【Objective】The objective of this paper was to analyze the genetic mechanisms of nitrogen use efficiency (NUE), and to explore the loci and candidate genes associated nitrogen (N) efficient traits, to provide support for the N-efficient molecular breeding and genetic improvement of sweetpotato.【Method】A total of 129 sweetpotato cultivars from all over the world were treated with N deficiency (0 mmol·L-1) and normal N (14 mmol·L-1). A hydroponic experiment was conducted to facilitate the genome-wide association study (GWAS) of six phenotypic traits (shoot biomass increment, root biomass increment, shoot N accumulation, root N accumulation, shoot N physiological utilization efficiency, and root N physiological utilization efficiency) of sweetpotato at the seedling stage. The N-efficient candidate genes were identified based on the GWAS and subsequently- verified using RT-qPCR.【Result】There were wide variations among the six traits related to NUE in sweetpotato under the normal N and N deficiency treatment conditions. The coefficient of variation (CV) of the shoot biomass increment under the N deficiency treatment condition was the greatest at 69.5%. The CV of the root N physiological utilization efficiency under N deficiency treatment condition was the smallest at 12.1%. All five traits were significantly correlated except for root N physiological utilization efficiency. The MLM model was used to conduct a GWAS of the six phenotypic trait values. A total of 134 QTL and 888 SNP loci were identified as being significantly associated with four out of the six traits, namely, shoot biomass increment, root biomass increment, root N accumulation, and shoot N physiological utilization efficiency. A total of 93 SNP markers across ten regions were significantly associated with shoot N physiological utilization efficiency with a high reliability. Six N efficiency candidate genes were obtained via gene annotation. RT-qPCR verified that the three candidate genes (itf01g08120.t1, itf01g22030.t1 and itf01g221000.t2) encoded glutamate dehydrogenase, NPH3 protein and TIP41-like protein, respectively, which warrants further research.【Conclusion】A total of 888 SNP loci associated with N utilization traits were detected in 129 sweetpotato cultivars. Among these, 93 SNP loci were significantly associated with shoot N physiological utilization efficiency, and six candidate genes were identified. Preliminary verification indicated that the itf01g08120.t1, itf01G2203.t1 and itf01g22100.t2 genes hold promising value for further research.

为建立甘薯苗期耐低钾能力评价体系,筛选耐低钾和低钾敏感型甘薯材料,通过水培试验设置了低钾胁迫(0 mmol L -1 K 2 O)和正常钾处理(10 mmol L -1 K 2 O),对来自国内外不同薯区的214份甘薯品种（系）材料进行培养,收集生物量、钾积累量、钾含量、钾利用效率等11个性状表征值,计算各指标耐低钾胁迫指数。利用综合隶属函数法,进行主成分分析、回归分析和聚类分析,综合评价各甘薯材料耐低钾能力。结果表明,不同甘薯材料在2个钾水平下的生物量和钾吸收利用特征均有明显差异;低钾胁迫下地上部干重（SB）、地上部干物质增加量（SBI）、根系干物质增加量（RBI）、总干物质增加量（PBI）、地上部钾积累量（KAS）、根钾积累量（KAR）、总钾积累量（KAP）、地上部钾含量（KCS）和根系钾含量（KCR）等9个指标与正常钾处理相比均降低29%以上,而根冠比（RSR）和钾生理利用效率（KUE）分别提高29.63%和120.56%。低钾胁迫下,不同甘薯材料的SB、SBI、PBI、KAS、KAP、KCS、KCR和KUE等8个指标的变异系数均高于正常钾处理。对11个指标的耐低钾胁迫指数进行主成分分析,选择了3个主成分,累计方差贡献率达82.86%; 11个指标的耐低钾敏感指数均与耐低钾综合评价值（Y）极显著相关。选择了SBI、RBI、PBI、KAS、KAR、KAP等6个指标作为筛选评价指标,根据聚类热图分析将214份甘薯材料划分为耐低钾型、中间型和不耐低钾型;方差分析表明,耐低钾型品种与其他类型品种相比具有较高的耐低钾胁迫指数,Y值也排列前位,验证了聚类结果的准确性。综合本研究结果, SBI、RBI、PBI、KAS、KAR、KAP等6个指标可作为甘薯苗期耐低钾能力筛选的首选指标;筛选出甘薯苗期耐低钾能力最强的6个品种,分别为济紫薯18号、广紫薯2号、龙薯710、泰中6号、胜利百号、龙薯9号。

从氮高效候选基团的定位及表达分析着手,概述作物中氮高效利用的分子生物学研究进展,并对甘薯的氮高效利用的分子学研究进行展望,以期为培育氮高效型甘薯品种与氮高效遗传位点挖掘提供参考.

