To investigate the effect of plant growth regulators (PGRs)on the yield and phytohormone in sweet potato,the experiments were conducted with the spraying of PGRs at the beginning of enlargement stage in Jinan experimental base of SAAS.The effects of PGRs on the yield,dry matter distribution,photosynthesis and the phytohormone in root and leaf were investigated in three types (exuberant,general and feeblish of over ground part) sweet potato under field conditions.The results showed that the PGRs increased the root yield of sweet potato,enhanced the transfer of assimilation to the root.The mixture of CCC and DA-6 increased the photosynthetic rate of Xushu 18 and the effect of S3307 on the photosynthesis of 3 varieties was not significant compared with the contrast,and there was no significant relationship between the effect of PGRs on the photosynthesis and root yield.The treatment of S3307 decreased the concentration of leaf IAA in 3 sweet potato varieties,and decreased leaf ZR and GA₃ content in middle expansion period of Jishu 18,and decreased the leaf ZR and ABA content in later expansion period of Xushu 18,and the treatment of S3307 increased the leaf ABA content in middle and later expansion period and the root IAA content in front and middle expansion period of Jishu 18 and Xushu 18,and the IAA content in root of Shangshu 0110 was improved by S3307 during the expansion period.The mixture of CCC and DA-6 decreased the leaf IAA content in middle and root and leaf ZR content in later expansion period of Jishu 18,and decreased the leaf IAA,ZR,ABA and root ZR content in fronter expansion period of Xushu 18,and decreased the leaf GA₃ in froner stage and the ZR content in later expansion stage.The mixture of CCC and DA-6 in increased the root ABA,GA₃ and leaf ZR content in fronter stage and leaf ABA content in middle stage and root IAA content during the expansion stage of Jishu 18,and increased the leaf ZR content in froner stage and root GA₃ and ZR,leaf IAA and ABA content in middle stage and root IAA content in later expansion period of Xushu 18,and increased the root ZR and ABA in the whole period and leaf ZR content in middle stage and leaf GA₃ content in later expansion stage of Shangshu 0110.The treatment of PGRs changed the trend of phytohormone content of sweet potato on a certain extent,and promoted the transfer of assimilation from leaf and stem to the root,increasing the yield of tuberous root.The effect of PGRs on the photosynthesis varied with variety type,which was not the main effect of tuberous root yield.

As an important component of plant cell wall,expansins have effects on loosening and increasing the flexibility of cell wall,and are thought to have function in many process of plant growth. To study potential function of expansin gene family in potato,we investigated expansin gene family with the whole genome database to analyse its structure,phylogenetic relationship and expression profiles. Potato genome contained 33 expansin genes which belonged to 4 subfamilies (EXPA (21),EXPB (5),EXLA (1) and EXLB (6)) located on 11 different chromosomes. Expansin proteins ranged from 194 aa to 488 aa in size and had conserved domains. All 33 Expansin proteins were predicted to localize in extracellular. Gene structure analysis revealed that seventy percent(23/33) expansin genes had 2-3 introns. Transcriptome analysis showed that the potato expansin genes expressed highly in root,stem,stolon,mature fruit and tuber.

In view of a series of problems of a large number of inputs bringing the low utilization rate of water and fertilizer and nutrient loss in current production of high yield of potato,the effect of different fertilizer treatments on the yield,quality and the fertilizer utilization ratio of potato under mulching drip irrigation were studied in this paper under open field conditions.The different fertilizer treatments were composed of CK(No fertilizer),D1(1 245 kg/ha of slow-released of fertilizer),D2(1 500 kg/ha of compound fertilizer) and D3(675 kg/ha of water soluble fertilizer),and with farmers' conventional irrigation fertilization treatment CF(1 500 kg/ha of compound fertilizer with furrow irrigation) for comparison.The results indicated that different fertilization treatments under drip irrigation conditions increased the plant height,root length,root volume,leaf area index,chlorophyll content and plant fresh weight of potato and reduced the MDA content and SOD activity of potato.The test results also indicated that compared with conventional furrow irrigation fertilization,the treatments of D1,D2 and D3 with drip irrigation under mulch film promoted the potato on the absorption and accumulation of soil nutrients,increased the potato production by 18.4%,13.3% and 26.0% respectively.Starch content increased by 10.3%,5.5%,15.1% respectively,and the crude protein content increased by 12.9%,8.6% and 13.8% respectively.While the soluble sugar content reduced by 5.6%,2.4% and 15.3%respectively.Especially the D3 treatment with drip fertigation increased the fertilizer utilization ratio of nitrogen,phosphorus and potassium by 22.7%,20.5% and 23.5% respectively.From the point of view of the efficiency of agricultural use and the partial productivity of fertilizer,phosphate fertilizer was higher than that of nitrogen fertilizer and potassium fertilizer.Therefore,we should pay attention to the promotion of fertigation technology and the scientific application of fertilizer in potato production.

