No abstract

Random amplified polymorphic DNA (RAPD) markers were used to assess intraspecific variability and relationships in aerial yam (Dioscorea bulbifera L.). A total of 23 accessions from different geographic locations in Africa, Asia, and Polynesia were analyzed by 10 arbitrarily chosen GC-rich decamer primers. Using cesium chloride purified genomic template DNA, highly reproducible polymorphic fingerprints were generated by all 10 primers, resulting in a total of 375 informative characters. Only eight bands were monomorphic among all investigated accessions. A binary character matrix was generated by scoring for presence/absence of a band at a particular position, transformed into a matrix of pairwise distances using either the Jaccard or a simple matching coefficient, and analyzed by neighbour joining, UPGMA (unweighted pair group method with arithmetic averaging) cluster analysis, or split decomposition. All methods of data evaluation resulted in similar groupings that reflected the geographical origin of the samples. The African accessions formed a distinct isolated group, whereas Asian and Polynesian accessions proved to be more heterogeneous. With two exceptions (var. suavior and var. sativa), the RAPD data supported previous varietal classification based on morphological characters. Stepwise reduction of the number of evaluated characters did not affect branching patterns of the trees above a minimum threshold of 150. Key words : Dioscorea bulbifera, random amplified polymorphic DNA (RAPD), genetic variation, genetic relatedness.

We have used random amplified polymorphic DNA (RAPD) analysis to characterize eleven cultivars of the five economically most important yam species grown in Jamaica (Dioscorea alata, D . cayenensis, D . rotundata, D . trifida and D . esculenta) . Amplification of genomic DNA samples with nine different arbitrary 10mer primers revealed a total of 338 different band positions, ranging in size from 0 .3 to 2 .5 kb . RAPD patterns proved to be highly reproducible and somatically stable . While no variation was observed among plants belonging to the same cultivar, a large number of intervarietal and interspecific polymorphisms enabled us to reliably discriminate between all Jamaican cultivars investigated .

Four different molecular techniques were used to assess relationships among 21 accessions of Guinea yam (Dioscorea rotundata and Dioscorea cayenensis) and 21 accessions belonging to seven putative progenitor species. Random amplified polymorphic DNA (RAPD) and microsatellite-primed PCR (MP-PCR) analysis yielded 246 informative characters that were transformed into a matrix of pairwise distances and analyzed by neighbor joining or split decomposition. Both methods gave congruent results. Well-separated groups were formed that corresponded to their species designation. Dioscorea rotundata and D. cayenensis accessions were clearly separated from each other, supporting the concept that both are distinct species. Two morphological intermediates grouped together with D. rotundata. All investigated species fell into two main clusters, one comprising D. rotundata, D. cayenensis, Dioscorea abyssinica, Dioscorea liebrechtsiana, and Dioscorea praehensilis, the other comprising Dioscorea smilacifolia, Dioscorea minutiflora, Dioscorea burkilliana, and Dioscorea togoensis. The same grouping was also obtained by comparative sequence analysis of chloroplast DNA, which supports earlier studies of nuclear rDNA variation and chloroplast restriction fragment length polymorphisms. We also analyzed the same set of Dioscorea samples with the recently developed random amplified microsatellite polymorphism (RAMPO) technique. A series of diagnostic RAMPO bands was identified that clearly distinguished between D. rotundata and D. cayenensis. Some of these bands could also be traced back to the putative progenitors of both species. The evolutionary origin of Guinea yam is discussed in light of the present results.

Effects of inoculation with arbuscular endomycorrhizal fungi (Acaulospora scrobiculata and Glomus mosseae) on acclimatization and growth of chrysanthemum (Dendrathema glandiflora Tzevelev) plants, propagated in vitro, under different conditions of fertilization (0, 20, and 40 mg·L-1 of NPK) were studied. Mycorrhizal colonization did not influence surviving percentage of chrysanthemum plantlets during the acclimatization stage; however, we could colonize the developing roots and reduce the amount of inoculum needed and beneficial effects on plant growth were obtained during early stages of colonizing. Plant growth in greenhouse was regulated by synergism between the effect of endomycorrhizal fungus type and soil fertilization with N, P, and K. Effects of A. scrobiculata were observed as an increasein number of leaves, leaf area, stem diameter, root volume and fresh and dry weight of leaves, stem and root. The G. mosseae fungus improved N, P, Mg, and Zn content in leaves; P, K, Ca, Mg, and Zinc in stem and Ca content in root. On the other hand, A. scrobiculata only increased N content in leaves, stem and roots; P content in leaves and roots, and Ca content in stem. Percentage of mycorrhizal colonization on roots was affected by adding N, P, and K to soil. The highest values were obtained with fertilization doses of 20 mg·L-1. The number of spores of mycorrhizal fungi was increased by adding fertilizer to soil (40 mg·L-1 of NPK).