Groundnut Breeding Research Articles

Evaluation of groundnut (<i>Arachis hypogaea</i> L.) advanced breeding lines for resistance to cercospora leaf spots and rust diseases in Kano State, Nigeria

Cercospora leaf spots and rust diseases are among the biotic factors that cause yield reduction in groundnut. However, screening groundnut breeding lines that are tolerant to these diseases and having higher yield potentials would help farmers and breeders to make the right choice for cultivation or for further improvement. Therefore, this study was conducted to evaluate 18 groundnuts advanced breeding lines and 2 improved/local varieties against these diseases, during July-October 2016 rainy season in a field designated as endemic to Cercospora leaf spots and rust diseases, at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) Research Farm at Minjibir, Kano, Nigeria. Significant differences (p<0.01) were observed in all the traits studied (viz., days to 50% flowering, normalised difference vegetation index, pod yield (Kg/ha), fodder yield (Kg/ha), 100 seed weight (g), disease incidence (%) and disease severity) except chlorophyll content. The top nine (9) high yielding breeding lines (ICGV's-IS 13980, 07947, 07828, 09011, ICGX-IS's 11003, 11057, 13011, ICGV-SM 07539 and ICG 5891) were all resistant to early leaf spot, moderately resistant to late leaf spot and rust except ICGV's-IS 07828, 09011 and ICGX-IS 13011 which were susceptible to rust.Keywords: Cercospora, Rust, Groundnut, Resistance, Yield

Genetics of Stay-Green Trait and Its Association with Leaf Spot Tolerance and Pod Yield in Groundnut

Despite its importance in providing income and food for smallholder farmers, fodder for livestock, and improving soil fertility through biological nitrogen fixation, groundnut yields are lowest on farmers’ fields in Sub-Saharan Africa due to biotic and abiotic constraints. Foliar fungal diseases account for over 80% reduction in groundnut productivity in some parts of Ghana. Unfortunately, chemical control of these foliar diseases has not yielded the desired results. Meanwhile, advances in phenotyping for disease tolerance in other crops have established a strong relationship between stay-green trait and foliar disease tolerance. However, this relationship has not been explored in groundnut. This study was designed to determine the genetic control of the stay-green trait and its relationship with leaf spot disease severity in groundnut. Twenty-five advanced groundnut breeding lines with varying degrees of tolerance for leaf spot tolerance were evaluated under diseased and disease-free conditions, after which four were selected for genetic studies. Results showed significant (p<0.001) differences among the genotypes for early leaf spot (ELS), late leaf spot (LLS), leaf area under greenness (LAUG), SPAD chlorophyll meter readings (SCMR), and yield traits. Leaf spot diseases caused 4.95 t·ha−1 (64.54%) pod yield reduction in CHINESE, the widely cultivated groundnut variety in Ghana. There was a strong correlation between LAUG and ELS (r = 0.82, p<0.001) and LLS (r = 0.63, p<0.001), and genotypes that were stay-green had tolerance to both diseases. Stay-green trait in groundnut was detected to be under the control of a single recessive gene and hence may be used to select for ELS and LLS resistance.

Improved Arachis hypogeae variety effect on grain yield, fodder quality and livestock growth

The hypothesis that improved groundnut (Arachis hypogea) varieties could improve seed and fodder yield and livestock growth performance was evaluated in two experiments: 1) an agronomic trial to determine the yield and yield component of groundnut varieties; and 2) fodder quality of groundnut varieties and its effect on growth performance of sheep. Four improved groundnut varieties (early-maturing: Yenyawoso, late-maturing: Azivivi, Obolo and Mani pinta) were evaluated for 2 yr in a randomized complete block design with four replications in the agronomic and livestock feeding trials. The results from the agronomic trial showed that the late-maturing varieties had significantly higher pods/plant, pod size, seed and fodder yields than Yenyawoso. Obolo had significantly higher seed yield whilst Azivivi had significantly higher fodder yield among the late-maturing varieties. The fodder quality and feeding trial showed that Yenyawoso had significantly higher dry matter, crude protein and resulted in significantly higher live weight gain of Djallonke rams than the other varieties. The Mani pinta variety had significantly higher live weight gain among the late-maturing varieties. Smallholder crop-livestock farmers interested in both seed and livestock growth could use Mani pinta, those interested in only seed yield could use Obolo and those interested in quality fodder for fattening of small ruminants could use Yenyawoso. Thus, groundnut breeding programs could consider fodder quality in addition to seed and fodder yield as selection criteria to develop varieties that best fit into crop-livestock farming systems.

