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Developing and
enhancing the
genetics of economically-important
cucurbits

Cucurbitaceae '96/EUCARPIA VI

"Cucurbits Towards 2000"

Section: Genetics & Breeding

Abstracts


The Effects of Season and Irradiation Doses on Haploid Embryo Production in Cucumber (Cucumis sativus L.)

G. Çaglar1 and K. Abak2

1Horticultural Research Institute, Erdemli, Icel, Turkey, and 2Department of Horticulture, Faculty of Agriculture, University of Cukurova, Adana, Turkey

The effects of season and the doses of 300, 450 and 600 Gy gamma irradiation on in situ parthenogenetic haploid embryo induction in cucumber genotypes were investigated. Two gynoic hybrids (Gamar F1 and Seraset F1) and two local open pollinated cultivars (Dere and Gengelkoy) were used. We obtained many fruits, seeds and embryos from the four genotypes with pollination by irradiated pollen. However, the season and irradiation does significantly affect the haploid embryo yield. The best season was between May and September. The maximum values were reached in June (4.52 embryo/fruit) and in July (8.00 embryo/fruit) with the use of gamma-300 dose. The 300 Gy dose led to the highest embryo production with means of 1.66 and 2.66 embryos per fruit in two consecutive years.


Interspecific Hybridization of Cucumis sativus x Cucumis melo, as a Potential Way to Transfer Resistance to Pseudoperonospora cubensis

A. Lebeda1, E. Krístková2 and M. Kubaláková3

1Palacký University, Faculty of Natural Sciences, Department of Botany, 772 36 Olomouc-Holice, Czech Republic, 2Research Institute of Crop Production, Praha; Gene Bank Division, 772 36 Olomouc-Holice, Czech Republic, and 3De Montfort University, Norman Borlaug Institute for Plant Science; Institute of Experimental Botany, Academy of Sciences of the Czech Republic, SokolovskA 6, 772 00 Olomouc, Czech Republic

Abstract. The aim of this work was to transfer resistance to cucumber downy mildew (Pseudoperonospora cubensis) from Cucumis melo to Cucumis sativus. The attempt of overcoming the crossing barriers resulting from different chromosome number of both species was based on the combination of two techniques - classic pollination of intact Cucumis sativus plants by the pollen of C. melo followed by cultivation of excised young seeds and embryos in vitro. In the period 1992-1994, a set of C. sativus cvs. Zidovická produkta, Marketmore, Bílské, Melnické and Alert F1 and breeding lines SM- 6022, SM-6514, SM-6511, and SM-6026 were pollinated by C. melo genotypes M 320 'Nantais oblong', M 323 (PMR 5 line), MR 1, PI 124112, PI 124111 and PI 200819 In four cycles. During pollination, the biologically active substances (IBA, 2,4D, BAP, 4CPA, AgNO3 and glycine) in lanolin paste were applied on the cucumber flower stem or stigma to promote better development of fruits, seeds and embryos. Ten to twenty days after pollination, the hybrid fruits were picked, measured and examined for the presence of seeds or embryos. The excised seeds and/or embryos were cultivated in vitro on solid MS and E20A medium with addition of biologically active substances (2,4D, glycine, BAP, NAA). If the embryo developed and the cell structures were formed their hybrid character was evaluated using isozyme analysis (peroxidase, acid phosphatase, esterase). The enormously high polyploidy avoid using the DNA-flowcytometry. In the I. cycle, 21 fruits were analyzed and 23.8% of them contained seeds but no embryo was found. In the II. cycle, 205 fruits were analyzed, 10.7% contained seeds and 2.9% embryos. In the III. cycle, 85 fruits were analyzed and 67.1% contained seeds and 37.6% contained embryos. In cycle IV., 77 fruits were analyzed and 75.3% of them contained seeds and 71.44 embryos. The crossing ability is primarily influenced by genotype of both partners. Best results were obtained with C. sativus lines SM-6022, SM-6514 and SM-6026 and C. melo genotypes MR-1 and PI 200819. The application of biologically active substances on cucumber flowers during pollination did not positively influence the formation of embryos. The in vitro pre-cultivation of intact (whole) extirpated seeds on solid MS or E20E medium with an active substances followed by a cultivation of embryos resulted in detection of developing embryos. In four cases, the formation and differentiation of callus was observed. The strong tendency to polyploidize was a reason of an undifferentiated callus formation from embryos. The hybrid character of two embryos was verified using isozyme analysis. For the first time, the viable interspecific hybrid embryos were produced and initiation of their callogenesis and partly rhizogenesis or callogenesis was observed. In cycle IV., two embryos developed into flowering plants. They originated from the crossing between cucumber breeding lines and C. melo MR-1. Their morphological and physiological characteristics are under study.


