SEIJO Jose Guillermo
congresos y reuniones científicas
Characterization of cultivated and wild species of Arachis (section Arachis) by means of FISH and GISH.
SEIJO, JG; ROBLEDO, G; LAVIA, G.
Workshop; Generation Challenge Programme workshop ; 2008
Generation Challenge Program
Characterization of cultivated and wild species of Arachis (section Arachis) by means of FISH and GISH Guillermo Seijo, Germán Robledo and G. Lavia Arachis is a South American native genus that comprises around 80 species arranged in nine sections on the basis of morphology, cross compatibility and cytogenetics. Section Arachis is the most derived and it is composed by 29 wild diploid species (2n=2x=20, 2n=2x =18) and two allopolyploids (2n=4x=40), A. hypogaea (peanut) and A. monticola. As opposed to the modern peanut cultivars, that generally have a narrow genetic base, wild species are genetically diverse and possess a number of genes for peanut improvement. However, the relatedness of wild species with the cultigen is still unresolved and the subject is a matter of intense research. In this context we have used molecular cytogentics to investigate species relationship within section Arachis and to provide further information on the genetic origin of peanut. The 5S and the 18S-25S rRNA genes were physically mapped by fluorescent in situ hybridization (FISH) in all botanical varieties of cultivated peanut Arachis hypogaea, in A. monticola, and in 21 wild diploid species. A detailed karyotype analysis including the FISH signals and the heterochromatic bands was carried out for all the species. The size, number, and chromosome position of FISH signals and heterochromatic bands are similar in all A. hypogaea varieties and A. monticola, but vary among the diploid species. The bulk of the chromosome markers mapped together with GISH analysis suggest that: 1) karyotype variability is geographically structured and revealed several natural groups among wild species; 2) species traditionally included within the B genome may be segregated in at least two different genome types; 3) peanut originated upon domestication of A. monticola and 4) A. duranensis and A. ipaensis are the most probable ancestors of both tetraploid species.