Traits In Peanut Research Articles

Identification of main effect and epistatic quantitative trait loci for morphological and yield-related traits in peanut (Arachis hypogaea L.)

An effort was made in the present study to identify the main effect and epistatic quantitative trait locus (QTL) for the morphological and yield-related traits in peanut. A recombinant inbred line (RIL) population derived from TAG 24 × GPBD 4 was phenotyped in seven environments at two locations. QTL analysis with available genetic map identified 62 main-effect QTLs (M-QTLs) for ten morphological and yield-related traits with the phenotypic variance explained (PVE) of 3.84–15.06%. Six major QTLs (PVE > 10%) were detected for PLHT, PPP, YPP, and SLNG. Stable M-QTLs appearing in at least two environments were detected for PLHT, LLN, YPP, YKGH, and HSW. Five M-QTLs governed two traits each, and 16 genomic regions showed co-localization of two to four M-QTLs. Intriguingly, a major QTL reported to be linked to rust resistance showed pleiotropic effect for yield-attributing traits like YPP (15.06%, PVE) and SLNG (13.40%, PVE). Of the 24 epistatic interactions identified across the traits, five interactions involved six M-QTLs. Three interactions were additive × additive and remaining two involved QTL × environment (QE) interactions. Only one major M-QTL governing PLHT showed epistatic interaction. Overall, this study identified the major M-QTLs for the important productivity traits and also described the lack of epistatic interactions for majority of them so that they can be conveniently employed in peanut breeding.

Identification of transposable element markers associated with yield and quality traits from an association panel of independent mutants in peanut (Arachis hypogaea L.)

To identify marker–trait associations (MTAs) for yield and quality traits in peanut, genic and nongenic Arachis hypogaea transposable element (AhTE) markers were employed in a population consisting of independent mutants from several parents. The population was field-evaluated during the rainy seasons of 2014 and 2015, and genotyped with 110 AhTE markers to check the polymorphisms for AhMITE1 transposition. The gene diversity index ranged from 0.00 to 0.50 with average of 0.35, indicating low to moderate genetic diversity in the population. Diversity analysis indicated the grouping of mutants derived from each parent in respective subgroups. Marker–trait association analysis for 110 markers and 40 traits resulted in 132 highly significant MTAs, represented by 58 AhTE markers for 39 traits. Nutritional traits recorded the highest number of MTAs (38), followed by agronomic traits (35), productivity traits (31), foliar disease resistance (23), and taxonomic traits (5). Seventeen MTAs with phenotypic variance explained (PVE) value above 50 % were observed for resistance to late leaf spot (LLS) and rust, plant height, and pod width. The genic and nongenic AhTE markers associated with the above traits were analyzed for their genomic location and functional annotation so that the significance of these loci can be analyzed in the future.

Chromosomes A07 and A05 associated with stable and major QTLs for pod weight and size in cultivated peanut (Arachis hypogaea L.).

Co-localized intervals and candidate genes were identified for major and stable QTLs controlling pod weight and size on chromosomes A07 and A05 in an RIL population across four environments. Cultivated peanut (Arachis hypogaea L.) is an important legume crops grown in>100 countries. Hundred-pod weight (HPW) is an important yield trait in peanut, but its underlying genetic mechanism was not well studied. In this study, a mapping population (Xuhua 13×Zhonghua 6) with 187 recombinant inbred lines (RILs) was developed to map quantitative trait loci (QTLs) for HPW together with pod length (PL) and pod width (PW) by both unconditional and conditional QTL analyses. A genetic map covering 1756.48cM was constructed with 817 markers. Additive effects, epistatic interactions, and genotype-by-environment interactions were analyzed using the phenotyping data generated across four environments. Twelve additive QTLs were identified on chromosomes A05, A07, and A08 by unconditional analysis, and five of them (qPLA07, qPLA05.1, qPWA07, qHPWA07.1, and qHPWA05.2) showed major and stable expressions in all environments. Conditional QTL mapping found that PL had stronger influences on HPW than PW. Notably, qHPWA07.1, qPLA07, and qPWA07 that explained 17.93-43.63% of the phenotypic variations of the three traits were co-localized in a 5cM interval (1.48Mb in physical map) on chromosome A07 with 147 candidate genes related to catalytic activity and metabolic process. In addition, qHPWA05.2 and qPLA05.1 were co-localized with minor QTL qPWA05.2 to a 1.3cM genetic interval (280kb in physical map) on chromosome A05 with 12 candidate genes. This study provides a comprehensive characterization of the genetic components controlling pod weight and size as well as candidate QTLs and genes for improving pod yield in future peanut breeding.

