| Tissue culture methodology can be a tool in augmenting traditional plant breeding systems. In vitro cultures were made of six Arkansas grown rice (Oryza sativa L.) cultivars, Tebonnet, Newbonnet, Starbonnet, Mars, Lemont, and Nortai, two IRRI accessions, Acc. 28735 and Acc. 32576, and two USDA-ARS germplasm accessions, PI 433904 and PI 373453. Mature embryos cultured on Ms (Murashige and Skoog) medium were the explant source. The effects of temperature (20 or 28 C), 2,4-D concentration (.05, 1.0, or 2.0 mg/L), and light (light or dark) on callus growth were investigated. Plants were regenerated by culturing calli on a 2,4-D-free MS medium. Callus fresh weight induced at 28 C was significantly greater than that cultured at 20 C, but plant regeneration was higher from callus grown at 20 C. Although 1.0 mg/L of 2,4-D increased callus growth, plant regeneration was best from callus grown on media containing 0.5 mg/L of 2,4-D. Light enhanced callus growth, but did not affect plant regeneration.; Effects of kinetin (0.5 mg/L), tryptophan (100 mg/L), and sucrose concentrations (15, 30, and 60 g/L), were tested on callus growth and subsequent plant regeneration of 'Starbonnet' and 'Newbonnet'. Starbonnet callus growth was not increased by the addition of kinetin to the induction medium, but in combination with tryptophan it was markedly increased. Conversely, callus growth increased twofold for 'Newbonnet' when the kinetin was added to the medium but was reduced significantly when kinetin and tryptophan were combined. Plant regeneration increased in Newbonnet callus on media containing kinetin and tryptophan together. Sucrose did not affect callus growth significantly, but plant regeneration was greater at 60 g/L for Starbonnet and at 15 and 30 g/L for Newbonnet.; In selection of calli tolerant to alachlor, plants regenerated from one callus of PI 433904 after it was transferred to regeneration media from a medium containing 10 mg/L alachlor. Also, one callus from PI 373453 cultured on media containing 100 mg/L alachlor regenerated plants after subculturing on regeneration media.; Regenerated plants from several rice cultivars were grown to maturity, and their seeds were germinated on a medium containing 0.0, 1.0, 2.0, or 4.0 mg/L of alachlor. Only one line, with a 1.25% survival rate, tolerated 4 mg/L of alachlor. A few lines showed tolerance to 1.0 and 2.0 mg/L alachlor. |
