Abstract
The actual conditions of the market distribution of Japanese Rhododendron section Brachycaryx was investigated in Kanagawa Prefecture to reach guidelines for planting concerning genetic diversity in its natural habitat. We found that producers do not have obligations to show species names of plants after the survey at the wholesale market, and that growing environment of seed trees should cause the hybrid-plants after the survey at nurseries. There was little possibility of pollen introduction into natural habitat from nurseries in the study area after the analysis of geographic distribution of natural habitats, nurseries, and selling places. However, pollen exchange between natural habitats and nurseries may change the genetic heterogeneity in natural habitats in the case where nurseries are inside of the foraging range of main pollinators, and where the arrangement of nurseries in a landscape are suitable for pollinators to move. Concerning this state and these analyses, three problems to be solved were recognized : (1) Species name of plants is to be rightly recognized at the wholesale market, (2) Give care not to produce hybrid-plants, and (3) Species for cultivation is to be restricted at nurseries near natural habitats. Guidelines to solve these problems were devised : 1) Producers precisely identify the plants at nurseries, and 2) Species names identified by producers should be open to the public at the wholesale market, concerning issue (1), 3) Mix-planting of multi- (sub) species of seed trees is to be avoided at nurseries, and 4) Seeds for nursery plants should be collected from pure seed trees, concerning issue (2), and 5) Foraging range of major pollinators, Bombus species is to be surveyed, 6) Area inside the foraging range of main pollinators needs the special care not to cultivate the species that naturally survive, and 7) Species for cultivation should be restricted according to the arrangement of nurseries outside of the foraging range of major pollinators, concerning issue (3).
