Cytological and RAPD data revealed genetic relationships among nine selected populations of the wild bramble species, Rubus parvifolius and R. coreanus (Rosaceae)

Abstract

Rubus parvifolius L. and R. coreanus Miq. are the two morphologically distinct, endemic wild brambles in East Asia that may be useful in raspberry breeding and cultivar development. In this study, genetic relationships among a total of nine populations of these two species, collected from Sichuan Province in southwestern China, were investigated by cytological and RAPD analyzing. With the exception of ploidy levels, R. parvifolius and R. coreanus had similar cytological features. Six R. parvifolius populations included diploids, triploid, tetraploid, and mixed diploid-tetraploid cytotype plants; among them, the population that produced the fewest seeds was the triploid, while the three R. coreanus populations were all diploid. But obvious genetic differentiation between R. parvifolius and R. coreanus was revealed by RAPD markers, the Euclidean's GS coefficient generated by UPGMA cluster analysis between R. parvifolius and R. coreanus was only 0.442, about half of that observed within species. Both genetic relationships among these populations and the origin of polyploidy in R. parvifolius populations are also discussed.

Phylogenetic insight into subgenera Idaeobatus and Malachobatus (Rubus, Rosaceae) inferring from ISH analysis

“…Rubus parvifolius was more genetically variable when compared with R. coreanus [ 13 , 56 ]. Extensive crossing and formation of natural hybrids with many species from both subgenera Idaoebatus and Malachobatus were found in R. parvifolius [ 18 , 19 , 21 - 23 ].…”

“…Chromosome preparation was followed the procedures of Wang et al [ 13 ]. Briefly, root tips from cutting propagation canes were pretreated in 0.002 mol · L −1 8-hydroxyquinoline at 4°C for 4 h, and fixed in Carnoy’s I solution (absolute ethanol : glacial acetic acid = 3 : 1, v/v) at 4°C for about 24 h. The fixed root tips were hydrolyzed in 1 mol · L −1 HCl at 60°C for 30-40 s, stained with Carbol Fuchsin, and then squashed with 45% acetic acid.…”

“…Interestingly, R. parvifolius in subg. Idaeobatus had various ploidy levels, with di-, tri-, tetraploid, and mixed diploid-tetraploid [ 13 ]. Not only are the phylogenetic relationships between these species unknown, we also don’t even know to what extent ploidy level varies among them.…”

“…There are also some differences in the color of canes and prickles, most of which were reddish brown but a few were green. Moreover, R. parvifolius exhibited not only abundant molecular variation, but also various ploidy levels and conspicuous different karyotypes (with 2 x , 3 x , 4 x , and cytotype mixture of 2 x and 4 x ), whereas another widely-distributed species R. coreanus revealed typical morphology and highly uniform ploidy (2 x ) and karyotype [ 13 ]. Interestingly, both two species often grow sympatrically with those species from both Idaeobatus and Malachobatus .…”

“…It is possible to determine the genomic homology between species and identify chromosome composition of hybrids by genomic in situ hybridization (GISH) [ 25 , 27 ]. Previous studies on cytogenetics on Rubus were mostly limited to chromosome counting [ 6 , 11 , 19 , 20 , 28 - 31 ] or traditional karyotype analysis [ 12 , 13 , 18 , 21 - 23 , 32 , 33 ]. FISH with 45S rDNA was established in R. parvifolius [ 34 ] and callus lines from European and American countries [ 35 ].…”