Characterization, differentiation, and molecular marker analysis of blackberry germplasm

Genetic relationships within blackberry germplasm (Rubus subgenus Rubus L.) have not been thoroughly studied. Several studies were undertaken to differentiate cultivars through molecular markers and determine genetic linkages for important traits. Differentiation of blackberry and raspberry cultivars for genetic identification was performed with several Rubus genotypes. Differences were realized among cultivars for both RAPD markers and pedigree analysis. Differences among the blackberry cultivars were evident.; Nuclear ribosomal DNA internal transcribed spacer regions (ITS) of six Rubus cultivars were sequenced, but revealed little genetic variation among blackberry cultivars. Distinctions between blackberry and red raspberry cultivars were revealed. ITS region sequences do not appear to differentiate among closely related blackberry genotypes for purposes of cultivar discrimination.; Pedigrees of 32 cultivars were traced to their founding clones. Genetic contribution (GC), maximum potential similarity, inbreeding coefficient, and coefficient of relationship were calculated for all genotypes. Nineteen founding clones contributed to the 32 genotypes, ranging from <1% to ∼19% mean GC. The top three founding clones for mean GC conferred nearly 50% to the 32 genotypes in this study, suggesting a somewhat narrow genetic base.; A test of 147 of SSR markers to screen raspberry and blackberry parental genotypes for use in mapping populations that segregate for important traits was done to determine possible inter-species and inter-genera transferability with amplification and level of polymorphism among parents. Up to 32 of the SSR primer pairs tested may be useful for genetic mapping in the blackberry population and at least one raspberry population. However, there is a need for developing additional SSR primer pairs for genetic mapping for both raspberry and blackberry.; Two marker types, RAPD and SSR, were used to find linkages to two morphological traits in blackberry. A random sample of 98 plants from a population of 200 was assayed to find molecular markers that co-segregate with the two traits. Three putative markers were identified for the floricane fruiting trait (two SSRs and one RAPD, chi2 = 4.09 to 9.99, P < 0.001 to 0.043). Five potential RAPD markers were found for the thorny trait (chi 2= 3.88 to 10.23, P < 0.001 to 0.048).