As a key enzyme in the starch and sugar metabolic pathways in sweet potato (Ipomoea batatas (L.) Lam.), the vacuolar invertase (EC 3.2.1.26) IbβFRUCT2 is involved in partitioning and modulating the starch and sugar components of the storage root. However, the post-translational regulation of its invertase activity remains unclear. In this study, we identified three invertase inhibitors, IbInvInh1, IbInvInh2, and IbInvInh3, as potential interaction partners of IbβFRUCT2. All were found to act as vacuolar invertase inhibitors (VIFs) and belonged to the plant invertase/pectin methyl esterase inhibitor superfamily. Among the three VIFs, IbInvInh2 is a novel VIF in sweet potato and was confirmed to be an inhibitor of IbβFRUCT2. The N-terminal domain of IbβFRUCT2 and the Thr39 and Leu198 sites of IbInvInh2 were predicted to be engaged in their interactions. The transgenic expression of IbInvInh2 in Arabidopsis thaliana plants reduced the starch content of leaves, while its expression in the Ibβfruct2-expressing Arabidopsis plants increased the starch content of leaves, suggesting that the post-translational inhibition of IbβFRUCT2 activity by IbInvInh2 contributes to the regulation of the plant starch content. Taken together, our findings reveal a novel VIF in sweet potato and provide insights into the potential regulatory roles of the VIFs and invertase-VIF interaction in starch metabolism. These insights lay the foundation for using VIFs to improve the starch properties of crops.

为探索更加合理的甘薯耐荫性评价方式,通过人工遮荫,研究弱光下29个不同甘薯品种(系)的农艺性状、光合指标、产量变化等,并采用不同的评价分类方式对其进行耐荫性评价.结果表明:不同品种(系)在同一单项指标下的耐荫系数不同,同一品种(系)的不同单项指标耐荫系数也存在差异,其中以气孔导度、净光合速率、非光化学猝灭系数和蒸腾速率等光合指标的变异系数较大,分别为69.07％,67.55％,61.91％和49.99％;茎干质量、蔓长、叶面积指数及分枝数的变异系数中等,分别为28.70％,24.90％,24.84％及24.13％.以茎干质量、净光合速率或非光化学猝灭系数等单项指标评价分类结果与产量减幅规律不符,而采用主成分分析、隶属函数分析和聚类分析等方法进行耐荫性综合评价结果更加可靠.

Sweet potato [Ipomoea batatas (L.) Lam.] is an important food and industrial crop. Its storage root is rich in starch, which is present in the form of granules and represents the principal storage carbohydrate in plants. Starch content is an important trait of sweet potato controlling the quality and yield of industrial products. Vacuolar invertase encoding gene Ibβfruct2 was supposed to be a key regulator of starch content in sweet potato, but its function and regulation were unclear. In this study, three Ibβfruct2 gene members were detected. Their promoters displayed differences in sequence, activity, and cis-regulatory elements and might interact with different transcription factors, indicating that the three Ibβfruct2 family members are governed by different regulatory mechanisms at the transcription level. Among them, we found that only Ibβfruct2-1 show a high expression level and promoter activity, and encodes a protein with invertase activity, and the conserved domains and three conserved motifs NDPNG, RDP, and WEC are critical to this activity. Only two and six amino acid residue variations were detected in sequences of proteins encoded by Ibβfruct2-2 and Ibβfruct2-3, respectively, compared with Ibβfruct2-1; although not within key motifs, these variations affected protein structure and affinities for the catalytic substrate, resulting in functional deficiency and low activity. Heterologous expression of Ibβfruct2-1 in Arabidopsis decreased starch content but increased glucose content in leaves, indicating Ibβfruct2-1 was a negative regulator of starch content. These findings represent an important advance in understanding the regulatory and functional divergence among duplicated genes in sweet potato, and provide critical information for functional studies and utilization of these genes in genetic improvement.

