Effects Of Climate Change On Resistant And High Photosynthetic Efficiency Cultivars Of Soybean And Their Main Pests

Increasing concentrations of greenhouse gases such as CO2 and the resulting increase of global temperatures in the atmosphere are two distinctive features of global climate change.The concentration of atmospheric carbon dioxide has been increased by more than 40%,from 280 to 400 ppm since the industrial revolution to now,and it is predicted that atmospheric CO2 concentration will increase up to approximately 900 ppm by 2100.Since 1900s,the global average temperature has risen by 0.7? due to the elevated CO2 and other greenhouse gases,meanwhile,the global average temperature will increase 1-4.5? in the next 100 years.And,China is one of the countries those with the most significant characteristic of global climate warming.The increasing concentration of carbon dioxide and temperature in the atmosphere have impacts on plants' growth and yield,as well as phytochemical composition.At the same time,it may affect the physiology of herbivorous insects directly or indirectly,change their feeding and then affect the production of crops.The changes in the concentration of CO2 in the atmosphere mainly negitively influence the chewing insects by affecting the host plants.Besides,many sucking insects show positive responses to the increasing concentration of CO2.At present,most researches focus on the direct impact of temperature change on the development and reproduction of insects.Additionally,climate warming will lead to an increase in insect population.The earliest research on resistance to leaf-chewing insects in soybean is dated from late 1960s.In the field of identification of the resistance germplasm in and out of the country,soybean cultivar Lamar(PI533604)is considered highly resistant against Spodoptera litura.HN41(Ha 91-6045)is a highly photosynthetic efficiency soybean variety selected and bred through cross-breeding by Heilongjiang Academy of Agricultural Sciences,and it has general resistance to Aphis glycines.With the development of climate change,we chose elevated CO2(eCO2),increased temperature(highT),the combined increase of the concentration of CO2 and temperature(eCO2+highT)as three environmental factors of climate change,and we studied the effects of these climate environmental factors on soybean and its target Lepidoptera pest and major Hemiptera pest.By considering excellent soybean varieties and their control varieties both at home and abroad,and closely linking to the actual production practice,we discussed:effects of climate change on plant chemistry,growth,yield of resistant soybean and feeding of S.litura;effects of climate change on high photosynthetic efficiency soybean,and the population abundance of Aphis glycines Matsumura.Main results for this study are as follows:1.Effects of climate change on soybean1)eCO2:increased the biomass and seeds'yield of soybean;increased the foliar sugar content and C/N ratio,and reduced the foliar nitrogen content of the resistant(cv.Lamar)and susceptible(cv.JLNMH)soybean;promoted the photosynthesis(increased the net photosynthetic rate and intrinsic water use efficiency,reduced the stomatal conductance and transpiration rate),and increased the foliar contents of soluble constituents(sucrose,soluble proteins,total free amino acids)of the high(cv.HN41)and common(cv.ZD35)photosynthetic efficiency cultivars of soybean.Under eCO2:the increased difference in seeds weight of the resistant and susceptible cultivars of soybean,thus,it can be supposed that the yield of Lamar soybean would improve greater in elevated CO2;the increased difference in biomass and root/shoot ratio of the high and common photosynthetic efficiency cultivars of soybean,we can propose that the growth of HN41 soybean would be better in elevated CO2.2)highT:there were slight increases in the growth and yield of soybean,but most of the effects were not significant;the effects of foliar sugar and nitrogen content,and C/N ratio of the resistant(cv.Lamar)and susceptible(cv.JLNMH)soybean were mostly insignificant;the effects of photosynthesis and foliar contents of soluble constituents of the high(cv.HN41)and common(cv.ZD35)photosynthetic efficiency cultivars of soybean were also mostly insignificant.3)eCO2+highT:increased the biomass and seeds' yield of soybean;increased the foliar sugar content and C/N ratio and reduced the foliar nitrogen content of the resistant(cv.Lamar)and susceptible(cv.JLNMH)soybean;promoted the photosynthesis and increased the foliar contents of soluble constituents and root/shoot