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  • Author or Editor: Robert L. Jarret x
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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).

Open Access

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.

Free access

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.

Free access

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).

Free access

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.

Open Access

The polymerase chain reaction (PCR)-based DNA amplification fingerprinting (DAF) approach was used to investigate genetic relationships among 30 U.S. sweetpotato (Ipomoea batatas L. Lam.) genotypes including heirloom cultivars and recent releases. Phenogram, pairwise similarity matrix, and principal coordinate plots were developed based on Jaccard's coefficients using band-sharing data generated by seven octamer primers. All cultivars showed unique fingerprint patterns indicating the utility of DAF in cultivar identification. Many heirloom cultivars such as `Creole' and `Porto Rico' were readily differentiated from recently developed cultivars. Modern cultivars such as `Jewel', `Carver', `Nugget', and `Scarlet' exhibited a high degree of similarity reflecting ancestral relatedness. `Regal' and `Excel', recently developed using a population-based breeding approach, showed greater divergence from all other cultivars. Those cultivars, developed as a result of somatic mutations, exhibited high levels of genetic similarity to their normal-type parents and yet had distinct fingerprint profiles. With few exceptions, genetic relationships derived from DAF data appear to be consistent with available pedigree information.

Free access

Abstract

The effects of the components of Lam's 1977 potato nutrient medium on adventitious shoot formation were systematically evaluated. A low concentration (0.03 mg/liter) of naphthaleneacetic acid (NAA) stimulated shoot initiation and increased survival of tuber discs of potato (Solanum tuberosum L.). Indoleacetic acid (IAA), however, did not affect shoot initiation in the concentration range from 0 to 10 mg/liter. Both 6-benzyl-amino purine (BA) at 0.3, 1.0, and 3.0 mg/liter and N6-(4-hydroxy-3-methyl-but-2-enylamino)-purine (zeatin) at 0.3 and 1.0 mg/liter stimulated adventitious shoot formation while N6-furfurylaminopurine (kinetin) had no effect. Sucrose was essential for shoot formation with a concentration of 30 g/liter being optimal. Although not essential, i-inositol enhanced the initiation of adventitious shoots at concentrations of 60 and 100 mg/liter. Casein hydrolysate and additional inorganic phosphate had no promotive effect on shoot formation and adenine sulfate was inhibitory at all concentrations examined.

Open Access