In order to investigate the relationship of nitrogen fertilizer(N) and planting density(D) with the yield, quality and starch pasting properties of fresh edible sweetpotato, the field experiments were carried out in 2017 and 2018 using Xushu 32 and Xuzishu 5 as the research subjects, and setting three nitrogen fertilizer levels and five planting densities. The results showed that:The storage root yield of the two varieties decreased with the increase of nitrogen application, while first decreased and then increased with the increase of density. In general, the maximum storage root yield came from the treatment of N0(0 kg/ha) nitrogen level and D1(43 785 plant/ha) density level; Nitrogen application reduced the dry matter rate and significantly increased the protein content in the two sweetpotato varieties. With the increase of planting density, the dry matter rate, starch content and protein content of the two cultivars generally increased first and then decreased. The reduced sugar showed a downward trend, while the soluble sugar content fluctuated, which was the lowest at D3 level; On the whole, the peak viscosity, hot paste viscosity and breakdown value of starch in the two varieties were significantly reduced and the setback value was significantly increased, resulting in the decline of cooking and eating quality. The peak viscosity, hot paste viscosity, breakdown value and cool paste viscosity fluctuated with the increase of density; the maximum values were from the D3 level for Xushu 32, and from the D2 level for Xuzishu 5. The effects of nitrogen application and planting density on RVA spectrum of sweetpotato starch were different among varieties and characteristics. Based on the results of this experiment, applying a large amount of nitrogen to a plot with high soil fertility reduced the storage root yield of sweetpotato, and negatively affected the nutritional quality and edible quality. At the density level of 43 785 plants/ha, the storage root yield was the highest. However, proper increase of density was beneficial to the improvement of nutritional quality, cooking quality and eating quality.

In order to find out the effect of different potassium doses on the yield and nutrient utilization of purple sweet potato,it provides theoretical and practical basis for the rational application of potash fertilizer. Using design of randomized block experiment,field experiment and chemical analysis method,the different amount of potassium application on low fertility soil accumulation of dry matter,yield and its components purple sweet potato factor,NPK factor accumulation,the effects of potassium use efficiency were studied. The results showed that dry matter accumulation in roots of purple sweet potato was higher than that of K₀ treatment during the growth of sweet potato,when the amount of potassium was 180 kg/ha,the accumulation of root dry matter reached the maximum. Potassium had effect on the accumulation and distribution of dry matter,increased the number of potatoes and single potato weight,and could increase the yield of sweet potato and obtain the largest yield increase when the rate of potassium application was 180 kg/ha. Compared with the K₀,the yield increased by 20.78% and 26.19%,respectively,in 2016 and 2017,and the difference was significant(P <0.05).Compared with K₀ treatment,potassium could promote the absorption of nitrogen and phosphorus in purple sweet potato,significantly increased the accumulation of whole plant nitrogen and phosphorus,and increased the maximum growth rate of K₃. The accumulation amount of the root and the whole plant nitrogen increased by 75.38% and 65.75% respectively,and the cumulative phosphorus accumulation increased by 45.24% and 60.28%,respectively,and difference was significant(P <0.05). Besides,potassium fertilizer treatments could also increase the utilization ratio of potash fertilizer and agronomic efficiency. Compared with K₀,apparent utilization and agriculture utilization increased by 47.82 percentage points and 158.11%,respectively,and the difference was significant(P <0.05). Therefore,the optimum application dosage of potassium fertilizer was confirmed to be 180 kg/ha.

