Response Of Potato Starch Accumulation And Yield Formation To Different Phosphorus Application Rates

To explore the response mechanism of potato tuber starch accumulation and yield formation to different phosphate fertilizer application rates in semi-arid rain-fed area in southern Ningxia.In 2018 and 2019,the main cultivar in the southern mountainous region of Ningxia,namely Qingshu No.9 as the test material.The test uses a random block design to set five phosphorus levels T1(P2O5:Okg/hm2),T2(P2O5:60kg/hm2),T3(P2O5:120kg/hm2),T4(P2O5:180kg/hm2)and T5(P2O5:240kg/hm2)under the same nitrogen and potassium conditions(N:180kg/hm2?K2O:45kg/hm2),with no fertilizer as the control(CK).The effects of different phosphate fertilizer application rates on potato growth and development,dry matter accumulation and distribution,leaf photosynthesis and physiological characteristics,starch content and key enzyme activities of starch synthesis,yield and yield components were studied.And RNA-seq technology was used to screen genes for tuber starch synthesis.The result show that:1.Appropriate phosphorus application can increase potato plant height,stem thickness,leaf area index(LAI),SPAD value,and dry matter accumulation.Under different treatments,potato plant height and stem thickness increased gradually and the value of T3 treatment was the largest.Appropriate amount of phosphorus can maintain high LAI in the later stages of growth.In 2018 and 2019,the LAI was the largest under T3 treatment,which was 168.93%and 38.89%higher than CK.Under different treatments,the SPAD value changed in a single-peak curve,reached a peak 60 days after emergence,and the SPAD value was the highest in T3 treatment.The accumulation of total dry matter of potato under different treatments conforms to the slow-fast-slow "S" curve change.With the increase of phosphorus application,the dry matter accumulation of potato leaves,above-ground stems and tubers increased,and the dry matter quality of potato plants was the highest when the phosphorus application was 120 kg/hm2.The dry matter accumulation of tubers in 2018 and 2019 was T3>T2>T4>T5>T1>CK and T3>T4>T2>T5>T1>CK.When the amount of phosphorus applied exceeded 120 kg/hm2,the LAI and above-ground dry matter accumulation of potatoes decreased rapidly,causing the early senescence of potato plants,which was not conducive to the later transfer of photosynthetic products to tubers.2.The photosynthetic rate(Pn),transpiration rate(Tr),PSII maximum photochemical efficiency(Fv/Fm),PSII potential activity(Fv/Fo),and PI of potato functional leaves showed single-peak curve changes under different phosphorus application.Under T3 treatment,the photosynthetic and fluorescence parameters of potato functional leaves were significantly higher than those of other treatments,which was most beneficial to the photosynthesis of potato and promoted the accumulation of photosynthetic products.Appropriate amount of phosphorus can reduce the degree of membrane lipid peroxidation in potato leaves,reduce cell membrane permeability,malondialdehyde and proline content,increase superoxide dismutase(SOD),peroxidase(POD),and catalase(CAT)activity.The protective enzyme activity was the highest under T3 treatment,which could effectively alleviate the premature aging of potatoes.3.Under different treatments,the amylose content of potato tubers increased first and then decreased.The amylose content of T1-T5 treatment in 2018 and 2019 significantly increased by 0.17,0.49,2.15,2.41,2.02 and 0.02,0.46,2.61,2.36,1.53 percentage points compared with CK.Amylopectin and total starch content gradually increased.The content of amylopectin and total starch was the largest when the phosphorus application was 120kg/hm2.The starch accumulation rate decreased sharply with the increase of phosphorus application at 60 days after potato emergence.T3 treatment potato starch accumulation rate decreased slowly and significantly higher than other treatments,which is more conducive to starch accumulation.The total starch accumulation of potato under different treatments conforms to the "S" growth curve.The maximum rates of starch accumulation under different treatments in 2018 and 2019 were T4>T5>T3>T2>CK>T1 and T3>T4>T5>T2>T1>CK.Path analysis showed that the key enzyme activity of starch synthesis is closely related to the accumulation of amylose,amylopectin and total starch.UGPase and SBE are not good for amylose synthesis.Amylopectin content is most affected by SSS and SBE.Total starch content is regulated by five key enzymes for starch synthesis.4.Different genes related to potato tuber starch metabolism under different phosphorus application rates.Preliminary screening of differential genes involved in the regulation of starch metabolism pathways in T1,T2,T3,T4,T5 treatment compared with CK were:5(2 up-regulated expressions,3 down-regulated expressions),4(4 are up-regulated expressions),7(1 up-regulated expressions,6 down-regulated expressions),0,2(2 are down-regulated expression).It indicates that the amount of phosphate fertilizer will affect the expression of genes related to potato tuber starch metabolism,and then affect the potato tuber starch synthesis.5.Significant differences between potato yield and yield components under different phosphorus application rates.Appropriate amount of phosphorus is beneficial to increase potato weight per hole,number of large potatoes and yield,and reduce number of small potatoes.Under T3 treatment,the potato weight per hole and the number of large potatoes were higher than those of other treatments,and the number of small potatoes were lower than those of other treatments.With the increase of phosphorus application,the yield of potato increased first and then decreased.2018 and 2019 potato production and net gains are greatest under T4 and T3 treatments,respectively.In 2018 and 2019,compared with CK,the yield of potatoes under T1-T5 treatment increased by 7.49%,19.87%,40.11%,45.84%,38.02%and 7.24%,21.38%,57.13%,40.23%,24.30%.Correlation analysis showed that there was a significant positive correlation between potato tuber yield and the number of large potatoes,and a significant negative correlation with the number of small potatoes.Therefore,the appropriate amount of phosphorus is beneficial to increase the potato weight per hole,the number of large potatoes,reduce the number of small potatoes,and then increase the yield.