Browsing by Subject "Perlhirse"

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Pearl millet breeding in West Africa : steps towards higher productivity and nutritional value
(2018) Pucher, Anna Ida; Haussmann, Bettina
The enormous human population growth in West Africa (WA) in combination with serious production constraints is very problematic condition for food security. The alarming status of micronutrient deficiency in WA exacerbates this situation. For smallholder farmers improved and nutritious crop varieties derived from plant breeding could be a major contributor to enhancing agricultural productivity and reducing malnutrition. Pearl millet (Pennisetum glaucum (L.) R. Br.) is due to its high tolerance to drought and heat, capable to grow under very harsh environments, and is therefore a staple crop in Sahelian WA. Development of multiple pearl millet breeding approaches will be crucial to exploit the potential of this crop.The main goal of this study was to establish a scientific basis for more efficient pearl millet breeding in WA with a specific focus on achieving higher productivity and nutritional value. In order to accomplish this goal, the following objectives were defined: (I) to characterize a broad set of WA pearl millet accessions and to investigate their diversity and geographic patterns based on their phenotype; (II) to identify the potential and strategies to increase the micronutrient level in WA pearl millet; (III) to evaluate the performance of population hybrids and to derive initial strategies of pearl millet hybrid breeding in WA based on combining ability and heterotic patterns; and (IV) to identify molecular markers for the male-fertility restoration locus (Rf) for the A4 cytoplasmic-genic male-sterility (CMS) system in pearl millet using a genotyping-by-sequencing (GBS) based linkage map. The major results and conclusions of the four studies are summarized in the following:Characterization of a collection of 360 WA pearl millet landraces at six sites in WA identified wide ranges for 12 agro-morphological traits, which indicated a tremendous diversity. Principal component analysis revealed very large diversity within individual countries, and a high genetic admixture among WA pearl millet landraces. The high admixture indicates that heterotic grouping based on morphological distance or geographic distance is not possible. The published data of this study gives national breeders a basis to utilize this germplasm.In the second trial, pearl millet grain iron and zinc densities showed significant genetic variation in a set of 72 WA landraces evaluated at three sites and moderate-to-high heritability, which emphasizes a high potential for biofortification. Identified landraces with moderately high and stable micronutrient densities appear suitable for use in future WA biofortification breeding. Due to significant positive correlations among grain iron, zinc and other mineral densities and non-significant correlations between grain yield and mineral densities, selection for high grain iron and zinc density can be performed simultaneously without a negative effect on grain yield or contents of other micronutrients.The third trial evaluated 100 population hybrids and their 20 parental populations (with four parental open-pollinated varieties from each of five WA countries) at six environments and showed hybrid superiority of, on average, 16.7% compared to their parental populations (with a max. of 73%), reflecting the great potential of hybrid breeding. The mean grain yield of hybrids based on inter-country crosses did not differ significantly from intra-country crosses. Geographic distance between parents was not correlated with panmictic midparent heterosis, indicating that heterotic grouping based on geographic distance is not expedient. However, crosses between accessions from Niger/Nigeria and Senegal were outstanding, thus initial heterotic pools could be based on this information. In the long term, sustainable pearl millet hybrid breeding will require combining ability studies to develop heterotic groups.Within the fourth trial, a high-density linkage map based on single nucleotide polymorphism (SNP) markers produced by GBS was generated using a F2 mapping population, which segregated for fertility restoration of the A4 CMS system. A major Rf locus was found on linkage group 2, which was verified by cross-validation showing a very high quantitative trait locus (QTL) occurrence (97%). The QTL explained 14.5% of the phenotypic variance, which was below expectation because the segregation ratio of male-fertile and male-sterile plants (3:1) indicated monogenic dominant inheritance of this trait. The two KASP markers developed for the QTL will support high-throughput screening for the Rf locus and will facilitate the development of male parental pools exhibiting the fertility restoration, which is an essential step to enable economic pearl millet hybrid seed production. We can conclude that WA pearl millet breeding has the potential to increase the pearl millet productivity and nutritional value by utilizing the enormous pearl millet diversity in hybrid and biofortification breeding programs.
