sign in sign up
<<
Home , Armenian cucumber, Benincaseae, Cucumber, Cucumis, Cucumis melo, Cucurbitoideae

Genetic resources of the and their morphological description (English-Czech version)

E. KŘÍSTKOVÁ1, A. LEBEDA2, V. VINTER2, O. BLAHOUŠEK3

1Research Institute of Crop Production, Praha-Ruzyně, Division of Genetics and Breeding, Department of Gene Bank, Workplace Olomouc, Olomouc-Holice, Czech Republic 2Palacký University, Faculty of Science, Department of , Olomouc-Holice, Czech Republic 3Laboratory of Growth Regulators, Palacký University and Institute of Experimental Botany Academy of Sciences of the Czech Republic, Olomouc-Holice, Czech Republic

ABSTRACT: Czech collections of Cucumis spp. genetic resources includes 895 accessions of cultivated C. sativus and C. melo species and 89 accessions of wild species. Knowledge of their morphological and biological features and a correct taxonomical ranging serve a base for successful use of germplasm in modern breeding. List of morphological descriptors consists of 65 descriptors and 20 of them are elucidated by figures. It provides a tool for Cucumis species determination and characterization and for a discrimination of an infraspecific variation. Obtained data can be used for description of genetic resources and also for research purposes.

Keywords: ; ; ; germplasm; data; descriptors; infraspecific variation; Cucumis spp.; wild Cucumis species

Collections of Cucumis genetic resources include grains and ovules, there are clear relation of this not only cultivated species C. sativus () taxon with the order Passiflorales (NOVÁK 1961). Based and C. melo () but also wild Cucumis species. on latest knowledge of cytology, cytogenetics, phyto- Knowledge of their morphological and biological fea- chemistry and molecular genetics (PERL-TREVES et al. tures and a correct taxonomical ranging serve a base for 1985; RAAMSDONK et al. 1989), a new taxonomical successful use of germplasm in modern breeding. classification of this family was created by JEFFREY Czech collection of Cucumis genetic resources is main- (1989). The family is subdivided into two subfamilies. tained in Olomouc by the Gene Bank Workplace of the The subfamily Zanonioideae comprises species with Research Institute of Crop Production (RICP) (KŘÍST- a low economic impact. All economically important KOVÁ, LEBEDA 1995). It consists of 794 C. sativus species are included in the subfamily accessions, 101 C. melo accessions and 89 accessions of (Table 1). wild species (C. africanus, C. anguria, C. heptadactylus, Within Cucurbitaceae the tribe Melothrieae with the C. myriocarpus, C. prophetarum, C. zeyheri) (KŘÍSTKO- genus Cucumis are considered the most important ones VÁ 2002a). Morphological data obtained during observa- under climatic conditions of the Middle . The tion of wild Cucumis species do not always coincide with genus Cucumis is represented by 32 species (KIRKBRI- description of some species in monographs. The taxono- DE 1993). Besides cucumber (Cucumis sativus L.) and mical ranging of some accessions should be re-conside- melon (C. melo L.), the species C. anguria (West Indian red. An international descriptor list for cultivated and wild gherkin) and C. metuliferus (African horned cucumber) Cucumis species was not elaborated till now. are commercially explored in several areas as well. A set of morphological descriptors for genetic resour- Other wild species originating mostly from arid and/or ces of the genus Cucumis should serve a tool for species semi-arid regions of , respectively, are cultivated determination and for a discrimination of infraspecific as ornamental (C. dipsaceus – “hedgehog ”, variation. C. myriocarpus – “gooseberry gourd”) (RUBATZKY, YAMAGUCHI 1997). , BOTANICAL CHARACTERIZATION, KARYOLOGICAL STATUS, Origin, gene pool and crossing ability BIOCHEMICAL AND MOLECULAR of Cucumis spp. MARKERS OF CUCUMIS SPP. The South Africa is considered to be a centre of di- Taxonomy of the family Cucurbitaceae versity for the genus Cucumis. The Indian centre, espe- cially area under Himalayan mountains is probably the The genus Cucumis belongs to the family Cucurbi- centre of diversity of C. sativus. This species represents taceae (WHITAKER, DAVIS 1962), order . an compact and isolated group and a subgenus Cucumis. According to specific morphological features of , The second subgenus Melo is divided into three groups.