【Objective】The objective of this article was to establish a low-N tolerance evaluation system for sweetpotato varieties, to screen low-N-tolerant genotypes and evaluate different N efficiency categories and to provide a theoretical basis for studying the low-N-tolerant physiological mechanism of sweetpotato varieties and mining N-efficient genes.【Method】Under the treatment of low N stress (0 mmol·L-1) and normal N application (14 mmol·L-1) of hydroponic experiment. Selected 126 sweetpotato varieties from different sweetpotato areas at home and abroad, we collected eleven indicators, including the shoot biomass, shoot biomass increase, root biomass increase, plant biomass increase ratio, root-to-shoot ratio, vine length, root length, leaf number, CCI, nitrogen accumulation, nitrogen physiological utilization efficiency, and calculated the low-N tolerance index of all indicators. The study carried out principal component analysis by using the comprehensive membership function method, regression analysis and cluster analysis to comprehensively evaluate the low-N-tolerant sweetpotato varieties and N efficiency types.【Result】1) Under low N level, the average of the shoot biomass, shoot biomass increase, root biomass increase, plant biomass increase ratio, vine length, root length, leaf number, CCI, and N accumulation of 126 tested sweetpotato varieties was lower than that under normal N level, while the average of root-to-shoot ratio and nitrogen physiological utilization efficiency were higher than that under normal N level; 2) The variation coefficient of shoot biomass, shoot biomass increase, root biomass increase, plant biomass increase ratio, root-to-shoot ratio, vine length, root length, leaf number, nitrogen accumulation, nitrogen physiological utilization efficiency at low-N stress was higher than that at normal N level, and the amplification of them were ranked as shoot biomass increase>plant biomass increase ratio>root biomass increase>leaf number>shoot biomass>nitrogen physiological utilization efficiency>nitrogen accumulation>root length> root-to-shoot ratio>Vine length; 3) The principal component analysis was carried out on the low-N-tolerant index of eleven indicators, extracted three principal components, the cumulative variance contribution rate of which was 72.67%, and calculated the comprehensive evaluation Y-value; 4) The correlation between the low-N-tolerant index of shoot biomass, shoot biomass increase, root biomass increase, plant biomass increase ratio, leaf number, vine length, root length, root-to-shoot ratio, nitrogen accumulation, nitrogen physiological utilization efficiency and the Y-value were highly significant (P<0.01), among them, the correlation of shoot biomass increase, root biomass increase, plant biomass increase ratio, nitrogen accumulation and shoot biomass was higher, with the correlation coefficients of 0.85, 0.86, 0.81, 0.79 and 0.73, respectively; 5) The regression equation of the Y-value screened eight indicators to evaluate low-N tolerance of sweetpotato varieties, and the cluster analysis on eight indicators showed that the sweetpotato genotypes were classified into three types, low-N-tolerant, intermediate, and low-N-sensitive. The agronomic traits and N efficiency traits of three sweetpotato categories were analyzed by variance analysis.【Conclusion】Shoot biomass, shoot biomass increase, root biomass increase, root length, vine length, leaf number, nitrogen accumulation and nitrogen physiological utilization efficiency were selected as the low-N tolerance evaluation indicators of sweetpotato; The study screened 7 low-N-tolerant sweetpotato varieties: 13104-2/Zishu1, Yibinhongxinshu, Zhezishu 2, Yuzi 3, Yuzi 6, Luozi 1 and Yuzixiang 10; The results of variance analysis showed that the low-N-tolerant varieties performed better than the intermediate and the low-N sensitive varieties, and there are significant difference in five traits: shoot biomass, shoot biomass increase, root biomass increase, vine length and nitrogen accumulation.

