질소이용효율이 높은 벼품종 육성 연구 = Studies on Breeding Varieties of High Physiological Nitrogen-Use Efficiency in Rice

다국어 초록 (Multilingual Abstract)

Crop variety having high nutrient-use efficiency is a prerequisite to meet the need of environment-friendly crop cultivation. A few studies on genetics and breeding for physiological nitrogen-use efficiency (PNUE; grain yield /absorbed N) in rice initiated recently with the elucidation of varietal differences, which suggested the possibility of high PNUE varieties. A project for breeding high PNUE rice varieties has been carried out in our laboratory, and the results obtained so far are briefly summarized here. Genotypic variations in PNUE under both N-fertilized (100kg/ha) and unfertilized conditions were significantly high using varieties of various origin and plant architecture, and PNUE was much higher in improved HYV than in land varieties. Path analysis revealed that harvest index was a major character contributing to PNUE. PNUE was lowered by the heavy application of N fertilizer. The variances of general combining ability for yield-related characters were higher than the variances of specific combining ability in both N-fertilized and unfertilized conditions, indicating that additive effects were more important than dominance effects. Dasanbyeo and Guichow out of parents were the best combiners for biomass production, yield, and crop growth rate in F1. Genetic similarities among parents were estimated to be useful in predicting the yield heterosis in F1 under N-fertilized condition. The genetic segregations of dry-matter and PNUE in F2 were continuous. Heritabilities for yield-related characters varied along characters and populations. Heritabilities for yield were increased with generation advance and were much higher in N-unfertilized condition than in N-fertilized condition. Genetic gain after selection for yield was significantly higher in N-unfertilized condition than in N-fertilized condition. However, the selection response for yield was negligible in case that the plants were grown in N-unfertilized condition after selection in N-fertilized condition and vice versa. Selection for PNUE in early generations was effective in both N-fertilized and -unfertilized conditions, implying that high PNUE lines could be bred by selection after hybridization. Promising lines having both high yield and high PNUE were selected in F3 and F4. The selection with generation advance for the lines is in progress for genetic fixation.