14 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 15 C. zeyheri 2 (2n=4x) 2 2 C. ficifolius C.prophetarum

2 I C. myriocarpus C. sativus

2 3

C. anguria C. melo

2 1

C. zeyheri C. metuliferus (2n=2x) 2 2

C. dipsaceus C. figarei

Fig. 1. Crossability polygon of Cucumis species (NIJS, VISSER 1985) Obr. 1. Polygon křižitelnosti druhů Cucumis (NIJS, VISSER 1985) I. Cucumis subgenus Cucumis, 1. Cucumis subgenus Melo, Metuliferus group, 2. Cucumis subgenus Melo, Anguria group, 3. Cucumis subgenus Melo, Melo group ♂ ♀ crossing direction/ směr křížení moderately to strongly self-fertile and cross-fertile hybrids středně až vysoce fertilní kříženci sparingly self-fertile and moderately cross-fertile hybrids kříženci zřídka fertilní při samoopylování, středně fertilní při křížení self-sterile, usually not cross-fertile hybrids kříženci sterilní při samoopylování, obvykle sterilní při křížení inviable or seedlings neživotná semena nebo semenáčky Absence of line indicates that seeded were not obtained. Absence linie indikuje, že nebyly získány plody se semeny.

C. melo forms an independent group Melo. Other Afri- C. hystrix. Gene pools of C. melo were not exactly defi- can species form the group Anguria (e.g. C. anguria, ned till now. C. africanus, C. dipsaceus, C. zeyheri) and a group Me- The genetic differences between both subgenera are tuliferus (C. metuliferus, C. myriocarpus, C. sagittatus) a reason of the cross-incompatibility of C. sativus with (JEFFREY 1989). A precise description of Cucumis spe- other Cucumis species and limits the progress in cucum- cies and a study of their cross-ability (NIJS, CUSTERS ber breeding. The successful interspecific hybridization 1989; RAAMSDONK et al. 1989) (Fig. 1) contribute to is related to the development of biotechnological meth- the elucidation of evolutionary relations within genus ods (LEBEDA et al. 1993), e.g. embryo culture techni- and a determination of accessions of genetic resources. ques that can rescue hybrid embryos (LEBEDA et al. Recent taxonomy of the genus Cucumis elaborated by 1999), a protoplast fusion (JARL et al. 1995; FELLNER, KIRKBRIDE (1993) is given in Table 2. LEBEDA 1998) and a somatic hybridization (DABAUZA The primary gene pool of C. sativus consists of one et al. 1998). New valuable characters can be introduce species C. hardwickii, which is frequently considered to the cucumber and melon through trans- as a variety of C. sativus. Secondary gene pool includes formation (VALLÉS, LASA 1994; NISHIBAYASHI et al.

14 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 15 Table 1. Basic taxonomical classification of the family Cucurbitaceae (adopted according toJ EFFREY 1989) Tabulka 1. Základní taxonomické členění čeledi Cucurbitaceae (upraveno podle JEFFREYE 1989)

Subfamily Tribe Genus Podčeleď Tribus Rod Zanonioideae Zanonieae together 18 genera (about 80 species) celkem 18 rodů (asi 80 druhů) Cucurbitoideae together 100 genera (about 745 species) celkem 100 rodů (asi 745 druhů) Melothrieae Cucumis (n = 7.12) Schizopeponeae Schizopepon (n = 10) Joliffieae (n = 11.14) Trichosantheae (n = 11) Benincasa (n = 12) (n = 11) (n = 11) (n = 13) Cucurbiteae (n = 20) Cyclanthereae (n = 8) Sicyoeae (n = 12) n = number n = počet chromozomů

