Source: UNIVERSITY OF PUERTO RICO AT MAYAGUEZ submitted to
BREEDING TROPICAL VEGETABLE CROPS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0182637
Grant No.
(N/A)
Project No.
PR00391
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Oct 1, 1999
Project End Date
Sep 30, 2005
Grant Year
(N/A)
Project Director
Ortiz, C. E.
Recipient Organization
UNIVERSITY OF PUERTO RICO AT MAYAGUEZ
P. O. BOX 9000
MAYAGUEZ,PR 00681
Performing Department
AGRONOMY & SOILS
Non Technical Summary
The vegetable industry in Puerto Rico has taken on considerable importance on the island as less and less land is dedicated to growing sugarcane. There continues to be a strong local demand for traditional vegetable crops. Research must focus on cultivar improvement for tropical-type sweet potato and tropical pumpkin or calabaza. Puerto Rico has the potential to increase local tropical sweet potato production. New tropical pumpkin cultivars are needed with improved disease and insect resistance and better fruit quality.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2021429108050%
2021450108050%
Knowledge Area
202 - Plant Genetic Resources;

Subject Of Investigation
1450 - Sweet potato; 1429 - Cucurbits, other;

Field Of Science
1080 - Genetics;
Goals / Objectives
In FY 1996-97, the production of sweet potato in Puerto Rico was estimated at 2000 t, supplying about 18% of the local demand while imports totaled 9,077 t. Local sweet potato production is concentrated in the southern coast under an essentially mechanized system. The AES recommends various traditional cultivars for sweet potato production in the southern coast. Some of these cultivars have limited acceptance among producers because they are adapted neither to the edaphic/meteorological conditions of the area or to the management system used for sweet potato production in this area. Other cultivars selected in the 1960s have shown low yield stability and high variability in root size and morphology. Because of the limited choices of locally developed cultivars, sweet potato producers rely upon imported cultivars. Tropical pumpkin occupies second place in terms of the amount of revenue generated by vegetable crops. It is consumed throughout the Caribbean and Latin America, as well in the US mainland where it is important in a growing Hispanic market. Currently US production of tropical pumpkin is limited to Puerto Rico and subtropical areas of Florida, although temperate types of the same species (butternut squash) are grown in many other states. The UPR-AES has maintained a small pumpkin research program for many years. During the past 10 years the focus of the program has varied, depending on the source of funding, but has not emphasized cultivar development. Rather, the research has focused on germplasm enhancement: screening for resistance to diseases and insects, including powdery and downy mildew, whitefly, and silverleaf, as well as modification of growth habit (selection for compact plant type). One cultivar, `Soler', has been released from this program. Although this cultivar is widely grown on the island, other cultivars are needed with improved disease and insect resistance and better fruit quality. The pumpkin research program has evaluated a large amount of germplasm, including a large portion of the US National Germplasm System, and has initiated the development of both broad and narrow base breeding populations. The program has developed a very broad genetic base that should yield useful adapted cultivars in the future. There appears to be ample market opportunities in Puerto Rico and the US mainland to expand production of tropical pumpkin. New cultivars developed from an effective breeding program can add value for both the grower and consumer of tropical pumpkin. 1.To collect and introduce new sweet potato clones for direct selection as cultivars or to produce new clones by crossing selected parents. 2.To evaluate and select among new clones for potential cultivar or germplasm releases using a systematic quantitatively based evaluation protocol. 3.To develop improved breeding populations of both long and short-vined tropical pumpkin. 4.To select superior tropical pumpkin genotypes from breeding populations for testing and release as new cultivars.
Project Methods
Surveys will be conducted among consumers and producers to update preferences and varietal needs. Farmer interviews will be conducted to determine important characteristics that cultivar must possess for optimum adaptation to field conditions. Sweet potato clones imported, locally available, and local landraces will be incorporated into the project. New clones will be produced using the polycross crossing technique. A randomized complete block design with at least three replicates will be used. For the preliminary evaluations, plots will consist of 15 plants spaced at 30 cm within the bed. During the crop cycle, visible symptoms of fungus/bacteria and nematode diseases will be recorded. Prior to harvest, hills will be inspected for damage by the sweet potato weevil. Plots will be harvested mechanically. Yield will be recorded and tolerance to skin injury will be quantified by standard methods. Descriptive data on root shape and surface defects will be taken on the basis of the sweet potato descriptors. Storage roots of the superior clones will be evaluated quantitatively for dry matter, starch content, and sugars. Concentrations of glucose, sucrose, fructose and maltose will be determined using a modification the HPLC method. Tropical pumpkins will be planted in various seasons (hot and mild weather conditions) and harvested sequentially for earliness. Advanced clones will be furthered tested in private farms throughout the south coast. An intrapopulation improvement program using half-sib recurrent selection will be carried out for both short and long-vined types. Half-sib, rather than selfed or full-sib families, will be used because of the difficulty of successfully obtaining selfs in tropical material. In addition to the populations already available, other populations will be developed during the first two years of the project. Cycles of recurrent selection will be carried on continuously in at least one each of the long and short-vined populations over the course of the 5 year project. Test for powdery mildew, whitefly and virus resistance will take place both in the field and greenhouse. Long-vined genotypes typically have a 4-5 month life cycle, while short-vined genotypes can be harvested once-over in 3 months. Thus, as many as 4 cycles of recurrent selection will be completed for short-vined populations, while only 2.5 to 3 cycles of selection will be carried out for long-vined populations over the course of the project. Beginning after two cycles of recurrent selection, lines will be selfed out of the recombinant populations for testing and possible release as pure lines or synthetic cultivars. The improved populations themselves could also be released as an open-pollinated cultivar. Efficient screening techniques for virus and whitefly resistance will be developed. ELISA diagnostic kits will be used to identify viruses present in commercial pumpkin fields. Whitefly and silverleaf screening techniques using cages will be developed. Advanced breeding lines available from previous research or introduced from other programs will be tested as they become available.

