Basic Characteristics Of Rapeseed Varieties (Brassica Napus L.) With Different Types Of Nitrogen Use Efficiency For Grain Production

Field experiments were carried out to study basic characteristics of rapeseed varieties (Brassica napus L.) with different types of nitrogen use efficiency for grain production.73 conventional rapeseed varieties were cultured in 2006-2007 (2007 treatment), and 98 conventional rapeseed varieties were cultured in 2007-2008 under two nitrogen fertilizer levels (2008N0 treatment and 2008N1 treatment). At beginning flowering stage, dry matter weight (DMW)and the nitrogen content of different organs (leave and stem) were tested, and at maturing stage agronomic characteristics, DMW and the nitrogen content of different organs (stem, shell and seed) were tested. The tested rapeseed varieties were classified into 6 types (A, B, C, D, E, F) based on their nitrogen use efficiency for grain production level by the MinSSw method, agronomic characteristics and nitrogen accumulation and distribution of different types were studied. According to 2008N0 and 2008N1 treatments, the tested rapeseed varieties were classified into 3 types (low type, middle type and high type) under different nitrogen fertilizer levels, then these varieties were divided into six types (L→L, M→L, M→M, M→H, H→M, H→H) baded on change of different types from low nitrogen fertilizer to high nitrogen fertilizer, responses of NUEg on nitrogen fertilizer were studied. In order to study relationships between photosynthetic characteristic of leaf and NUEg, SPAD value and photosynthetic parameters were tested at seeding stage in 28 cultivars. To study heterosis, GCA, SCA and heritability of NUEg, six parents (Zheshuang 3,Yangyou7, ZJ1, Shilijia, Ningyou 14, Huyou 16) and their F1 combinations from 6×6 complete double allele crosses were tested under two levels of nitrogen application in 2008-2009. The purposes of these studies were to investigate the basic characteristics of rapeseed with higher nitrogen use efficiency for grain production and to provide fundamental information for genetic improvement of nitrogen use efficiency in rapeseed breeding and feasible cultivation measures designment. Results were as following:1. There are there indexes of nitrogen use effiency from plant itself including nitrogen use efficiency for grain production (NUEg), nitrogen use efficiency for plant biomass(NUEp) and nitrogen harvest index (NHI). Change trends of these indexes were consistent.The study of path analysis indicated that NUEg on yield was biggest. Change ranges of NUEg were more bigger. So NUEg was a more suitable index to indicate nitrogen efficiency than NUEp and NHI.2. Nitrogen use efficiency for grain production differed greatly among rapeseed varieties used in this study. Range of NUEg was from 15.73 g.g-1 to 21.20g.g-1 in 2007 treatment, from 13.61 to 19.16 g.g-1 in 2008N0 treatment,from 12.28 g.g-1 to 16.54g.g-1, and mean value was 18.66 g.g-1,16.76g.g-1 and 4.51 g.g-1, respectively. With the increasing of soil fertilizer and nitrogen fertilization, NUEg decreased.There were fourteen varieties in E or F types in different treatments, and they were HY04, SY01, SY03, SY07, YN06, YN07, YN14, Hongyou3, Huyou 15,Ningyou18, Xiang 05483, Xiang 05484, Xiang 05487 and Yangyou 7。3. There were significant positive correlations between Fv/Fm and NUEg in 2008N0 and 2008N1 treatments. SPAD values were significantly positive correlated with NUEg in 2008N0 treatment. With the increasing of nitrogen fertilization, SPAD value, Pn, and qP increased, and qN decreased.4. With increasing of NUEg, plant height, number of primary banches and number of pods per area with different type varieties increased. Sink capacity (total number of seeds) increased with increasing of NUEg, and there were significantly positive correlations between total number of seeds and NUEg (r2007=0.4057**, r2008=0.5945**, r2009=0.5412**). The study of path analysis indicated that the indirect influence of number of pods on NUEg was biggest, and secondary was number of seeds per pod.5. In the aspect of dry matter accumulation and distribution, the effect of DMW at beginning flowering on NUEg was slight.There were significantly positive correlations between dry matter accumulation after flowering and NUEg, biomass and NUEg. With increasing of NUEg, DMW of shell, yield and the ratio of DMW of seed to biomass with different type varieties increased, the ratio of DMW of stem to biomass decreased. The study of multiple regression analysis indicated that yield and DMW of shell significantly effected NUEg. The study of path analysis indicated that the indirect influence of yield on NUEg was most important, and secondary was DMW of shell. To increasing NUEg it was needed to increase dry matter accumulation from beginning flowering stage to maturing stage, and promote photosynthate to transport from stem to pods, so as to increase dry matter accumulation in pods, especially increase yield.6. In the aspect of nitrogen accumulation and distribution, correlations between the amount of nitrogen accumulation at beginning flowering stage and NUEg, the total amount of nitrogen accumulation at maturing stage were not significant. But there were significantly negative correlations between nitrogen accumulation and distribution of stem and shell and NUEg, and there were significantly positive correlations between the amount of nitrogen of seed, NHI and NUEg. The studies of multiple regression analysis indicated that amounts of nitrogen of different organs at maturing stage significantly effected NUEg. To increase NUEg, increasing nitrogen accumulation of seeds was important, and at the same time decreasing nitrogen accumulation of stem and shell was also important.7. There were different effects of nitrogen fertilizer on NUEg. Results showed that the number of different types (L→L, M→L, M→M, M→H, H→M, H→H) was 14,8,21,6,19 and 30, respectively. Though studying variety characteristics of different types, results showed that in the varieties from low type to high type by nitrogen application (M→H), added values of the number of seeds per pod, yield and the total number of seeds were larger, arid added values of nitrogen accumulation of stem and shell, ratio of nitrogen accumulation of stem and shell to total nitrogen accumulation were smaller. Decreasing values of ratio of nitrogen of seed to total nitrogen accumulation were smaller. The trends of the varieties from high type to low type by nitrogen application (M→L, H→M) were opposite.8. Through testing NUEg of six parents and their F1 combinations from 6×6 complete double allele crosses, results showed that positive heterosis of NUEg was significant. NUEg were likely affected by additive effects, dominance effects and cytoplasm effects by variance analysis of combining ability. The correlation analysis of parents and F1 combinations showed that famale selection was important. In the aspect of heritability, results showed that broad heritability were higher in different treatments. Additive effects and dominance effects were all significant in low nitrogen fertilizer and dominance effects were significant in high nitrogen fertilizer.