METHODS TO INCREASE THE STARCH CONTENT OF POTATO-TUBER CALLUS-TISSUE

Attempts were made to increase the starch content of callus tissue fro m tubers of cvs Lemhi Russet and Russet Burbank by varying growth regu lator concentration, sugar source, sugar concentration, temperature an d callus shape. Starch content was always higher in media containing n o growth regulators. Callus spread over the media contained more starc h than unbroken rectangular or cube-shaped callus. Sucrose was superio r to glucose and fructose for starch formation. A sucrose concentratio n of 20% produced more starch than lower concentrations. Callus growth decreased as the sucrose concentration increased. 'Lemhi Russet' call us incubated with 80% sucrose at 20, 25 and 30-degrees-C contained 1.2 , 0.4 and 0.8% starch respectively, which was much higher than in 'Rus set Burbank' callus. With varying amounts of mannitol as an osmoticum in 8% sucrose, the most starch was found in the medium containing 5% m annitol.