Sweet potato virus disease (SPVD) is one of the main virus diseases in sweet potato [Ipomoea batatas (L.) Lam] that seriously affects the yield of sweet potato. Therefore, the establishment of a simple, rapid and effective method to detect SPVD is of great significance for the early warning and prevention of this disease. In this study, the experiment was carried out in two years to compare the grafting method and side grafting method for three sweet potato varieties, and the optimal grafting method was selected. After grafting with seedlings infected with SPVD, the symptomatic diagnosis and serological detection were performed in 86 host varieties, and the differences in SPVD resistance were determined by fluorescence quantitative PCR (qRT-PCR) and nitrocellulose membrane enzyme-linked immunosorbent assay (NCM-ELISA). The results showed that the survival rate of grafting by insertion method was significantly higher than that by side grafting method, and the disease resistance of different varieties to sweet potato virus disease was tested. The detection method established in this study can provide theoretical basis for identification and screening of resistant sweet potato varieties.

马铃薯是典型的喜钾作物,钾肥施用量对于马铃薯产量具有较大影响,钾高效品种的利用不仅可减少钾肥的用量,还可提高肥料的利用效率从而减少农田生态环境的污染.为此,研究采用二因素裂区试验设计,设低钾水平(75 kg/hm2)和高钾水平(300 kg/hm2),选用20份西南地区代表性马铃薯品种(系)为材料,对其开展了钾素吸收和利用效率研究,并对其进行了聚类分析.结果表明,参试品种(系)在两个钾素水平下钾素吸收和利用效率的相关参数存在显著差异;钾素吸收效率在低钾水平下与植株含钾量呈极显著正相关,在高钾水平下与块茎含钾量呈显著正相关;钾素利用效率在低钾水平下与植株含钾量呈极显著负相关(rK75=-0.523**);基于钾素营养效率可将20个马铃薯品种分为4类,其中双高效型代表性品种(系)有'黔芋6号'和'378711.7',双低效型有'08CA0710'和'09307-830',高钾高效型有'米拉'中薯19',低钾高效型有'华渝5号'郑薯5号'.两钾素水平下的单株块茎产量的变异系数较大,可以作为评价钾素利用效率的首选指标.

Knowledge of genetic variations can provide clues into the molecular mechanisms regulating key crop traits. Sweet potato (Ipomoea batatas (L.) Lam.) is an important starch-producing crop, but little is known about the genetic variations in starch biosynthesis and sucrose metabolism genes. Here, we used high-throughput sequencing of pooled amplicons of target genes to identify sequence variations in 20 genes encoding key enzymes involved in starch biosynthesis and sucrose metabolism in 507 sweet potato germplasms. After filtering potential variations between gene copies within the genome, we identified 622 potential allelic single nucleotide polymorphisms (SNPs) and 85 insertions/deletions (InDels), including 50 non-synonymous SNPs (nsSNPs) and 12 frameshift InDels. Three nsSNPs were confirmed to be present in eight sweet potato varieties with various starch properties using cleaved amplified polymorphic sequence (CAPS) markers. Gene copy with loss of the fifth intron was detected in IbAGPb3 genes, and loss of multiple introns were observed in IbGBSS1-1 genes and various among germplasms based on intron length polymorphism (ILP) markers. Thus, we identified sequence variations between germplasms in 20 genes involved in starch biosynthesis and sucrose metabolism, and demonstrated the diversity in intron-loss alleles among sweet potato germplasms. These findings provide critical genetic information and useful molecular markers for revealing regulatory mechanism of starch properties.

为构建便捷的马铃薯(Solanum tuberosum)耐荫性综合评价体系并发掘耐荫种质,以35个马铃薯品种(系)为实验材料,测定块茎膨大期遮荫下植株叶片叶绿素含量、光合能力和叶绿素荧光等光合参数及收获后块茎单株产量和淀粉含量等指标.根据耐荫系数,利用主成分分析法、隶属函数法、聚类分析法和逐步回归分析法进行综合评价.通过主成分分析将马铃薯耐荫性相关的13个单项光合指标转换为6个综合指标,代表了全部信息的87.51％.以此计算各种质的隶属函数值,并以主成分的贡献率进行加权,最终获得所用材料耐荫性的综合评价值(D值).根据D值聚类分析结果将35个马铃薯分为4类,其中Eshu10和Lishu6分别为耐荫性最强和最弱的品种.通过逐步回归分析建立了马铃薯耐荫性评价数学模型:D=0.060+0.106Gs+0.214qP+0.143NPQ.同时,用该评价体系鉴定为耐荫性强的品种(系)在遮荫后其产量和/或淀粉含量等指标减幅均低于耐荫性弱的种质,表明该评价体系可用于快速评价和预测马铃薯种质的耐荫性.