Farmers’ perceived constraints to groundnut production, their variety choice and preferred traits in eastern Ethiopia: implications for drought-tolerance breeding

ABSTRACTGroundnut (Arachis hypogaea L.) is an important food and cash crop globally. The eastern region of Ethiopia is known for its groundnut production despite the low productivity attributable to diverse biotic and abiotic stresses and socioeconomic constraints. The objective of this study was to assess farmers’ perceived production constraints, variety choice, and preferred traits of groundnut in eastern Ethiopia to guide future groundnut variety development and release. Participatory rural appraisal studies were conducted in two major groundnut-producing districts (Babile and Fedis) in eastern Ethiopia. Data were collected through a semi-structured questionnaire, transect walks, and focus group discussions. All respondent farmers widely cultivated local or obsolete, introduced varieties because of a lack of seed of modern groundnut cultivars. Ninety percent of respondents reported drought stress, mainly occurring during the flowering stage, as the leading constraint to groundnut production. Other groundnut production constraints included poor soil fertility (reported by 88% of respondents), lack of access to improved seed (67%), pre-harvest diseases (59.5%), use of low yielding varieties (52.5%), inadequate access to extension services (41.5%), limited access to credit (21.5%), and limited availability of improved varieties (18.5). Farmer-preferred traits included high shelled yield (reported by 27.67% of respondents), early maturity (16.84%), tolerance to drought stress (13.67%), market value (11.17%), good seed quality (10%), adaptability to local growing conditions (5.8%), and resistance to diseases (5.17%). Therefore, the aforementioned production constraints and farmer-preferred traits are key drivers that need to be integrated into groundnut breeding and variety release programs in eastern Ethiopia.

Genetic diversity in groundnut (Arachis hypogaea L.) based on reaction to biotic stresses and productivity parameters

A set 184 mini core genotypes along with twelve checks of groundnut were evaluated for their reaction to Spodoptera litura, late leaf spot and rust at hotspot location in addition to their studies on eight productivity traits to assess the genetic diversity during rainy season of 2017. D2 analysis based on the aforesaid traits grouped the196 genotypes into twenty-five clusters. Maximum inter cluster distance was between cluster XXIII and cluster VI (836.06) while the same for intra cluster was in cluster IV (95.94). Genotypes with resistance to different biotic stresses were distributed mainly in different solitary clusters. Cluster XIV (ICG 5051) and cluster XII (ICG 76) had genotypes with resistance to Spodoptera litura.The genotype, (ICG 12625) also belonging to solitary cluster XVIII had shown resistance to late leaf spot while the genotypes in clusters XVII (ICGV 87157) and cluster XXII (ICG 13723) had resistance to rust. Number of primary branches per plant (48.41%), hundred seed weight (13.13%), reaction to Spodoptera litura (11.33%), and yield per plant (8.33%) mainly contributed to diversity in the groundnut mini core. The genotypes, ICG 5051, ICG 76, ICG 12625, ICG 76 and ICG 4412 may serve as diverse sources for resistance to different biotic stresses in groundnut. ICG 2381, a multiple stress resistant genotype (Spodoptera litura, late leaf spot and rust) in the cluster IV can be utilised in the multiple stress resistance breeding in groundnut.

Farmers’ perceptions of drought and other production constraints, drought mitigation options, and their implications for groundnut breeding in Uganda

A participatory rural appraisal was conducted in selected groundnut growing areas of Uganda to determine how smallholder farmers perceive and cope with drought, identify farmers’ constraints, and study the production systems, and varietal preferences in groundnut production. Majority of farmers surveyed, agreed that drought is a major production constraint. The local drought perceptions were described by farmers (55.7%) as warm/hot windy conditions in eastern (55.7%), while in the northern region, little rainfall (82.5%) and hot sunny weather in the mid-western region (48.3%). The majority of farmers surveyed, 81.7%, 77.6%, and 86.6% from eastern, northern and mid-western region, respectively, indicated that the major impact of drought was low yields. However, most of farmers especially from northern and mid-western grow landraces and use early planting to cope with drought. Therefore, knowledge of farmers’ perceptions on drought and coping strategies provides an entry point for improving farmers’ preferred varieties for drought tolerance.

