IMPROVED ISOLATED MICROSPORE CULTURE EFFICIENCY IN MEDIUM WITH MALTOSE AND OPTIMIZED GROWTH-REGULATOR COMBINATION IN JAPONICA RICE (ORYZA-SATIVA)

The influence of maltose and growth regulators on microspore culture r esponse was investigated in japonica rice. High frequency of callus in duction of isolated microspores was obtained with liquid medium contai ning MS salts, 100 mg 1(-1) myo-inositol, 1 mg 1(-1) thiamine-HCl, 500 mg 1(-1) glutamine, 60 g 1(-1) maltose, and several growth regulators . The effect of maltose on promoting callus formation was associated w ith keeping a high proportion of swollen microspores after 5 day precu lture and increasing the microspore division rate on the 3rd day after culture initiation. No significant effect of maltose in place of sucr ose on plantlet regeneration was seen in regeneration medium. Among th e growth regulators tested, the combination of auxin 2,4-dichloropheno xyacetic acid (1 mg 1(-1)), naphthaleneacetic acid (1 mg 1(-1)), and c ytokinin (6-benzyl-aminopurine 1 mg 1(-1)) in the medium proved to be much better for callus formation than in the other media, and the perc entage of callusing microspores of that medium reached 0.86%. Indole-3 -acetic acid (0.5 mg 1(-1)) and kinetin (2 mg 1(-1)) in regeneration m edium were beneficial for green plantlet differentiation. The results also showed that the frequencies of microspores initial division, call us formation and green plant regeneration varied among genotypes no ma tter what kind of growth regulator and sugar were used. Xiushui 117 wa s the best variety for callusing followed by 02428 & Taipei 309. Taipe i 309 showed a good ability for green plantlet regeneration.