ratio of the high(cv.HN41)and common(cv.ZD35)photosynthetic efficiency cultivars of soybean.Under eCO2+highT:the increased differences in seeds weight of the resistant and susceptible cultivars of soybean,hence,we can speculate that the yield of Lamar soybean would be improved greater in the future under climate change;the increased difference in seeds weight of the high and common photosynthetic efficiency cultivars of soybean,so we can speculate that the yield of HN41 soybean would be improved greater with the development of climate change in the future.2.Climate change altered growth,development and reproduction of Spodoptera litura fed on resistant and susceptible soybean1)It can be concluded from the three-year data that S.litura fed on soybean that was grown under eCO2:prolonged the duration of larva and pupa;decreased the pupation rate,larval and pupal weight,and fecundity;increased the feeding amount and excretion amount;the relative growth rate(RGR),efficiency of conversion of ingested food(ECI),and efficiency of conversion of digested food(ECD)of 4th instar larvae Were all decreased,and the relative consumption rate(RCR)and approximate digestibility(AD)were increased.Most of the effects achieve significant results.The foliar sugar content(or C/N ratio)of soybean was significantly positive correlated with the larval and pupal life-span,feeding-and excretion amount per larva,and net consumption per larva of S.litura,and was significantly negative-correlated with the foliar N content of soybean,the larval weight,pupal weight(except susceptible soybean JLNMH),and fecundity of S.litura.The increments of feeding amount per larva of S.litura that was fed on resistant soybean were less than 50%of the increments of S.litura which was fed on susceptible soybean under elevated C02,and the larval life-span of S.litura fed on resistant soybean(cv.Lamar)was prolonged more obviously than that of S.litura fed on susceptible soybean(cv.JLNMH)under elevated CO2.2)S.litura fed on soybean grown under highT:the duration of pupa was significantly reduced;the larval weight,fecundity,and pupation rate did not change significantly;the ECD and ECI of 4th instar larvae were increased significantly;the pupal weight was reduced significantly(fed on Lamar);the duration of larva was reduced significantly,feeding amount and net consumption were decreased significantly,RGR of 4th instar larvae were increased significantly(fed on JLNMH).3)S.litura fed on soybean that was grown under eCO2+highT:the larval weight and pupation rate were reduced significantly;the feeding amount,excretion amount and net consumption were increased significantly;the RCR and AD of 4th instar larvae were increased significantly;the ECD was reduced significantly;the duration of larva was prolonged significantly,pupal weight and fecundity were decreased significantly,RGR and ECI were reduced significantly(fed on Lamar);the duration of pupa was prolonged significantly(fed on JLNMH).3.Effects of different photosynthetic efficiency soybean on the population abundance of Aphis glycines under climate changeThe amount of aphid occurrence on the high(cv.HN41)and common(cv.ZD35)photosynthetic efficiency cultivars of soybean were increased significantly under eCO2 and eCO2+highT,and had a gain effect on the aphid population.The amount of aphid occurrence also increased under highT in 2013 and 2014.To be summarized,elevated CO2 and combined increase of the concentration of CO2 and temperature could improve the growth of soybean,and increased temperature only had no effect on soybean growth.Elevated CO2 and combined increase of the concentration of CO2 and temperature brought negative effects on the growth,development and reproduction of S.litura.Furthermore,the damage of S.litura in the field was increased due to the increase of food intake.But the resistant soybean Lamar would maintain the resistance of the target Lepidoptera pest,S.litura and the yield would be greatly improved;and the susceptible soybean JLNMH will face the increasing risk of food intake.No matter the resistant or susceptible cultivars of soybean,the damage of S.litura in the field will not become worse under the condition of increased temperature alone.No matter the elevated CO2,increased temperature,or combined increase of the concentration of CO2 and temperature,the amount of aphid occurrence will increase on the high(cv.HN41)and common(cv.ZD35)photosynthetic efficiency cultivars of soybean,in the future under the climate change,meanwhile,the soybean field will face the risk of increasing population of aphids.