Assessing variability for disease resistance and nutritional quality traits in an interspecific collection of groundnut (Arachis hypogaea)

AbstractRust and late leaf spot (LLS) resistance sources involving Arachis batizocoi, A. duranensis, A. cardenasii and A. sps Manfredi‐5 were identified from field evaluation of interspecific derivatives (IDs) of groundnut in a disease nursery for two seasons. Although the sources displayed low levels of resistance compared to currently cultivated lines, they contribute allele diversity in groundnut breeding that has so far relied on alleles contributed from A. cardenasii for disease resistance. Multiple disease‐resistant and agronomically superior IDs, ICGVs 11379, 10121, 10179, 05097, 02411 and 00248 involving A. batizocoi, A. duranensis and A. cardenasii can be used in breeding for groundnut improvement. Genetic variability for resistance to rust and LLS, yield and nutritional quality traits was influenced by genotype, environment and genotype × environment interaction effects in individual and pooled analyses. In case of FAD (fatty acid desaturase)‐mutant alleles that govern high oleic trait, allele mining of IDs (110) showed that frequency of mutation in ahFAD2B is rare, whereas of ahFAD2A is common. High oleic lines were not detected among the IDs.

Characterization of groundnut (Arachis hypogaea L.) collection using quantitative and qualitative traits in the Mediterranean Basin

This study was conducted to determine the genetic diversity and relationship among 256 groundnut genotypes of which 132 belong to subsp. hypogaea (Arachis hypogaea L.) and 124 to subsp. fastigiata (Arachis fastigiata L.). The collection was evaluated for eight quantitative and five qualitative traits during three consecutive years under Mediterranean climate conditions. Coefficient of variation (CV) significantly differed among the genotypes for all the studied quantitative traits ranged from 9.10 to 33.98%, while the highest CV was recorded for seed yield. The subspecies of hypogaea and fastigiata displayed significant differences for quantitative traits except for numbers of pods per plant and seed yield. Principal component analyses showed that the first three principal components accounted for 68.14% variation for quantitative traits. Major traits that accounted for the variation by the three principal components (PCs) include days to the first flowering, days to 50% flowering, number of pods per plant and shelling percentage. The groundnut collection also offers wide seed coat color diversity which affects the crop marketability. The information on variations in quantitative and qualitative traits identified in the present investigation provided useful genotypes which would be serving parents. These parental genotypes can be used in groundnut breeding programs to develop desirable cultivars in Mediterranean Basin and globally.

Adaptability and stability analysis of groundnut genotypes using AMMI model and GGE-biplot

Unpredictable rainfall, variations in farm inputs, crop-diseases, and the inherent potential of genotypes are among the major factors for low and variable crop yield. Fourteen elite groundnut genotypes were examined in 14 environments to analyze adaptability and stability of genotypes, and identify mega-environments if they exist. Additive main effect and multiplicative interaction (AMMI) model, cultivar-superiority measure, and genotype plus genotype-by-environment (GGE) biplot analysis were used for data analysis. The environment (69.8%) and genotype-by-environment interaction (GEI) effects (21.4%) were dominating the genotypic effect (8.8%). The GEI was significant (P < 0.01), and two distinct environments (mega-environments) were identified, suggesting separate national groundnut breeding strategies for Babile and Pawe. ICGV-94100 and ICGV-97156 were stable and had the highest-yield at Babile and Pawe, respectively. The higher heritability value was recorded in more homogeneous and favorable environments, indicating the genetic potential of groundnut genotypes were better attained in more homogeneous and favorable environments. AMMI model, cultivar-superiority measure, and GGE biplots were helpful methodologies and complemented each other to evaluate the adaptability and stability of groundnut genotypes in diverse environments.

SSR markers associated to early leaf spot disease resistance through selective genotyping and single marker analysis in groundnut (Arachis hypogaea L.)

