54 research outputs found

    The first SSR-based genetic linkage map for cultivated groundnut (Arachis hypogaea L.)

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    Molecular markers and genetic linkage maps are pre-requisites for molecular breeding in any crop species. In case of peanut or groundnut (Arachis hypogaea L.), an amphidiploid (4X) species, not a single genetic map is, however, available based on a mapping population derived from cultivated genotypes. In order to develop a genetic linkage map for tetraploid cultivated groundnut, a total of 1,145 microsatellite or simple sequence repeat (SSR) markers available in public domain as well as unpublished markers from several sources were screened on two genotypes, TAG 24 and ICGV 86031 that are parents of a recombinant inbred line mapping population. As a result, 144 (12.6%) polymorphic markers were identified and these amplified a total of 150 loci. A total of 135 SSR loci could be mapped into 22 linkage groups (LGs). While six LGs had only two SSR loci, the other LGs contained 3 (LG_AhXV) to 15 (LG_AhVIII) loci. As the mapping population used for developing the genetic map segregates for drought tolerance traits, phenotyping data obtained for transpiration, transpiration efficiency, specific leaf area and SPAD chlorophyll meter reading (SCMR) for 2 years were analyzed together with genotyping data. Although, 2–5 QTLs for each trait mentioned above were identified, the phenotypic variation explained by these QTLs was in the range of 3.5–14.1%. In addition, alignment of two linkage groups (LGs) (LG_AhIII and LG_AhVI) of the developed genetic map was shown with available genetic maps of AA diploid genome of groundnut and Lotus and Medicago. The present study reports the construction of the first genetic map for cultivated groundnut and demonstrates its utility for molecular mapping of QTLs controlling drought tolerance related traits as well as establishing relationships with diploid AA genome of groundnut and model legume genome species. Therefore, the map should be useful for the community for a variety of applications

    Extraordinary high allelic diversity in a groundnut (Arachis hypogaea L.) germplasm collection assayed by robust and informative SSR markers

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    The ability to identify genetic variation is indispensable for effective management and use of genetic resources in crop breeding. Genetic variation among 189 groundnut..

    High level of natural variation in a groundnut (Arachis hypogaea L.) germplasm collection assayed by selected informative SSR markers

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    The ability to identify genetic variation is indispensable for effective management and use of genetic resources in crop breeding. Genetic variation among 189 groundnut (Arachis hypogaea L.) accessions comprising landraces, cultivars, a mutant, advanced breeding lines and others (unknown genetic background) representing 29 countries and 10 geographical regions was assessed at 25 microsatellite or simple sequence repeat loci. A high number of alleles (265) were detected in the range of 3 (Ah1TC6G09) to 20 (Ah1TC11H06) with an average of 10.6 alleles per locus. The polymorphism information content value at these loci varied from 0.38 (Ah1TC6G09) to 0.88 (Ah1TC11H06) with an average of 0.70. A total of 59 unique alleles and 127 rare alleles were detected at almost all the loci assayed. Cluster analysis grouped 189 accessions into four clusters. In general, genotypes of South America and South Asia showed high level of diversity. Extraordinary level of natural genetic variation reported here provides opportunities to the groundnut community to make better decisions and define suitable strategies for harnessing the genetic variation in groundnut breeding

    Phenotypic assessment of groundnut response to key abiotic stress

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    Groundnut is an important oil seed crop, grown under rainfed conditions and often exposed to abiotic stresses including drought and salinity. In the past few years we have screened a large number of germplasm of groundnut, including transgenic groundnut over expressing rd29::DREB1A, and found large variations for traits that are known to be important under drought and for salinity tolerance based on yield under stress conditions. Large differences in TE were observed in the non-transgenic germplasm that was explained by differences in lower transpiration rate (g/cm2). Moreover, the differences in TE were related to differences in the response of transpiration to higher VPD, i.e. low TE genotypes had sustained transpiration increase above 2.0 kPa, whereas, the high TE genotypes limited their transpiration above that VPD threshold. Several transgenic events had also enhanced water use efficiency across several water regimes which was also explained by lower transpiration rate (g/cm2) and stomatal conductance. These had enhanced root growth under drought stress that led to increased water uptake when grown in long/large PVC tubes. Under salinity stress, the striking finding was that Na accumulation was not responsible for the large differences in the observed seed yield; rather, higher salt tolerance appeared to be related to a tight control of plant water loss, where the tolerant germplasm had a lower transpiration rate (g/cm2), likely involving higher ABA content. Therefore, TE differences in groundnut appear to be strongly related to stomata regulation, which also appears to have a strong role under saline stress
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