Genome-Wide Association Study of Major Agronomic Traits Related to Domestication in Peanut.

Peanut (Arachis hypogaea) consists of two subspecies, hypogaea and fastigiata, and has been cultivated worldwide for hundreds of years. Here, 158 peanut accessions were selected to dissect the molecular footprint of agronomic traits related to domestication using specific-locus amplified fragment sequencing (SLAF-seq method). Then, a total of 17,338 high-quality single nucleotide polymorphisms (SNPs) in the whole peanut genome were revealed. Eleven agronomic traits in 158 peanut accessions were subsequently analyzed using genome-wide association studies (GWAS). Candidate genes responsible for corresponding traits were then analyzed in genomic regions surrounding the peak SNPs, and 1,429 genes were found within 200 kb windows centerd on GWAS-identified peak SNPs related to domestication. Highly differentiated genomic regions were observed between hypogaea and fastigiata accessions using FST values and sequence diversity (π) ratios. Among the 1,429 genes, 662 were located on chromosome A3, suggesting the presence of major selective sweeps caused by artificial selection during long domestication. These findings provide a promising insight into the complicated genetic architecture of domestication-related traits in peanut, and reveal whole-genome SNP markers of beneficial candidate genes for marker-assisted selection (MAS) in future breeding programs.

Novel Mutations in Oleoyl‐PC Desaturase (ahFAD2B) Identified from New High Oleic Mutants Induced by Gamma Rays in Peanut

To diversify the sources of the high‐oleate trait in peanut (Arachis hypogaea L.), the broad‐based interspecific derivative with inherent resistance to major foliar diseases, GPBD‐4, was subjected to chemical (ethyl methanesulfonate) and physical (γ rays) mutagenesis, resulting in significant variation in fatty acid profile of mutant progenies as tested by gas chromatography in advanced (M4) generations. From these mutant progenies, two stable high‐oleic (>70%) mutant lines, GM 4‐3 and GM 6‐1, were chosen for molecular characterization of ahFAD2B by cloning and sequencing. We report here the identification of two novel mutations (1085A‐G and 1111G‐A) in oleoyl‐PC desaturase (ahFAD2B) of high‐oleic mutant line GM 6‐1 and the latter single transition 1111G‐A in another high‐oleic mutant line GM 4‐3. The deduced amino acid sequence comparison of the parental genotype, GPBD‐4, with normal‐oleic (∼50%) and high‐oleic (>70%) mutant lines indicated the common change from glycine to serine at 372 from start codon due to the common single‐nucleotide polymorphism (SNP, 1111G‐A) observed in both the high‐oleic mutant lines. Another amino acid change from glutamate to glycine was also found in the mutant line GM 6‐1 because of the additional SNP it had at 1085A‐G in the coding region of ahFAD2B. These novel mutations identified in the new high‐oleic mutant lines could be used for marker‐assisted selection for the high‐oleate trait, and these foliar disease‐resistant, high‐oleic mutant lines could serve as additional valuable genetic resources for oil quality improvement in future peanut breeding programs.

