| In this research,the maize(Zea mays L.)cultivar "Xianyu698" was utilized to explore the effect of controlled release urea(CRU)and conventional urea(U)on the formation and accumulation of starch and grain filling characteristics.Two field trials(2017&2018)with five treatments:T1:U basal N fertilizer 150 kg·ha-1+U at V10 of 75 kg·ha-1;T2:CRU basal N 75 kg·ha-1+U basal N 75 kg·ha-1+U at V10 N 75 kg·ha-1;T3:CRU basal N 150 kg·ha-1+U basal N 75 kg·ha-1;T4:CRU basal N 225 kg ha-1,and an unfertilized control(CK).The growth and development of maize,the synthesis of starch and amylase,grain filling process and yield were compared under different treatments.In addition,the maize starch synthesis genes were screened and analyzed using RNA-seq technique.The results show that:1.Both CRU and U were as beneficial to the growth of maize,increasing the plant height,leaf area index(LAI),SPAD value of functional leaves and dry matter accumulation.Plant height with greatest in the T3 treatment,286.32 cm in 2017 and 352.10 cm in 2018.CRU was able to maintain relatively high SPAD value and LAI,and delay plant senescence in the later growth stages.LAI was highest in the T4 treatment,41.74%and 20.09%higher than the CK in 2017 and 2018 respectively.The total dry matter accumulation in different treatments in 2017 and 2018 was T3>T2>T4>T1>CK.In 2017,T3 was 15.75%,5.79%,0.07%and 1.02%higher than CK,T1,T2,and T4,respectively;In 2018,T3 was 16.36%,9.76%,3.30%and 7.72%higher than CK?T1,T2 and T4?respectively.The rational proportion of CRU and U was beneficial to maize dry matter accumulation,which is conducive to increase production.2.The use of CRU and U significantly increase the starch content and improve the properties of key starch synthesis enzymes,and maintain high amylose accumulation rate in the late filling stage.The amylose content(13.01%),amylopectin content(70.83%)and total starch content(83.84%)of grains were highest in T2.In the process of grain filling,the amylose content was the most affected by GBSS activity,while the amylopectin content and total starch content were most affected by UDPG-PPase activity.However,the activities of other enzymes also influence starch accumulation through indirect interaction with the grain filling process.3.Application of CRU incorporated with U can significantly affect the grain filling in maize.The maximum grain-filling rate,grain weight at the time of maximum grain-filling rate and the grain filling duration determined 99.9%of 100-grain weight.Grain weight at maximum grain filling rate had the greatest direct effect(R2=0.9995).By comparing all treatments,the grain filling process of maize could be significantly influenced in T2 treatment.4.The genes related to starch metabolism in maize grains were different among different treatments.RNA-Seq analysis showed that there were significant differences in the differentially expressed genes between treatments.There were 131(75 up 56 down),561(216 up 345 down),367(263 up 104 down),381(222 up 159 down)genes differentially expressed in T1 and T2,T3,T4,respectively.There were 3(1 up 2 down),6(2 up 4 down),3(3 up),4(2 up 2 down)genes differentially expressed in the starch synthesis process,respectively.This study preliminarily suggested that the combination of CRU and U(T2 and T3)can regulate the synthesis of maize starch genes,affecting starch synthesis.5.Combined application of CRU and U significantly increased grain yield and economic returns.In 2017 yield was highest in T2(12.11 t/hm2),and lowest in CK.Yield in T1,T2,T3 and T4 treatments were 12.58%,25.88%,19.13%and 17.26%higher than the CK,respectively.In 2018,T3 produced the highest grain yield(14.60 t/hm2);T1,T2,T3 and T4 yield were 4.53%,8.91%,10.19%and 5.13%higher than CK,respectively.The economic benefits were highest in T2;In 2017 and 2018 returns in the T2 treatment were 16544.35 Yuan/hm2 and 18924.50 Yuan/hm2,respectively. |
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