Genetic Relationships of Michelia L. Species Revealed from ISSR Markers

Michelia L. is a popular genus for urban landscapes and gardens. However, the genetic relationship among Michelia plants is unclear, which limits the further studies of its molecular phylogeny and ornamental breeding work. ISSR makers were applied to analyze genetic relationships among 25 Michelia taxa. Sixteen primers with the most polymorphic bands were selected for this study. A total of 239 useful markers between 250 to 2500 base pairs were generated. Among them, 87.9% of bands were polymorphic markers. The average number of markers for each taxon was 128.3. These polymorphic bands had frequencies ranging from 0.06 to 0.98. The genetic distance ranged from 0.28 between M. foveolata Merr. ex Dandy and its variety M. foveolata var. cinerascens Y.W. Law et Y.F. Wu to 0.47 between M. chapensis Dandy and M. shiluensis Chun et Y.F. Wu. Cluster analysis showed that M. maudiae Dunn was apparently an outgroup to other species. M. foveolata var. cinerascens should be accepted as a legitimate variety, not lumped to its species. M. platypetala Handel-Mazzetti is a legitimate species and DNA ISSR markers did not support it as a variety. A new species, Michelia nanyueshanensis Y.J. Yang et X.L. Jin, was proposed and it should be much closer to M. floribunda Finet & Gagnepain genetically. These results indicated that ISSR makers should be powerful techniques for determining genetic relationships in Michelia, which is important for future genetic improvement, identification, conservation, and breeding of Michelia.