1996). Knowledge in C. sativus breeding was treated by or rarely breakaway hairs. Majority of species has a uni- TATLIOGLU (1993). form type of pubescence on the petioles. C. sagittatus and C. thulinianus have two pubescence types uniform- Morphological description of Cucumis spp. ly mixed over the entire petiole, and C. myriocarpus has three types separated into distinct zones on the petioles, Plants have a bicolatheral vein fascicles and in their retrose-strigose on the base, hirsute in the middle, and tissues, there are cystoliths (NOVÁK 1961). A specific antrorse-strigose at apex. blade is circular, kidney metabolism of terpens leads to the production of cucur- shaped, triangular ovate, somewhat cordate to subcor- bitacins which can cause a poisoning of human and ani- date, narrowly to shallowly ovate, or rarely eliptic or mals (FERGUSON et al. 1983). triangular in outline, sometimes acute to broadly so, Following morphological description is based on data or truncate to subtruncate, rarely obtuse, sagittate, or of CHRTKOVÁ (1990), KIRKBRIDE (1993) and RU- hasttate at the base, with or sometimes without a basal BATZKY, YAMAGUCHI (1997). Plants are annual herbs, sinus, three to five palmately lobed, with three to five exceptionally semishrubs, usually having a trailing or angled portions, from shallow to deeply lobed and with climbing growth habit, although some cucumber and a sharp to round sinuses. The apex is acute, acuminate, melon have a bush habit. Root systems, rarely or rarely obtuse. Central leaf lobe is symmetrical, entire woody (C. trigonus) are extensive, but usually shallow, or sometimes pinnatifid. Leaf margin is dentate, double rarely tuberous (C. kalahariensis). Stems are angled, dentate to entire. Lateral leaf lobes are asymmetrical, or sulcate, not aculeate or rarely aculeate (C. aculeatuc, sometimes symmetrical, entire or sometimes pinnatifid. C. ficifolius), variously pubescent or rarely glabrous, A leaf surface is rough to smooth to the touch. with nonbreakaway hairs or rarely breakaway hairs Flowers are unisexual – pistillate or staminate, but (C. sacleuxii). hermaphrodite flowers also occur. They are very often in The branching pattern is sympodial. Nodes are ge- the group of cucumber. Sex expression is under niculate or not geniculate. Each node has a single leaf genetic control but it is influenced by environment and/ and a simple (sometimes curling), except of or chemical treatment (TRONÍČKOVÁ, PROCHÁZKOVÁ C. humifructus which has a fascicle of 5–8 tendrils and 1984). The inflorescence is unisexual, most species are of C. rigidus which lacks them. Tendrils of C. insignis monoecious. C. humifructus has only androgynous in- are either simple and bifid. Tendrils are variously pubes- florescence (i.e. inflorescence with both male and fema- cent, rarely glabrous or rarely aculeate. le flowers and the female flower below the male ones). are simple and petiolate. Petioles differs C. metuliferus has mainly unisexual inflorescence and in length (with regard to the length of a leaf blade). a few gynecandrous ones (i.e. inflorescence with both Petioles are not aculeate or rarely aculeate, variously female and male flowers and the female flower above pubescent or rarely glabrous, with nonbreakaway hairs the male ones). Cultivated forms of C. sativus have

16 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 17 Table 2. Taxonomy of the genus Cucumis (KIRKBRIDE 1993) Tabulka 2. Taxonomie rodu Cucumis (KIRKBRIDE 1993)

Distribution Cucumis spp. Počet chromozomů (n) Rozšíření Subgenus Cucumis Asia C. sativus L. 7 , Sri Lanka, Burma, C. sativus L. var. hardwickii 7 India C. hystrix Chakravarty 7 India, Myanmar (Burma), China, Thailand Subgenus Melo (Miller) C. Jeffrey Section/Sekce Aculeatosi Kirkbride Serie Myriocarpi Kirkbride C. myriocarpus Naudin subsp. myriocarpus 12 Lesotho, Mozambique, S. Africa, Zambia subsp. leptodermis (Schweickerdt) 12 S. Africa, Lesotho Jeffrey & Halliday

