Abstract
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.
Highlights
Sorghum (Sorghum bicolor (L.) Moench) is a traditional cereal crop in Zimbabwe and it ranks fourth in production after maize, wheat, and pearl millet (FAO, 2006)
The sorghum landraces and commercial cultivars used in this study showed significant variability in their seed proanthocyanidin levels
The genotypes used in this study were collected from different parts of Zimbabwe and the fact that about 35%. Of these sorghums were high in PAs may be an indication that this random sample was almost representative of the national sorghum germplasm
Summary
Sorghum (Sorghum bicolor (L.) Moench) is a traditional cereal crop in Zimbabwe and it ranks fourth in production after maize, wheat, and pearl millet (FAO, 2006). Sorghum utilization is generally influenced by the presence. Of polyphenolic compounds that are produced in large quantities in grain and vegetative tissues of many cultivars (Waniska, 2000). The polyphenolic compounds of sorghum such as the proanthocyanidins (PAs), known as condensed tannins, have protein binding properties, which tend to reduce the nutritional quality of sorghum based diets in both livestock and humans
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