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Universität Hohenheim (2015)

Towards understanding the genetics of tolerance to low soil phosphorus conditions in West African pearl millet

Gemenet, Dorcus Chepkesis

Titre : Towards understanding the genetics of tolerance to low soil phosphorus conditions in West African pearl millet

Erkenntnisse zur genetischen Toleranz gegenüber Bodenphosphor-Mangelbedingungen in West-Afrikanischer Perlhirse

Auteur : Gemenet, Dorcus Chepkesis

Université de soutenance : Universität Hohenheim

Grade : Doctor of Philosophy in Agricultural Science 2015

Résumé
About two hundred and twenty three million people are undernourished in Sub-Saharan Africa (SSA) with 11 million people being food insecure in the Sahel region of West Africa (WA). A growing global population and climate change are expected to exacerbate this situation and present new challenges on global food production. Phosphate rock, a non-renewable resource is expected to be depleted in about 40-400 years depending on the source of information but a phosphorus (P) peak (where P demand exceeds P supply) is likely to occur before 2040. The effects of limited global P supply are expected to be felt more by resource poor smallholder farmers in SSA. This is also the region already with the lowest inorganic fertilizer use and highly weathered P deficient soils. Given these factors, breeding for low-P tolerance in crop plants offers the main environmental friendly and economically feasible strategy for improving crop productivity under low-P soils for smallholder farmers in WA conditions. This will not only contribute towards food security in the short term but also in the long term by contributing towards the efficient use of a scarce resource.
In the Sahel region of WA where pearl millet is the staple cereal, it contributes to food security by providing calories as well as contributing towards nutritional security by providing higher iron and zinc levels than most staple cereals. Despite this fact, the available pearl millet germplasm had never been evaluated for grain yield performance under low-P conditions within this region prior to this study and the magnitude of the genetic component of variation had not been tested from a breeding perspective. To fill in this knowledge gap, three genotype groups : open-pollinated varieties, inbred lines and their testcrosses were evaluated in large-scale multi-environment trials in four countries under two P-levels between 2010 and 2012. In addition, the open-pollinated varieties and inbred lines were evaluated for P-efficiency related traits at early growth stage in pot conditions and at mature plant stage under field conditions (inbred lines only). The main aim of these evaluations was to explore the prospects of plant breeding for improving pearl millet grain yield under low-P conditions in WA. We sought to achieve the following specific objectives : (i) to estimate quantitative-genetic parameters for grain yield in order to establish a selection strategy for pearl millet targeting P-limited environments in WA ; (ii) to determine the relationship between P-efficiency related traits and grain yield in order to make inferences on which target traits should be considered in adapting pearl millet to low-P conditions in WA ; and (iii) to identify genetic regions underlying quantitative traits which are related to P-efficiency based on diversity array technology (DArT) markers.

Mots clés  : Low-soil phosphorus tolerance , West Africa , Pearl millet , Selection strategy ; Institut für Pflanzenzüchtung, Saatgutforschung und Populationsgenetik

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