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Plant regeneration from stem segment-derived friable callus of “Fonio” (Digitaria exilis (L.) Stapf.)

Ntui, Valentine O., Azadi, Pejman, Supaporn, Hasthanasombut, Mii, Masahiro
Scientia horticulturae 2010 v.125 no.3 pp. 494-499
Digitaria exilis, small grains, grain crops, in vitro regeneration, callus culture, micropropagation, genetic improvement, plant breeding, seedlings, explants, stems, culture media, 2,4-D, amino acids, cultivars, benzyladenine, zeatin, gibberellic acid, rooting, diploidy
“Fonio” (Digitaria exilis (L.) Stapf.) is a member of the grass family with excellent culinary and nutritional properties. In spite of its economic values, hardly has any improvement work been done. To enhance genetic improvement of this grain, plant regeneration protocol was developed using 8 cultivars. Stem segments of 5mm long excised from 1 month-old seedlings germinated in vitro were cultured on 6 types of media for friable callus induction. Best result was obtained on Murashige and Skoog (MS) medium supplemented with 2mgl⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D) and 1gl⁻¹ casamino acid, where 91.3, 88.9 and 87.8% of the explants formed friable calli in cultivars ‘Kurelep', ‘Churiwe' and ‘Agyong', respectively. Shoots appeared when friable calli were transferred to two regeneration media, i.e., MSBZ (MS medium+0.022mgl⁻¹ 2,4-D, 0 .22mgl⁻¹ 6-benzylaminopurine (BA), 0.22mgl⁻¹ zeatin) and MSBG (MS medium+0.5mgl⁻¹ BA, 0.1mgl⁻¹ gibberellic acid). The highest frequency of plant regeneration was attained on MSBG, with 91.7% of the friable calli forming shoots in cultivar “Churiwe”. Regenerated plants were rooted on hormone free MS medium. Flow cytometric analysis revealed 100% of the regenerants to be diploid. The protocol developed here can be used in the transformation of “Fonio” to increase the yield potential of this crop by incorporating characteristics such as disease resistance and stress resistance.