Response of Peanut to Nitrogen Fertilizer Levels and Foliar Zinc Spraying Rates in Newly Reclaimed Sandy Soils

Two field experiments were conducted at the Farm of the Faculty of Agriculture, Demo, Fayoum University, Egypt, during 2014 and 2015 summer growing seasons to study the effect of three nitrogen levels i.e., 15, 30 and 45 kg N fad-1 (fad=4200 m2) and foliar spraying with zinc rates i. e. (Zero, Water as a control), 50, 0.75 and 1.00 g Zn L-1 on yield and its attributes of peanuts (variety Giza 6). The experimental design was a split - plot in RCBD with three replications, where nitrogen levels and foliar spraying of zinc rates were allocated in the main and sub plots, respectively.1- The adopted either N levels or Zn foliar application rates and their interactions significantly influenced all measured parameters in 1st and 2nd seasons. Increasing N levels up to 45 kg N fad-1 significantly increased most measured characteristics namely, seed, straw and pod yields, number of pods plant-1, weight of pods plant-1, number of seeds plant-1, weight of seeds plant-1, weight of 100 pods and weight of 100 seed, seed oil yield, N%, protein %, and protein yield of groundnut in1st and 2nd seasons. On the contrary, seed oil % and N- use Efficiency traits exhibited different trend, where the values significantly decreased with increasing N levels. 2-The assessed Zn foliar application rates, up to 1.00 g L-1 resulted in gradual significant increases for the abovementioned characteristics.3- Regarding the interaction effect, it is obvious that most peanut traits under study e.g. yield, yield attributes and quality exhibited higher values due to the interaction of 45 KNfed-1 level and foliar Zn application at 1.00 gL-1 rate. Due to the mentioned interaction, pod yield (t fed-1) and seed oil (%) parameters, as an average of both seasons, amounted to 2.51 t fed-1 and 47.89%, respectively. Likely, number ofseed plant-1 exhibited similar trend with value comprised to 58.00 in 1st season. In addition, number of pod plant-1, seed yield (t fed-1), seed oil yield (t fed-1) and seed protein % with values reached to 34.67, 1.58, 0.76 and 26.10%, respectively, in 2nd season. 4- Positive and highly significant correlations were obtained between oil yield ton fed-1 and seed yield ton fed-1, r = 0.995** and 0.992**. Negative and highly significant correlations were obtained between seed yield ton fed-1 and seed oil % equals - 0.539** and - 0.691**, respectively, in 1st and 2nd seasons.

Genetic mapping of yield traits using RIL population derived from Fuchuan Dahuasheng and ICG6375 of peanut (Arachis hypogaea L.)

The genetic architecture determinants of yield traits in peanut (Arachis hypogaea L.) are poorly understood. In the present study, an effort was made to map quantitative trait loci (QTLs) for yield traits using recombinant inbred lines (RIL). A genetic linkage map was constructed containing 609 loci, covering a total of 1557.48 cM with an average distance of 2.56 cM between adjacent markers. The present map exhibited good collinearity with the physical map of diploid species of Arachis. Ninety-two repeatable QTLs were identified for 11 traits including height of main stem, total branching number, and nine pod- and seed-related traits. Of the 92 QTLs, 15 QTLs were expressed across three environments and 65 QTLs were newly identified. Twelve QTLs for the height of main stem and the pod- and seed-related traits explaining more than 10 % of phenotypic variation showed a great potential for marker-assisted selection in improving these traits. The trait-by-trait meta-analysis revealed 33 consensus QTLs. The consensus QTLs and other QTLs were further integrated into 29 pleiotropic unique QTLs with the confidence interval of 1.86 cM on average. The significant co-localization of QTLs was consistent with the significant phenotypic correlations among these traits. The complexity of the genetic architecture of yield traits was demonstrated. The present QTLs for pod- and seed-related traits could be the most fundamental genetic factors contributing to the yield traits in peanut. The results provide a good foundation for fine mapping, cloning and designing molecular breeding of favorable genes in peanut.

