Direct Somatic Embryogenesis and fertile Plants from Rice Root Cultures

Globular pro-embryos were produced from rice ( Oryzae sativa L.) roots cultured on modified Murashige and Skoog salts and vitamins, supplemented with 100 mg L -1 myo-inositol. 100 mg L -1 thiamine, 200 mg L -1 casein hydrolysate, 30 gL -1 sucrose, and 1 to 10 µM 2,4-D and/ or 1 to 10 µM NAA. The optimum auxin concentration for the formation of rice pro-embryos was 10 µM NAA combined with 10 µM 2,4-D. Somatic embryos showing distinct coleoptile and coleorrhiza were formed from proembryos following their transfer to an embryo development medium containing 2.5 µM 2.4-D and 1 µM kinetin. Somatic embryos were germinated in a medium devoid of growth regulators, and the rice plantlets were acclimated and grown into fertile plants in the greenhouse. Histological examination of 1 to 3-micrometer transverse sections of rice-root explants that were cultured 5d on medium containing 10 µM 2,4-D and 10 µM NAA revealed that the somatic embryos originated from the pericycle/endodermis region of the rice roots .