Seedball technology development for subsistence-oriented pearl millet production systems in Sahelian West Africa
(2019) Nwankwo, Charles Ikenna; Herrmann, Ludger
The objectives of this study were to review the potential of the local material-based innovation – i.e. the seedball technology, at enhancing pearl millet seedlings establishment under Sahelian conditions, identify its potential constraints as well as applicability, chemically and mechanically optimize the seedball, and validate its performance under Sahelian field conditions. Seedball is a local seed pelleting techniques that aims at improving seedlings performance and to stabilize yield. First, the potential local materials such as sand, loam, wood ash, gum arabic, termite soil, charcoal as well as animal dung as the seedball components were identified and reviewed. These materials were selected based on their affordability to the local farmers. Potential constraints to seedball applicability as well as adoption in the Sahel were evaluated, and options for adaptation were discussed with the farmers. Afterwards, mechanical and chemical optimization of the seedball technology in several greenhouse experiments were conducted, followed by a germination test of the optimized seedball in the Sahelian field. Lastly, the mechanism of pearl millet seedlings root and shoot enhancement was investigated using micro-suction cup and computer tomography. Our evaluation showed that the materials needed for seedball production are locally available at affordable costs. The seedball technology totally conforms to the agronomic management practices in the African Sahel. In addition, the socio-economic status as well as cultural practices seemed not to reduce the chances of seedball technology adoption in this region. Our greenhouse studies showed that the seedball base dough, from which about ten 2 cm diameter-sized seedballs can be produced, is derived from the combination of 80 g sand + 50 g loam + 25 ml water. Either 1 g mineral fertilizer or 3 g wood ash can be added as nutrient additive to enhance early biomass of pearl millet seedlings. With respect to nutrient additives, ammonium fertilizers and urea hampered seedlings emergence. Wood ash amended (Sball+3gAsh) and mineral fertilizer-amended seedballs (Sball+1gNPK)enhanced shoot biomass by 60 % and 75-160 %, root biomass by 36 % and 94 %, and root length density of pearl millet by 14 % and 28 %, respectively, relative to the control. Again, the mineral fertilizer amended seedball in particular enhanced root dry matter by 227 %, compared to the control. Although the shoot nutrient content was not clearly enhanced by the seedball, nutrient extraction, calculated as the product of biomass yield and nutrient content, was higher in the nutrient-amended seedballs, compared to the conventional sowing. In Senegal, optimized seedballs showed over 95 % emergence in an on-station trial, indicating its viability in the Sahel region. With respect to seedball enhancement mechanism, the mineral fertilizer-amended seedball in particular promoted root growth within the vicinity of the seedball as early as 7 days after planting. The analysis of the sampled soil solution revealed that P as well as other cations and anions, observed through EC measurement, were released by the seedball in direct proximity of the seedball. Most likely, the nutrient release by the seedball triggered the observed fine root growth and overall higher root biomass of pearl millet seedlings. However, due to nutrient depletion in the root zone, nutrient supplementation was needed after three weeks after sowing to further promote growth of the well-established seedlings. At the Sahelian field, where seedlings enhancement is decisive for higher panicle yield in pearl millet, nutrient amended seedballs can potentially increase panicle yield under subsistence production. The seedball technology is cheap, and seems to have favorable conditions for adoption in the Sahel, coupled with its minimal seed usage and simple sowing on the sandy soil. A recommendation will be to conduct long-term, on-farm as well as on-station field trials, testing the seedball technology under different seasonal weather conditions. Pearl millet and sorghum are the major Sahelian staple crops. Fonio (Digitaria spp) is often neglected despite its high nutritional values. It is, therefore, recommended to test the seedball technology on the other fine-grained cereal crops.
