Studies on Agronomic Traits of African Rice (Oryza glaberrima Steud.) III. Some grain morphological aspects of domestication and decrement

Abstract

To identify some characteristics of Oryza glaberrima in grain morphology, length (L), width (W) and thickness (T) of unhusked grain were determined for two cultivated species, i.e. O. sativa and O. glaberrima, three African wild species, i.e. O. breviligulata, O. longistaminata and O. punctata, and three Asian wild species, i.e. O. perennis, O. sativa var. spontanea and O. officinalis. O. glaberrima and O. breviligulata, which belong to the Series Glaberrima, showed flatter grain shape than 4 species of Series Sativa, i.e. O. sativa, O. sativa var. spontanea, O. perennis and O. longistaminata. The two species from Series Glaberrima were positioned within the following ranges in W/T, L/T and L/W: W/T> 1.45, L/T>3.75, L/W> −4.88× W/T + 9.95. The two cultivated species had larger grain volume than six wild rice species. The ancestral species, such as O. perennis and O. breviligulata can be characterized among wild species by the large grain volume. Large grain cultivars were found in abundance in African O. sativa varieties as compared to Indian varieties. Although a large difference in grain volume could not be found between the two cultivated species, weedy strains of O. glaberrima, which have not been grown as cultivated species, had apparently smaller grain volume. These results suggest that the decrement of O. glabenima had been done centering around strains of small grain, and that selection pressure for large grain was strong in Africa over that in Asia. © 1995, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.