Genetic erosion of sorghum (Sorghum bicolor (L.) Moench) in the centre of diversity, Ethiopia

Abstract

The Ethiopian region is characterised by a wide range of agro-climatic conditions, which accounted for the enormous resources of agro-biodiversity that exist in the country. The most important of these resources is the immense genetic diversity of the various crop plants in the country. Of these, one of the most on farm genetically diverse crops is sorghum. Since the advent of formal breeding in particular after green revolution, genetic diversity of most crops has been threatened worldwide. In order to assess on farm genetic erosion (GE), various research methodologies were employed. These were focused group interviews with 360 farmers, on farm monitoring and participation with 120 farmers, key informant interviews with 60 farmers and development agents, and semi-structured interviews with 250 farmers. Besides, diversity fairs were done with over 1200 farmers. Notwithstanding the complexity of assessing GE, it was assessed by various methods; namely, by temporal method (comparing 1960 and 2000 collections), area method, and semi-structured interview method at individual, community or wereda level and causes of varietal loss from other various perspectives. Farmers perceived GE as the reduced importance of the variety as indicated by lower proportion in the varietal portfolio. The five most important factors for varietal loss at individual farmers' level were reduced benefit from the varieties, drought, Khat expansion, reduced land size and introduction of other food crops respectively. GE was not affected by wealth groups and ecological regions. Farmers do not make simple replacement as a strategic mechanism for genetic resources management. GE at regional level was quantified by temporal and spatial method. There was a complementation not rivalry between farmer varieties (FVs) and improved varieties (IVs). The whole process of GE is explained by three models, namely: Bioecogeographic enhanced genetic erosion model, Farmer induced genetic erosion model and Farmer-cum-bioecogeographic genetic erosion model. As aforementioned, sorghum genetic erosion behaviour is completely different from other food crops such as tetraploid wheat. The prediction in the late seventies that complete erosion of FVs by IVs by the end of the eighties, the principle of GE that competition between IVs and FVs, favours the former and results in the replacement of the latter is not valid in the context of sorghum in Ethiopia. Hence, maintenance of the on farm genetic diversity of sorghum is a reality but GE is rhetoric.

On-Farm Diversity and Genetic Erosion of Tetraploid Wheat Landraces in Ambo and Dandi Districts, West Shewa, Ethiopia

“…The authors reported that landraces that are less preferred in terms of agronomic value and end-use, introductions have become increasingly important while late maturing types were found to be vulnerable to genetic erosion. Mekbib (2008a) reported genetic erosion in sorghum for eastern Ethiopia caused by reduced benefits from the varieties, drought, khat expansion, reduced land size and introduction of other food crops. In the present investigation drought, fire, and war are not factors for genetic erosion.…”

Genetic erosion of barley in North Shewa Zone of Oromiya Region, Ethiopia

“…Eticha et al (2010) indicated that, a high yielding improved barley variety (HB-1307) is currently expanding and accelerating the loss of barley varietal diversity. On the contrary, Mekbib (2007) reported that improved varieties of sorghum were not the reasons for genetic erosion of FV's in the context of eastern Ethiopia and they contributed to the genetic enrichment of the existing on farm genetic diversity.…”

“…(Mekonen, 1997;Tesemma, 1991;Mekonen and Mekbib, 1993) as cited in Tsegaye and Berg (2007). On the contrary, Mekbib (2007) reported that there was no genetic erosion based on the number of FVs in sorghum.…”

Spatial variation in biodiversity, soil degradation and productivity in agricultural landscapes in the highlands of Tigray, northern Ethiopia

“…Those studies concerned varietal diversity in sorghum (Sorghum bicolor) (Mekbib 2008;Mulatu and Belete 2001;Teshome et al 1999), wheat (Triticum spp.) (Di Falco et al 2007;Kebebew et al 2001), finger millet (Eleusine coracana) (Tsehaye et al 2006), and tef (Eragrostis tef) (Assefa et al 2001).…”