Random amplified polymorphic DNA (RAPD) based assessment of genetic relationships among some Zimbabwean sorghum landraces with different seed proanthocyanidin levels

Knowledge of genetic distances between genotypes is important for efficient organization and conservation of plant genetic resources for crop improvement programs. In this study genetic distances between genotype pairs (complements of Jaccard's similarity coefficient) were estimated from Random Amplified Polymorphic DNA (RAPD) data collected from 48 Zimbabwean sorghum landraces. These varieties showed variation in their seed proanthocyanidin (PAs) levels with 16 and 29 of them having detectable and non-detectable PA levels respectively. RAPDs revealed considerable genetic variation between the varieties used and 2.7 polymorphisms per primer were obtained.  Ninety nine polymorphic RAPD bands were used to calculate genetic distances and the mean genetic distance between the genotypes was 0.494 (± 0.113) with a range of 0.051 to 0.761. A multidimensional scaling (MDS) plot of the distance matrix revealed two distinct clusters of cultivated and wild sorghums. No clustering of genotypes according to their seed proanthocyanidin levels was revealed by MDS analysis; also the mean genetic distances of genotypes in the low, medium and high PA categories were not different from each other and none of them was significantly different from the mean genetic distances between all the groups. The RAPD markers used in the present study could not distinguish between sorghums with different PA levels in their seeds; however, the protocol established could be useful in further analysis of this trait in near isogenic lines.   Key words:  Genetic distances, multidimensional scaling, proanthocyanidins, Random Amplified Polymorphic DNA (RAPD), Sorghum bicolor, Zimbabwe.