Groundnut (Arachis hypogaea L.) is an important oilseed and food crop of the world. Breeding for disease resistance is one of major objectives in groundnut breeding. Early leaf spot (ELS) is one of the major destructive diseases worldwide and in West Africa, particularly in Burkina Faso causing significant yield losses. Conventional breeding approaches have been employed to develop improved varieties resistant to ELS. Molecular dissection of resistance traits using QTL analysis can improve the efficiency of resistance breeding. In the present study, an ELS susceptible genotype QH243C and an ELS resistant genotype NAMA were crossed and the F2 population genotypic and F3 progenies phenotypic data were used for marker-trait association analysis. Parents were surveyed with 179 simple sequence repeat (SSR) markers out of which 103 SSR markers were found to be polymorphic between the parents. These polymorphic markers were utilized to genotype the F2 population followed by marker-trait analysis through single marker analysis (SMA) and selective genotyping of the population using 23 resistant and 23 susceptible genotypes. The SMA revealed 13 markers while the selective genotyping method identified 8 markers associated with ELS resistance. Four markers (GM1911, GM1883, GM1000 and Seq13E09) were found common between the two trait mapping methods. These four markers could be employed in genomics-assisted breeding for selection of ELS resistant genotypes in groundnut breeding.

Molecular Mapping of Oil Content and Fatty Acids Using Dense Genetic Maps in Groundnut (Arachis hypogaea L.).

Enhancing seed oil content with desirable fatty acid composition is one of the most important objectives of groundnut breeding programs globally. Genomics-assisted breeding facilitates combining multiple traits faster, however, requires linked markers. In this context, we have developed two different F2 mapping populations, one for oil content (OC-population, ICGV 07368 × ICGV 06420) and another for fatty acid composition (FA-population, ICGV 06420 × SunOleic 95R). These two populations were phenotyped for respective traits and genotyped using Diversity Array Technology (DArT) and DArTseq genotyping platforms. Two genetic maps were developed with 854 (OC-population) and 1,435 (FA-population) marker loci with total map distance of 3,526 and 1,869 cM, respectively. Quantitative trait locus (QTL) analysis using genotyping and phenotyping data identified eight QTLs for oil content including two major QTLs, qOc-A10 and qOc-A02, with 22.11 and 10.37% phenotypic variance explained (PVE), respectively. For seven different fatty acids, a total of 21 QTLs with 7.6–78.6% PVE were identified and 20 of these QTLs were of major effect. Two mutant alleles, ahFAD2B and ahFAD2A, also had 18.44 and 10.78% PVE for palmitic acid, in addition to oleic (33.8 and 17.4% PVE) and linoleic (41.0 and 19.5% PVE) acids. Furthermore, four QTL clusters harboring more than three QTLs for fatty acids were identified on the three LGs. The QTLs identified in this study could be further dissected for candidate gene discovery and development of diagnostic markers for breeding improved groundnut varieties with high oil content and desirable oil quality.

Development and Evaluation of a High Density Genotyping \u2018Axiom_Arachis\u2019 Array with 58\u2009K SNPs for Accelerating Genetics and Breeding in Groundnut

Single nucleotide polymorphisms (SNPs) are the most abundant DNA sequence variation in the genomes which can be used to associate genotypic variation to the phenotype. Therefore, availability of a high-density SNP array with uniform genome coverage can advance genetic studies and breeding applications. Here we report the development of a high-density SNP array ‘Axiom_Arachis’ with 58 K SNPs and its utility in groundnut genetic diversity study. In this context, from a total of 163,782 SNPs derived from DNA resequencing and RNA-sequencing of 41 groundnut accessions and wild diploid ancestors, a total of 58,233 unique and informative SNPs were selected for developing the array. In addition to cultivated groundnuts (Arachis hypogaea), fair representation was kept for other diploids (A. duranensis, A. stenosperma, A. cardenasii, A. magna and A. batizocoi). Genotyping of the groundnut ‘Reference Set’ containing 300 genotypes identified 44,424 polymorphic SNPs and genetic diversity analysis provided in-depth insights into the genetic architecture of this material. The availability of the high-density SNP array ‘Axiom_Arachis’ with 58 K SNPs will accelerate the process of high resolution trait genetics and molecular breeding in cultivated groundnut.