S. Africa, Angola, Botswana, Namibia, C. africanus L. 12 Zimbabwe C. quintanilhae R. Fernandes & A. Fernandes ? S. Africa, Botswana C. heptadactylus Naudin 24 S. Africa C. calahariensis Meeuse ? Botswana, Namibia Serie Angurioidei Kirkbride C. anguria L. var. anguria 12 both vars./obě vars.: Angola, Botswana, Cape Verde, Malawi, Mozambique, Namibia, var. longaculeatus Kirkbride 12 S. Africa, Sierra Leone, Swaziland, Tanzania, Zaire, Zambia, Zimbabwe Kenya, Madagascar, Tanzania, Uganda, C. sacleuxii Paillieux & Bois 12 Zaire C. carolinus Kirkbride ? Ethiopia, Kenya Ethiopia, Kenya, Somalia, Tanzania, C. dipsaceus Ehrenberg ex Spach 12 Uganda C. prophetarum L. 12 subsp. prophetarum Egypt, Mali, Mauritania, Nigeria, Senegal, Somalia, Sudan, , Iraq, Israel, Oman, Qatar, Saudi Arabia, Yemen, Socotra, Syria, United Arab Emirates, Jordan subsp. dissectus (Naud.) C. Jeffrey Chad, Egypt, Ethiopia, Kenya, Mauritania, Niger, Rwanda, Somalia, Tanzania, Uganda, Saudi Arabia, Yemen C. pubituberculatus Thulin ? Somalia Lesotho, Mozambique, S. Africa, C. zeyheri Sonder 12 (24) Swaziland, Zambia, Zimbabwe C. prolatior Kirkbride ? Kenya C. insignis C. Jeffrey 12? Ethiopia C. globosus C. Jeffrey 12? Tanzania C. thulinianus Kirkbride ? Somalia Ethiopia, Kenya, Rwanda,Tanzania, C. ficifolius A. Richard 12 (24) Uganda, Zaire Ethiopia, Kenya, Rwanda, Tanzania, C. aculeatus Cogniaux 24 Uganda, Zaire Ethiopia, Chad, Kenya, Niger, Nigeria, C. pustulatus Naudin ex Hooker 12, 48, 72 Sudan, Tanzania, Uganda, Saudi Arabia, Yemen C. meeusei C. Jeffrey 24 S. Africa, Botswana, Namibia

16 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 17 Table 2 (continuing) – Tabulka 2 (pokračování)

Chromosome number (n) Distribution Cucumis spp. Počet chromozomů (n) Rozšíření C. jeffreyanus Thulin ? Ethiopia, Kenya, Somalia C. hastatus Thulin ? Somalia C. rigidus E. Meyer ex Sonder ? S. Africa, Namibia C. baladensis Thulin ? Somalia Serie Metuliferi Kirkbride Angola, Botswana, Ethiopia, S. Africa, Kenya, Malawi, Mozambique, Namibia, Senegal, Sudan, Swaziland, Tanzania, C. metuliferus E. Meyer ex Naudin 12 Uganda, Zaire, Zambia, Zimbabwe, Cameroon, Central African Republic, Liberia, Burkina Faso, Yemen C. rostratus Kirkbride ? Ivory Coast, Nigeria Section/Sekce Melo (Miller) Kirkbride Serie Hirsuti Kirkbride S. Africa, Angola, Botswana, Burundi, Congo, Kenya, Malawi, Mozambique, C. hirsutus Sonder 12 Sudan, Swaziland,Tanzania, Zaire, Zambia, Zimbabwe Serie Humifructosi Kirkbride S. Africa, Ethiopia, Angola, Kenya, C. humifructus Stent 12 Namibia, Zaire, Zambia, Zimbabwe Serie Melo (Miller) Kirkbride C. melo L. Africa, Iran, Afghanistan, Myanmar (Burma), China, India, Japan, Pakistan, subsp. melo 12 Malesia, New Guinea, , Figi, Papua New Guinea Africa, Saudi Arabia, Yemen, China, Myanmar (Burma), India, Japan, Korea, Nepal, Pakistan, Sri Lanka, Thailand, subsp. agrestis (Naudin) Pangalo 12 Malaysia, Indonesia, New Guinea, Philippines, Australia, Guam, Papua New Guinea, Samoa, Solomon Islands, Tonga C. sagittatus Peyritsch 12 S. Africa, Angola, Namibia

