Analyse der genetischen Diversität von wildwachsenden Futterpflanzen aus der Sahelzone in Westafrika anhand von RAPD - Markern




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Brachiaria and Zornia belong to the most important wild forage plants in the Sahel region of West Africa. Due to their heat- and aridity resistance they are welladapted to extreme climate and able to overcome great deviations in precipitation during the rainy season. Extensive agriculture and overstocking are destroying huge parts of the productive landscape in the Sahel (shortage of forage plants). These regions aregenerally not very suitable for agriculture, so the millet fields are given up after a few years. This is followed by an increase in desertification processes. Due tothe great importance of these forage plants, both to the local agricultural economy and also in plant breeding, an international project for their comprehensiveanalysis has been established. The main target is to build an initial database for further projects, i.e. the establishment of guidelines for in situ conservation. The work presented here is an investigation of the genetic diversity of Brachiaria and Zornia over a study area of about 2000 km2. Plant samples werecollected in several years at 34 test sites and analysed using RAPD-markers. For Brachiaria, 309 samples from 25 locations were analysed with 10 primers. A few samples were analysed morphologically (Prof. Scholz, FU Berlin) andfive species of Brachiaria could be determined (B. xantholeuca, B. nidulans, B. orthostachys, B. ramosa, B. lata). Using the RAPD method the same samplescould be discriminated into five groups by cluster analysis. A 100 % correspondence between morphological and molecular genetic analysis was observed,whereby a characterisation of these five species of Brachiaria was possible. The five species showed a high genetic diversity and most of the study sites couldbe discriminated using RAPD markers. For some locations a differentiation of the two or three collection years was observed, introducing the term 'temporalgenotypes'. For B. xantholeuca, the genetic similarity at test sites within a radius of 50 km enabled their combination into ecotypes. B. xantholeuca therefore exhibits a highregional homogeneity, while B. nidulans and B. orthostachys are more location specific. 80 samples from Zornio glochidiata were analysed using six primers. The genetic variability was high showing a huge inter-individual heterogeneity. For thatreason a differentiation neither of test sites nor the three collecting years was possible. More extensive molecular genetic investigation is necessary to gain a better understanding of the regional and temporal effects in wild forage plants. Ofparticular interest will be RAPD analyses of the forage plants Alysicarpus, Dactyloctenium and Cenchrus.




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