Browsing by Person "Haussmann, Bettina"

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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.
Sorghum breeding strategies for phosphorus-limited environments in Western Africa : from field to genome level
(2014) Leiser, Willmar Lukas; Haussmann, Bettina
A growing world population juxtaposed with dwindling phosphorus (P) resources present new challenges to current and future global agricultural production. The burden of depleting phosphorus resources is particularly felt in sub-Saharan Africa (SSA). The expected doubling of its population by 2050 and the widespread poor soil fertility will pose an enormous task to future food security in SSA. Plant breeding can be considered as one major factor to improve agricultural production under these harsh low-input conditions. Nevertheless, until recently there have been no thorough breeding efforts to enhance crop production for low-P soil conditions in SSA. Sorghum (Sorghum bicolor L. Moench) is the world’s fifth and Africa’s second most grown cereal crop. Sorghum is a staple crop of SSA and is mostly grown in resource poor regions under low-input cropping conditions, with the largest share in West Africa (WA). Its good adaptation to harsh environmental conditions makes it an important crop for the arid and semi-arid regions, hence a crop vital for food security and increasingly farm income in WA. Breeding sorghum specifically targeting P-limited soils is considered as one of the major challenges for future food production and can serve millions of smallholder farmers in WA. Nevertheless, plant breeders are mostly reluctant to conduct breeding experiments under low-input conditions due to a higher spatial variability of soil properties leading to a lower response to selection. In an unprecedented large scale multi-environment experiment from 2006-2012 in three WA countries, namely Mali, Senegal and Niger, 187 WA sorghum genotypes were evaluated for their performance under P-sufficient and P-deficient conditions. The main goal of this study was to establish a breeding strategy for sorghum targeting P-limited environments. In order to establish such a strategy, the following objectives were defined: (I) to evaluate the impact of spatial models on genotypic selection in low-input field trials, (II) to develop a selection strategy for sorghum targeting P-limited environments, based on quantitative genetic parameters and (III) to identify genomic regions influencing sorghum performance in P-limited environments using modern genomic tools. The major findings of this study can be summarized as follows: Spatial models can increase the precision and efficiency especially of low-input field trials and may lead to different genotype rankings. Hence spatial models and/or adequate field designs are necessary tools for efficient genotype selection under low-input conditions and must be considered in a breeding program targeting P-limited conditions. Sorghum performance is severely impeded by low-P soil conditions and shows large grain yield and plant height reductions and delayed flowering. Nevertheless, WA sorghum is generally well adapted to low-P soil conditions and shows a large exploitable genetic variation for P efficiency. Direct selection under low-P conditions is feasible, necessary and more efficient than indirect selection under high-P conditions and should be pursued in a breeding program targeting P-limited environments. Landrace genotypes are more specifically adapted to low-P conditions and show a higher P acquisition capacity, Durra and Guinea race sorghums show a similar specific low-P adaptation, hence these genotype groups are very promising source germplasm for further breeding efforts. Photoperiod sensitive genotypes show less delay in heading, a higher P acquisition rate and a specific low-P adaptation, hence should be considered for climate and low-P resilience breeding. Selection for low P concentration of grain can be used to enhance internal P use efficiency, therefore decreasing further soil P mining. WA sorghum shows a large genetic diversity, hence providing a valuable source for genetic studies examining the underlying genetics of low-P adaptation. There are many genomic regions involved in sorghum adaptation to low-P soil conditions. Nevertheless, some regions could be identified as major contributors, showing large effects on and strong associations to genotypic performance. Molecular markers in sorghum homologs of the major P efficiency gene PSTOL1 from rice stably enhanced P uptake and crop performance through an increased root growth of sorghum under low-P soil conditions and can be used in marker assisted selection for grain yield production under P-limited conditions. Furthermore, it was observed that grain yield production under P-limited conditions and Al-tolerance are pleiotropically regulated by the same genomic region and most probably the same gene SbMATE. Molecular markers of this region and within the gene SbMATE should be used for marker assisted selection to simultaneously enhance the tolerance to two of the most serious abiotic stresses for sorghum in WA, Al toxicity and P deficiency. WA Guinea race sorghums are an excellent source not only for low-P specific alleles, but also for Al-tolerance and represent therefore an excellent source germplasm for allele mining and marker assisted selection. Genomic selection appears to be a very promising approach to further increase the response to selection. But methods giving more weight to single molecular markers linked to Al-tolerance should be considered. The laid out results show that breeding sorghum specifically targeting P-limited conditions is necessary and feasible using advanced statistical models and modern genetic tools, and should be pursued as a major selection criterion in WA sorghum breeding programs. Nevertheless, only by combining agronomic and socio-economic measures with plant breeding efforts, millions of WA smallholder farmers can be reached and major yield increases can be expected in the near future.
