A study on yield improvement by character amelioration in edible canna

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Edible canna (Canna edulis Ker-Gawl.) grows up to 3 m high and sometimes falls down by the strong wind and decreases productivity. We tried to estimate optimum plant height with minimum risk of lodging with maximum dry matter production and yield by combining a mathematical model with attributes of plant growth. The projected side-view area of aboveground parts which reflects growth vigor was large and determined by the three parameters : plant height, width of stock base and stand angle. The causal factors of lodging were related mainly to morphogenic characters of the large aboveground parts. They were ascribed to the large projected area in terms of external force such as wind and to the own weight moment in terms of internal force which was added by its aerial weight. The increase in stem inclination in the late growth stage was due to the swelling of rhizomes. It was concluded that the shortening of plant height to about 2 m at the late growth stage was preferable for a high yield : this mitigates 10-20 % of external force and about 50 % of internal force from the risk of lodging after the middle growth stage. Based on these results, we tried to obtain suitable plants by the use of tissue culture method. As there was no previous result on edible canna, we examined the growth of shoot-tip under combinations of BA, IBA and NAA on agar or liquid medium. The agar medium at 8 g L^<-1> was the best and BA (5 mg L^<-1>) + IBA (1 mg L^<-1>) was the best combination for explant growth and low BA + high IBA was the best one for root growth. The application of colchichine was not successful because we have obtained doubled-chromosome cells but they did not differentiate to plantlet until now.