Progress 10/01/99 to 09/30/05

Outputs
In order to better understand the relationships between various components of yield, a path analysis study was carried out in two diallels of land races of tropical pumpkin. Average fruit weight and number of fruit per plant were the two variables having the most important impact on yield, with average fruit weight showing a greater effect. New tropical pumpkin cultivars developed during the first 4 years of this project were tested in a variety of environments (locations and planting seasons). Two cultivars, PRShortvine1 and PRLongvineSLR showed a performance superior to that of other materials, and were similar in yield to that of the standard cultivar `Soler.' The final field trials of these two cultivars are being analyzed, and formal release of these cultivars is expected during 2006. Inheritance of resistance to silverleaf, a whitefly-induced physiological disease, was studied. We propose the symbol Sl (Silverleaf) for the single incompletely dominant gene that results in susceptibility to silverleaf. Plants homozygous recessive for the gene sl are resistant to silvering. The cultivar PRLongvine SLR carries resistance to silverleaf. During this project we carried out a series of studies to better understand genetic relationships between tropical pumpkin (Cucurbita moschata) and its closely related species, particularly C. argyrosperma and C. sororia. We observed a high level of compatibility between sororia and argyrosperma, no matter the direction of the cross. There was a high degree of compatibility between either argyrosperma or sororia with moschata when the former species were used as the female parent. Incompatibility was observed in the reciprocal cross where moschata was used as the maternal parent. Plants, fruits and seeds of F2 and backcross populations appeared to be normal. Monogenic morphological traits had expected segregations in interspecific backcrosses, thus suggesting a high degree of homology between these two species. The high level of compatibility observed should make it easy to move traits of interest from one species to another. Sweet potato varieties accepted by the local market are primarily those within the tropical-type. Tropical-type describes varieties intermediate in sweetness that exhibit white, cream or light yellow-fleshed roots. Regarding varietal choices, major local producers are limited to the landrace Dominicana, which dominates the market. Genotypes tested as entries PR-98-022 to be named Camuy and PR-98-40 to be named Pujols were selected. Both genotypes yielded better than Dominicana in both experimental and in semi-commercial plots and had similar sweetness and starch content and have demonstrated tolerance to over-the-top use of herbicides. A polycross was established and total count of open pollinated seeds collected was estimated at 12,000. Obtained progeny will continue under evaluation within another project.

