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

摘要

Growth and survival after maturity were studied of 26 japonica, 37 indica, and 41 O. glaberrima cultivars to clarify the annuality and perenniality of two cultivated species. Plants 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 sowing. The number of new tillers appearing from maturity to 225 days after maturity was greatest in japonica varieties 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 varieties, 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. All japonica cultivars, except two, survived longer than 225 days after maturity. Most indica varieties survived longer than 225 days after maturity, but several cultivars died in the early stages after maturity. All O. glaberrima cultivars, except one, died before 225 days after maturity. It is concluded that O. sativa included both annual and perennial cultivars, whereas O. glaberrima is a 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.