Fog water harvesting providing stability for small Bedwe communities lives in North cost of Egypt

Water shortage is a serious problem faced by the national security of Egypt. Two field experiments were conducted at Marsa Matrouh Agricultural Research Farm during summer seasons of 2013 and 2014 using drip irrigation system, to evaluate the effect of some fog water harvesting models (f.w.h.m) of model-1, model-2, model-3 and model-4 under some farmyard manure (FYM) rates (20, 30, 40m3)/fad on groundnut productivity.Results cleared that model-1 exposed its superiority on the total water amount harvested during the two seasons that led to give significant greatest values of, pods, seeds yield/plant or /faddan, biological yield/fad., shelling %, seed and harvest index, seed protein and oil percentage and water use efficiency, and also that model confirmed its superiority and led to give the lowest percentage of number of seeds/pod, number of pods and seed/100 (g). It is worthy to mention that, (f.w.h) model-1 also led to enhance peanut yield as compared to the other (f.w.h.m) during the two experimental seasons. Results revealed that, increasing (FYM) improves the most values of the previous peanut traits significantly, during the two seasons, and on the other hand, peanut shelling %, number of pod and seeds per pod decreased significantly by increasing the added amount of (FYM) /fad.The interaction between f.w.h.m and (FYM) rates showed significant effect on, growing plant and per fad. Peanut plants under the condition of f.w.h model-1 fertilized by 30 or 40m3 of that fertilizer gave best significant values for most studied peanut traits compared with other treatments.

Fog Water Collection for Agriculture Use (Peanut Irrigation) Under Semi- Arid Region Conditions in North Coast of Egypt

Two field experiments were conducted at Marsa Matrouh Agricultural Research Farm during summer seasons of 2013 and 2014 using drip irrigation system, to evaluate the effect of some fog water harvesting models (f.w.h.m) of, (Double mesh had 220 stitches/cm2 (model-1), Single layer mesh touching each other had 220 stitches/cm2 (model-2), Double mesh had 120 stitches/cm2 (model-3) and Single layer mesh touching each other had 120 stitches /cm2 model-4) under some farmyard manure rates (20,30,40 m3)/fad on groundnut productivity. Results indicated that, there were differences between studied factor, (f.w.h) model-1, was significant exposed its superiority on the total water amount harvested it during the two seasons led to give significant greatest values of pods, seeds yield/ Fadden, biological yield/fad., seed and harvest index, and water use efficiency. It is worthy to mention that, also led to enhance yield as compared by the other (f.w.h.m) during the two experimental seasons. Results revealed that, by increasing the amount of the added farmyard manure to improve the most values of the previous peanut traits significantly, during the two seasons. The interaction effect between f.w.h.m and farmyard manure rates showed significant effect, grow in peanut plants under the condition of f.w.h model-1 and fed by 30 or 40 m3 of that fertilizer gave best significant values for most studied peanut traits compared with other treatments.

Leaf aquaporin transcript abundance in peanut genotypes diverging in expression of the limited-transpiration trait when subjected to differing vapor pressure deficits and aquaporin inhibitors.

A plant trait currently being exploited to decrease crop yield loss under water-deficit conditions is limited-transpiration rate (TRlim ) under high atmospheric vapor pressure deficit (VPD) conditions. Although limited genotype comparisons for the TRlim trait have been performed in peanut (Arachis hypogaea), no detailed study to describe the basis for this trait in peanut has been reported. Since it has been hypothesized that the TRlim trait may be a result of low leaf hydraulic conductance associated with aquaporins (AQPs), the first objective of this study was to examine a possible correlation of TRlim to leaf AQP transcriptional profiles in six peanut cultivars. Five of the studied cultivars were selected because they expressed TRlim while the cultivar York did not. Transcripts of six AQPs were measured. Under exposure to high vapor pressure deficit, cultivar C 76-16 had decreased AQP transcript abundance for four of the six AQPs but in York only one AQP had decreased abundance. The second objective was to explore the influence of AQP inhibitors mercury and silver on expression of TRlim and AQP transcription profiles. Quantitative RT-PCR data were compared in cultivars York and C 76-16, which had the extreme response in TR to VPD. Inhibitor treatment resulted in increased abundance of AQP transcripts in both. The results of these experiments indicate that AQP transcript abundance itself may not be useful in identifying genotypes expressing the TRlim trait under high VPD conditions.

