Genotypic differences in root traits of rice (Oryza sativa L.) seedlings grown under different soil environments

We investigated mainly root traits of rice (Oryza sativa L.) seedlings grown under four soil conditions (i.e. anaerobic, aerobic, low and high soil density) in thin and long transparent polyvinyl chloride tubes for 21 days. Using 70 rice varieties from four agricultural ecotypes (i.e. japonica upland (JU), japonica lowland (JL), indica upland (IU), and indica lowland (IL)), we examined the effects of genotypes, environment and their interaction on seminal root length (SRL), seminal root thickness (SRT), number of crown roots (NCR), root and shoot dry weight (RDW and SDW) and root/shoot ratio (R/S ratio). The significant effects of genotype, environment and their interaction on all the traits were detected. Rice varieties could be clearly classified into their own ecotypes by a combined principle component analysis (PCA) for NCR, SRT, and SDW. Seventy rice varieties could be separated into upland and lowland varieties based on the scores of the first principle component (PC) and, among upland varieties, JU varieties could be separated from IU varieties based on the scores of the second PC. JU varieties had longer and thicker seminal roots than the other varieties in aerobic soil conditions, indicating that these varieties may be more suitable for aerobic soil conditions from the view point of the seedling establishment.