S. Africa (South Africa) = Jižní Afrika many types of sexual expression (e.g. monoecious, glabrous. Corolla fused into a basal tube. Corolla leaves gynoecious, andromonoecious, androdiecious, herma- are elliptic to broadly so, ovate to shallowly so, obovate froditic etc.). to narrowly so, or rarely oblong or broadly triangular in Male inflorescence consists of solitary flowers, or fas- outline, narrowly to broadly acute or obtuse, and someti- ciculate, racemose, paniculate, or rarely modified com- mes also mucronate at the apex. Three are free, pound dichasial from 1–18 flowered, sessile or rarely with separation from the free portion of the hypanthium pedunculate. Male inflorescence are often multiflowered above the ovary. Two of them are 2-thecate and one and are rarely branched. When the inflorescences are 1-thecate. Filaments are terete or radially compressed in branched, the male flowers are always pedicellate. Male cross section, glabrous or with basal puberculence and flowers are 5-merous, pedicel is terete or rarely sulcate glabrous apically. Anther theceae is sigmoid, glabrous in cross section, variously pubescent or rarely glabrous, with the edges shortly pubescent. Anther connective is without bracteoles or rarely subtended by a bracteole extended, obovate, oblong to narrowly so, transversely (C. heptadactylus). Calyx consists of 5 or rarely 4 lobes, broadly oblong, or ovate, unilobate or rarely bilobate, linear to oblong or narrowly to broadly triangular in obtuse or rarely acute in apex, minutely papillate, some- outline, acute to narrowly so in apex, variously pubes- times smooth, or rarely glabrous, fimbriate or crenulate cent or rarely glabrous. Corolla is yellow, infundibular at the apex. Disc is cylindrical or rarely consisting of or rarely campanulate, variously pubescent or rarely three papillae, glabrous.

18 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 19 Female flowers are solitary or rarely in fasciclate abiotic factors (LEBEDA, DOLEŽAL 1995; STAUB et al. inflorescences, sessile arise from leaf axils, very often 1996a,b; HOREJSI et al. 2000). from secondary branches. They are pedicellate and 5-merous. Pedicel is terete or sulcate in cross section, Classification and morphological types variously pubescent, with nonbreakaway hairs or ra- of C. sativus rely with breakaway hairs. Hypanthium is hour-glass shaped. The constricted portion and the lower bulge From the viewpoint of a practical use of fruits, cucum- fused to the ovary. The upper bulge of hypanthium bers are divided into and ones. A common is free from the ovary. Free portion of hypanthium is practice in the past was to use young fruits for pickling campanulate. Ovary has 3–5 placentas with numerous and later on, the biggest but green as salad (e.g. cv. horizontal ovules. Calyx has five, occasionally 4 or Delikates). An exact recent infraspecific classification of 6 lobes of the same shape as male flowers. Corolla is C. sativus was not elaborated till now. PODEŠVA (1959) yellow, infundibular, with the same shape and types of listed following cucumber forms: pubescence as male flower. Corolla tube is present or f. viridis: small warty and “spiny” fruits predominantly absent. Three staminodes are present or rarely absent, for pickling (e.g. From Znojmo, From Paris); separating from the free portion of hypanthium above f. flavus: smooth yellow fruits with shape and size of the ovary. Style is terete in cross section, glabrous, a hen egg (e.g. Russian cornishons); subtented by a circular disc or rarely lacking one. f. albus: elongated, thick, white fruits (e.g. White from Stigma