Small Genomes in Tetraploid Rubus L. (Rosaceae) from New Zealand and Southern South America

The genus Rubus contains crop wild relatives of raspberries and blackberries. Rubus subgenera Micranthobatus and Comaropsis are endemic to the Southern Hemisphere in trans-Pacific Ocean environments of Australasia, South America, and the Falkland Islands. The United States Department of Agriculture, National Clonal Germ-plasm Repository (NCGR) houses a Rubus genebank of living plants, including representatives of subgenera Micranthobatus and Comaropsis. Previously, accessions were determined by chromosome counts to be tetraploid. Our objective was to examine the nuclear DNA content (C values) of the tetraploid R. cissoides, R. parvus, R. schmidelioides, R. squarrosus, and R. geoides in contrast with those of diploid and tetraploid black raspberries (R. occidentalis) and diploid red raspberry (R. idaeus subsp. idaeus). Nuclear DNA content was determined using flow cytometry. Surprisingly, the C values of these species were significantly smaller than an autotetraploid clone of R. occidentalis or other tetraploid genotypes, and numerically equivalent to about the size of triploid raspberries. The small genomes may provide clues concerning the evolution of these subgenera.