants are shrivelled and smaller than normal. Alternaria diseases infect almost all brassica plants, the most important hosts are oilseed brassicas. The fungus is a facultative parasite, what means that it can survive on living hosts as well as on dead plant tissue. Infected plant debris is in most circumstances the primary source of inoculum. The spores can be dispersed by wind to host plants in the field or to neighbouring brassica crops. This is why cross infections often occur in areas where different brassica crops are cultivated in close proximity. The disease spreads especially fast when the weather is wet and the plants have reached maturity. ''Alternaria brassicae'' is well adapted to temperate regions while ''Alternaria brassicicola'' occurs primarily in warmer parts of the world. Temperature requirement for ''Alternaria japonica'' is intermediate.<ref name="Rimmer" /> There exist some wild accessions of ''Brassica rapa'' subsp. ''pekinensis'' with resistance to ''Alternaria brassicae'' but not on commercial cultivars. These resistances should be included to breeding programmes. ''Alternaria'' epidemics are best avoided by management practices like at least 3 years non-host crops between brassica crops, incorporation of plant debris into the soil to accelerate decomposition and usage of disease-free seeds.<ref name="Rimmer" />

Anhracnose is a brassica disease caused by ''Colletotrichum higginsianum'' that is especially damaging on napa cabbage, pak choi, turnip, rutabaga and tender green mustard. The symptoms are dry pale gray to straw spots or lesions on the leaves. The recommended management practices are the same as for ''Alternaria'' diseases.<ref name="Rimmer" />

Black root is a disease that infects mainly radish, but it also occurs on many other brassica vegetables inclusively napa cabbage. It caused by the fungus ''Aphanomyces raphani''. The pathogen can persist for long times in the soil, therefore crop rotations are an essential management tool.<ref name="Rimmer" />

White leaf spot is found primarily in temperate climate regions and is important on vegetable brassicas and oilseed rape. The causal organism is ''Mycosphaerella capsellae''. The symptoms are white spots on leaves, stems and pods and can thus easily be confused with those of downy mildew. The disease spreads especially fast with rain or moisture and temperature is between {{cvt|10 and 15|°C}}.<ref name="Rimmer" />

Yellows, also called Fusarium wilt, is another ''Brassica'' disease that infects oilseed rape, cabbage, mustards, Napa cabbage and other vegetable brassicas. It is only a problem in regions with warm growing seasons where soil temperatures are in the range of 18 to 32&nbsp;°C. The causal organism is ''Fusarium oxysporum ''f. sp.'' conlutinans''. Napa cabbage is relatively tolerant to the disease; mostly the only external symptoms are yellowing of lower, older leaves. The disease is soil borne and can survive for many years in the absence of a host. Most cruciferous weeds can serve as alternate hosts.<ref name="Rimmer" />

Damping-Off is a disease in temperate areas caused by soil inhabiting oomycetes like ''Phytophthora cactorum'' and ''Pythium'' spp. The disease concerns seedlings, which often collapse and die.<ref name="Rimmer" />

Other diseases that infect napa cabbage:

* black leg or phoma stem cancer: ''Leptosphaeria maculans'' * clubroot: ''Plasmodiophora brassicae'' * Downy mildew: ''Hyaloperonospora brassicae'' * Powdery mildew: ''Erysiphe cruciferarum'' * ''Rhizoctonia solani'' * ''Sclerotinia sclerotiorum''

=== Bacterial diseases === Bacterial soft rot is considered one of the most important diseases of vegetable brassicas. The disease is particularly damaging in warm humid climate. The causal organisms are ''Erwinia carotovora'' var. ''carotovora'' and ''Pseudomonas marginalis'' pv. ''marginalis''. The rot symptoms can occur in the field, on produce transit or in storage. Bacteria survive mainly on plant residues in the soil. They are spread by insects and by cultural practices, such as irrigation water and farm machinery. The disease is tolerant to low temperatures; it can spread in storages close to 0&nbsp;°C, by direct contact and by dripping onto the plants below. Bacterial soft rot is more severe on crops which have been fertilized too heavily with nitrogen, had late nitrogen applications, or are allowed to become over-mature before harvesting.<ref name="Rimmer" />

Black rot, the most important disease of vegetable brassicas, is caused by ''Xanthomonas campestris'' pv. ''campestris''.<ref name="Rimmer" />

=== Virus diseases === source:<ref name="Rimmer" /> * Cucumber mosaic virus * Radish mosaic virus * Ribgrass mosaic virus * Turnip crinkle virus * Cardamine chlorotic fleck virus * Turnip mosaic virus * Turnip yellow mosaic virus

=== Insect pests === source:<ref name="Cook"/><ref name="Kirk">Kirk, W. D. (1992). Insects on cabbages and oilseed rape. Richmond Publishing.</ref><ref>{{Cite journal |last1=Li |first1=Xiao-Ming |last2=Zhu |first2=Xiu-Yun |last3=Wang |first3=Zhi-Qiang |last4=Wang |first4=Yi |last5=He |first5=Peng |last6=Chen |first6=Geng |last7=Sun |first7=Liang |last8=Deng |first8=Dao-Gui |last9=Zhang |first9=Ya-Nan |date=2 December 2015 |title=Candidate chemosensory genes identified in Colaphellus bowringi by antennal transcriptome analysis |journal=BMC Genomics |volume=16|article-number=1028 |doi=10.1186/s12864-015-2236-3 |doi-access=free |pmid=26626891 |pmc=4667470 }}</ref> * large white butterfly ''(Pieris brassicae)'' * cabbage root fly ''(Delia radicum)'' * cabbage seed weevil (''Ceutorhynchus assimilis'') * cabbage looper * cabbage beetle (''Colaphellus bowringi'') * diamondback moth * small white butterfly ''(Pieris rapae)'' * aphids * cucumber beetles * stink bugs * Vegetable weevils * Mole crickets * cutworms

=== Other pests and diseases === Aster yellows is a disease caused by a phytoplasm.<ref name="Rimmer" />

Nematodes are disease agents that are often overlooked but they can cause considerable yield losses. The adult nematodes have limited active movement but their eggs contained within cysts (dead females) are readily spread with soil, water, equipment or seedlings.<ref name="Rimmer" />

Parasitic nematode species that cause damage on napa cabbage: * ''Heterodera schachtii'' * ''Meloidogyne hapla'' * ''Nacobbus batatiformis'' * ''Rotylenchulus reniformis''

==See also== * Nabemono * '''''<small>{{portal-inline|Food}}</small>'''''

== References == {{Reflist}}

==External links== *{{Commons category-inline|Brassica rapa subsp. pekinensis}}

{{Brassica}}

{{Taxonbar|from=Q13360268}} {{Authority control}}

Category:Asian vegetables Category:Brassica Category:Chinese cuisine Category:Leaf vegetables