CYTOLOGICAL ANALYSIS OF EARLY MICROSPORE DIVISIONS AND EMBRYO FORMATION IN CULTURED SOYBEAN ANTHERS

Young inflorescences of two Brazilian soybean cultivars (IAS 5 and RS 7) were subjected to 4 degrees C pretreatment for 0, 5, and 10 days. C ytological examinations of the lit vitro anthers were done during the first four weeks of culture. The cold pretreatment had no clear effect on the frequencies of symmetrical-binucleate microspores or multinucl eate grains. The multinucleate grains might originate either by symmet rical or assymmetrical division. The best medium for callus and embryo induction was B5 long containing 2.0 mg l(-1) 2,4-dichlorophenoxy ace tic acid and 0.5 mg l(-1) benzyladenine. The frequency of anthers/call i with embryos was about 2% in all cultivars. Histological analysis of such embryos showed that they were similar to zygotic embryos.