Quantitative trait locus analysis of agronomic and quality-related traits in cultivated peanut (Arachis hypogaea L.).

Key message SSR-based QTL mapping provides useful information for map-based cloning of major QTLs and can be used to improve the agronomic and quality traits in cultivated peanut by marker-assisted selection. Cultivated peanut (Arachis hypogaea L.) is an allotetraploid species (AABB, 2n = 4× = 40), valued for its edible oil and digestible protein. Linkage mapping has been successfully conducted for most crops, and it has been applied to detect the quantitative trait loci (QTLs) of biotic and abiotic traits in peanut. However, the genetic basis of agronomic and quality-related traits remains unclear. In this study, high levels of phenotypic variation, broad-sense heritability and significant correlations were observed for agronomic and quality-related traits in an F 2:3 population. A genetic linkage map was constructed for cultivated peanut containing 470 simple sequence repeat (SSR) loci, with a total length of 1877.3 cM and average distance of 4.0 cM between flanking markers. For 10 agronomic traits, 24 QTLs were identified and each QTL explained 1.69–18.70 % of the phenotypic variance. For 8 quality-related traits, 12 QTLs were identified that explained 1.72–20.20 % of the phenotypic variance. Several QTLs for multiple traits were overlapped, reflecting the phenotypic correlation between these traits. The majority of QTLs exhibited obvious dominance or over-dominance effects on agronomic and quality traits, highlighting the importance of heterosis for breeding. A comparative analysis revealed genomic duplication and arrangement of peanut genome, which aids the assembly of scaffolds in genomic sequencing of Arachis hypogaea. Our QTL analysis results enabled us to clearly understand the genetic base of agronomic and quality traits in cultivated peanut, further accelerating the progress of map-based cloning of major QTLs and marker-assisted selection in future breeding.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-015-2493-1) contains supplementary material, which is available to authorized users.

The Effects of Irrigation Level and Genotype on Pod-Filling Related Traits in Peanut (Arachis hypogaea)

In peanut (Arachis hypogaea), pod-filling is an important biological stage that is strongly influenced by the availability of water. It also has genetic component; since genotypes vary considerably in their pod-filling potential. We studied the effects of irrigation level, genotype and the Irrigation Level × Genotype interaction on pod-filling and other pod-related traits of peanut. Four peanut genotypes, including three Virginia-types and one Peruvian-type which differ considerably in their pod-filling potential, were examined under field conditions. Four irrigation treatments were applied (60%, 80%, 100% and 120%) in a factorial experimental design. A significant irrigation-treatment effect was observed for the two main pod-filling related traits, meat content and dead-end ratio, in all of the genotypes studied. The irrigation level significantly affected gross pod weight, 100-pod weight and 100-seed weight, but did not have any significant effects on pod yield per plot or pod size distribution. Therefore, our study suggests that reduction in irrigation directly influence the developing pods, as a result of low water availability/potential in the pod’s surrounding environment. The effect of irrigation was most significant at the lowest irrigation level (60%); whereas a milder effect was observed in the 80% irrigation treatment, indicating that, in some cases, it is possible to reduce irrigation down to 80% without affecting the pod-filling components. Although the Irrigation × Genotype interaction was not statistically significant, some genotypes were found to be more strongly affected by the low-irrigation treatments. Also, irrigation level significantly affected the incidence of pod wart and the pod color variables, suggesting that higher irrigation should be applied in order to address these marketing-related traits. This trial serves as a fundamental study for understanding the pod-filling components that are influenced by the irrigation level in peanut.

Correction: Genomewide Association Studies for 50 Agronomic Traits in Peanut Using the ‘Reference Set’ Comprising 300 Genotypes from 48 Countries of the Semi-Arid Tropics of the World

Correction: Genomewide Association Studies for 50 Agronomic Traits in Peanut Using the ‘Reference Set’ Comprising 300 Genotypes from 48 Countries of the Semi-Arid Tropics of the World

Genomewide association studies for 50 agronomic traits in peanut using the 'reference set' comprising 300 genotypes from 48 countries of the semi-arid tropics of the world.

