Callus Induction and Plant Regeneration in Elite U.S. Rice Lines

Four California and one Texas rice (Oryza sativa L.) cultivars were examined for potential use in tissue culture studies. Under varying 2,4‐dichlorophenoxyacetic acid (2,4‐D) and kinetin levels embryogenic calli derived from mature seed ranged in weight from 0 to 502 mg after 4 wk. Addition of kinetin allowed a 2‐ to 10‐fold increase in embryogenic callus size for ‘M‐202’, ‘Calmochi‐101’, and ‘Lemont’. The frequency of embryogenic callus formation across different 2,4‐D and kinetin levels was highest with ‘S‐201’ (0.93 to 1.00) and lowest with Lemont (0.00 to 0.44). Mean green shoot number varied from 0 to 14.2 (100 mg)−1 embryogenic callus 8 wk after initiation of regeneration. Similar numbers of shoots were derived from compact, friable, and leafy callus types. S‐201 and Calmochi‐101 developed green shoots from virtually all regions of the embryogenic callus while the others formed shoots from the underside of regenerating tissue. Frequency of albino shoots ranged from 0.00 to 0.045 for the five cultivars. Albino shoots from California cultivars were detected only in regeneration medium containing 0.1 mg L−1 6‐benzylaminopurine (BAP). L‐202 and S‐201 were identified as the best cultivars for cell culture studies. Data from these cultivars suggest that the California rice germplasm should respond equally as well to in vitro manipulation as other non‐U.S, strains.