Maximum node production rate and main culm node number contributions to yield and yield-related traits in rice

Preliminary studies have suggested that maximum node production rate and main culm node number may be useful as selection criteria in breeding for improved rice (Oryza sativa L.) cultivars. The objective of this research was to determine the significance of the direct effects of maximum node production rate and main culm node number on 15 yield-related traits (filled grain percentage, mass per panicle, maximum tiller density, number of degree-days to heading, LAI at heading, number of spikelets per panicle, particle density, plant height, panicle length, and the masses of panicles, leaves, and stems at heading and at harvest) and their subsequent direct effects on grain yield. Correlation and path analyses were used to analyze data from field experiments involving 15 lines that represented the combinations of low and high levels of four important yield determinants - maximum number of tillers, grain mass, main culm node number, and particle mass. Maximum node production rate had a negative direct effect on degree-days to heading (p = -0.35) and positive direct effects on maximum tiller density (p = 0.59), panicle mass at harvest (p = 0.48), panicle density (p = 0.40), LAI at heading (p = 0.37), panicle weight (p = 0.36), and on the masses of leaves (p = 0.39), panicles (p = 0.35), and stems (p = 0.32) at heading. Main culm node number had significant direct effects on degree-days to heading (p = 0.98), plant height (p = 0.75), LAI at heading (p = 0.54), maximum tiller density (p = 0.33), stem mass at harvest (p = 0.53), and the masses of stems (p = 0.58), leaves (p = 0.54), and particles (p = 0.42) at heading. Five of the traits that maximum node production rate and main culm node number directly affected (degree-days to heading, mass per panicle, panicle density, and stem mass at heading and harvest) had subsequent direct effects on grain yield. (c) 2005 Elsevier B.V. All rights reserved.