Modern maize varieties going local in the semi-arid zone in Tanzania

BMC Evolutionary Biology

Anne K Brysting¹  Paul R Berg¹  Kristoffer H Ring²  Ola T Westengen¹ 

[1] Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Box 1066 Blindern, NO-0316 Oslo, Norway;Centre for Development and the Environment (SUM), University of Oslo, Box 1166 Blindern, NO-0317 Oslo, Norway

关键词: Creolization;    Hybridization;    Adaptation;    Seed systems;    Open pollinated varieties;    Crop evolution;   

Others  :  858148
DOI  :  10.1186/1471-2148-14-1

 received in 2013-09-04, accepted in 2013-12-18,  发布年份 2014

【 摘 要 】

Background

Maize is the most produced crop in Sub-Saharan Africa, but yields are low and climate change is projected to further constrain smallholder production. The current efforts to breed and disseminate new high yielding and climate ready maize varieties are implemented through the formal seed system; the chain of public and private sector activities and institutions that produce and release certified seeds. These efforts are taking place in contexts currently dominated by informal seed systems; local and informal seed management and exchange channels with a long history of adapting crops to local conditions. We here present a case study of the genetic effects of both formal and informal seed management from the semi-arid zone in Tanzania.

Results

Two open pollinated varieties (OPVs), Staha and TMV1, first released by the formal seed system in the 1980s are cultivated on two-thirds of the maize fields among the surveyed households. Farmer-recycling of improved varieties and seed selection are common on-farm seed management practices. Drought tolerance and high yield are the most important characteristics reported as reason for cultivating the current varieties as well as the most important criteria for farmers’ seed selection. Bayesian cluster analysis, PCA and F_ST analyses based on 131 SNPs clearly distinguish between the two OPVs, and despite considerable heterogeneity between and within seed lots, there is insignificant differentiation between breeder’s seeds and commercial seeds in both OPVs. Genetic separation increases as the formal system varieties enter the informal system and both hybridization with unrelated varieties and directional selection probably play a role in the differentiation. Using a Bayesian association approach we identify three loci putatively under selection in the informal seed system.

Conclusions

Our results suggest that the formal seed system in the study area distributes seed lots that are true to type. We suggest that hybridization and directional selection differentiate farmer recycled seed lots from the original varieties and potentially lead to beneficial creolization. Access to drought tolerant OPVs in combination with farmer seed selection is likely to enhance seed system security and farmers’ adaptive capacity in the face of climate change.

【 授权许可】

   
2014 Westengen et al.; licensee BioMed Central Ltd.

【 图 表 】

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