is copular, lobate, or sometimes entire or sub- Paris); lobate, with 1–6 or rarely 9 finger-like projections on f. longus: elongated, cylindric, smooth fruits, green to the margin. yellow-green in colour (e.g. Mladoboleslavské salát- Fruits are pendulous. Cucumber fruit can develop nice, Rollison’s Telegraph, Goliath); parthenocarpically. The pedicel is sulcate or sometimes f. fastigiatus: small fruits in clusters (e.g. Persian clus- terete in cross section, variously pubescent or rarely tered, From Muromsk); glabrous. Fruit is spherical, oval, oblong, elongated f. opheocarpus: very long, curved, snaked fruits (usual- or blocky in shape and variable in size. Fruit surface ly cultivars); varies in the number and size of scattered spiny tuber- f. variegatus: light green fruits with yellow or brown cles (warts), or sharp soft hairs. It can be smooth and spots and stripes (e.g. Japanese, chiva, King Alexan- glabrous, sometimes deeply ridged or covered with a der); corky (reticulate) netting (e.g. for C. melo). Skin colour f. sikkimiae: big, elongated, ovoid fruits, yellowish and varies from pale to very dark green, sometimes with brown-red netted (e.g. Indian netted). longitudinal indentations or stripes. In maturity the skin Fresh market types of cucumbers have usually fruits colour is white cream to orange brown. Inferior flesh with length to diameter ratio of about 4:1, thick skin, colour can be white, green, pink, or orange. A unique somewhat pointed stem and ends, and usually feature of some C. melo cultivars is the formation of an white, preferable few spines. Cucumber types for pick- abscission layer between peduncle and a fruit that coin- ling usually have fruits with length to diameter ratio of cide with fruit maturation. 2.5:1, light green colour and thin skin, relatively blocky Mature seeds have white, cream to yellow colour, they at the stem and blossom ends, and many surface warts. are smooth, compressed, ovoid to elliptic, immarginate, Cucumber cultivars are generally classified into fol- with an acute edge, unwinged or rarely apically winged. lowing groups (RUBATZKY, YAMAGUCHI 1997; GEOR- C. humifructus (“aardvarc cucumber”) develops its GE 1999): fruits below ground. 1. Field cucumbers, with prominent white or black spi- nes; Karyological status, biochemical and molecular 2. English cucumbers – greenhouse or forcing type of markers of Cucumis spp. parthenocarpic cucumbers with seedless fruits; Species C. sativus, C. sativus var. hardwickii (C. hard- 3. Sikkim cucumber, originated in India, with reddish wickii), C. hystrix and C. callosus (not mentioned brown skins of fruits; 4. Oriental-type cucumber, popular in Japan and China, by KIRKBRIDE 1993) have the chromosome number 2n = 14, the same value for other Cucumis species va- thin skinned, usually long and slender with conside- rable warts and spines; ries from 24 to 72, when n = 12 is multiplied (KIRKBRI- 5. Smoot-skinned Beit Alpha types, most popular in DE 1993) (Table 2). and north Africa, with light coloured, The mapping of Cucumis (HELM, HEMLE- thin skinned fruits; BEN 1997; HOSHI et al. 1998) and the study of bio- chemical and molecular markers provide the bases for 6. Lemon cucumber produces a round, creamy yellow the determination of duplicates within collections of skin fruit with large five-carpel cavity. Its sex genetic resources for the discrimination of differences expression is andromonoecious. among accessions (KATO et al. 1998) and for the iden- Very small, immature cucumber fruits are erroneously tification of suitable markers for resistance to biotic and referred to as gherkins.