Variation, Correlation and Path-Coefficient Study in Groundnut Breeding Lines of Odisha

Thirty two F6 progenies with along with 4 released varieties as parents were evaluated in R.B.D for yield and its component traits grown in rabi season showed a wide range of variation in all the 10 morphometric traits including yield. The genotypic source of variations were highly significant (at 1% level) for all the traits. The P.C.V. and G.C.V. estimates were high for haulm yield per plant and low for harvest index and shelling percent. The rest of the characters exhibited medium PCV and GCV. However, low values of G.C.V. were observed in shelling percentage and harvest index indicated that they are controlled largely by non-additive gene action and selection would be less effective, so there is need to create variability either by hybridization or mutation followed by selection. High heritability and high genetic advance indicated that these traits are mainly governed by additive gene action. Hence, improvement of these traits would be more effective through the phenotypic selection. Moderate heritability and genetic advance (GAM) as percent of mean for plant height, pod number per plant, kernel number per plant, kernel yield and pod yield indicated the additive and non additive gene actions for these traits and phenotypic selection would be effective to some extent. Kernel yield per plant had the highest direct positive effects on pod yield per plant followed by number of kernels per plant and 100 kernel weight. All other characters through these three characters made major indirect contribution towards pod yield. Plant height, number of branches per plant and number of pods per plant exhibited greater influence on pod yield per plant via kernel number per plant and kernel yield per plant. Haulm yield and harvest index influenced indirectly on pod yield through kernel weight and kernel number respectively. Present study thus indicated that kernel yield per plant, number of kernels per plant, hundred kernel weight followed by plant height and number of branches per plant were identified as the most important yield components and due emphasis should be placed on these characters while selecting for high yielding genotypes in Spanish bunch groundnut. But OGZ5 and OGZ6 recorded highest pod and kernel yield per plant with haulm yield although exhibited moderate chlorophyll and protein values is due to the balance in the physiological parameters contributing towards yield. Chlorophyll, protein and yield were not related in the same magnitude and direction in all the crosses. OGZ5 & OGZ6 may be identified as promising line for high protein content (25%) and (31%) with moderate chlorophyll and higher yield. Out of 36 genotypes evaluated the genotypes like OGZ5, OGZ2, R 2001-3A, OGZ6 and OGX4 were sorted out to be promising in respect of high yield. The higher productivity in these promising lines is due to a combination of various morpho- physiological traits and which could be ascribed as the basis of potential productivity in groundnut. High yield of different promising entries could be attributed to taller plant height, moderate to high number of branches /plant and number of pods per plant and moderately high 100 kernel weight, may serve as the basis of yield vigour which could be utilized as important selection criteria for prediction and realization of high yield in groundnut.

Profitability of groundnut-based cropping systems among farmers in Hong local government area of Adamawa state, Nigeria

Groundnut is an important cash crop and a good source of vegetable oil to resource-poor farmers. The study examined the Profitability of Groundnut–based Cropping Systems among farmers in Hong Local Government Area of Adamawa State, Nigeria. Specifically, the socio-economic characteristics of the farmers were described, their cropping systems identified, and the profitability of groundnut-based cropping systems determined. Multi-stage random sampling was used in selecting one hundred and twenty respondents used for the study. Data collected were analyzed using descriptive statistics, gross margin and profitability ratios. The result of the analysis revealed that majority (60%) of the farmers were female, having an average household size of 8 people and had some level of formal education. Two groundnut-based cropping systems were identified, namely; groundnut/sorghum and sole groundnut cropping systems. The analysis of cost and returns revealed a total variable cost of N18,931.68/ha in groundnut/sorghum enterprise, while that of sole groundnut enterprise was N20,244.40/ha. On the returns from production, the total revenue from groundnut/sorghum production was N66,273.950/ha while that of sole groundnut enterprise was N77,319.40/ha. The profit from groundnut/sorghum production was N47,324.27/ha, while that of sole groundnut production was N57,075.00/ha indicating the later to be more profitable than the former. Sole groundnut production had higher profitability index, higher rate of return on investment and higher rate of return on variable cost than groundnut/sorghum production. Based on the findings the study recommended that farmers cultivate groundnut solely. Government and donor agencies should encourage groundnut breeding researches so as to raise the productivity of existing groundnut seeds. KEYWORDS : Groundnut, Production, Cropping System, Profitability

Potential of Kersting’s groundnut [Macrotyloma geocarpum (Harms) Maréchal &amp; Baudet] and prospects for its promotion