Genes Affecting Stem and Fruit Color Intensity of Straightneck Squash

Harry S. Paris

Agricultural Research Organization, Newe Ya'ar Research Center, P.O. 1021 Ramat Yishay 30095, Israel

'Early Prolific Straightneck' is a straightneck-type squash cultivar having dark stems and fruits which are light in color when young but intensify during development. It was crossed with 'Vegetable Spaghetti' and with other stocks of known genotype in order to identify the genes responsible for its dark stems and developmentally intense coloration. The results indicated that a weaker allele of gene D, named Ds, is responsible for the dark stems, but that this allele has no effect on fruit coloration. Gene L-2 was found to be responsible for the intensification of fruit color during development.


Evaluation of a Melon Collection for Diseases Resistances

M. Pitrat1, G. Risser1, F. Bertrand2, D. Blancard2, H. Lecoq2

INRA, Station dAmélioration des Plantes Maraîchères (1) and Station de Pathologie Végétale (2), BP 94, F-84143 Montfavet cedex (France)

The Cucumis melo collection maintained at INRA in Avignon (France) is not representative for the complete diversity of melon; for instance accessions from Africa and central and south America are under-represented. A part (635 accessions) of this collection has been evaluated with at least one of the following pathogens.

Fusarium wilt has been tested in artificial inoculation with races 1, 2 and 1-2. Resistance to race 1 (400 accessions tested) was found mainly in accessions from Eastern and Central Asia (resp. 56 % and 30 %). Resistance to race 2 (353 acc. tested) was observed mainly in accessions from Central Asia, Russia and France (resp. 46 %, 31% and 30%). Resistance to race 1-2 (271 acc. tested) was observed only in accessions from Eastern Asia.

A few accessions (58) have been tested with Pyrenochaeta lycopersici. Most of them were moderately susceptible or resistance except accessions from Central Asia which were highly susceptible.

No high level of resistance to scab (Cladosporium cucumerinum) has been found among 261 accessions tested. Moderate level of resistance were found in accessions from North America, Spain and Eastern Asia.

About 400 accessions were tested with different strains of powdery mildew. Almost all were resistant to races 0 of Sphaerotheca fuliginea and Erysiphe cichoracearum. Only a few genotypes from Central Asia were susceptible to races 0. Resistances to races 1 and 2 of S. fuliginea was observed mainly in accessions from North America, Western Asia and India. But resistance in american or Near East genotypes is the result of breeding programs and the original sources of resistance were indian genotypes. Resistance to race 1 of E. cichoracearum was very frequent in accessions from Spain, North America or India (resp. 90, 38 and 32 %). Here again resistance in american genotypes is the result of breeding programs conducted for a long time.

Among 367 accessions tested for downy mildew (Pseudoperonospora cubensis) only 3 accessions from India and one from Eastern Asia were highly resistant.

The only source of resistance to Zucchini Yellow Mosaic Virus (ZYMV) was from India. Necrotic reaction with F pathotype of ZYMV has been observed on 36 % of 531 accessions, mainly from Central Asia and Spain (76 % and 71 % resp.). The lowest frequency was observed in genotypes from Eastern Asia (10 %).

Resistance to Melon Necrotic Spot Virus (MNSV) has been found in 7 % of 532 tested accessions mainly from North America (29 %).

Watermelon Mosaic Virus type Morocco (WMV-M) induces on some genotypes a necrotic reaction. This reaction was frequently observed in accessions from Eastern Asia and France (77 and 56 % resp). Among 341 tested accessions, resistance to this virus was found in accessions from India and North America (19 and 17 % resp).

In conclusion, India and Eastern Asia are very important sources of disease resistance. Some particular accessions are highly interesting because they are multi-resistant (for instance PI 161375, MR-1, PI 124112, PI 414723). Conversely no unique resistance was observed in accessions from Central Asia. Only 4 out of 138 accessions tested with 7 different pathogens were susceptible to all of them.


