Genetic relationships between Rubus parvifolius and R. coreanus (Rosaceae), and preliminary identification one of their putative hybrids

Rubus parvifolius L. and R. coreanus Miq. are two morphologically distinct, endemic wild bramble species in East Asia.The two species are sympatric in southwest of China. Natural hybrids between R. parvifolius and R. coreanus do generally occur. In this study, chromosomal, palynological, RAPD and ISSR markers were developed to identify R. parvifolius, R. coreanus and their putative hybrids. UPGMA model-based clustering of the genetic data indicated that two genetic units existed in these populations. One contained twenty-one accessions, mainly characterized by R. parvifolius and R. coreanus with typical morphological features (“pure”).The other was composed of sixteen accessions, which shared an intermediate morphology with the R. parvifolius and R. coreanus (“hybrid”). These results showed obvious genetic differentiation between their potential parents and among individuals of hybrids themselves in the long evolutionary history by several hybridization events. A triploid accession R03-10 (2n=3x=21), was identified as a probable natural hybrid of R. parvifolius and R. coreanus based on morphological, chromosomal and palynological identifications. The species R. parvifolius, an important resource involved in the hybridization, multipolyploidization and speciation of the genus Rubus, is discussed.