Genetic Diversity in Sorghum (Sorghum bicolor (L.) Moench) GermpJasm From Ethiopia and Eritrea.
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Date
2001-06
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Addis Ababa University
Abstract
Infonnation about the amount and distribution of genetic variation in gennplasm collections is
important for efficient management of gennplasm collections and for effective utilization of
such materials in plant breeding. Sorghum (Sorghum bie%r (L.) Moench) is one of the most
important cereals worldwide and its tolerance to drought makes it particularly important in
semiarid tropical regions, including Ethiopia and Eritrea. The significance of sorghum
gennplasm from these countries for worldwide improvement of sorghum is also well
acknowledged. However, there is limited infonnation about the amount and distribution of
genetic variation in sorghum gennplasm from these countries. In this thesis, the amount and
pattems of distribution of genetic variation was detennined in cultivated sorghum (s. bie%r
ssp. bie%r) gennplasm collections from Ethiopia and Eritrea using morphological traits,
allozymes and random amplified polymorphic DNA (RAPD) markers. A similar investigation
was made on wild sorghum (s. bie%r ssp. vertieillijlorum) from Ethiopia using RAPD
markers.
The results show that the materials exhibit a wide range of variation for quantitative
traits and a high Shannon-Weaver diversity index (il= 0.90) for 10 qualitative traits. In
contrast, the level of allozyme variation was found to be low (mean expected heterozygosity =
0.024). The level of RAPD variation was found to be intermediate both in cultivated (il=0.53) and wild sorghum (H= 0.49). The lack of correspondence among the three levels of
variation revealed by these methods points at the difficulty of making prediction of variation
of one based on the other and explanations are provided for the possible causes of the
disparity. Despite the disparity in the levels of variation from the three data sources (i.e. ,
morphological traits, allozymes and RAPD markers), the structure of the variation was fOlmd
to be similar for all the data sources. In all, the within accessions, regions and the within
adaptation zones variation accolmted for a large portion of the total variation compared with
the between accessions, regions and the between adaptation zones variation. Based on these
results, sampling more accessions within each regions and adaptation wnes and more
individuals within populations are suggested as future sampling strategies. Grouping of the
materials into lowland, intermediate and highland elevations seems to be justified only for
discriminant analysis of quantitative traits, otherwise, there was no convincing evidence that
such materials are genetically substructured. Regions with overall high diversity are identified
and suggested for in situ conservation. The results from quantitative trails indicate that
accessions from Eritrea could be important sources of genes for early maturity. Detailed
implications of the results for germplasm conservation and utilization are discussed and future
lines of research are suggested.
Key words: alJozymes; genetic variation; germplasm; morphological variation; RAPD; Sorghum bicolor
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Keywords
genetic variation, germplasm, morphological variation, RAPD, Sorghum bicolor, allozymes