Kersting’s groundnut is a tropical crop, highly nutritious, adapted to drought-prone areas. The crop is neglected both by researchers and by policy makers. This paper aimed at providing relevant information on the current status of the crop and the prospects to promote its improvement and production. To this end, available papers addressing any of the following aspect: distribution, nutritional value, cropping systems, post-harvest processing, usages, value chains, conservation status, genetic diversity and improvement of Kersting’s groundnut were reviewed. In West Africa, the crop provides substantial income for rural population. Kersting’s groundnut has several medicinal uses and cultural values as well. However, because of its intensive labor requirement, low yield and non-availability of improved varieties, its cultivation is declining and it is even disappearing gradually in some growing areas. The promotion of the crop’s value chains is an option for reversing the declining trend in Kersting’s groundnut cultivation. In recent years, some progress has been recorded in the collection, characterization and ex situ conservation of the crop. Thus, there are currently about 100 accessions conserved in various gene banks in Benin, Ghana, France and Belgium. This is still insufficient as compared to the genetic resources available in ex situ for most of the grown legume crops. To cope with this, extensive germplasm collection and their systematic characterization and evaluation coupled with new generation genomic tools need to be undertaken. For this purpose, genomic resources developed for Kersting’s groundnut-related species will be valuable assets. The exploitation of genomic resources will enable the development of core and mini-core collections for conservation and breeding purposes. In addition, the use of genomic resources will speed up Kersting’s groundnut breeding programs. Furthermore, the genetic base of the crop is extremely narrow and there is a need to broaden it for substantial genetic gain in breeding programs. For this purpose, mutation induction has been proposed as technique to increase variability in the Kersting’s groundnut germplasm. Invest in Kersting’s groundnut research is key to ensure the conservation and exploit the potential of the crop.

Towards a genotypic adaptation strategy for Indian groundnut cultivation using an ensemble of crop simulations

Climate change has been projected to significantly affect agricultural productivity and hence food availability in the coming decades. The uncertainty associated with projecting climate change impacts is a barrier to agricultural adaptation. Despite uncertainty quantification becoming more prominent in impact studies, the thorough quantification of more than one uncertainty source is not commonly exercised. This work focuses on Indian groundnut and uses the General Large Area Model for annual crops (GLAM) to investigate the response of groundnut under future climate scenarios, develop a genotypic adaptation strategy, and quantify the main uncertainty sources. Results suggest that despite large uncertainty in yield projections (to which crop- and climate-related sources contribute 46 and 54 %, respectively) no-regret strategies are possible for Indian groundnut. Benefits from genotypic adaptation were robust towards the choice of climate model, crop model parameters and bias-correction methods. Groundnut breeding for 2030 climates should be oriented toward increasing maximum photosynthetic rates, total assimilate partitioned to seeds, and, where enough soil moisture is available, also maximum transpiration rates. No benefit from enhanced heat stress tolerance was observed, though this trait may become important as warming intensifies. Managing yield variability remains a challenge for groundnut, suggesting that an integral approach to crop adaptation that includes year-to-year coping strategies as well as improvements in crop management is needed across all India.

Use of microsatellite markers for the assessment of bambara groundnut breeding system and varietal purity before genome sequencing.

Maximizing the research output from a limited investment is often the major challenge for minor and underutilized crops. However, such crops may be tolerant to biotic and abiotic stresses and are adapted to local, marginal, and low-input environments. Their development through breeding will provide an important resource for future agricultural system resilience and diversification in the context of changing climates and the need to achieve food security. The African Orphan Crops Consortium recognizes the values of genomic resources in facilitating the improvement of such crops. Prior to beginning genome sequencing there is a need for an assessment of line varietal purity and to estimate any residual heterozygosity. Here we present an example from bambara groundnut (Vigna subterranea (L.) Verdc.), an underutilized drought tolerant African legume. Two released varieties from Zimbabwe, identified as potential genotypes for whole genome sequencing (WGS), were genotyped with 20 species-specific SSR markers. The results indicate that the cultivars are actually a mix of related inbred genotypes, and the analysis allowed a strategy of single plant selection to be used to generate non-heterogeneous DNA for WGS. The markers also confirmed very low levels of heterozygosity within individual plants. The application of a pre-screen using co-dominant microsatellite markers is expected to substantially improve the genome assembly, compared to a cultivar bulking approach that could have been adopted.

Construction of a genetic linkage map and QTL analysis in bambara groundnut.