马铃薯是重庆优势特色作物之一,但其安全生产受到晚疫病的严重威胁.马铃薯生产中种植抗病品种是防控马铃薯晚疫病最为经济有效和环境友好的途径.为了了解来自国内外不同种质的晚疫病抗性基因组成以及确定在重庆市具有晚疫病抗性的马铃薯品种(系),本研究以218份来自国内外的品种(系)为材料,进行了6个晚疫病抗性(R)基因分子标记检测,同时进行了田间晚疫病抗性评价及室内接种鉴定和筛选.研究结果显示,6个R基因的分子标记在供试材料中均有分布,但分子标记的组成不尽相同,主要分为4大类.第Ⅰ类含有具有广谱抗性基因的RB,晚疫病抗性评价表现为中抗以上;第Ⅲ类缺失R2 family基因标记,绝大部分表现为晚疫病敏感型;第Ⅱ类和第Ⅳ类中分别主要含有3个R基因(R2 Family+R3a+R3b)标记类型和4个R基因(R1+ R2 Family+R3a+R3b)标记类型,这两类材料中表现出一定比例的晚疫病抗性水平,但第Ⅳ类中出现抗性表现的比例高于第Ⅱ类.结果 说明含有RB基因标记贡献了较高的晚疫病抗性,缺失R2 famlily基因标记的材料可能不利于晚疫病抗性,利用这些基因标记辅助筛选有助于提高重庆地区晚疫病抗性育种效率.本研究评价了218份马铃薯材料6个重要R基因组成,并筛选出重庆地区表现抗性的多个材料,为新品种(系)的推广应用以及抗病育种选育提供了科学依据,同时为发掘新的抗病基因提供了遗传资源.

为提高甘薯作物的产量和效益,探讨土壤容重和耕作层土壤厚度对甘薯产量和品质的影响,以期为甘薯生产提供指导.以渝薯6号为材料,采用二因素随机区组设计方法,盆栽模拟试验,分期测定甘薯块根的各项指标.研究分层设置土壤容重的处理方式对甘薯根系生长,块根产量及品质的影响.在底部土壤容重为1.6 g/cm3、下层土壤为8～32 cm的时候,淀粉含量达到最大值29.98％,极显著高于空白对照;在底部土壤容重为1.5 g/cm3,底层土壤厚度为16～32 cm时,块根质量最大(为0.68 kg).试验结果表明,过高的土壤容重会造成SOD活性、MDA含量、淀粉含量增加,但不利于产量增加;下层土壤厚度减少有利于甘薯产量的提高,却不利于淀粉累积.

中国种业发展历经数年并取得长足进步,本文从育种平台机制 、创新人才 、创新投入 、创新效率等方面详细分析了我国种业技术创新能力的现状与成就,同时对比发达国家,指出了我国种业技术创新能力在机制 、设备 、技术 、自主创新 、知识产权保护方面的不足,为我国种业技术创新能力提升提供了参考和努力方向.

种业企业竞争力决定企业的生存和发展.立足我国种业企业实际,通过数据比较与详细分析,着重阐述现阶段我国种业企业处于深度调整期的产业发展特点、 市场营收利润及国内上市种业企业核心竞争力等方面的现状特点及存在的不足,为科学制定提高我国种业企业竞争力的合理化建议提供依据和参考.

To explore the correlation and to discuss the classification standard of hardness and dry-matter content of sweetpotato, collected and determined 129 sweetpotato varieties (lines) by using sclerometer and drying method, respectively, and the linear regression equation was established based on the correlation between hardness and dry-matter content values. The dry-matter content and hardness of storage root in the 129 sweetpotato varieties (lines) could be divided into five grades with normal distri-bution, which proportions were 10.00%, 19.12%, 40.88%, 20.88%, and 9.12%, respectively. There were significant differences in hardness among different parts of storage root, ranking as: the core site of radial cutting surface > the middle site of radial cutting surface > the tail site of axial cutting surface > the head site of axial cutting surface > the core site of axial cutting surface > the middle site of axial cutting surface. There was significant positive correlation between hardness and dry-matter content of storage root. By using the mean value of hardness at core and middle parts of storage root after radial cutting, the dry matter content could be well predicted by using the regression equation y = 0.6743x+3.6184 (20 ≤ x ≤ 60, R2 = 0.712192). This equation was validated in evaluation of the dry matter content in 20 sweet potato varieties (lines), and the relative error between estimated value and measured value was 0.2%. This result demonstrated that the equation obtained in this study could be used for accurate, fast and low cost measurement of dry matter content in sweetpotato production and breeding.