Impacts
Two new tropical pumpkin cultivars were developed with fruit quality superior in color and texture to that of the most commonly grown cultivar in Puerto Rico. Both cultivars have improved flesh color that provides the consumer with additional health benefits since darker orange color is associated with higher levels of beta-carotene, an important anti-oxidant. For the grower, the new cultivar with a semi bush growth habit can be more easily managed than the to traditional vine types. The other new cultivar is a more traditional long-vine variety that has improved insect resistance compared to that of the commonly grown cultivar. These traits will benefit the grower by reducing costs of pest control. We also studied the ability of different species of tropical pumpkins to cross-pollinate. There is a high level of compatibility between the species we studied (they are like first cousins). This compatibility will allow breeders to move traits of interest (such as better resistance) from one species to another. However, it also means that undesirable genes from one species (including genetically engineered genes) are able to move to another species with relative ease. This knowledge can be useful when growing various tropical pumpkin species in the same area. It should be noted that some varieties of these species also grow in temperate climates. Newly selected sweet potato genotypes have been accepted among farmers within the small farm system. About 30 requests of propagation material of new varieties have been processed.

Publications

  • Rivera-Hernandez, M., L. Wessel-Beaver and J. X. Chaparro. 2005. Molecular phylogenetic analysis of genes of the carotenoid pathway in Cucurbita. HortScience 40(4):1039. (abstract)
  • Wessel-Beaver, L., O. Roman-Hernandez and L. Flores-Lopez. 2006. Performance of New Tropical Pumpkin Genotypes for Puerto Rico under Varying Cultural Practices. J. Agric. Univ. P. R. (submitted).
  • Espitia-Camacho, M., F.A. Vallejo-Cabrera, D. Baena-Garcia, and L. Wessel-Beaver. 2005. Path Analysis of Yield Components in Tropical Pumpkin. J. Agric. Univ. P. R. (Accepted for publication).
  • Wessel-Beaver, L. 2005. Release of `Soler' Tropical Pumpkin. J. Agric. Univ. P.R. (Accepted for publication). Sanjur, O., D.R. Piperno, T.C. Andres, and L.Wessel-Beaver. 2005. Using molecular markers to study plant domestication: The case of Cucurbita. In: D.M. Reed (ed.), Biomolecular archaeology: Genetic approaches to the past. Center for Archaeological Investigation, Occasional Paper No. 32, Southern Illinois University, Carbondale.


Progress 01/01/04 to 12/31/04

Outputs
Six new tropical pumpkin (Cucurbita moschata) genotypes (two open pollinated populations and five lines) were evaluated on the basis of yield, quality and pest resistance of the standard cultivar `Soler.' Two genotypes (PRShortvine-1 and PRLongvineSLR) were tested at two within row planting distances (0.9 m and 1.9 m). Soler was planted at 0.9 m. Lines E0305-1, E0305-2 E0305-3 and E0305-4 were planted at 1.9 m. Lines E0305-1 and E0305-2 were highly susceptible to the melonworm, Diaphania hyalinata. Those same lines, as well as PRShortvine-1, were also susceptible to downy mildew, Pseudoperonospora cubensis. Flesh color of the new genotypes tended to be more orange than that of Soler. All genotypes produced similar yields. Within-row planting distance had no effect on yield and no effect on fruit size of PRShortvine-1. PRLongvineSLR produced a greater number of smaller fruits at the 1.9-m planting distance. Seed production in fruits of PRShortvine-1 and PRLongvineSLR was similar to that of Soler. Despite some shortcomings, PRShortvine-1 and PRLongvineSLR are two advanced open-pollinated populations that merit consideration for formal release on the basis of their field performance, good fruit quality and ability to produce economical amounts of seed in a seed production program. Two elite sweet potato clones were compared in southern Puerto Rico on the basis of yield, sugar content and alcohol insoluble solids to the recommended cultivars Miguela and Dominicana. Yield of elite clones was better than that of the standards. On average, percentage of alcohol insoluble solids for new clones 98-22 and 98-40 were 73 and 78% both higher than that of the standards, and indicative new clones are starchier. Percentages of maltose and sucrose after baking of clone 98-22 were 3.6 and 9.9, respectively higher than that of Miguela but lower than that of Dominicana. Among clones, 98-40 had the least maltose and sucrose content. As the standards, new clones are susceptible to the sweet potato weevil. We are considering formal release based on their ability to produce commercial sweet potato of good appearance and appropriate sweetness for the fresh market.

