Seasonal Dynamics of Nonstructural Carbohydrate Partitioning in 15 Diverse Rice Genotypes

The presence of significant variation among rice (Oryza sativa L.) genotypes in total nonstructural carbohydrates (TNC) that is related to grain yield should be of interest to rice breeders. The effects of four important yield‐determining traits (maximum number of tillers, grain weight, panicle node number, and panicle size) on the TNC concentrations of plant structures at heading and harvest were determined. Path analysis was used to determine the path coefficients of the effect of changes in TNC content (Δ TNC) in leaves or stems on Δ panicle TNC at various stages of crop maturation. Fifteen rice genotypes were used in this study (‘Lemont’, ‘Teqing’, and 13 inbred lines obtained from a Lemont × Teqing cross) to represent the combinations of low and high levels of the four important yield determinants. Field experiments were conducted during the 1994 and 1995 cropping seasons at the Texas A&M University Agricultural Research and Extension Center, Beaumont, TX. Path coefficients for the significant direct effects of Δ stem TNC on Δ panicle TNC were −0.46 for the early‐ to late‐heading period and −0.59 for the late‐heading to grain hardening period. Significant genotype × developmental stage × plant structure interaction suggested the potential for selection of rice lines with high TNC concentration in stems at heading. Linear contrasts indicated that low‐grain weight genotypes had higher stem TNC concentration at harvest, which in turn suggested for the selection of high‐grain weight genotypes.