Peanut is an important and nutritious agricultural commodity and a livelihood of many small-holder farmers in the semi-arid tropics (SAT) of world which are facing serious production threats. Integration of genomics tools with on-going genetic improvement approaches is expected to facilitate accelerated development of improved cultivars. Therefore, high-resolution genotyping and multiple season phenotyping data for 50 important agronomic, disease and quality traits were generated on the ‘reference set’ of peanut. This study reports comprehensive analyses of allelic diversity, population structure, linkage disequilibrium (LD) decay and marker-trait association (MTA) in peanut. Distinctness of all the genotypes can be established by using either an unique allele detected by a single SSR or a combination of unique alleles by two or more than two SSR markers. As expected, DArT features (2.0 alleles/locus, 0.125 PIC) showed lower allele frequency and polymorphic information content (PIC) than SSRs (22.21 alleles /locus, 0.715 PIC). Both marker types clearly differentiated the genotypes of diploids from tetraploids. Multi-allelic SSRs identified three sub-groups (K = 3) while the LD simulation trend line based on squared-allele frequency correlations (r2) predicted LD decay of 15–20 cM in peanut genome. Detailed analysis identified a total of 524 highly significant MTAs (pvalue >2.1×10–6) with wide phenotypic variance (PV) range (5.81–90.09%) for 36 traits. These MTAs after validation may be deployed in improving biotic resistance, oil/ seed/ nutritional quality, drought tolerance related traits, and yield/ yield components.

Correlation between SSR Markers and Agronomic Traits in Peanut ( Arachis hypogaea L.)

Correlation between SSR Markers and Agronomic Traits in Peanut ( <i>Arachis hypogaea</i> L.)

Peanut antioxidants: Part 1. Genotypic variation and genotype-by-environment interaction in antioxidant capacity of raw kernels

The potential to select for antioxidant traits in peanut (Arachis hypogaea L.) kernels by conventional plant breeding was investigated by oxygen radical absorbance capacity (ORAC) assay of (a) 32 full-season maturity genotypes grown at Kairi Research Station in 2008/09; and (b) a subset of ten genotypes with diverse antioxidant capacities grown in five different production regions in Queensland in 2009/10 and 2010/11. There were significant levels of variation of more than 25% relative standard deviation (RSD) in antioxidant capacity among the 32 tested genotypes; and that genotype, environment, and genotype-by-environment (G × E) interaction all significantly (P < 0.05) affected trait expression. Analysis of the G × E data confirmed the heritability of antioxidant capacity, which has not been previously quantified, whereby genotype explained 44% of the phenotypic variation on a plot basis and 82% on an entry mean basis. This indicated that there was substantial genetic control of antioxidant capacity in peanut kernels, but also that it will be important to characterize environmental interaction to enable plant/seed selection in the Breeding Program. The research also highlighted the utility of the ORAC assay for screening germplasm and provided practical advice on design of varietal assessments using antioxidant screenings.

Heritability and Genetic Relationships for Drought‐Related Traits in Peanut

ABSTRACTWater‐use efficiency is often genetically correlated with specific leaf area (SLA) and leaf C isotopic composition (δ13C) in peanut (Arachis hypogaea L.). The objectives of this study were to examine the effects of environment, genotype, and genotype × environment interaction on SLA, δ13C, harvest index (HI), and yield and to estimate heritability and the genetic relationships. Fifteen genotypes were tested at two locations with different drought intensities for 2 yr. The additive main effects and multiplicative interaction analysis based on yield data divided eight environments (locations × treatments × years) into four clusters, which reflected a gradient in drought stress, indicating yield trait is a good indication of drought stress. The genotype Exp8‐12 was identified as a best drought tolerant germplasm across environments. Heritability estimates for HI (0.68 to 0.89) and δ13C (0.75 to 0.89) were higher than those for SLA (0.31 to 0.88) and yield (0.12 to 0.65). A positive but small genetic correlation coefficient (rg) (0.26) was found between HI and yield, and low to moderate rg (0.14 to 0.55) were observed between HI and SLA. A relative high negative genetic correlation rg (−0.81 to −0.57) was found between δ13C and yield. In theory, the high heritability and no G×E interaction for δ13C make it possible a surrogate that can be used to assess drought tolerance in peanut breeding.