DNA-binding One Zinc Finger (Dof) transcription factors are widely involved in various life activities of plants. Forty-six IbDof genes from sweetpotato cv. Taizhong 6 with a highly conserved Dof domain structured as a C2C2-type zinc finger were identified and named from IbDof1 to IbDof46 according to their position on the chromosomes. IbDof family could be divided into four subgroups (A-D), which shared the similar motifs and gene structures. Motif 1 and Motf 2 occurred in all of the identified IbDofs, Motif 5 and Motif 9 only occurred in subgroup A, and Motif 6-Motif 8 and Motif 10 only occurred in subgroup D. Twelve segment duplicated gene pairs and five tandem duplicated gene pairs of IbDofs (IbDof2/IbDof3, IbDof12/IbDof13, IbDof9/IbDof10, IbDof28/IbDof29, and IbDof32/IbDof33) contributed to the expansion of IbDof family in sweetpotato. The average divergence times of segmental duplication gene pairs and tandem duplicated gene pairs seemed to have emerged 35.22 MYA and 1.86 MYA, and the Ka/Ks ratios of the paralogous IbDofs were range from 0.07 (IbDof12/IbDof13) to 0.68 (IbDof6/IbDof25). Tirty-eight orthologous IbDof gene pairs between sweetpotato and their wild relative species Ipomoea trifida were involved in duplicated genomic blocks based on synteny analysis. Transcriptome analysis indicated different subgroups expressed specifically in various tissues, and IbDofs in the same subgroup also revealed different expression tends. Various hormones and stresses response element were identified in the promoters of IbDof genes, and qRT-PCR demonstrated specific IbDof genes responded to various environmental stresses, including cold, drought, salt, and H2O2. Most IbDof genes were regulated by cold treatment; IbDof10 and IbDof14 were up-regulated by drought treatment; IbDof-2, -14, -37, -41, -43 were up regulated by high salt stress; and IbDof-8, -10, -25, -41 were up regulated by H2O2 treatment. In summary, our result indicated that IbDof family genes coordinately regulated the growth and development of sweetpotato and been involved in the various abiotic stresses process.

This study aims to explore the effect of phosphorus (P) application on the economic yield, quality, P accumulation, and P utilisation efficiency of purple-fleshed sweetpotato and to provide a basis for the P efficient utilisation and high crop yield. Field experiments were conducted in 2018-2019, and five P application rates (0, 10.9, 21.8, 32.7, and 43.6 kg P/ha, expressed as P0, P1, P2, P3, and P4, respectively) were set. The results showed that P application significantly increased the yield and commodity potato yield of purple-fleshed sweetpotato, and that of P3 treatment was the highest, followed by P2 treatment. P application also increased the starch content in the storage root and increased the reducing sugar and soluble sugar (except for P2 treatment). P fertiliser supply significantly increased P accumulation and dry matter production of purple-fleshed sweetpotato during the growth period of 90 to 120 days. When the P application rate was over 21.8 kg/ha, the fertiliser investment rate, apparent P utilisation efficiency and P agronomic efficiency decreased with the increase of the application rate. Considering all the indexes, the supply of 21.8 kg/ha P fertiliser can meet the demand for high economic yield and P efficient utilisation in purple-fleshed type sweetpotato under the condition of this experiment.

[目的]研究30个不同甘薯种植区土壤样品,探索不同地区土壤特征差异及其对甘薯的影响.[方法]分析不同甘薯种植区土壤样品的养分(速效磷、速效钾、pH值、土壤有机碳和全氮)及微结构特性(孔隙度、粒径).[结果]不同地区养分和土壤微观结构差别较大,如来自黑龙江肇源的土壤全氮(1.27 g/kg)、速效磷(64.23 mg/kg)、速效钾(353.0 mg/kg)、有机碳(15.94 g/kg)、孔隙占有率(32.47％)、砂粒占比(3.41％),与来自新疆叶城的土壤全氮(0.06 g/kg)、速效磷(7.23 mg/kg)、速效钾(60.5 mg/kg)、有机碳(1.18g/kg)、孔隙占有率(30.09％)、砂粒占比(23.56％)形成显著性差异;同一地区不同取样点土壤微观结构也有差别,如来自新疆乌鲁木齐的土壤全氮(1.21 g/kg)、速效磷(37.29 mg/kg)、速效钾(443.0 mg/kg)、有机碳(12.36g/kg)、孔隙占有率(33.74％)、砂粒占比(0.21％),与新疆叶城的土壤同样形成显著性差异.[结论]土壤特征是影响甘薯产量形成的重要因素.

植物高亲和钾转运体HKT基因具有Na+(或K+)单向运输或Na+-K+共转运作用.为了探究甘薯高亲和钾转运体HKT的离子转运情况及其对非生物胁迫的响应,本研究克隆得到1个甘薯钾离子转运体IbHKT-like基因.生物信息学分析结果表明,IbHKT-like基因序列全长为1647 bp,编码548个氨基酸.IbHKT-like蛋白有2个TrkH(细菌钾转运系统Trk亚基)保守结构域,10个跨膜片段.进化树分析结果表明,IbHKT-like蛋白与旋花科的矮牵牛InHKT6氨基酸序列十分相似,相似度为90.63％.亚细胞定位结果显示,IbHKT-like蛋白主要定位在细胞质膜,在叶绿体中存在少量分布.组织特异性分析结果表明,IbHKT-like基因在叶中表达量最高.实时荧光定量PCR结果显示,IbHKT-like基因的表达受到低温、干旱、高盐及过氧化氢胁迫的诱导,说明IbHKT-like基因可能在甘薯抵御非生物胁迫中发挥着重要的作用.