| Taihu rice planting region is located in Yangtz River delta,which is one of the most developed areas in China,and temperature and solar radiation(T&R)resources are relative abundant in this region.Meanwhile,with the fast development of society and economy,rice quality,especially eating quality,has attracted more and more attention.Thus,a lot of good eating taste japonica rice(GETJR)cultivars have been bred,but the corresponding cultivated technology still needs further studies.How to promote T&R utilization efficiency of rice with good quality and high yields in Taihu rice planting region?This is a good question with practical meanings and abundant scientific connotations.In this study,the two types of GET JR were selected,including late-mature soft japonica rice(NG9108&SXG100),mid-mature soft japonica rice(FG1606&NG9108)and mid-mature non-soft japonica rice(FG3227&WYG80).Sowing date of rice was as a major method for T&R regulation,and these cultivars were separately sown every 7 days from May-10 to June-21 in 2017 and 2018.The field experiment was conducted in National Soil Quality Observation Experiment Station in Xiangcheng,Suzhou,China.The objects of this study focused on the following two points:(1)the responding mechanism of GETJR yield and quality to T&R ecology in Taihu rice planting region;(2)the suitable T&R ranges for both yield and quality and concomitant suitable sowing windows.The major results showed as follows.1.The effects of sowing date(SD)on the growth process of GETJR and the corresponding T&R.(1)The delayed SD shortened the GETJR growth process.For late-mature japonica rice soft rice(ZSWG)and mid-mature japonica rice(CSZG),as SD were delayed every 10 d,the lengths of sowing to jointing period(SJ)were shortened 3.1～3.4 d and 1.9～2.5 d,respectively;the lengths of jointing to heading period(JH)were shortened 2.8 d and 1.2～1.6 d,respectively;the lengths of heading to mature period(HM)were shortened 0.4-1 d and 0.2～0.4 d,respectively;the lengths of whole growth period(WGP)were shortened 4.9～5.7 d and 3.0～3.4 d,respectively.(2)Taking the whole growth period as an example,the observed values of averaged temperature(AT),effective cumulative temperature(ECT),average solar radiation(ASR),cumulative solar radiation(CSR)and average precipitation(AP)linearly decreased by 0.01～0.02℃,8.54～11.55℃ d,0.03 MJ m-2 d-1,10.16～14.00 MJ m-2 and 0.01 mm when SD was delayed one day.The observed values of diurnal temperature range(DTR)and average sunshine duration(ASD)did not significantly change among SD treatments.However,the delay of SD increased relative humidity(AH)values by 0.02%-0.03%per day.2.The response of GETJR yields to T&R.The delayed SD significantly decreased rice yields in two years.The yields of ZSWG,mid-mature non-soft japonica rice(CSZGC),and mid-mature soft japonica rice(CSZGR)separately decreased 77.4±16.8 kg hm-2,79.9±2.35 kg hm-2 and 71.1±7.59 kg hm-2 per year.The Lasso model revealed that ECT was the key factor affecting the GETJR yield.To achieve relative high yields,the suitable ECT ranges of ZSWG in the stages of SH,HM and WGP were 1737～1891℃ d,716～842℃ d and 2453～2713℃;the suitable ECT ranges of CSZG in the stages of SH,HM and WGP were 1601～1648℃ d,722～911℃ d and 2345～2534℃ d.3.The response of GETJR processing and appearance to T&R.AT in HM stage were the key meteorological factor that affected rice processing and appearance quality.As the AT in HM stage increased by 1℃,the brown rice rate of ZSWG,CSZGC and CSZGR decreased by 0.28%～0.44%,0.60%～0.68%and 0.45%～0.55%;the milled rice rate decreased by 0.90%～1.75%,0.65%～0.91%and 0.66%～0.85%;the head milled rice rate decreased by 0.80%～2.90%,0,73%～1.19%and 0.77%～1.09%;the chalkiness rate increased by 2.25%～2.95%,2.58%～2.84%and 2.77%～2.84%;and the chalkiness increased by 0.68%～1.09%,0.53%～0.76%and 0.53%～0.63%.We chose the processing quality grade-I(GB/T 17891-2017)as the high-grade standard,the suitable AT ranges of ZSWG,CSZGC and CSZGR in HM stage were 19.3～21.4℃,20.4～21.20C and 20.2～22.0℃ for high processing quality.We chose the appearance quality grade-III as the relative high-grade standard,and the suitable AT ranges of ZSWG,CSZGC and CSZGR in HM stage should be in 19.3～20.9℃,20.4～23.8℃ and 20.2～23.5℃ for high appearance quality.4.The response of GETJR cooking and eating taste quality to T&R.AT and ASR in HM stage were the key meteorological factors affecting rice cooking and eating taste quality.As the AT in HM stage increased by 1℃,the grain protein contents of ZSWG,CSZGC and CSZGR decreased by 0.13%,0.15%and 0.12%;the grain amylose contents decreased by 0.51%,0.49%and 0.25%;the gel consistency increased by 2.47 mm,2.56 mm and 2.70 mm;the eating quality scores increased by 2.83,2.56 and 2.01.As the ASR in HM stage increased by 1 MJ m-2 d-1,the breakdown values of RVA increased by 81.80 cP,49.36 cP and 55.43 cP,and the setback values of RVA decreased by 126 cP,76 cP and 53 cP.To achieve relative high eating quality,for ZSWG,CSZGC and CSZGR,the suitable AT ranges in HM stage were 21.1～23.6℃,22.4～26.6℃ and 23.2～26.9℃.5.The responses of starch physicochemistry,fatty acid and element contents to T&R.AT and ASR in HM stage were the key meteorological factors and consistently affected rice starch fine structure and fatty acid contents.(1)As the AT in HM stage increased by 1℃,the mid-size starch particle content decreased by 1.53%,the large-size starch particle increased by 1.59%,the ratio of ATR-FTIR 1045/1014 cm-1 increased by 0.33%,the relative crystallinity increased by 0.96%,the gelatinization enthalpy increased by 0.35 J g-1,and the gelatinization temperature increased by 1.07℃.fa-fp decreased by 0.11%,fa decreased by 0.24%,fb1-subl decreased by 0.10%,fbl-sub2 increased by 0.07%,fb2 increased by 0.11%,and fb3 increased by 0.26%.(2)As the AT in HM stage increased by 1℃,the contents of linolenic acid,linoleic acid,palmitic acid and stearic acid increased by 186 pg g-1,411 μg g-1,97 μg g-1 and 25 μg g-1.(3)The increase of AT in HM stage mainly increased the contents of Fe and Zn and decreased the content of Cd.Fe and Zn concentrations in the first sowing date treatment were 88.2%and 64.7%higher than those in the last sowing date treatment,and Cd concentrations in the first sowing date treatment were 70.2%lower than those in the last sowing date treatment.In summary,the variation characteristics of japonica rice yield and quality were successfully obtained through constructing the series of T&R ecology treatments by SD management in Taihu rice planting region.The influence of T&R on rice yield,processing and appearance quality,cooking and eating taste quality,rice starch fine structures,fatty acid contents and mineral element contents were comprehensively illustrated.Then,the optimal temperature ranges were explicitly determined that separately satisfied the requirements of high yields,high processing quality(grade-1),high appearance quality(grade-Ⅲ)and good eating taste quality.Finally,we proposed the suitable SD windows of Taihu rice planting region according to the comprehensive scores,historical meteorological conditions and crop rotations.The suitable SD of CSZG and ZSWG are May-24 to May-31 and May-10 to May-31,respectively,and the best SD was May 24 and May 10,respectively. |
PDF Full Text Request