In order to determine suitable planting method and density for fresh edible sweet potato planting in barren hilly in the central region of Shandong Province, L9 and J26 were used as test varieties under field conditions. Each variety was planted vertically and horizontally, with planting densities of 37 500 (D1), 52 500 (D2), and 67 500 plants/ha (D3). We studied the effects of different planting methods and densities on the dry matter accumulation, distribution, yield, and quality of fresh sweet potatoes. An increase in density increased the dry matter accumulation in the middle and late growth stages of the two varieties and significantly decreased the ratio of the dry matter distribution of the branch leaves of J26 planted vertically and horizontally. D2 treatment decreased the ratio of the dry matter distribution of the branch stems of L9 planted vertically and horizontally in the late growth stage and significantly increased the ratio of the dry matter distribution of the tuber roots of the two varieties planted vertically and horizontally in the middle growth stage. The D2 and D3 treatments significantly increased the ratio of the dry matter distribution of the tuberous roots of J26 planted vertically and horizontally in the late growth stage. For the two cultivars at the same transplanting method, D2 and D3 treatments significantly improved the soluble sugar content and starch content in tuberous roots and D2 treatment significantly increased the tuberous root yield of the two cultivars. Compared with vertical planting, horizontal planting significantly increased the dry matter accumulation in the early growth stage under D2 treatment and in late growth stage of J26 under D2 and D3 treatments and in the middle growth stage of L9 at the same density. Compared with vertical planting, horizontal planting increased the soluble sugar content of the tuberous roots of J26 under D1 treatment and that of L9 with different densities. Horizontal planting was also benificial for increasing tuberous root weight per plant and tuberous root yield of the two cultivars. With regard to yield and quality, horizontal planting + D2 treatment is the optimal combination under the test conditions.

The differences in nitrogen(N) uptake and utilization of different potato varieties at seedling stage in Northeast China were evaluated,and potato genotypes with high responsiveness to N were screened to provide a theoretical basis for the selection and mechanism study of potato N efficient genotypes. Pot experiment was used to compare the differences in the ability of different genotypes of potato to obtain N at the seedling stage under the three levels of N supply and their causes. The results showed that different N supply levels had significant differences in the ability of different genotypes to auumulate N. With the increased of N supply levels,the N accumulation of four potato varieties such as Dongnong 310,Yanshu 4,Kexin 13 and Kexin 22 increased significantly. The response rate was high,while the N accumulation of seven potato varieties such as Dongnong 308,Dongnong 311,Dongnong 312,Dongnong 316,Yanshu 9,Yanshu 7 and Kexin 19 had no significant increase,and the response to N was low. For the genotypes with high nitrogen responsiveness,the Nitrate reductase active(NRA),Glutamine synthetase active(GSA),and root activity a little bit increased significantly with increasing N supply levels,while the chlorophyll(SPAD)values increased less. The increase in N accumulation,NRA,GSA,root activity,and SPAD values were significantly greater than those with low N response. The correlations between N accumulation and NRA,GSA,SPAD,and root activity of potato under low N and high N conditions were analyzed. NRA and GSA activity could better reflect the N accumulation ability of potato during seedling stage,the ratio of SPAD and root activity. The reliability is better,and the strength of NRA and GSA activity can be used as an important indicator for evaluating the N uptake accumulation of potato seedlings.

Using the method of spraying calcium chloride solution on leaves,the influence of Ca-treatment on the growth and development of the continuous cropping potato were studied and the relevant mechanism was elucidated in this paper.The results showed that the treatment of spraying CaCl₂ solution could alleviate the inhibition on the growth of potato plants effectively caused by continuous cropping,thus improved the potato tuber yield,hardness and content of starch,vitamin C and soluble protein.The results also showed that spraying CaCl₂ solution reduced the decline in the content of chlorophyll and carotenoid,decreased the stomatal conductance and transpiration rate of the leaves,improved the net photosynthetic rate and water utilizing efficiency of the leaves,improved the content of proline and soluble sugar and the activities of SOD and CAT relatively,thus reduced the content of MDA and the reactive oxygen level in the continuous cropping potato seedlings leaves.So it could be concluded that the treatment of spraying CaCl₂ solution on the continuous cropping potato could improve the general resistance of the continuous cropping potato,and thus alleviated the continuous cropping obstacle,improved the growth,the tuber yield and nutrient,and the effects caused by spraying CaCl₂ solution should be closely related with the reduction of the leaves transpiration rate,the improvement of the leaves water status of the continuous cropping potato.

