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

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Marker-assisted introgression of a QTL region to improve rust resistance in three elite and popular varieties of peanut (Arachis hypogaea L.)

Leaf rust, caused by Puccinia arachidis Speg, is one of the major devastating diseases in peanut (Arachis hypogaea L.). One QTL region on linkage group AhXV explaining upto 82.62 % phenotypic variation for rust resistance was validated and introgressed from cultivar ‘GPBD 4’ into three rust susceptible varieties (‘ICGV 91114’, ‘JL 24’ and ‘TAG 24’) through marker-assisted backcrossing (MABC). The MABC approach employed a total of four markers including one dominant (IPAHM103) and three co-dominant (GM2079, GM1536, GM2301) markers present in the QTL region. After 2–3 backcrosses and selfing, 200 introgression lines (ILs) were developed from all the three crosses. Field evaluation identified 81 ILs with improved rust resistance. Those ILs had significantly increased pod yields (56–96 %) in infested environments compared to the susceptible parents. Screening of selected 43 promising ILs with 13 markers present on linkage group AhXV showed introgression of the target QTL region from the resistant parent in 11 ILs. Multi-location field evaluation of these ILs should lead to the release of improved varieties. The linked markers may be used in improving rust resistance in peanut breeding programmes

Sources of resistance to tobacco streak virus in Wild Arachis (Fabaceae: Papilionoidae) Germplasm

Article purchasedStem necrosis disease caused by Tobacco streak virus (TSV), first recognized in 2000, has emerged as a potential threat to peanut (Arachis hypogaea) in southern states of India. The virus induces severe necrosis of shoots leading to death of the plant, and plants that survive are malformed, with severe reduction in pod yield. All the currently grown peanut cultivars in India are highly susceptible to the virus. Therefore, wild relatives of peanut were evaluated to identify potential sources of resistance to TSV infection. In all, 56 germplasm accessions from 20 wild Arachis spp. in four sections (Arachis, Erectoides, Procumbente, and Rhizomatosae), along with susceptible peanut cultivars (JL 24 and K 1375), were evaluated for resistance to TSV under greenhouse conditions using mechanical sap inoculations. Systemic virus infection, determined by enzyme-linked immunosorbent assay (ELISA), in the test accessions ranged between 0 and 100%. Twenty-four accessions in section Arachis that had 0 to 35% systemically infected plants were retested, and systemic infection was not detected in eight of these accessions in repeated trials in the greenhouse. These are International Crops Research Institute for the Semi-Arid Tropics groundnut (ICG) accession nos. 8139, 8195, 8200, 8203, 8205, and 11550 belonging to A. duranensis; ICG 8144 belonging to A. villosa; and ICG 13210 belonging to A. stenosperma. Even though the resistant accessions had 0 to 100% TSV infection in inoculated leaves, TSV was not detected in the subsequently emerged leaves. This is the first report of TSV resistance in Arachis spp. The eight TSV resistant accessions are cross compatible with A. hypogaea for utilization in breeding for stem necrosis disease resistance

Phenotypic assessment of groundnut response to key abiotic stress

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

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

SSR-based genetic linkage map for cultivated groundnut (Arachis hypogaea L.) for QTL analysis and comparative mapping

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Groundnut and the Oilcrops Network

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Cultivar-dependent variation in food-feed-traits in groundnut (Arachis hypogaea L.)

A total of 860 cultivars and breeding lines of groundnut grown in the off (Rabi) season of 2001/02 post rainy season at ICRISAT centre head quarter in India were investigated for haulm fodder quality traits and relationships between haulm traits and pod yields. Haulm fodder quality traits chosen were nitrogen (N x 6.25 equals crude protein), in vitro digestibility and in vitro metabolisable energy content. The haulm fodder quality traits were analyzed by a combination of conventional laboratory techniques and Near Infrared Reflectance Spectroscopy (NIRS). Significant (P<0.0001) and livestock nutritionally important cultivars differences were found for all three traits. Thus haulm nitrogen content ranged from 1.2 to 2.3%, in vitro digestibility ranged from 51.7 to 61.1%, and in vitro metabolisable energy content ranged from 6.9 to 8.8 MJ/kg. No inverse relationships were observed between any of the haulm fodder quality traits and pod and haulm yields. Haulm fodder quality analysis was repeated for 12 check cultivars in 2002 and over the two years broad sense heritabilities (h2) for nitrogen, in vitro digestibility and in vitro metabolisable energy content were 0.72., 0.72 and 0.67, respectively. The findings of the present study suggest that pod yield, haulm yield and haulm fodder quality traits can be simultaneously improved to develop better dual purpose groundnut varieties

Genetic Options for Drought Management in Groundnut

Groundnut is one of the principal oilseeds in the world. It is cultivated on 24.8 million ha with a total production of 32.8 million t and an average productivity of 1.32 t ha-'. Developing countries account for 96.9% of the world groundnut area and 93.8% of total production. Production is concentrated in Asia (56.8% area and 66.5% production of the world) and Africa (38.0% area and 24.7% production). The groundnut productivity in Africa is only 0.86 t ha-' compared with 1.55 t hx1 of Asia. The world groundnut economy-facts, trends and outlook are desaibed in detail by Freeman et al., 1999. Briefly, in medium-term (i.e. up to 2010), 'groundnut production and consumption is likely to shift increasingly to developing countries; production will grow in all regions but most rapidly in Asia, slowly in sub-Saharan Africa and decline in Latin America; and utilizationwill continue to shift away from groundnut oil toward groundnut meal, specially confectionery products'

Genetic Options for Drought Management in Groundnut

Groundnut is one of the principal oilseeds in the world. It is cultivated on 24.8 million ha with a total production of 32.8 million t and an average productivity of 1.32 t ha-'. Developing countries account for 96.9% of the world groundnut area and 93.8% of total production. Production is concentrated in Asia (56.8% area and 66.5% production of the world) and Africa (38.0% area and 24.7% production). The groundnut productivity in Africa is only 0.86 t ha-' compared with 1.55 t hx1 of Asia. The world groundnut economy-facts, trends and outlook are desaibed in detail by Freeman et al., 1999. Briefly, in medium-term (i.e. up to 2010), 'groundnut production and consumption is likely to shift increasingly to developing countries; production will grow in all regions but most rapidly in Asia, slowly in sub-Saharan Africa and decline in Latin America; and utilizationwill continue to shift away from groundnut oil toward groundnut meal, specially confectionery products'