Association of nitrogen fixation to water uses efficiency and yield traits of peanut

Improvement of N2 fixation might be an effective strategy in peanut breeding for high yield under drought stress conditions. However, under water limited conditions peanut varieties having high water-use efficiency (WUE) are favorable. A pot experiment was conducted under greenhouse conditions at Khon Kaen University, Thailand during December 2002 to May 2003, and repeated during June 2003 to November 2003. Twelve peanut genotypes were tested under three water regimes to estimate the relationships between N2 fixed with biomass production, WUE and pod yield under drought stress conditions. N2 fixed biomass production; pod yield and WUE were reduced by drought stress. At 2/3 AW, Tifton-8 and KK 60-3 were the best genotypes for high N2 fixed and high WUE. ICGV 98324 and ICGV 98300 had high pod yield, whereas Tifton-8 had low pod yield. N2 fixed was positively correlated with biomass and WUE under mild drought conditions but negatively correlated with pod yield. Tifton-8 was the best genotype for N2 fixed and WUE, but it was a poor performer for pod yield under drought conditions. ICGV 98324 and ICGV 98300 had higher pod yield with lower N2 fixed and WUE than did Tifton-8. Results indicated that N2 fixed under drought conditions contributed to vegetative growth and water use efficiency rather than to pod yield. Improvement for high N2 fixed in peanut could lead to high biomass production and WUE but may not necessarily improve pod yield under drought stress conditions.

The relationship between root traits and aboveground traits in peanut (Arachis hypogaea L.)

Data of 12 peanut varieties were analyzed with a view to investigate the relationship between root traits and aboveground traits. Results showed that root biomass was positively correlated with aboveground biomass and total biomass at three stages of growth and development. Root activity at different growth stages were significantly and positively correlated with yield at the mature stage. However, a significant negative correlation was observed between yield and root/shoot ratio at the mature stage. It was concluded that the root system possessed a close relationship with aboveground parts, and keeping the root activity of peanut at the mature stage was essential for achieving high and stable yield.

An integrated genetic linkage map of cultivated peanut (Arachis hypogaea L.) constructed from two RIL populations

Construction and improvement of a genetic map for peanut (Arachis hypogaea L.) continues to be an important task in order to facilitate quantitative trait locus (QTL) analysis and the development of tools for marker-assisted breeding. The objective of this study was to develop a comparative integrated map from two cultivated × cultivated recombinant inbred line (RIL) mapping populations and to apply in mapping Tomato spotted wilt virus (TSWV) resistance trait in peanut. A total of 4,576 simple sequence repeat (SSR) markers from three sources: published SSR markers, newly developed SSR markers from expressed sequence tags (EST) and from bacterial artificial chromosome end-sequences were used for screening polymorphisms. Two cleaved amplified polymorphic sequence markers were also included to differentiate ahFAD2A alleles and ahFAD2B alleles. A total of 324 markers were anchored on this integrated map covering 1,352.1 cM with 21 linkage groups (LGs). Combining information from duplicated loci between LGs and comparing with published diploid maps, seven homoeologous groups were defined and 17 LGs (A1-A10, B1-B4, B7, B8, and B9) were aligned to corresponding A-subgenome or B-subgenome of diploid progenitors. One reciprocal translocation was confirmed in the tetraploid-cultivated peanut genome. Several chromosomal rearrangements were observed by comparing with published cultivated peanut maps. High consistency with cultivated peanut maps derived from different populations may support this integrated map as a reliable reference map for peanut whole genome sequencing assembling. Further two major QTLs for TSWV resistance were identified for each RILs, which illustrated the application of this map.