In order to unravel the infection mechanism of V.dahliae to potato,a binary construct contained GFP gene was transferred via Agrobacterium tumefaciens-mediated system into V.dahliae isolate VD012.47 positive transformants were obtained by hygromycin B selection and molecular verification.Eight tansformants were randomly selected to characterize the colony morphology,growth rate,conidia production,toxin production and pathogenicity.The results showed that three transformants could produce more microsclerotia compared with the wild type strain;whereas,one transforment produced less microsclerotia.The significant difference on the growth rate of eight transformants. The conidia production ability of the transformants were decreased to certain degree.except two among them were not remarkable overall.The average germination rate of all the tested transformants was lower than that of the wild strain after 8 h germination.Regarding to the toxin production,seven transformants showed increased tendency,while only one decreased compared with the wild type.The pathogencity results showed that,compared with wild strain,only one transformant showed increased tendency,the left two strains showed decreased pattern.

To explore the effect of potassium(K) and nitrogen (N) on yield and quality of tuber of sweet potato YS25 in soil with high fertility,used two factors of three levels completely randomized block design of experiment,with 3 N treatments(0,45,90 kg/ha) and 3 K₂O treatments (0,75,150 kg/ha),included 9 combinations of K and N treatments,were designed.The results showed that:High fertility soil nitrogen fertilizer could be added sweet potato vine length,shoot fresh weight,T/R value(Ratio of fresh weight of stem and leaf to fresh weight of underground),and improve the tuber of sweet potato protein, glucose and sucrose content and high fertility soil nitrogen fertilizer situation and root dry mass of fresh,the content of starch and fructose decreased.K fertilizer could significantly increase the root fresh and dry weight,potato rate and starch and glucose content;promote the sweet potato of Mg absorption,decreased the uptake of Ca by sweet potato.In nitrogen and potassium interaction conditions,sweet potato branching number,tuber number and Vc,protein,sucrose,glucose,fructose content with no fertilizer treatment were improved compared; fresh tuber yield and N fertilizer and potash fertilizer application interaction,namely when no N and K₂O 150 kg/ha,sweet potato yield reached the highest,with no fertilization treatment increased 10 825.5 kg/ha,an increased of 29.2%.At the same time in the implementation of N 90 kg/ha,without K₂O,the sweet potato yield was lowest,compared with no fertilization treatment was 1 435.5 kg/ha,a declined of 3.9%.Therefore,in the high fertility soil,the high yield and good quality of fresh edible sweet potato should be obtained by the application of no or less nitrogen fertilizer and the appropriate amount of potassium fertilizer.

In order to clarify the effect of phosphorus deficiency on root development and nutrient uptake of sweet potato.The sweet potato named Yanshu 25 was used as the experimental material,two treatments of phosphorus deficiency (P0) and normal phosphorus supply (P1) was set up,the growth characteristics and nutrient uptake of sweet potato roots under phosphorus deficiency were studied by gravel culture.The results showed that P deficiency could inhibit the growth of shoots and root parts of sweet potato and reduce the shoot and root biomass.Compared with normal phosphate,the total surface area,total root volume,the number of root tips and average diameter of sweet potato root increased with the prolongation of culture time,but its root activity decreased,total volume and total biomass were significantly lower than those of normal supply phosphorus treatment; Phosphorus deficiency could significantly increased the absorption of N,K,Ca,Mn,Cu in sweet potato root system,decreased the absorption of Mg,Fe in root system,while the N,K,Mg,Mn,Cu content increased and the Ca,Fe content decreased in shoot.Based on the above test results,phosphorus deficiency caused the growth and development of sweet potato ground and underground,but the sweet potato adapt to the lack of phosphorus environment by adjusting the root system and other root developmental parameters,so as to alleviate the effect of phosphorus deficiency on root nutrient uptake.