Strategies for sustainable pearl millet hybrid breeding in West Africa
(2020) Sattler, Felix; Haussmann, Bettina
Pearl millet [Pennisetum glaucum (L.) R. Br.] is grown by >90 million subsistence farmers, mostly in the drylands of Sub-Saharan Africa and India for human consumption and provides additionally fodder and building material. It is commonly grown in regions with 300 – 500 mm of precipitation, low soil phosphorus levels, and temperatures of >42°C), like its center of origin in West Africa (WA). Pearl millet is a highly heterozygous, diploid (2n = 2x = 14) C4 plant species with outcrossing rates of >70%. Yield levels increased largely in India and the US, while they almost stagnated in WA. Challenging, highly variable environments and a weak seed sector are largely contributing to these differences. To suggest a way forward this thesis was meant to guide heterotic group development for sustainable WA pearl millet breeding. The specific objectives were to (I) facilitate efficient use of pearl millet gene bank accessions, (II) identify diversity patterns, (III) validate the yield superiority and stability of pearl millet population hybrids over OPVs, (IV) derive a more comprehensive picture about combining ability patterns, and (V) develop a unified strategy for heterotic grouping and sustainable hybrid breeding. A total of 81 accessions acquired from the pearl millet reference collection was evaluated for resistance to Striga hermonthica (Del.) Benth. in one artificially infested field in Niger. A subset of 74 accessions was characterized in 2009 in multi-environment trials (MET) under low-input and fertilized conditions. The general superiority of local check varieties compared to the genebank accessions highlighted the importance of local adaptation, possibly lost during the ex situ conservation and regeneration. Nevertheless, the development and preservation of germplasm collections are important to maintain the rich genetic diversity. The MET identified several accessions as sources for specific traits of interest and revealed an immense diversity but also strong admixture. This admixture underlines the need to develop heterotic groups. Therefore, 17 WA open-pollinated varieties (OPVs) were crossed in a diallel mating design and tested together with their offspring in nine environments over two years in Niger and Senegal. Results from these MET verified large panmictic better parent heterosis (PBPH) effects with an average of 18% (1–47%) for panicle yield. A large G × E interaction variance was confirmed and it was not possible to define repeatable mega-environments. Importantly, yield stability was more pronounced in the population hybrids compared to their parental OPVs. Furthermore, a superior combining ability among selected OPVs from Niger vs. Senegal was revealed and the evaluated OPVs were clearly grouped by origin based on genetic information. Nevertheless, there was no significant relationship between genetic distance among OPVs and PBPH. These and earlier studies showed a large diversity, sufficiently large heterosis effects and high yield stability in experimental pearl millet population and topcross hybrids, offering a great opportunity for a regionally coordinated hybrid breeding approach. Therefore, we suggested a unified strategy with a continuous output of different hybrid types, specifically tailored to WA. First, existing diversity and combining ability pattern information on western WA and eastern WA cultivars forming loose groups that combine well with each other should be used. Selected genotypes with high general combining ability (GCA) and per se performance from eastern and western WA, respectively, are promising founder populations. Initiating a reciprocal recurrent selection (RRS) program, possibly supported by modern breeding tools, will diverge the two groups further, while improving the inter-pool per se performance. RRS in combination with continuous diversification of both pools allows distinct female and male pool development, line development and introgression of a cytoplasmic male sterility system. Creating OPVs and population hybrids early and aiming for long-term development of topcross hybrids from improved OPVs and newly derived lines is possible alongside the heterotic pool development. Additionally, the RRS lays the foundation for possible future single-cross hybrid breeding programs. The suggested framework is highly ambitious and requires long-term commitment, vision and financial resources. Considering the flexibility regarding single steps and the possibility to develop different types of varieties at every stage of the pool diversification, it has the potential to enhance gains from selection and, with the continuous output of new high-yielding and stable cultivars, to improve the livelihood of WA subsistence farmers substantially.
Towards understanding the genetics of tolerance to low soil phosphorus conditions in West African pearl millet
(2015) Gemenet, Dorcus Chepkesis; Haussmann, Bettina
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. There is significant genetic variation for pearl millet performance in low-P soils; hence genetic improvement for low-P conditions should be possible. Both wide and specific adaptation can be followed in breeding pearl millet varieties for low-P conditions in WA. Direct selection of pearl millet under low-P conditions is more efficient and should be carried out in breeding activities targeting low-P environments. Pearl millet in WA exhibits a wide genetic variation for P-uptake and internal use efficiency. P-uptake efficiency is more correlated to grain yield in pearl millet than P-utilization efficiency, and given the interactions among P, drought and other soil characteristics evident within the region, P-uptake efficiency under these conditions should be selected for. However, given the already low P content of the soils in the region and the low input conditions, genotypes selected for low-P environments should combine both P-uptake efficiency and internal P-utilization efficiency to avoid further depletion of the soils. Nine markers were associated with different P-efficiency-related traits such as P concentration in stover, P concentration in grain, P uptake and P utilization efficiency. Nine markers and thirteen markers were found to be associated with flowering time and grain yield respectively. Each of these markers individually explained between 5.5 to 15.9 % of the observed variations indicating the polygenic nature of low P tolerance in pearl millet. The results presented in the current study indicate potential of improving pearl millet grain yield under P-limited conditions through breeding both conventionally and through molecular technologies. Given the global P crisis, other agronomic, socio-economic and policy approaches need to be effected alongside breeding activities if the pearl millet production system should be made sustainable to ensure food security for current and future generations.