Stirring up sorghum hybrid breeding targeting West African smallholder farmers low input environments
(2019) Kante, Papa Ndiaga Moctar; Haussmann, Bettina
Food supply and income in rural areas of West Africa (WA) depend strongly on the local production, and mostly on farmers’ field production of root and tuber crops, and cereals. To feed an ever-increasing population in a context of climate-change and low-input cultural conditions, breeding for resilient crops can guarantee smallholder farmers food security and cash income for a sustainable rural development. Sorghum hybrids for WA were first explored in the early 1970s and hybrid crosses of Malian landraces with introduced Caudatum-race seed parents were evaluated in the early 80s. Although those hybrids exhibited good heterosis for grain yield, their lack of grain quality made them commercially unsustainable. Efforts by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) and its partners resulted in the first series of Guinea-race based hybrids. The short statured hybrids were evaluated in several on-farm farmer-managed yield trials, and showed satisfactory grain yield and quality under farmers’ cultivation conditions. Although taller- relative to shorter- height sorghum can help reduce risks of panicle loss by grazing transhumant cattle, no indication on the yield potential of the tall statured hybrids is available. The advances achieved by ICRISAT and its partners in hybrid development justified establishing a long-term hybrid breeding program to provide farmers with hybrids with sufficient grain yield and good grain quality under low input conditions. However, the lack of quantitative genetic information about the genetic value of new experimental hybrids and their parents (Guinea-Caudatum to complete Guinea background, from different WA origins), or about the efficiency of alternative selection methods for targeting yield performance in the predominantly low-input and phosphorous-deficient sorghum production conditions hinders sorghum hybrid development for this region. Sorghum hybrid breeding was commercially feasible only after the identification of a heritable and stable cytoplasmic male sterility (CMS) mechanism. Hybrid breeding in WA can benefit from molecular marker, especially for the fertility restoration/sterility maintenance of the predominant A1-type of CMS. The major outcomes of this thesis are presented as follow: Mean yields of tall hybrids were 3 to 17% (ranging from 6 to 28 g m−2) higher than that of the local check across all 37 on-farm farmer-managed environments and were highest (14–47%) averaged across the seven trials with the lowest mean yields. The yields of the new set of experimental hybrids were substantially superior to farmers’ local Guinea-race varieties, with 20 to 80% higher means over all hybrids in both low phosphorus (LP) and high phosphorus (HP) environments. Average mid-parent and better-parent heterosis estimates were respectively 78 and 48% under HP, and 75 and 42% under LP. Direct selection under LP was predicted to be 20 to 60% more effective than indirect selection under HP conditions, for hybrid performance under LP. The combining ability estimates provide initial insights into the potential benefit of germplasm from further east in West and Central Africa for developing a male parental pool that is distinct and complimentary to the Malian female pool. On chromosome SBI-05, we found a major A1 CMS fertility restorer locus (Rf5) explaining 19 and 14% of the phenotypic variation in either population. Minor quantitative trait loci (QTL) were detected in these two populations on chromosomes SBI-02, SBI-03, SBI-04 and SBI-10. In the third population, we identified one major A1 CMS fertility restorer locus on chromosome SBI-02, Rf2, explaining 31% of the phenotypic variation in the F2 mapping population. Pentatricopeptide repeat genes in the Rf2 QTL region were sequenced, and we detected in Sobic.002G057050 a missense mutation in the first exon, explaining 81% of the phenotypic variation in an F2:3 validation population and clearly separating B- from R-lines. The Guinea-race hybrids’ substantial yield superiorities over well adapted local Guinea-race varieties suggests that a strategy of breeding hybrids based on Guinea-germplasm can contribute to improving the livelihood of many smallholder farmers in WA. Although the usefulness of direct selection under LP for hybrid performance in the predominantly P-limited target environments was proven, companion evaluations of hybrids under HP would be desirable to identify also new hybrids that can respond to improved fertility conditions for sustainable intensification. The developed KASP marker stands as a promising tool for routine use in WA breeding programs.
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.