Impacts
If the tropical pumpkin variety PRShortvine-1 is released, it has the potential to be planted on 1,000 to 1,500 acres of land in Puerto Rico and to generate from $2 to $5 million dollars per year in income at the farm gate level. This variety would also likely be adapted to production areas in the southern U.S.

Publications

  • Wessel-Beaver, L., Cuevas, H.E., Andres, T.C. and Piperno, D.R. 2004. Genetic compatibility between Cucurbita moschata and C. argyrosperma. In: A. Lebeda and H. S. Paris (eds.) Progress in Cucurbit Genetics and Breeding Research, Proc. of Cucurbitaceae 2004, the 8 th EUCARPIA Meeting on Cucurbit Genetics and Breeding, Palacky University, Olomouc, Czech Republic, pp 393-400.
  • Wessel-Beaver, L., Sud-Gonzalez, J. and Cuevas-Marrero H. 2004. Morphological traits of possible use as species markers in Cucurbita moschata and C. argyrosperma. Cucurbit Genetics Coop. Rpt. 27 (in press).


Progress 01/01/03 to 12/31/03

Outputs
Three cycles of selection have been completed in PRShortvine, a population with semi-bush growth habit and superior fruit quality (flesh thickness, texture and color). Emphasis has been placed on selecting for appropriate fruit size and shape (fruit size and shape is still somewhat variable in the population). A second population, PRLongvineSLR, has undergone two cycles of selection. This long vine population derives from lines selfed out of the OP cultivar Soler, and is resistant to whitefly-induced silverleaf resistance (Soler is susceptible). These two populations, along with several inbred lines, selected from the PRShortvine population, are now ready for more extensive testing against the check variety Soler. A trial with large (20 m x 7 m) plots is in progress at the Isabela substation and two other similar trials are planned at two other locations. A protocol for DNA extraction in pumpkin, and for some initial molecular marker work, was begun. A field and molecular study of genetic compatibility between C. moschata and a sister species, C. argyrosperma, demonstrated a high degree of compatibility between these species when the latter is used as the female parent, but incompatibility in the reciprocal cross where C. moschata is used as the maternal parent. Plants, fruits and seeds of F2 and backcross populations appeared to be normal. Monogenic morphological traits had expected segregations in interspecific backcrosses, suggesting a high degree of homology between these two species. Finally, over the past year we have made a total of 10 plantings of 5 genotypes at each of two locations (planting approximately every 4 to 6 weeks) in order to study the effect of day length and temperature on growth and flowering. No general pattern relating to day length, nor average temperature, could be discerned. Genotype differences were due to internode length, not total number of leaves or nodes.

Impacts
Semi-bush types have been developed with fruit quality superior in color and texture to that of the most commonly grown variety in Puerto Rico. These traits are highly desirable to consumers. For the grower, semi bush tropical pumpkin can be more easily managed than traditional vine types. Traditional long-vine varieties are also being developed with an emphasis on incorporating insect, disease and virus resistance. These traits will benefit the grower by reducing costs of pest and disease control. We also studied the ability of different species of tropical pumpkins to be cross-pollinated. There is a high level of compatibility between the species we studied (they are like first cousins). This compatibility will allow breeders to move traits of interest (such as better resistance) from one species to another. However, it also means that undesirable genes from one species (including genetically engineered genes) are able to move to another species with relative ease. This knowledge can be useful when growing various tropical pumpkin species in the same area. It should be noted that some varieties of these species also grow in temperate climates.

