Annuality and perenniality characteristics and variation in Oryza sativa L. and O-glaberrima Steud.

The growth and survival. after maturity of 26 cultivars of japonica, 37 cultivars of indica, and 41 cultivars of O. glaberrima were examined to clarify the annuality and perenniality of two cultivated species. These cultivars were grown in pots and under light of natural day length with a suitable temperature regime. They were left uncut till 225 days after maturity, approximately one year after seeding. The number of new tillers appearing from maturity to 225 days after maturity was greatest in japonica and lowest in O. glaberrima. The number of living tillers increased with time for a short while after maturity and then decreased, although in japonica, it increased again 120 days after maturity and thereafter. The survival duration of cultivars after maturity was clearly longer for O. sativa than for O. glaberrima. In japonica, all of the Japanese cultivars and all of the foreign cultivars except two survived longer than 225 days after maturity. In indica, most cultivars survived longer than 225 days after maturity, but several cultivars died in the early stage after maturity. In O. glaberrima, all the cultivars except one died before 225 days after maturity. From these results, it was concluded that O. sativa included both annual and perennial cultivars, whereas O. glaberrima was monocarpic annual. It was inferred that O. sativa inherited its genetical characteristics from O. rufipogon, which was thought to be the ancestor of O. sativa and included both annuals and perennials, and O. glaberrima inherited its characteristics from O. barthii, which was annual.