Some physiological aspects of the domestication and improvement of rice (Oryza spp.)

Abstract

Abstract Forty-one lines representing seven species involved in both Asian and African domestication and improvement of rice were grown and compared under controlled environment conditions at 27/22°C. Kernel size varied over a four-fold range, being smallest in the wild Asian species, but there was no consistent increase in either grain or leaf size with domestication and improvement. Photosynthetic rate per unit leaf area tended to be lower in the African and wild Asian species than in O. sativa cultivars. Flag leaf photosynthesis remained high for longer in O. sativa than in other species. Leaf photosynthetic rate was positively correlated with leaf nitrogen content and with specific leaf weight across lines. The proportion of dry matter present as leaf varied little, but greater differences in leaf area ratio and specific leaf weight occurred. These affected variation in relative growth rate, which tended to be greatest at high leaf area ratios but least at high rates of photosynthesis. Percentage seed set and harvest index of the main shoot both increased with domestication and improvement. These findings are compared with those for other domesticated species.