Publications

  • Cuevas, H.E. and L. Wessel Beaver. 2003. Genetic compatibility between two species of tropical pumpkin. HortScience 38:735 (abstract)
  • Chesney, P., L. Wessel Beaver and D.N. Maynard. 2004. Tropical pumpkin intercropped with beans and cowpeas. HortScience (accepted for publication)
  • Wessel Beaver, L., J. Perez Arocho and O. Roman Hernandez. 2003. A comparison of the vegetative and reproductive performance of pumpkins of varying growth habit. Annual Meeting of the Sociedad Puertorriquena de Ciencias Agricolas, November 21, 2003, Guanyanilla, Puerto Rico. p. 11. (abstract)
  • Cuevas Marrero, H.E. 2003. Compatibilidad genetica y flujo de genes entre Cucurbita moschata y C. argyrosperma. M.S. Thesis. University of Puerto Rico, Mayaguez Campus, Mayaguez, Puerto Rico. 81 pp.


Progress 01/01/02 to 12/31/02

Outputs
Half sib recurrent selection in two breeding populations (a semi-bush and a long vine population) continues. The semi-bush population has gone through two and a half, and the long-vine population one and a half, cycles of selection. In addition to continued recurrent selection, inbred lines are also being selfed out of these populations. Studies on the inheritance of resistance to whitefly-induced silverleaf disorder, leaf mottling, and the relationship between these two traits are nearly complete. Genetic leaf mottling appears to be controlled by two genes and linked to silvering in the presence of silverleaf whitefly. Inheritance follows a model of recessive epistasis. In this model, a dominant gene results in mottle leaf (yellow or grey) while the recessive is greenleaf. The M gene expresses grey mottle only in the presence of the previously mentioned dominant gene. Silverleaf resistance appears to be closely or completely linked to the recessive m alele. A study on the effect of daylength and temperature on flowering and development in both long vine and semi-bush tropical pumpkin has been initiated but no data has been analyzed. Genetic compatibility and phylogenetic studies between Cucurbita moschata and the closely related species C. argyrosperma continue. It is clear that gene flow from C. moschata to C. argyrosperma populations (including the wild species C. sororia) can occurr easily. Progeny from crosses between these species are fertile in the F1 generation and beyond. Backcross (interspecific F1 x C. moschata) progeny segregated in the expected ratios (1:1 or 1:0) for the monogenic traits hard rind, bitterness and bush growth habit. This indicates a close homology between the two species. However, gene flow in the opposite directions, from C. argyrosperma to C. moschata is probably very limited. Work has begun to test the hypothesis that the two species are separated by a complementary nuclear-cytoplasmic incompatibility system. When comparing reciprocal backcrosses of the F1 interspecific hybrid with C. moschata all progeny are viable when C. moschata is used as the female parent, while only half of the progeny are viable when the reciprocal cross is made. These data suggest that if introgression of C. argyrosperma genes into C. moschata occurs, it occurs only indirectly via an interspecific genetic bridge. Finally, in collaborative work with the Smithsonian Tropical Research Institute we studied the relationship between rind phytoliths (silica bodies important in diagnosing the presence of Cucurbita species in archeological sites) and rind lignification. Both traits are controlled by a single dominant allele.

Impacts
Semi-bush types have been developed with fruit quality superior in color and texture to that of most commonly grown cultivars in Puerto Rico, traits desirable to consumers. For the grower, short vined tropical pumpkin can be more easily managed than traditional types. Traditional types are being developed with an emphasis on incorporating insect, disease and virus resistance.