In this paper,the experimental study of regulated deficit irrigation (RDI) of potato at different growth stages was carried out at Yimin Irrigation Experimental Station in Minle County in Hexi Oasis Region in 2016. The soil nutrient and soil water and heat in the different growth stages dynamics,growth dynamics,yield effects and water use efficiency were measured. The results showed that the water deficit of potato under drip irrigation was uniform and the utilization rate was high,which was beneficial to the full absorption and utilization of soil nutrient. The soil nutrient was the core of soil fertility and plant was indispensable in the growth and development.Regulated deficit irrigation under plastic film drip irrigation could effectively reduce the loss of soil available nutrients and improved the utilization efficiency of soil available nutrients.The water consumption of potato in different growing stages was affected by the degree of water deficit and the amount of water consumption decreased significantly with the increase of water deficit. The water consumption of potato during the whole growth period with regulation of water deficit was lower than that of full irrigation.It was found that the water use efficiency, irrigation water use efficiency and biomass of the potato were the highest during the tuber formation withslightly water-deficient (WD1), which was 29.04%, 33.22% and 6.59% higher than that of full irrigation all the time (CK control) significantly. Therefore,the mild water deficit irrigation in the tuber formation stage could keep the soil in the potato root area moist all the time,effectively reduce the leakage loss and the evaporation loss between the plants,improve the soil water,fertilizer and heat status,and improve the crop water use efficiency,without significantly reducing the final yield of potatoes.

In order to explore the correlation between pathogenesis related protein (PR protein) and potato disease resistance, the ability to resist soft rot, bacterial wilt and dry rot in potato was tested. In the previous potato disease resistance study, 17 family gene-binding transcriptome data of PRs were analyzed and the genes were screened, and PR1 was finally determined. The potato Atlantic variety was selected as the material, which was provided by Heilongjiang Academy of Agricultural Sciences. The StPR1 gene was cloned and analyzed by bioinformatics. F.sambucinum and F.avenaceum were used. And E.carotovora subsp. Carotovora Borgey (Ecc), E.chrysanthemi Burkholder. Atroseptica Dye (Ech), can cause soft rot and bacterial wilt. The specific analysis of StPR1 gene expression was carried out after inoculation of potato tuber with E. carotovora subsp. Mc Fadden et Dimock (Eca) and Ralstonia solanacearum (RS). The results showed that the StPR1 gene was 540 bp in length and encoded 179 amino acids. The hydrophobicity and hydrophilicity of the protein are predicted.The GRAV value of the PR1 protein sequence was between +4 and-3, containing hydrophilic and hydrophobic regions, and protein secondary structure. It is predicted to be a mixed protein. The tertiary structure of the protein is predicted to be a tightly complex helical structure with a SCP_PR-1_like conserved domain, which is highly similar to the pepper PR1 gene on an evolutionary branch. The results of qRT-PCR showed that the expression level of StPR1 gene was higher than that of bacterial stress in antifungal stress, and its ability to resist dry rot was better than that against soft rot and bacterial wilt. In summary, when the potato is attacked by external pathogens, StPR1 plays an important role in the disease resistance of the potato.In summary, when the potato is attacked by external pathogens, StPR1 plays an important role in the disease resistance of the potato.

In order to enrich molecular markers and position the bacterial wilt resistant gene loci in potato,an SSR-based genetic linkage map was constructed from a diploid population consisting of 123 individuals derived from a cross between two potato diploid clones (C and E) which harborer resistance to Ralstonia solanacearum in this study.A total of 864 simple sequence repeat primer pairs were designed according to the potato genome sequence and used to screen parents C and E for polymorphisms.Of 187 polymorphic loci,72.2% showed clear amplifiable and scorable bands in the F₁ population.Then a total of 135 locus were mapped to 12 linkage groups,of which the cumulative length was 948.4 cM,with an average marker interval of 7.03 cM,and 5 segregation distortion regions in three linkage groups.This study provided a set of new SSR markers for genetic map construction and increased saturation of map in potato.The relatively high density map may provide a useful reference for further identification,mapping of quantitative trait loci (QTL) and cloning of potato bacterial wilt resistance genes and marker-assisted breeding.