Performance of Tropical Pumpkin Inbreds and Hybrids

D. N. Maynard

University of Florida, Bradenton FL USA

Cucurbita moschata (Duchesne) Poir. is a pumpkin-like fruit that is grown throughout the tropics and subtropics. This species is also known as calabaza in Puerto Rico, auyama in the Dominican Republic, calabash or pumpkin in the English-speaking islands, ayote in Central America, and zapallo in South America. Plants are monoecious, and insects, primarily honeybees and bumblebees, are required for transfer of pollen from staminate to pistillate flowers. Fruits are produced along trailing vines that may spread up to 15 m from the base or crown of the plant. Each plant commonly produces two to five fruits; however, some selections may produce as many as nine fruits per plant. Fruit weight ranges from 2 to 20 kg. Fruit shape varies in unimproved types from globe, round, oval, obovate, pear, oblate and gourd, to elliptic. Likewise, there is much variation in rind color from green immature fruit to light-orange mature fruit and in rind pattern from piebald (pinta) to mottled. The rind may be smooth or warted. The fruit wall varies in color through several shades of yellow to orange and is from 2 to 8 cm thick.

Bush/short-vine and intermediate-vine length tropical pumpkin inbreds and hybrids have been developed and evaluated. Several of the short-vine hybrids produce yields that are equivalent or superior to those of the traditional long-vined inbreds. The short-vine hybrid plants generally produce fruit which is smaller and has thinner flesh than the long-vined inbreds so they may not be suitable where market requirements dictate large fruit. Soluble solids concentrations in fruit from the short-vined hybrids is equal or superior to that in fruit from traditional inbreds.


Inheritance of Peduncle Size in the Cucumber and Its Linkage Relationships with Other Characters

N. Fanourakis1, N. Golfinopoulou1, A. Stavrianou1, and E. Tzifaki2

1Technological Educational Institute, Heraklion Crate. 71500 Greece; 2Institute of Viticulture, Vegetable Crops and Floriculture, Heraklion Crete, 71110 Greece

Abstract. The fruit of cucumber is joined to the main stem by the peduncle which, in most varieties, is extended from one to several centimeters. Most European slicer varieties have a long peduncle which at harvest is cut either close to the plant, so that it accompanies the fruit to the market, or close to the fruit so it remains on the plant. Its presence is usually undesirable because it becomes wilted if remains on the fruit, or it is a point of infection by some diseases through the wound if it remains on the plant.

The way of peduncle size and its genetic relationships with some qualitative characteristics of cucumber were investigated. Line 786 which was found to have the longest peduncle was crossed with a local population which lacks peduncle. F1 plants were selfed and also backcrossed to either parent so that F2 and BC populations were generated. Parents, F1, F2, BCP1 and BCP2 generations were evaluated for peduncle size. Plants were also classified for sex expression, spine color and mature fruit color for possible linkage association with the peduncle size.

Arrangement of plants in discrete classes for peduncle size in the segregating generations was attempted to test the segregating ratios by x2 analysis. However the resulting phenotypic classes did not fit to known ratios of the Mendelian inheritance. A quantitative approach could probably explain better the inheritance of this characteristic. The observed ratios for the characteristics of sex expression, spine color, and mature fruit color within each class of peduncle size generally did not indicate significant deviations from the observed total ratio of each characteristic. Thus independent inheritance is suggested for the peduncle size and the characteristics of sex expression, spine color, and mature fruit color.


Two Independent Loci for White and White-Yellow Corolla in Cucurbita maxima Duch.

Aleksandra Korzeniewska

Department of Plant Genetics, Breeding and Biotechnology, Warsaw Agricultural University, Warsaw, Poland

Abstract. In the genus Cucurbita petals lighter than the typical yellow-orange or orange have been described twice. The character named light yellow corolla was described by Scarchuk in 1974 in Cucurbita pepo var. ovifera Alef. as a recessive trait (ly). Cream corolla was described for the second time by Roe and Bemis in 1977 in Cucurbita moshata cv. 'Butternut'. Colour was introduced from C. okeechobeensis Bailey. A two-loci hypothesis was accepted by the CGC Gene List Committee (Hutton and Robinson, 1992). Gene cr - cream corolla in homozygous stage cr/cr gives cream to nearly white petals, cr/+ yellow ones and +/+ orange. Gene i has been described as intensifier of cr gene for cream flowers. In this paper the occurrence of the white and white-yellow corolla in the third species C. maxima is analysed. The white corolla form was separated in the F5 from cross 'Ispanskaya x Emerald Squash'. The colour of the petals according to Ostwald tables (Ostwald Ed. A. Muster Schmidt Berlin S.W. 68) was defined as 1/VI/1ea/1. The margins of the petals of this form were less dentate and had tendency to curl in the upper part of the corolla. The form white-yellow corolla was isolated in the S3 generation from the cv. 'Rieesen-Melonen'. The petals had a slightly different shade (according to the Ostwald 1/VI/ga/2). In contrast to white corolla the petals were strongly dentate. In order to explain the mode of inheritance of the white and white-yellow corolla traits classical genetic analysis was performed. Each of the forms was crossed with an inbred line (138) characterised by intensely orange petals (according to Ostwald tables 1/XII/na/4). White and white- yellow corolla lines were crossed to analyse independent inheritance of both characters. These two lines were subsequently crossed with the yellow-green leaves line described earlier by Korzeniewska (1992). Hypothetical segregation ratios were checked by the chi square test. For the first time the inheritance of the characters white corolla (wc) and white-yellow corolla (wyc) in Cucurbita maxima Duch. was described. Both characters are recessive. The genes which cause them occur in distant loci. Dominant alleles of these genes complement with each other giving orange colour. The character white corolla and white-yellow corolla were not linked with the character yellow-green leaves. For a better evaluation of the character carotenoids in the petals should be analysed.