Publications

  • Serrano, E. 2001. Heterosis y perdida de vigor por cansanguinidad en cruces de lineas de calabaza Cucurbita moschata Duchense de zonas templadas y tropicales. M.S. Thesis. University of Puerto Rico, Mayaguez, Puerto Rico. 32 pages.
  • Flores-Lopez, L. and L. Wessel-Beaver. 2001. Performance of tropical pumpkins with compact growth habit under varying planting distances. HortScience 36(3):521. (Abstract)
  • Wessel-Beaver, L. and T. C. Andres. 2001. Potential gene flow between two tropical pumpkins: Cucurbita moschata and C. argyrosperma. Annual meeting of the Sociedad Puertorriquena de Ciencias Agricolas, Nov. 16, Centro de Bellas Artes, Caguas, Puerto Rico. p. 18. (Abstract)
  • Gonzalez-Roman, M. 2002. Herencia de plateado y su relacion con la expresion de moteado genetico en la calabaza (Cucurbita moschata Duchense). M.S. Thesis. University of Puerto Rico, Mayaguez, Puerto Rico. 49 pages.
  • Flores, L. E. 2002. Comportamiento de lineas e hibridos de tipo compacto de calabaza (Cucurbita moschata) a diferentes distancias de siembra. M.S. Thesis. Universisty of Puerto Rico, Mayaguez, Puerto Rico.
  • Piperno, D. R., I Holst, L. Wessel-Beaver, and T. Andres. 2002. Evidence for the control of phytolith formation in Cucurbita fruit by the hard rind (Hr) genetic locus: Archaeological and ecological implications. Proc. Nat. Academy Sci. 99:10923-10928.
  • Wessel-Beaver, L., S. Crooke, and L. Lepe. 2002. Fruit age, fruit storage, and seed storage period affect management of seed in a tropical pumpkin breeding program. 26th International Horticultural Congress Program. p. 435. (abstract)
  • Gonzalez-Roman, M. and L. Wessel-Beaver. 2002. Resistance to silverleaf disorder is controlled by a single recessive gene in Cucurbita moschata Duchense. Cucurbit Gen. Coop. Rpts. (accepted).
  • Nienhuis, J. and L. Beaver. 2002. Comparison of genetic diversity between Cucurbita moschata accessions from the Pairmani Bolivia and USDA germplasm banks. 26th International Horticultural Congress Program. p. 537. (abstract)
  • L. Flores and L. Beaver. 2002. Comportamiento de lineas e hibridos de calabaza (Cucurbita moschata) de tipo compacto a diferentes distancias de siembra. Annual Meeting of the Puerto Rican Society of Agricultural Sciences, November 15, 2002, Isabela, Puerto Rico. p. 19. (abstract)
  • H. E. Cuevas and L. Wessel Beaver. 2002. Compatibilidad genetica y flujo de genes entre Cucurbita moschata y Cucurbita argyrosperma. Annual Meeting of the Puerto Rican Society for Agricultural Sciences, November 15, 2002, Isabela, Puerto Rico. p. 20. (abstract)


Progress 01/01/01 to 12/31/01

Outputs
Two tropical pumpkin populations are being improved via half-sib recurrent selection. One and a half cycles of selection have been completed in the short-vine population. The short-vine (bushy) trait has been maintained. Fruit quality is superior to that of traditional long-vine cultivar `Soler'. Yield is less than that of `Soler', but very acceptable, considering a once-over harvest is carried out at about 90 days. The long-vine population was developed from silverleaf resistant progenies and is in the first cycle of selection. Some susceptible plants appeared in June 2001 under conditions of heavy whitefly populations. These plants were removed before anthesis. Fruits are smaller than Soler, but with thick, yellow flesh. Inheritance studies of silverleaf and leaf mottling confirm that mottle leaf is dominant to green leaf . Contrary to some previous work, this data shows silvering resistant x susceptible F2 progeny segregating 3:1, suggesting that silvering resistance is controlled by a single recessive gene. Interpretation of the data becomes more difficult when the data is combined. In these studies we also observed an additional phenotypic class, yellow mottle leaf. We have previously observed this phenotype, but its relationship to silvering and mottle leaf is not known nor has the trait been reported in any other literature. In this study, it was always associated with silverleaf resistance. Studies of phylogenetic relationships using mtDNA and other data suggest a very close relationship between C. moschata and C. argyrosperma. A compact plant type of sweetpotato has been selected among local landraces collected throught Puerto Rico. This clone have showns 20 percent more yield compare to that of traditional cultivars.

