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- Author or Editor: Robert L. Jarret x
Mature fruit of 295 accessions of Capsicum baccatum from the USDA/ARS Capsicum germplasm collection were characterized for fruit length, width, weight, and color. Mean fruit weight was determined to be 5.91 g with a range of 0.15 to 22.8 g. Mean fruit length was 6.01 cm with a range of 0.8 to 16.0 cm. Mean fruit width was 1.86 cm and a range of 0.5 to 4.75 cm. Distributions of all characteristics were positively skewed and failed the Kolmogorov-Smirnov test for normality. The distribution of fruit weight values was the most highly skewed, possibly reflecting a more intense human selection pressure for this characteristic. Distributions of fruit width, length, weight, and length:width were leptokurtic (long-tailed). Ninety-three percent of accessions were elongate. Mature fruit colors included red (73.6%), orange (19.7%), yellow (3%), green (0.3%), and mixed (3%). These data suggest that variability for mature fruit characteristics within this germplasm collection is considerable and that variability for fruit length, width, weight, and color is sufficient to provide the basis for the improvement of the aji crop.
Abstract
In recognition of the genetic vulnerability of sweet potato in the United States, a formal resolution to support the establishment of a repository for sweet potato germplasm was presented at the 1978 annual meeting of the Sweet Potato Collaborators Workgroup. This was followed, in 1980, by the convening of an ad hoc working group in Charleston, S.C., where the need for and the objectives of a clonal repository were discussed at length (International Board for Plant Genetic Resources, 1981). The principal recommendations of this working group were the designation of a U.S. clonal repository for conservation of sweet potato germplasm, the designation of the National Seed Storage Laboratory (NSSL) as a repository for botanical seed of lpomoea batatas L. (Lam.) and related species, and a recognition of the need for improved quarantine procedures, including those for virus assay and elimination. These recommendations are in accord with the needs and objectives of other national and international sweet potato research programs as identified at a recent planning conference in Lima, Peru (International Potato Center, 1988).
Patterns of diversity among thirty diploid clones of banana (Musa acuminata Colla.), collected in Papua New Guinea and the surrounding islands between 1987 and 1989, were examined genetically using the polymerase chain reaction (PCR) and random primers, to detect random amplified polymorphic DNA (RAPDs). PCR products were visualized on ethidium bromide stained agarose gels. Twenty of 60 random primers examined detected RAPDS in CTAB-extracted genomic DNA. Banding patterns ranged from very simple (1 or 2 bands/gel) to very complex (more than 20 bands/gel). All 30 Musa clones were distinguishable from each other based on their unique RAPD banding pattern. Principal component analysis (PCA) revealed several clusters of closely related clones within the materials examined. However, these clusterings were not correlated with either the geographic origin or the morphological characteristics of the clones. A role of the use of RAPDs in germplasm characterization is discussed.
Abstract
Leaf tissue extracts of Musa acuminata Colla diploid subspecies malaccensis, diploid M. balbisiana Colla, the triploid dessert banana cultivar ‘Valery’, the interspecific hybrid (acuminata × balbisiana) cooking banana cultivars ‘Chato’ and ‘Peli-pita’ and the triploid putative balbisiana-derived cultivars ‘Saba’, ‘Saba Puti’, and ‘Cardaba’ were subjected to isozyme analysis for four different enzymes. Isozyme banding patterns of the interspecific hybrids were generally additive and were a composite of the species-specific forms of each enzyme. Banding patterns for shikimate dehydrogenase, malate dehydrogenase, peroxidase, and phosphoglucomutase indicate that ‘Saba’, ‘Saba Puti’, and ‘Cardaba’ are acuminata × balbisiana hybrids.
The nuclear DNA content of 53 accessions from 24 Ipomoea (Convolvulaceae) species, including four sweetpotato cultivars, was determined by flow cytometry of DAPI-stained nuclei. Ploidy level and DNA content were significantly correlated within the genus, but more highly so within species that contained multiple cytotypes. DNA content of cultivated Z. batatas (L.) Lam. (4.8 to 5.3 pg/2C nucleus) and feral tetraploid I. batatas (3.0 to 3.5 pg/2C nucleus) was estimated from the known DNA content of chicken erythrocytes (2.33 pg), which were used as an internal standard. Tetraploid forms of Z. cordato-triloba Dennstedt also were identified. Ploidy analysis using flow cytometry is rapid and suitable for large-scale experiments such as studying the genetic structure of populations of Z. batatas and related species. Chemical name used: 4′,6-diamidino-2-phenylindole (DAPI).
The USDA gene bank currently maintains 668 accessions of cultivated sweetpotato and 219 accessions of related Ipomoea species. Information on the genetic diversity of the collection does not exist due to funding constraints. The development of a core collection would provide a subset of accessions that represent the genetic diversity of the main collection with a minimum of repetitiveness. The small size of the core collection would facilitate the evaluation of the accessions for economically important traits. The objective of this research is to develop a core collection of Papua New Guinea sweetpotato germplasm using the Amplified Fragment Length Polymorphisms (AFLPs) marker system. This approach to quantifying genetic diversity would later serve as a model for the development of a USDA sweetpotato germplasm core collection. The germplasm choosen for this study was collected from this crop's secondary center of genetic diversity based on its potential as a source of new traits. All genotypes were fingerprinted using four primer combinations that generated 224 markers. The molecular data was then analyzed using NTSYSpc 2.0 program to determine the relatedness of the genotypes. The molecular analysis showed a homogeneous genetic constitution. The extent of diversity among accessions was correlated with the geographic origin of the plant material.
The USDA gene bank currently maintains 668 accessions of cultivated sweetpotato and 219 accessions of related Ipomoea species. Information on the genetic diversity of the collection does not exist due to funding constraints. The development of a core collection would provide a subset of accessions that represent the genetic diversity of the main collection with a minimum of repetitiveness. The small size of the core collection would facilitate the evaluation of the accessions for economically important traits. The objective of this research is to develop a core collection of Papua New Guinea sweetpotato germplasm using the Amplified Fragment Length Polymorphisms (AFLPs) marker system. This approach to quantifying genetic diversity would later serve as a model for the development of a USDA sweetpotato germplasm core collection. The germplasm choosen for this study was collected from this crop's secondary center of genetic diversity based on its potential as a source of new traits. All genotypes were fingerprinted using four primer combinations that generated 224 markers. The molecular data was then analyzed using NTSYSpc 2.0 program to determine the relatedness of the genotypes. The molecular analysis showed a homogeneous genetic constitution. The extent of diversity among accessions was correlated with the geographic origin of the plant material.