Bambara groundnut (Vigna subterranea (L.) Verdc.) is an indigenous underutilized legume that has the potential to improve food security in semi-arid Africa. So far, there are a lack of reports of controlled breeding populations that could be used for variety development and genetic studies. We report here the construction of the first genetic linkage map of bambara groundnut using a F3 population derived from a "narrow" cross between two domesticated landraces (Tiga Nicuru and DipC) with marked divergence in phenotypic traits. The map consists of 238 DArT array and SSR based markers in 21 linkage groups with a total genetic distance of 608.3 cM. In addition, phenotypic traits were evaluated for a quantitative trait loci (QTL) analysis over two generations. A total of 36 significant QTLs were detected for 19 traits. The phenotypic effect explained by a single QTL ranged from 11.6% to 49.9%. Two stable QTLs were mapped for internode length and growth habit. The identified QTLs could be useful for marker-assisted selection in bambara groundnut breeding programmes.

Genomic Tools in Groundnut Breeding Program: Status and Perspectives.

Groundnut, a nutrient-rich food legume, is cultivated world over. It is valued for its good quality cooking oil, energy and protein rich food, and nutrient-rich fodder. Globally, groundnut improvement programs have developed varieties to meet the preferences of farmers, traders, processors, and consumers. Enhanced yield, tolerance to biotic and abiotic stresses and quality parameters have been the target traits. Spurt in genetic information of groundnut was facilitated by development of molecular markers, genetic, and physical maps, generation of expressed sequence tags (EST), discovery of genes, and identification of quantitative trait loci (QTL) for some important biotic and abiotic stresses and quality traits. The first groundnut variety developed using marker assisted breeding (MAB) was registered in 2003. Since then, USA, China, Japan, and India have begun to use genomic tools in routine groundnut improvement programs. Introgression lines that combine foliar fungal disease resistance and early maturity were developed using MAB. Establishment of marker-trait associations (MTA) paved way to integrate genomic tools in groundnut breeding for accelerated genetic gain. Genomic Selection (GS) tools are employed to improve drought tolerance and pod yield, governed by several minor effect QTLs. Draft genome sequence and low cost genotyping tools such as genotyping by sequencing (GBS) are expected to accelerate use of genomic tools to enhance genetic gains for target traits in groundnut.

Gene effects for resistance to groundnut rossette disease in exotic Valencia groundnuts

Two exotic Valencia groundnut ( Arachis hypogaea L.) breeding lines (NuMex-M 3 and Valencia C) with superior characteristics were introduced by National Legume Improvement Program at the National Semi-Arid Resources Research Institute (NaSARRI), from the United States of America, to broaden the Valencia germplasm base in Uganda. The materials were evaluated for biotic and abiotic stresses, but succumbed to groundnut rosette disease (GRD). For these superior lines to find utility in Uganda, they need further improvement by introducing resistance genes to GRD. A study was conducted at NaSARRI to determine nature of gene action controlling resistance to GRD, using the Exotic Valencia groundnut breeding materials. Six generations that included F 1 , F 2 , BC 1 P 1 and BC 1 P 2 populations, together with their parents (P 1 and P 2 ) of each of the six crosses, namely Valencia C (P 1 ) × ICGV-SM 90704 (P 2 ), Valencia C (P 1 ) × ICGV-SM 96801(P 2 ), Valencia C (P 1 ) × ICGV-SM 99566 (P 2 ), NuMex-M 3 (P 1 ) × ICGV-SM 90704 (P 2 ), NuMex-M 3 × ICGV-SM 96801 (P 2 ), and NuMex-M 3 (P 1 ) × ICGVSM 99566 (P 2 ), were evaluated for GRD resistance.The study reaveled additive and non-additive gene effects in the control of GRD resistance.Three types of epistatic gene effects, viz . additive × additive [i], additive × dominance [j] and dominance × dominance [l],were exhibited tocontrol GRD resistance. The component dominance × dominance [l] was more predominant in Valencia C × ICGV-SM 96801, NuMex-M 3 × ICGV-SM 96801, NuMex- M 3 × ICGV-SM 90704, NuMex-M 3 × ICGV-SM 99566 and Valencia C × ICGV-SM 99566 crosses. Opposite and significant signs of dominance [d] and dominance × dominance [l] components indicated the importance of duplicate epitasis in the latter crosses in the control of GRD resistance, which revealed a complex nature of inheritance of GRD resistance. Keywords: Arachis hypogaea , gene effects, GRD resistance