| Field experiments were conducted with 10 medium-maturity of Yongyou japonica/indica hybrids(MJIH),japonica conventional rice(JC),and indica hybrid rice(IH)as the materials during the year from 2014 to 2016 in Yangzhou,Jiangsu province,China.10 MJIH were divided into high-yielding(HYMJIH)and medium-yielding types(MYMJIH),based on their grain yield performance to identify plant-type traits underlying high yield of HYMJIH.On this basis,growth models were adopted to underlying yield superiority of MJIH compared with JC and IH,mainly on grain yield and its components,dry matter accumulation,nitrogen(N),phosphorus(P),and potassium(K)accumulation,and sink-source balance.This study was aimed to provide theorical and practical implications for planting MJIH in the middle and north zones of Jiangsu province.The main results were followings:1.HYMJIH and MYMJIH were separated from MJIH based on their grain yield performance.In our study,HYL were Yongyou 2638,Yongyou 2640,Yongyou 1610,Yongyou 1612,and Yongyou 1640,while MYL were Yongyou 1851,Yongyou 1852,Yongyou 1763,Yongyou 7753,and Yongyou 5854.IH had the highest panicle length,while HYMJIH had the highest grain weight per panicle and grain density.Except IHhad the highest number of spikelets in the low secondary branches,HYMJIH and MYMJIH had the significantly highest number of spikelets in other position of the panicle,especially in the upper secondary branches and the middle secondary branches of panicle.Leaf length and width of the top-three leaves of MYMJIH were the highest,followed by IH,HYMJIH,and JC.HYMJIH had consistently higher rolling rate of top-three leaves than the corresponding leavs of MYMJIH.HYMJIH had lowest leaf basic angle and dropping angle of the 1st and 2nd leaf in the top.Plant height of HYMJIH was 118.7 cm,higher than JC(96,6 cm),shorter than IH(132.9 cm)and MYMJIH(144.1 cm).HYMJIH had the highest dry weight per stem,dry weight per sheath,and dry weight per unit internode among the different types of rice varieties.Our results indicated that compared with JC and IH,HYMJIH showed more spikelets per panicle,especially in the upper secondary branches and the middle secondary branches of panicle.HYMJIH had erect and rolling upper three leaves compared with the check.HYMJIH also had proper plant height and enriched stem.2.JC showed higher tiller number compared with IH and MJIH during the growth period.MJIH showed lower tiller number while higher tiller percentage,in relative to JC and IH.Richards equation was adopted to simulate grain-filling in six parts of JC and IH.Logistic equation was adopted to simulate grain-filling of grains in lower secondary of MJIH,while Richards equation was adopted to simulate grain-filling in other five parts.IH showed the highest maximum grain-filling rate and mean grain-filling rate,followed by JC,and MJIH.MJIH showed the highest time for maximum grain filling rate and effective grain filling duration,followed by JC,and IH.MJIH showed the higher grain filling and grain-filling duration in the early,middle,and late stages compared with JC and IH.IH showed the highest mean grain-filling rate in the early,middle,and late stages,followed by JC,and MJIH.Our study showed that,compared with JC and IH,MJIH showed lower tillers development,lower peak in tillers,and higher tiller percentage relative to JC and IH.The superiority in grain filling of MJIH was mainly shown in early,middle,and late stages,which was mainly attributed to its higher grain-filling duration during such stages and more spikelets per panicle in six parts in the panicle.3.MJIH showed similar growth period compared with the check.Mean grain yield(t ha-1)of MJIH was 11.7 across two years,significantly higher than that of JC(10.8)and IH(10.0).Grain yield per day of MJIH was the highest,while that of IH was the lowest among different types of rice variety.Gompertz equation was applied in our study to simulate dry matter acuumulation among different types of rice variety.Maximun rate of biomass accumulation of IH was the highest,followed by MJIH,and JC.The time for maximum rate of biomass accumulation of MJIH was 62 d after transplanting,while 67 d for JC and 62 d for IH.MJIH showed higher dry matter accumulation during early,middle,and late stages,which was mainly attributed to its higher dry matter accumulation rate during such stages.Our study showed that MJIH showed similar growth period and higher grain yield.The superiority in dry matter accumulation of MJIH was mainly shown in early,middle,and late stages,which was mainly attributed to its higher dry matter accumulation rate during such stages.4.Growth models fit well dynamics in grain filling process and dry matter accumulation after heading of each rice variety(R2 higher than 0.985 and 0.981,respectively),and sink growth and source capacity were calculated using the parameters of fitted models.The sink growth(g m-2)and source capacity(g m-2)at population-plant level of MJIH were 922 and 872 respectively,both higher than the correspondings of JC(843,778)and IH(701,770).MJIH and JC showed positive source capacity-sink growth balance values(51 and 65 g m-2 respectively),while 1H showed the negative value(-69 g m-2).Sink activity of each variety showed increased firstly and decreased then,while source activity of each variety showed steady firstly and decreased then.Each variety showed higher source activity than sink activity until 20 d after heading,and opposite trend was observed then.Grain N concentration at maturity was negatively correlated with source-sink balance values(p<0.01),and source/sink ratio(p<0.01),indicating higher grain N concentration might disturb plant sink-source balance.Our results indicated that higher sink growth and source capacity were responsible for higher yield of MJIH over JC and IH.Grain yield of MJIH and JC