Screening Of Low Phosphorus Tolerant Germplasm Of Sweet Potato And Its Response To Phosphorus Fertilization

Phosphorus is one of the large amount indispensable of nutrients for plant growth and development,and China is the country with the largest sweetpotato cultivation area in the world.Sweetpotato production has a large demand for phosphorus fertilizer,and it is important for sweetpotato production to improve phosphorus utilization efficiency and not reduce yield while reducing phosphorus application.In this experiment,sweetpotato genotypes tolerant to low phosphorus were screened by hydroponics under low phosphorus conditions,phosphorus efficiency evaluation method was established,and phosphorus efficient varieties of sweetpotato were screened.The effects of different phosphorus levels on yield quality,growth and development,phosphorus uptake and utilization efficiency,photosynthetic characteristics and uptake and utilization of other nutrients in sweetpotato were studied under field production conditions,and suitable phosphorus fertilizer dosage for sweetpotato production was screened,and the main results were as follows:1.low phosphorus-tolerant sweetpotato germplasm resources were screened.Under hydroponic environment,five agronomic indicators（aboveground dry weight,belowground dry weight,root to crown ratio,vine length and leaf area）of the evaluation system for low phosphorus tolerance were used for cluster analysis,and the participating sweetpotato germplasm were classified into low phosphorus tolerant genotypes,moderately low phosphorus tolerant genotypes and non-low phosphorus tolerant genotypes,among which five germplasm resources,including19-J14-12 and 20-J20-2,were low phosphorus tolerant genotypes.2.The effects of different phosphorus fertilizer levels on the yield and quality of sweet potato were studied.Among the five treatments with different phosphorus levels under field production conditions,the yield of fresh sweet potato was highest at 45140.25 kg/hm²under P3 treatment（40.5 kg/hm²,phosphorus application,same below）,and the taste quality was best under P3 treatment,with a taste score of 82.5.The anthocyanin content was significantly higher under P2（20.25 kg/hm²）and P3（40.55kg/hm²）treatments with 114.367 mg/100g DW and 111.06 mg/100g DW,respectively.soluble sugar,sucrose and fructose contents decreased with increasing phosphorus application,while starch content increased with increasing phosphorus application.3.The effects of different phosphorus levels on the growth and development of sweet potato were studied.Among the five different phosphorus fertilizer treatments under field production conditions,the longest vine length of sweetpotato at all fertility stages was significantly longer under P4 treatment（81 kg/hm²）than P1,P2 and P3 treatments.The average number of branches,number of potatoes per plant,leaf area,net photosynthetic rate,transpiration rate and instantaneous water use efficiency of leaves at all fertility stages of sweetpotato were the highest under P3 treatment.The percentage of large and medium-sized potatoes per plant at maturity was highest under P3 treatment,reaching 64.16%.There were also significant differences between different phosphorus fertilizer levels on the accumulation of dry matter in the lower part of the ground at each fertility stage of sweetpotato.The chlorophyll content of sweet potato leaves was highest under P4 and P5 treatments.4.The effect of different phosphorus levels on the uptake and utilization of mineral elements in sweetpotato was studied.Among the five different phosphorus fertilizer treatments under field production conditions at harvest time,the P3 treatment had the highest agronomic efficiency,phosphorus uptake and apparent phosphorus utilization,reaching 214.95 kg-kg^-1,48.82%and 69.14%,respectively.The accumulation of mineral elements in all parts of sweetpotato was potassium,nitrogen and phosphorus in descending order;the accumulation of nitrogen,phosphorus,potassium,calcium and magnesium in sweetpotato plants under P3 treatment was higher than other treatments at all fertility stages.5.Candidate genes related to low phosphorus tolerance in sweetpotato were screened.Transcriptome sequencing was performed on sweet potato roots treated with low and normal phosphorus,and the molecular mechanism of low phosphorus tolerance in sweet potato was initially analyzed.After detection and analysis,a total of 303differentially expressed genes were obtained in two materials treated with different phosphorus levels,and KEGG differential gene enrichment analysis revealed significant enrichment mainly in ribosomes,oxidative phosphorylation,glycolysis/gluconeogenesis,carbon metabolism,citric acid cycle（TCA cycle）,and oxytocin signaling pathways,among which the citric acid cycle（TCA cycle）may be more important for low phosphorus tolerance treatment Among them,the citric acid cycle（TCA cycle）may have a more important role in low phosphorus tolerance.Among the genes with significant differential expression,g SPO-A1 and g SPO-B1 storage protein genes,PPO1＿DWL polyphenol oxidase family genes,and ns LTPs gene family were found to be probably closely associated with low phosphorus tolerance.