Literature cited:

  1. Hutton, M.G. and R.W. Robinson. 1992. Gene list for Cucurbita spp. Cucurbit Genet. Coop. 15:102-108.
  2. Korzeniewska, A. 1992. New genes in Cucurbita maxima Duch. Fifth Eucarpia Cucurbitaceae Symposium, July 27-31, 1992, Skierniewice-Warsaw, Poland, 75-78.
  3. Roe, N.E. and W.P. Bemis. 1977. Corolla colour in Cucurbita. J. Heredity 68:193-194.
  4. Scarchuk, J. 1974. Inheritance of light yellow corolla and leafy tendrils in gourd (Cucurbita pepo var. ovifera Alef). HortScience 9:464.


Leaf Yield Components and Nutritional Quality of Zambian Pumpkin (Cucurbita spp.: Cucurbitaceae) Landraces

C. Gwanama1 and K. Nichterlein2

1Department of Crop Science, University of Zambia, P.O. Box 32379, Lusaka, Zambia, and 2Plant Breeding and Genetics Section, International Atomic Energy Agency, P.O. Box 100, A-1400, Vienna, Austria

Abstract. Cucurbita species are extensively used for leaf consumption in Zambia. The current study had the objective of evaluating leaf yield potential and nutritional quality of 36 pumpkin landraces collected from the major agroecological zones of Zambia and to establish the leading selectable traits contributing to leaf yield. Two trials conducted at farms near Lusaka in 1994/5 revealed significant differences among the genotype means at p=0.05 for number of node with first female flower, length of internode with first female flower, length of primary vine, number of primary branches per main vine and number of leaves per plant. Significant correlations were obtained among leaf yield and its components, especially length of main vine (r=0.848**) and number of primary branches per main vine (r=0.905**). Number of primary branches per main vine had the highest direct effect on yield (0.6883) although length of main vine had a big contribution to yield via number of primary branches (0.6188). In general Cucurbita moschata landraces were more branching and leafy than C. maxima varieties. Additionally leaf crude protein analyses showed significant differences among genotype means. It is concluded that genetic variation exists in the germplasm collection and that number of primary branches per main vine is the most important yield component. Variation also exists in nutritional quality although commercialized cultivars are not superior to the rest.


29-D, A Melon Inbred with Multiple Diseases Resistances

Y. Cohen

Department of LIfe Sciences, Bar-Ilan University, Ramat-Gan, Israel

Cucumis melo PI 124111F was stabilized for resistance to downy mildew, powder mildew race 1 and 2 and Fusarium wilt races 0, 1, and 2. This line was crossed to a susceptible Ha'ogen type and then backcrossed to a susceptible orange-flesh cantaloupe. 20-D was selected after 10 generations of selections and selfing. 29-D is resistant to downy mildew caused by Pseudoperonospora cubensis, powdery mildew caused by races 1 and 2 of Sphaerotheca fuliginea and races 0, 1, and 2 of Fusarium oxysporum f. sp. melonis. This inbred line produces a vigorous vine with globular, netted, sutured fruits. The fruit has a small cavity and mild orange flesh. TSS is ca. 12%. 29-D combines beautifully with various partners such as Ananas types, cantaloupes and charantias. F1 hybrid plants are resistance, under field conditions, to downy mildew, powder mildew race 1, and Fusarium wilt. Resistance to race 2 of powdery mildew is incomplete. F1 fruit type was strongly affected by the partner used for crossing.

 

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Page citation: Wehner, T.C., Cucurbit Genetics Cooperative;
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send questions to T.C. Wehner; last revised on 30 August, 2005