Studies On Identification And Heredity Of Nitrogen Efficiency Indexes

Nitrogen nutrition efficiency of hybrids popularized in shanxi province for recent year and some inbred lines were identified in 2000 year .Eight inbred lines with significant difference in nitrogen efficiency were selected to constitute complete dialed-cross combination ,planted in low N level in 2001year. Twelve hybrids with different nitrogen efficiency were planted in low N and high N levels. The results of identification x correlation path, heredity analysis were as follow:1. Two kind of maize hybrids did not exist, one was genotype with high tolerance to low N level and high sensitivity of response to N fertility, the other genotype with low tolerance to low N level and low sensitivity of response to N fertility.2. There is no close relationship between assess indexes, this reflected complex of nitrogen nutrition efficiency and also showed one hybrid hardly incorporated several characters closely related with nitrogen efficiency, so indexes should be carefully selected.3. Two kind of maize hybrids with high nitrogen efficiency showed different nitrogen nutrition system, one genotype gained high grain yield by high N uptake efficiency, The other genotype by high N utilization efficiency and high N harvest index.4. Under low N condition, grain yield of hybrid with high tolerance to low N was positively high correlation with N utilization efficiency (NUE), path analysis indicated direct effect of NUE was biggest among characters, therefore, breeding of high tolerance to low N should emphasize on NUE on the basis of certain N accumulation .N harvest index and post-silk N accumulation should be given attention to. Breeding of high-yield genotype with high sensitivity to N fertility should put emphasis on selection of high sensitivity of N accumulation. And selection of steady-yield genotype with low sensitivity to N fertility stressed high sensitivity of nitrogen utilization efficiency.5. Under low N condition, broad-sense heritabitilities of several characters were positively high, ranged from 75.99-82.35. N harvest index with high narrow-sense heritabitity was mainly dominated by additive gene effect, dominance and epistasis gene effect played role in grain yield, nitrogen utilization efficiency and nitrogen harvest index (NHI), with low narrow-sense heritability.6. The general combining ability (GCA) of material analysis showed 478 and 89-1 were excellent in nitrogen efficiency, Huangzhao4's GCA of NUE was greater than other inbred line,GCA of N accumulation and N harvest index .of S121 and 107 showed high positive effect, they could be used in nitrogen nutrition genetic improvement.7. Consideration of secondary traits could improved selection efficiency . under low N condition, grain yield was significantly correlation with dry weight of root, root-shoot ratio, gain weight per 1000, anthesis-silking interval, dry weight of cob-three-leaf, N accumulation of rob-three-leaf was closely related to N accumulation. There was Highly correlation between harvest index (HI) and NUE and NHI. The secondary traits could be used as adjuvant index of nitrogen nutrition efficiency.