were limited by sink,and more attention should be paid to increasing sink in their breeding projects and cultivation managements.Alought IH showed negative source-sink balance values,pre-stroed assimilates accumulated in the stem would also contribute to fill grains,it was still not sure whether grain yield of IH was limited by source or not.5.Nitrogen accumulation amount(kg hm-2)of MJIH,JC,and IH was 251.8,213.9,and 201.3,respectively across two years.MJIH showed higher nitrogen accumulation per 100 kg grain compared with JC and IH in both years.MJ-IH at maturity showed higher nitrogen accumulation in leaf compared with JC and IH.Nitrogen accumulation in stem of JC was the highest,followed by MJIH and IH.MJIH and IH both showed higher nitrogen accumulation in panicle compared with JC.MJIH showed higher rate of nitrogen accumulation in leaf to total nitrogen accumulation,followed by JC and IH.JC showed significantly higher rate of nitrogen accumulation in stem to total nitrogen accumulation,compared with MJIH and IH.IH showed higher rate of nitrogen accumulation in panicle to total nitrogen accumulation,compared with MJIH and JC.Gompertz equation was applied in our study to simulate nitrogen acuumulation among different types of rice variety.Each variety type showed dynamics in nitrogen accumulation showed increase firstly decrease then.Maximum nitrogen accumulation rate(kg hm-2 d-1)of MJIH was 4.6,significantly higher than JC and IH.The time for maximum nitrogen accumulation rate of JC was observed at 43-44 d after transplanting,42-43 d after transplanting for MJIH,and 41-42 d for IH.MJIH showed higher nitrogen accumulation in early,middle,and late stages compared with JC and IH.Higher nitrogen accumulation in middle stage of MJIH was attributed to its higher duration day and nitrogen accumulation rate,while higher nitrogen accumulation in early and late stages of MJIH were attributed to its higher nitrogen accumulation rate.6.When values were averaged across two years,total phosphorus accumulation(kg hm-2)of MJIH was 75.4,significantly higher than JC(62.2)and IH(57.7).IH showed the highest phosphorus efficiency for grain yield,followed by JC,and MJIH.Phosphorus accumulation in grain per 100 kg grain of MJIH was 0.65,higher than JC(0.59)and IH(0.58).MJIH showed higher phosphorus accumulation in the leaf and stem at jointing compared with JC and IH.MJIH showed lower phosphorus accumulation in the leaf,higher phosphorus accumulation in the panicle,at heading compared with JC and IH.MJIH showed moderate phosphorus accumulation in the stem at heading between JC and IH.Little difference in the phosphorus in the leaf at maturity among test rice variety types was observed.MJIH showed lower phosphorus accumulation in the stem,higher phosphorus accumulation in the panicle,at maturity compared with JC and IH.Gompertz equation was adopted to simulate phosphorus accumulation after transplanting of MJIH,while Logistic equations were adopted to simulate phosphorus accumulation after transplanting of JC and IH.The maximum phosphorus accumulation rate of MJIH was observed at 50-52 d after transplanting,while 59-60 d after transplanting for JC,and 61-63 d after transplanting for IH.The phosphorus accumulation rate of MJIH was higher compared with JC and IH.MJIH showed the highest phosphorus accumulation in the middle and late stages,while the lowest phosphorus accumulation in the early stage,among the tested rice variety types.MJIH showed the highest phosphorus accumulation rate and the duration in the middle and late stages,while the lowest phosphorus accumulation rate and the duration in the early stage,among the tested rice variety types.Our study showed that compared with JC and IH,MJIH showed higher phosphorus accumulation in the leaf and stem at jointing,in the panicle at heading and at maturity stages,and total nitrogen accumulation amount.The superiority in phosphorus accumulation of MJIH was shown in middle and late stages.Higher phosphorus accumulation in middle and late stages of MJIH was attributed to its higher phosphorus accumulation rate and duration day.7.When values were averaged across two years,total potassium accumulation(kg hm-2)of MJIH was 296.0,significantly higher than JC(282.1)and IH(259.6).MJIH showed significantly higher potassium efficiency for grain yield,compared with JC and IH.JC showed the highest potassium accumulation in grain per 100 kg grain,followed by IH and MJIh.IH showed higher potassium accumulation in leaf at jointing compared with MJIH and JC.MJIH showed higher potassium accumulation in stem at jointing,compared with JC and IH.JC showed higher potassium accumulation in leaf at maturity compared with MJIH and IH.MJIH showed higher potassium accumulation in stem and panicle at maturity,compared with JC and IH.Gompertz equation was adopted to simulate potassium accumulation dynamics after transplanting of MJIH,JC and IH.MJIH and IH showed similar maximum potassium accumulation rate,higher than that of JC.The time for maximum potassium accumulation rate of MJIH was occurred at 40-41 d after transplanting,while 41-42 d after transplanting for JC and 39-41 d after transplanting for IH.MJIH showed higher potassium accumulation in the early,middle,and late stages compared with IH and JC,and its higher potassium accumulation in the early and late stages was mainly attributed to its higher potassium accumulation rate in these stages.Our study showed that compared with JC and IH,MJIH showed higher total potassium accumulation and potassium use efficiency.MJIH showed higher potassium accumulation in the early,middle,and late stages,and its higher potassium accumulation in the early and late stages was mainly attributed to its higher potassium accumulation rate in these stages. |
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