18 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 19 Table 3. Infraspecific classification ofC. melo (PITRAT et al. 2000) Tabulka 3. Infraspecifická klasifikaceC. melo (PITRAT et al. 2000)

C. melo Subspecies/Poddruh Morphological characteristics/Morfologická charakteristika Group/Skupina English name/Anglický název subsp. agrestis Jeffrey short hairs on ovary/krátké trichomy na semeníku var. conomon Thunberg Oriental pickling melon var. makuwa Makino var. chinensis Pangalo var. momordica Roxburgh Snap melon var. acidulus Naudin subsp. melo Jeffrey long hairs on the ovary/dlouhé trichomy na semeníku var. cantalupensis Naudin Netted melon, var. reticulatus Séringe var. adana Pangalo var. chandalak Pangalo var. ameri Pangalo var. inodorus Jacquin Winter melon/ Meloun Vladimírův var. flexuosus Linnné Snake or serpent melon, var. chate Hasselquist var. tibish Mohamed var. dudaim Linné Pomegranate, Queen Anne’s pocket melon var. chito Morren Mango melon, peach melon

Classification and morphological types of C. melo Seeds are sown in mid- to end April to the sterile substrate (Perlite) in plastic pots (5–10 seeds) and at The species C. melo expresses the largest variability a cotyledon stage seedlings are transplanted to the plas- in the fruit size, shape, colour, texture and within tic pots (diameter of 8.5 cm) with garden soil (two seed- the genus Cucumis (WHITAKER, DAVIS 1962). Its re- lings per pot) in the glasshouse (day/night temperatures cent infraspecific classification proposed by PITRAT et of 20–25°C/10–15°C). The plantlets are transplanted, at al. (2000) is based on the critical analyses of previous a stage of two–three true leaves, to the isolation cages systems (e.g. from NAUDIN, ALEFELD, PANGALO, spaced of 2.3 × 5.5 m each, covered by glass or by plas- GREBENŠČIKOV, FILOV, JEFFREY, ROBINSON and tic net, to four rows with 10 “nests” each. Two weeks DECKER-WALTERS) and a study of morphology of later, seedlings except of the best developed one are cut a contemporary spectrum of cultivars and wild forms. out and removed from the nest. One accession is repre- The phenotypic expression of this variation was ana- sented by 20 (minimum) or 40 (optimum) plants. Plants lyzed also by molecular methods RAPD and ISSR are trained vertically, watered and protected against di- (STEPANSKY et al. 1999). C. melo is divided into two seases and pests. Before flowering a small colonies of subspecies, subsp. agrestis with five groups and subsp. honey- are placed to each cage. Harvested seeds are melo with eleven groups (Table 3). dried, cleaned and stored in glass jars under temperature of –5°C (active collection) or at –18°C (basic collection) STANDARDS FOR REGENERATION in the main store of the Research Institute of Crop Pro- AND EVALUATION duction in Praha-Ruzyně. Detailed regeneration protocol is given by KŘÍSTKOVÁ (2002b). Regeneration Morphological and biological characters Plants of the genus Cucumis are cross-pollinated by insects. Basic information on regeneration of Cucumis The set of morphological descriptors (Table 4) pro- spp. is given by GEORGE (1999). During regeneration vides the tools for species determination within the of acccession in the Gene Bank Workplace RICP in genus Cucumis and for a characterization of Cucumis Olomouc the international standards and the method infraspecific morphological variability. It was elaborated of the regeneration accepted by the National Council on the base of study of genetic resources in Gene Bank for Plant Genetic Resources of the Czech Republic are RICP, Workplace in Olomouc, Cucumis spp. monograph followed. (KIRKBRIDE 1993), the descriptor lists published by

20 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 21 IBPGR (ESQUINAS-ALCAZAR, GULICK 1983), with Resistance to biotic and abiotic factors regard to the descriptor list and codes for Cucumis spp. from Northcentral Regional Plant Introduction Station The resistance to biotic and/or abiotic factors respec- Ames (USA), (ANONYME 1989), the descriptor for Cu- tively, must be evaluated in a separate trials (e.g. in cumis sativus L. published by VIR in Leningrad (USSR) growth chambers after artificial inoculation of patho- (ANONYME 1980) and Guidelines UPOV for conduct gen) using an exact and published method, e.g. LEBEDA of tests for distinctness, homogeneity and stability of (1986). Cucumis sativus (1978) and (1987). The The group of the most important diseases of Cu- terminology of botanical morphology and elaboration cumis spp. includes (CMV), of figures is based on FUTÁK et al. (1966), SUGDEN mosaic virus 2 (WMV-2), yellow (1984), SLAVÍKOVÁ (1988) and BOBÁK et al. (1992). mosaic virus (ZYMV), angular leaf spot (Pseudomo- The list contains 65 descriptors and 20 of them are nas lachrymans), cucumber (Pseudo- elucidated by figures (Annex). Highly discriminating peronospora cubensis) and cucurbit descriptors are marked with an asterisk (*) in the first (, Sphaerotheca fuliginea). column of the Table 4. Letter “S” indicates a species The economically important pests of Cucumis spp. are characterizing descriptor, state of descriptor marked spider mite (Tetranychus urticae), whitefly (Trialeuro- with a letter “I” discriminates an infraspecific variation, des vaporariorum), thrips (Thrips tabaci, Frankliniella letters in brackets are of a secondary significance. occidentalis), aphids (, A. craccivor, Explanation of descriptor states are followed by A. middletoni, Macrosiphum euphorbiae, Myzus persi- examples of corresponding Cucumis species with li- cae) and root-knot nematodes of the genus Meloidogyne terature cited and/or by accession number of genetic (SCHWARZ et al. 1996). resource. The most important abiotic factors are low temperatu- The format for a creation of this descriptor list follows re, high temperature, high soil salinity, soil acidity, high the rule given by the National Council for Plant Genetic soil moisture and high humidity. Resources of the Czech Republic and obtained data will be implemented to the central documentation of plant Acknowledgements genetic resources EVIGEZ. Description data of Cucumis spp. genetic resources accessions will be available on Authors thank VERONIKA KŘÍSTKOVÁ for her tech- the Czech web site of national database of plant genetic nical assistance in elaborating of tables and figures in resources: www.vurv.cz. Annex. This research was developed within the fra- For an adequate documentation of germplasm obtai- mework of the National Programme of Conservation ned data must be supplemented by the characterization and Utilization of Plant Genetic Resources (Ministry of and/or evaluation site descriptors according to IPGRI. of the Czech Republic).

20 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 HORT. SCI. (PRAGUE), 30, 2003 (1): 14–42 21