In vitro and in vivo evaluation of Arachis paraguariensis and A. glabrata germplasm

Apart from possessing important traits needed for improvement of the cultivated peanut (Arachis hypogaea L.), wild Arachis species are grown for forage and ornamental purposes. In the first phase of this research, a series of in vitro experiments led to the development of high frequency regeneration procedures for Arachis paraguariensis Chodat and Hassl. and Arachis glabrata Benth.;Both auxin type and concentration in the culture medium had significant influence on root formation although application of auxin may not always be necessary for rooting, it is essential for early emergence of root primordia. Plantlets that were allowed to form roots on medium lacking auxin showed significantly enhanced plantlet vigor and root length, even though root emergence was delayed. For A. glabrata, the frequency of regeneration was improved along with reduced production of phenolic compounds when 6-benzylaminopurine (BAP) was substituted with 6-gamma-gamma-(Dimethylallylamino)-purine (2ip) in the culture medium.;The most suitable regeneration procedure was then combined with the antimitotic agent colchicine to induce chromosome doubling of diploid A. paraguariensis . The induced autotetraploids from A. paraguariensis had fewer stomata, but more hair-like trichomes per unit leaf area compared to their diploid precursor. The best results in which 39% and 43% of the explants produced tetraploid plants resulted from treatment with 0.5% colchicine for 4 h and 8 h, respectively. Treating explants with high concentrations of colchicine for 24 h proved to be very lethal.;In the second phase, in vivo evaluations of A. paraguariensis and A. glabrata germplasm with specific emphasis on forage yield, disease resistance and seed production were conducted. In vivo evaluation of A. glabrata led to the discovery of the seed production potential of the two cultivars 'UF Peace' and 'UF Tito'. Additionally, the result from field evaluation of two genotypes of A. paraguariensis confirmed higher resistance to C. arachidicola leaf spot than cultivated peanut. The findings from this study should contribute towards genetic improvement of the wild Arachis species, as well as the enhancement of gene introgression into cultivated peanut.