Stress-mediated regeneration from mature embryo-derived calli and gene transfer through <i>Agrobacterium </i>in<b> </b>rice <i>(Oryza sativa)</i>

332-339Mature seed embryos of five different genotypes of indica rice namely, IR72, IR36, rasi, mahsuri and jaya produced calli (100%) on MS medium supplemented with 2,4-D (10μM). A high frequency of plantlet formation (100% for rasi) was obtained when calli were regenerated on hormonal (10 μM , Kn and 5 μM, NAA) medium solidified with 1.6% of agar instead of 0.8% which is normally employed. This simple water stress treatment was effective for plantlet regeneration even in the absence of hormones. The stress treatment was also effective in other indica genotypes of rice which normally regenerate poorly on a basal or a hormone-supplemented media, and promoted shoot regeneration from long term callus cultures of rice variety rasi. Use or'mature seed embryos for Agrobacterium-mediated transformation resulted in GUS expression in scutellum and shoot region of 4-days old germinated embryos.