Crossability of naturalized and cultivatedLythrumtaxa

摘要

Lythrumcultivars Morden Pink, Morden Gleam, and Dropmore Purple, and a wild population ofLythrum salicariafrom Lockport, Manitoba were artificially self- and cross-pollinated. Success of pollination and fertilization was measured in terms of the percentage of resulting capsules and the average numbers of viable seeds per capsule. Germination tests were used to measure the viability of seeds produced as a result of successful crosses. Cultivars rarely produced seeds as a result of selfing but many crosses with wild plants or with other cultivars were fertile. As expected, legitimate (i.e., different style morphs) wild crosses were highly fertile, but other crosses gave high fertility, especially those in which 'Morden Gleam' was the provider of pollen or ovules. Although some sterility was indicated in 'Dropmore Purple' and perhaps 'Morden Pink', neither are sufficiently sterile to be considered safe for ornamental flower gardens. Most illegitimate crosses yielded greatly reduced seed outputs in comparison to legitimate crosses, but there were some exceptions. Germinability of ripe seeds from any cross was high and averaged 98. Cultivars ofLythrumare capable of contributing viable seed and (or) pollen to the spread of purple loosestrife. The sale of cultivars, regardless of parentage, should be prohibited.Key words: purple loosestrife,Lythrumspp., interfertility, hybridization.