Use of Wild Arachis Species/Introgression of Genes into A. hypogaea L.

Abstract

Abstract The use of wild Arachis L. in cultivar improvement programs has been considered an option for more than 50 yr. Both A. Krapovickas and W.C. Gregory, independently, made interspecific hybridizations in the 1940s. However, only three cultivars have been released as a result of interspecific hybridizations, and only one of those has a clearly identifiable genetic component from the wild species. Several breeding lines have been reported and several germplasm releases are documented from Texas, North Carolina, and ICRISAT. At least four potential options exist for transferring genes from wild Arachis to the cultigen: a) The hexaploid pathway consists of crossing a diploid wild species directly with A. hypogaea, doubling the chromosome number to the hexaploid level, then backcrossing for several generations to restore the tetraploid condition. Several options are possible in this pathway involving various crossing schemes prior to crossing a diploid hybrid with A. hypogaea. North Carolina and ICRISAT have had success with this pathway. b) The diploid/tetraploid pathway has been the most successful in Texas to date. This pathway involves crossing diploid species (two to several), doubling the chromosome number of the hybrid, then crossing to A. hypogaea and backcrossing with selection for the desired character. This pathway is most successful when both A-and B-genome species are involved. Germplasm lines and a cultivar have been released in Texas using this pathway. c) Another diploid/tetraploid pathway could be to double chromosome numbers of diploid species and cross the amphiploids directly with A. hypogaea. Several attempts have been made with this technique, but no germplasm releases have been reported, in large part because sterility is too great when both A and B genomes are not included in the hybrid. Many of the sections/species of wild Arachis are so greatly isolated from A. hypogaea that plant transformation will be the likely method to introduce genes into the cultigen. d) Molecular methods of “inserting” genes into peanut that have been modestly successful and include use of Agrobacterium spp., electroporation, and direct DNA delivery techniques such as the gene gun, whiskers, and sonication. No releases have resulted.