Horticultural Cultivars Research Articles

Importance of Introgressive Hybridization in the Development of Invasive Lythrum salicaria

Since its evolution as an invasive species in Quebec (1930s), L. salicaria has spread across North American wetlands virtually unchecked. Initially, it was theorized that the rapid invasion was due to the absence of phytophagous insects (present in the native habitat). However, evolutionists theorized that invasive characteristics probably arose from introgressive hybridization with a native species (L. alatum), since their ecotypes overlap. Several horticultural cultivars are also fertile interspecific hybrids. These two species differ for diagnostic traits (number of flowers/axil, plant height, phyllotaxy, style morphology, seed dormancy). Minnesota L. salicaria populations were examined for evidence of introgression. Lythrum salicaria introgressive genotypes were found for all diagnostic traits. Seed dormancy was the most common, i.e., OP seed showed significant seed dormancy (F = 5.2, P = 0.024). Such hybrids would have adaptive advantages as weeds, having evolved for each ecotype by introgression with locally adapted L. alatum populations.

Genetic Relationships among Weedy Purple Loosestrife (Lytrhum salicaria L.) Populations and Cultivars

Starch gel electrophoresis of plant proteins was used to genetically identify purple loosestrife (Lythrum spp.) cultivars and weedy populations. Preliminary determinations were made as to what degree weedy loosestrife populations were related (or genetically similar) to populations of L. alatum, L. virgatum, and horticultural cultivars. Cluster analysis of the data indicated that native L. alatum was genetically different from all populations of purple loosestrife and cultivars examined. The L. salicaria and L. virgatum cultivars, as groups, were not genetically distinguishable from the weedy populations analyzed. Seven cultivars of L. salicaria origin analyzed as a group were not distinguishable from the eight cultivars of L. virgatum origin, indicating that separation by cultivar origin may not be feasible. While the two “groups” were not distinguishable, most individual cultivars could be distinguished from one another by isozyme phenotype. Genetic variation was high within populations of weedy purple loosestrife but low among populations, which is characteristic of polyploid, perennial plant species that are widely distributed. Geographic location did not consistently correlate with genetic similarity.

バラの花粉外壁の形態計測分析

Pollen grain morphology of 125 taxa of roses was examined by using scanning electron microscope (SEM) and by subsequent principal component analysis, in order to clarify the phylogenetic relationships. Nine categories of pollen-surface type were confirmed by scrutinizing ridge and perforation features on pollen exine. Species belonging to a botanical section or cultivars belonging to a horticultural cultivar group showed specific pollen exine patterns, and it was suggested that the specific pollen exine pattern transmits well from wild species to cultivars during several generations.A principal component analysis using six quantitative traits of pollen grains well separated the groups of roses. The wild species with high ploidy levels and the many cultivars belonging to the Hybrid Tea and Floribunda groups were distinguishable from the wild species of low ploidy level and from the other cultivar groups by the score of the first principal component. The species of the section Pimpinellifoliae and their related cultivars were characterized by the score of the second principal component, and the species of the section Indicae and their related cultivars by the score of the third principal component.Thus, the features of the perforations and ridges of the pollen exine seem to be good tools to distinguish each botanical section or horticultural cultivar group in roses.

Pollen Yield from Olive Tree cvs. Manzanillo and Swan Hill in Closed Urban Environments

Abstract Airborne pollen concentrations (grains/m3) within and near trees of 2 cultivars of Olea europaea L. were studied during the 30-day pollination period at 2 urban sites in Tucson, Ariz. ‘Manzanillo’, the dominant horticultural cultivar, was compared to the fruitless ‘Swan Hill’. Air sampling using a Burkard trap was undertaken from 2 Apr. until 1 May 1985; during this period, 95% of the 1985 Olea pollen was airborne. Peak atmospheric Olea pollen concentrations at both sites occurred on 14 Apr. 1985. Pollen concentrations around the ‘Manzanillo’ site ranged from 7 grains/m3 to 6196 grains/m3 per day. At the ‘Swan Hill’ site, daily totals were an order of magnitude less, from 5 to 309 grains/m3 per day. Hourly pollen concentrations for the ‘Manzanillo’ site on the peak day varied from 1000 to 18,133 grains/m3 per hr. Hourly values at the ‘Swan Hill’ site on the peak day varied from 7 to 896 grains/m3 per hr. Both sites exhibited rapidly increasing pollen concentrations at sunrise with a sharp increase for the ‘Manzanillo’ site between 1100 to 1300 hr. Both cultivars produced about 85,000 pollen grains per anther. An unknown anatomical or physiological factor in ‘Swan Hill’ inhibits stomial rupture, resulting in 85% inhibition of anther dehiscence and pollen-shedding.

ERGOT ALKALOID CONTENTS OF Ipomoea lacunosa, I. hederaceae, I. trichocarpa, AND I. purpurea SEED

Total ergot alkaloids extracted from seed of native, wild-type morning glories (i.e, pitted morning glory (Ipomoea lacunosa L.), ivyleaf morning glory (I. hederaceae (L.) Jacq.), cotton morning glory (I. trichocarpa Ell. var. torreyana (Gray) Shinners) and tall morning glory (I. purpurea (L.) Roth)) and quantified by spectrophotometry as ergonovine maleate equivalents were 0.001–0.004% (i.e., −2.1 to 7.8%) of the total alkaloids present in a horticultural cultivar (I. tricolor Cav ’Heavenly Blue’) which contained 0.052% total alkaloids in the seed. Thus, negligible psychotomimetic hazard exists from these levels of alkaloids in the wild-type morning glory seeds. Major alkaloids found in these native species were separated and identified by two-dimensional thin-layer chromatography and co-chromatography with authentic standards. Major alkaloids were chanoclavine, elymoclavine, penniclavine, agroclavine, ergonovine, ergonovinine, ergosine, and ergosinine. Alkaloids varied between morning glory species.Key words: Morning glory, chanoclavine, elymoclavine, pennicalvine, agroclavine, ergonovine