Androgenic Response of Cultured Anthers and Microspores of Sorghum

Sorghum anthers with uninucleate microspores were dissected out of spikelets and plated on MS, B5 and N6 media with kinetin, NAA and 2,4-D. The callus induction frequencies (percentage of anthers plated) for the 3 hybrids tested were 60, 20-30 and 15-20%, for CSH 9, CSH 5 and CSH 12R, respectively. Uninucleate microspores showed the most cell division, and cultures of anthers at earlier (small cells without vacuoles) or later (binucleate microspores) stages did not show any androgenic response. The highest response was obtained at 26°C. After 12 d the anthers on all media, especially B5 and N6 started to turn black. Sucrose was more effective at inducing divisions (50-60% of microspores) than maltose (15-20%). Combined treatment with NAA and 2,4-D at 2.0 mg/litre induced divisions. When NAA and 2,4-D (2 mg/litre) were combined with kinetin at 0.05, 0.1, 0.15 and 0.2 mg/litre, the response increased, with a maximum number of multicellular microspores observed at 0.2 mg/litre kinetin. Microcalli that were growing within the anthers after 20-30 d of culture were transferred to MS medium; irregular masses of calli were observed after 30 d. It is concluded that sorghum microspore cultures may be less dependent on genotype or culture conditions than are anther cultures.