Induction of symmetrical nucleus division and multi-nuclear structures in isolated microspores of sugarcane (Saccharum officinarum L.)

In this study, the effects of floret sterilization with sodium hypochlorite, cold stress, heat shock, 2,4-dichlorophenoxyacetic acid and colchicine treatment on microspore viability and induction of symmetrical nuclei divisions were assessed in six genotypes of sugarcane. The highest microspore viability was observed when florets were sterilized with 3.0% and 3.5% sodium hypochlorite in all genotypes tested. More viable microspores were obtained in the cultures exposed to 4 °C. A sharp decrease was observed in viability at higher temperature pretreatments in all genotypes tested. Microspores with 6-10 nuclei were achieved in cultivars ‘L62-96’ and ‘CP57-614’ (5% and 18%) when cultures were pretreated at 4 °C. The nuclei division was strongly inhibited in the cultures exposed to 33 °C and 37 °C. High frequency of 3-5 nuclei microspores were obtained when 25 and 50 mg l-1 2,4-D were applied in the induction medium. Multinuclear microspores were only observed in cultivars ‘L62-96’ and ‘CP57-614’ (4% and 16%) and in the presence of 25 mg l-1 colchicine, however, its higher level (100 mgl-1) strongly inhibited nuclei division of cultured microspores. Symmetrical nucleus division could be induced in microspores of sugarcane when appropriate genotypes, temperature pretreatment and optimum level of 2,4-D and colchicine were used.