Monoploid genotypes (2n = x = 12), derived by anther culture of a diplandrous genotype of Solanum phureja, a South-American diploid potato species, were examined for their utility in germplasm development. Nine monoploid genotypes and the diploid anther-donor plant were grown in photoperiod chambers at The Southeastern Plant Environment Laboratories (SEPEL) at North Carolina State University to examine the effect of photoperiod on tuber yield and to determine the variability for critical photoperiod for tuberization. Significant differences were found among the monoploid genotypes for total tuber weight and tuber number. Longer photoperiod treatments both decreased and delayed tuberization. Axillary tuber formation from single-node cuttings was used to estimate the onset of tuber induction and demonstrated variability among monoploid genotypes for critical photoperiod for tuberization. Leaf-disc culture of 24 monoploid genotypes yielded calli which regenerated plants from three genotypes. SDS-polyacrylamide gel electrophoresis of leaf extracts demonstrated variability among diploid and tetraploid calliclones of one monoploid genotype for total protein banding pattern. Absence of stainable pollen and lack of seed set after crosses to diploid species and tetraploid cultivars illustrated infertility among doubled (2n = 2x = 24) and twice doubled (2n = 4x = 48) monoploid-derived lines. Flow-cytometric analysis of pollen obtained from the diploid anther-donor genotype grown under three photoperiods at SEPEL yielded two populations of pollen based on propidium iodide staining of DNA. These populations corresponded to pollen separation based on size parameters alone, introducing the potential for flow sorting of pollen to increase seed set in 4x-2x crosses to tetraploid cultivars. Protoplast isolation from in vitro material and extraction of leaf nuclei both in vitro and in vivo were performed on the anther-donor plant, one of its anther-derived monoploids, and a diploid and tetraploid plant derived from callus culture of the monoploid genotype. Flow-cytometric analysis of propidium-iodide Stained cells and nuclei showed a greater ploidy stability for plant material grown in vitro and a limit to endopolyploidization imposed by initial ploidy level. Flow-cytometric analysis of protoplast-derived nuclei from nine monoploid genotypes derived from anther culture of a single diploid genotype exhibited Significant differences for 4C DNA content, but not for 1C DNA content, indicating that ploidy stability, rather than monoploid status per se, is influenced by genotype. / Ph. D.