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ABSTRACT: Although an important oil crop, peanut has only 162,030 expressed sequence tags (ESTs) publicly available, 86,943 of which are from cultivated plants. More ESTs from cultivated peanuts are needed for isolation of stress-resistant, tissue-specific and developmentally important genes. Here, we generated 63,234 ESTs from our 5 constructed peanut cDNA libraries of Ralstonia solanacearum challenged roots, R. solanacearum challenged leaves, and unchallenged cultured peanut roots, leaves and developing seeds. Among these ESTs, there were 14,547 unique sequences with 7,961 tentative consensus sequences and 6,586 singletons. Putative functions for 47.8 % of the sequences were identified, including transcription factors, tissue-specific genes, genes involved in fatty acid biosynthesis and oil formation regulation, and resistance gene analogue genes. Additionally, differentially expressed genes, including those involved in ethylene and jasmonic acid signal transduction pathways, from both peanut leaves and roots, were identified in R. solanacearum challenged samples. This large expression dataset from different peanut tissues will be a valuable source for marker development and gene expression analysis. It will also be helpful for finding candidate genes for fatty acid synthesis and oil formation regulation as well as for studying mechanisms of interactions between the peanut host and R. solanacearum pathogen.
Journal of Plant Research 05/2012; · 1.75 Impact Factor
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ABSTRACT: The Arachis genus is native to South America, and contains 70–80 described species assembled into nine sections. A better understanding
of the level of speciation and taxonomic relationships is a prerequisite to the effective use of Arachis species in peanut breeding programs. Forty-eight genotypes representing 19 species in 6 sections were evaluated to assay
the genetic variability within and among species, and 10 recombinant lines and those parents were identified with introgression
of Arachis species chromosome segments into A.
hypogaea genome using SRAP markers. Sixty of sixty-four SRAP primers tested were selected for DNA amplification reactions. A dendrogram
and principal component analysis were constructed based on 353 SRAP polymorphic bands of the accessions. The number of scored
polymorphic bands per each primer combination varied from 1 to 25 with an average of 5.9 per reaction. Estimates of genetic
distance among the 48 accessions Arachis species ranged from 0.11 to 0.76. A-genome accessions 475845 (A. duranensis), and 331197 (A. villosa) were most closely associated to A.
hypogaea. The first two PCAs accounted for 77.74% (62.02 and 15.72%) of the total variation observed and separated the different genomic
groups. SRAPs also identified introgression of Arachis species chromosome segments into A.
hypogaea. genome with 10 recombinant lines and those parents. The present results indicated that SRAPs can be used to determine the
genetic relationships among species of the different sections of the genus Arachis and to identify introgression of Arachis genus chromosome segments into A.
hypogaea genome.
KeywordsArachis genus-Genomic affinities-Interspecific hybrids-SRAP
Genetic Resources and Crop Evolution 04/2012; 57(6):903-913. · 1.55 Impact Factor
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ABSTRACT: The peanut (Arachis hypogaea) is an important oil crop. Breeding for high oil content is becoming increasingly important. Wild Arachis species have been reported to harbor genes for many valuable traits that may enable the improvement of cultivated Arachis hypogaea, such as resistance to pests and disease. However, only limited information is available on variation in oil content. In the present study, a collection of 72 wild Arachis accessions representing 19 species and 3 cultivated peanut accessions were genotyped using 136 genome-wide SSR markers and phenotyped for oil content over three growing seasons. The wild Arachis accessions showed abundant diversity across the 19 species. A. duranensis exhibited the highest diversity, with a Shannon-Weaver diversity index of 0.35. A total of 129 unique alleles were detected in the species studied. A. rigonii exhibited the largest number of unique alleles (75), indicating that this species is highly differentiated. AMOVA and genetic distance analyses confirmed the genetic differentiation between the wild Arachis species. The majority of SSR alleles were detected exclusively in the wild species and not in A. hypogaea, indicating that directional selection or the hitchhiking effect has played an important role in the domestication of the cultivated peanut. The 75 accessions were grouped into three clusters based on population structure and phylogenic analysis, consistent with their taxonomic sections, species and genome types. A. villosa and A. batizocoi were grouped with A. hypogaea, suggesting the close relationship between these two diploid wild species and the cultivated peanut. Considerable phenotypic variation in oil content was observed among different sections and species. Nine alleles were identified as associated with oil content based on association analysis, of these, three alleles were associated with higher oil content but were absent in the cultivated peanut. The results demonstrated that there is great potential to increase the oil content in A. hypogaea by using the wild Arachis germplasm.
PLoS ONE 01/2012; 7(11):e50002. · 4.09 Impact Factor
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ABSTRACT: Bacterial wilt (BW) caused by Ralstonia solanacearum is an important constraint to peanut (Arachis hypogaea L.) production in several Asian and African countries, and planting BW-resistant cultivars is the most feasible method for controlling the disease. Although several BW-resistant peanut germplasm accessions have been identified, the genetic diversity among these has not been properly investigated, which has impeded efficient utilization. In this study, the genetic relationships of 31 peanut genotypes with various levels of resistance to BW were assessed based on SSR and AFLP analyses. Twenty-nine of 78 SSR primers and 32 of 126 AFLP primer combinations employed in this study were polymorphic amongst the peanut genotypes tested. The SSR primers amplified 91 polymorphic loci in total with an average of 3.14 alleles per primer, and the AFLP primers amplified 72 polymorphic loci in total with an average of 2.25 alleles per primer. Four SSR primers (14H06, 7G02, 3A8, 16C6) and one AFLP primer (P1M62) were found to be most efficient in detecting diversity. The genetic distance between pairs of genotypes ranged from 0.12 to 0.94 with an average of 0.53 in the SSR data and from 0.06 to 0.57 with an average of 0.25 in the AFLP data. The SSR-based estimates of the genetic distance were generally larger than that based on the AFLP data. The genotypes belonging to subsp. fastigiata possessed wider diversity than that of subsp. hypogaea. The clustering of genotypes based on the SSR and AFLP data were similar but the SSR clustering was more consistent with morphological classification of A. hypogaea. Optimum diverse genotypes of both subsp. hypogaea and subsp. fastigiata can be recommended based on this analysis for developing mapping populations and breeding for high yielding and resistant cultivars.
Journal of Genetics and Genomics 07/2007; 34(6):544-54. · 1.88 Impact Factor
