Effect Of Nitrogen Rate On Tillering Of Nipponbare And Yangdao 6 And Its Molecular Mechanism

Nipponbare and Yangdao 6 were used as experimental materials to study the effect of nitrogen rate on tillering of rice.The molecular mechanism was further studied based on the transciptome data determined by RNA-seq.The results were as follows:1.Effect of nitrogen rate on growth characteristics of Nipponbare and Yangdao 6The leaf emergence rate of bo thrice varieties increased with the increase of nitrogen rate.The leaf color(SPAD value)was consistent with the trend of nitrogen rate.The plant height of the two varieties essentially increased with the increase of nitrogen rate.The height of Nipponbare was higher than that of Yangdao 6 under the same nitrogen rate at 4-leaf stage.With the growth and development,the plant height of Yangdao 6 was higher than that of Nipponbare at 8-leaf stage.The dry weight of different organs of the two varieties increased with the increase of nitrogen rate at 4-leaf age and 6-leaf age.The dry weight of tillers increased with the increase of nitrogen rate at 8-leaf age.Under the same nitrogen rate,the increase of the dry weight of different organs was more at 6-leaf age to 8-leaf age than at 4-leaf age to 6-leaf age.The dry weight of different organs of Yangdao 6 was higher than that of Nipponbare.2.Effect of nitrogen rate on physiological aspects of Nipponbare and Yangdao 6The nitrogen concentration of roots of the two varieties was lowest at LN treatment and highest at MN treatment at 4-leaf age.The nitrogen concentration of stems and leaves increased with the increase of nitrogen rate.Nitrogen rate significantly affected the nitrogen concentration of different organs of the two varieties,and the nitrogen concentration of leaves had extremely significant differences between varieties.Nitrogen concentration of different organs increased with the increase of nitrogen rate at 7-leaf age,and there were extremely significant differences between the varieties and nitrogen rate.At 9-leaf age,nitrogen concentration of stem leaves and tiller leaves both increased with the increase of nitrogen rate.In addition to nitogen concentration of roots,nitrogen concentration of different organs had extremely significant differences between the varieties.Nitrogen rate significantly affected nitrogen concentration of roots、stem leaves and tiller leaves.At 4-leaf age,glucoseconcentration of different organs was highest under LN treatment,glucose concentration of roots had extremely significant differences between the varieties.Nitrogen rate had extremely significant effect on glucose concentration of each part.Glucose concentration of each part showed no significant change with the change of nitrogen rate at 7-leaf age.At 9-leaf age,glucose concentration of roots decreased with the increase of nitrogen rate,while glucose concentration of tiller shoots was opposite.3.Effect of nitrogen rate on occurrence of tillering of Nipponbare and Yangdao 6The tiller number with nitrogen treatment was higher than that without nitrogen treatment.At the early stage of tillering,the appropriate amount of nitrogen is beneficial to the increase of tiller number.While using more nitrogen could not promote the occurrence of tillering,and even reduced tiller number.At the late stage of tillering,tiller number of both varieties increased with the increase of nitrogen rate,and tiller number of Nipponbare was higher than that of Yangdao 6.At 4-leaf age and 7-leaf age,tiller number had an extremely significant positive correlation with nitrogen concentration of each part.At 9-leaf age,tiller number had a significant or extremely significant positive correlation with nitrogen concentration of every tissue except of root.Tiller number had significant negative correlation with glucose concentration of stem and leaves at 4-leaf age,had significant negative correlation with glucose concentration of stem and tiller leaves at 7-leaf age,had significant negative correlation with glucose concentration of tiller leaves at 9-leaf age.4.Effect of nitrogen rate on yield,yield components and nitrogen absorption at maturity stage of Nipponbare and Yangdao 6Yield,nitrogen absorption of leaves,stems,panicles and whole plant at maturity stage all increased with the increase of nitrogen rate.Nitrogen use efficiency(NUE)of Nipponbare increased and then decreased with the increase of nitrogen rate,reaching its maximum under N10 treatment.NUE of Yangdao 6 peaked under NO treatment,and was always higher than that of Nipponbare under the same nitrogen rate.The agronomic efficiency(AE)of the two varieties increased and then decreased with the increase of nitrogen rate,reaching the maximum under N10 treatment.5.Transcriptome analysis of Nipponbare and Yangdao 6Based on the analysis of transcriptome date,we found that the differential expressed genes between the two varieties at the same nitrogen rate were significantly more than those between the same variety at different nitrogen rate.The number of genes being altered by varieties showed less on glutamine and auxin-related genes than those by nitrogen rate.The number of genes being affected by varieties showed more on tillering,NAM,starch,fructose,glucose,nitrate,glutamic acid,ammonium and cytokinin-related genes than those influenced by nitrogen rate.