Impacts
New cultivars developed from this breeding program can add value for both the grower and consumer of tropical pumpkin and tropical type sweet potato. Short vined tropical pumpkin and compact type sweet potato can be more easily managed than to traditional types. Genetic resistance to pests would reduce the need for insecticides, thus reducing costs of tropical pumpkin production in an environmentally sound manner.

Publications

  • No publications reported this period


Progress 01/01/00 to 12/31/00

Outputs
With tropical pumpkins emphasis was on population development, testing of short-vine materials, and germplasm evaluation. To develop a long-vine breeding population, 48 S1 families we evaluated. Attention was given to whitefly and silverleaf resistance. The best 10 families will be recombined to form a long-vine breeding population. A short-vine population was developed and 34 half sib families from that population are under evaluation. The best 7 families will be recombined for the next cycle of selection. Experimental short-vine hybrids were tested under different planting distances. The recommended planting density for the long-vined types of tropical pumpkins is 1.8 x 1.8 m. To determine the appropriate in-row planting distance, six compact tropical pumpkin experimental hybrids were planted at 0.9, 1.4 and 1.8 m. Yields averaged 30,150 kg/ha. This yield compares very favorably with that of traditional types that produce similar yields but with multiple harvests. Yields at the 0.9 and 1.4 in-row planting distance were not different and were superior to plots planted at 1.8 m. Planting compact types at the traditional distance of 1.8 m reduced yield to 70 percent of that of more densely planted plots. An in-row planting distance of 1.4 m (with 1.8 m between rows) will likely optimize yield and fruit size in these genotypes. New materials from South America were evaluated and seed increased by selfing. Included were accessions from Colombia (11), Panama (7), Brazil (1), Bolivia (selfed progeny from 2 accessions), and Paraguay (selected progenies of a single accession with silvering resistance), as well as a series of F1 crosses among and between various accessions of Cucurbita moschata, C. argyrosperma, C. sororia, C. ecuadorensis, C. ficifolia, and C. pepo. A genetic compatibility study was carried out using C. moschata as the only source of pollen for C. argyrosperma and C. sororia. This is believed to be the first study clearly documenting gene flow in the field from C. moschata to C. argyrosperma and C. sororia. For tropical-type sweet potatos, 130 genotypes were evaluated in Eastern Puerto Rico. A polycross was planted, but seed set was low. The evaluation of the 7 elite clones in three locations is underway.

Impacts
Additional work is needed before the release of experimental lines either as improved germplasm or as horticultural varieties.

Publications

  • WESSEL-BEAVER, L. 2000a. Evidence for the center of diversity of Cucurbita moschata in Colombia. Cucurbit Genetics Cooperative Report 23:54-55.
  • WESSEL-BEAVER, L. 2000b. Cucurbita argyrosperma sets fruit in fields where C. moschata is the only pollen source. Cucurbit Genetics Cooperative Report 23:62-63.


Progress 01/01/99 to 12/31/99

Outputs
Tropical-type sweet potato (Ipomoea batatas): One hundred twenty-three accessions have been assembled as baseline germplasm to be evaluated under field conditions for physical characteristics of the storage root and diseases. Accessions include tropical, staple and substaple types. Tropical pumpkin (Cucurbita moschata): A planting of tropical germplasm from Bolivia, Colombia, Ecuador and Panama was initiated in October 1999. A limited number of pollinations were harvested because of excessive rain. This germplasm has been replanted; evaluation is in progress.

Impacts
(N/A)

Publications

  • No publications reported this period