The starch properties of the storage root (SR) affect the quality of sweet potato (Ipomoea batatas (L.) Lam.). Although numerous studies have analyzed the accumulation and properties of starch in sweet potato SRs, the transcriptomic variation associated with starch properties in SR has not been quantified. In this study, we measured the starch and sugar contents and analyzed the transcriptome profiles of SRs harvested from sweet potatoes with high, medium, and extremely low starch contents, at five developmental stages [65, 80, 95, 110, and 125 days after transplanting (DAP)]. We found that differences in both water content and starch accumulation in the dry matter affect the starch content of SRs in different sweet potato genotypes. Based on transcriptome sequencing data, we assembled 112336 unigenes, and identified several differentially expressed genes (DEGs) involved in starch and sucrose metabolism, and revealed the transcriptional regulatory network controlling starch and sucrose metabolism in sweet potato SRs. Correlation analysis between expression patterns and starch and sugar contents suggested that the sugar-starch conversion steps catalyzed by sucrose synthase (SuSy) and UDP-glucose pyrophosphorylase (UGPase) may be essential for starch accumulation in the dry matter of SRs, and IbβFRUCT2, a vacuolar acid invertase, might also be a key regulator of starch content in the SRs. Our results provide valuable resources for future investigations aimed at deciphering the molecular mechanisms determining the starch properties of sweet potato SRs.

Sweet potato/maize relay-cropping mode is considered as the main farming practices of dry land in Southwest China. Although relay-cropping would cause the reduction of fresh tuber yield, it still remained unclear that the reason was shade resulted from maize or genotype of sweet potato. The present work aims at exploring the effects of maize (Zea mays L.) plant-type on photosynthetic physiology and yield of sweet potato (Ipomoea balatas L.) in relay-cropping system. Besides, three plant-types maize cultivars including compact, semi-compact and expanded type were used for relay-cropping with different sweet potato cultivars ('Yushu-2', 'Yushu-6' and 'Nanshu-88') in field. The results showed that the photosynthetically active radiation (PAR) was declined with the increase of expansion of maize plant-type, which decreased by 77.5%, 80.1% and 82.1% respectively. When relay-cropped with extended maize, the yield reduction rate of sweet potato was the highest (67%). The shade-resistance of different genotype of sweet potatoes was different, and the yield reduction rate of 'Yushu-2' was the lowest (37.01%). Through conducting correlations analysis, it showed that fresh tuber yield had significant positive correlation with Effective Quantum Yield (Y(II)) and significant negative correlation with Non Photochemical Quenching Coefficient (NPQ). In terms of 'Yushu-2', the proportion of heat dissipation was the lowest, and its light quantum efficiency was higher than others. As a result, its reduction rate of yield was lower than the other two. We suggested that compact maize cultivar relay-cropping with strong shade-resistance sweet potato cultivar should be mainly applied in practice of sweet potato.

[目的]利用分子标记技术,构建甘薯遗传连锁图谱,并分析甘薯淀粉含量性状的QTL位点,为高淀粉含量甘薯种质资源利用及甘薯分子标记辅助育种提供理论和实践依据.[方法]以高淀粉含量品种万薯5号为母本、低淀粉含量品种商丘52-7为父本建立杂交群体,利用EST-SSR标记,采用“双假测交”策略和运用JoinMap4.0软件,分别构建双亲遗传连锁图谱,并结合F1(201 2、201 3年)群体表型数据采用区间作图法对淀粉含量性状进行QTL检测.[结果]利用1 679对EST-SSR引物筛选出的1 045对多态性引物检测F1群体的标记基因型,获得了1 418个标记位点.分别对上述获得的父母本多态性标记进行遗传连锁分析,在LOD≥5.0情况下,分别构建父母本的连锁遗传图谱.采用642个标记的多态性位点构建母本连锁群74个,其中,21 5个标记位点位于连锁图谱上,占标记多态性位点总数的33.5％.每个连锁群上有2-11个标记位点,连锁群长度在0.6-129.4 cM,图谱总长为3 826.07 cM,标记间平均距离为17.80 cM.属于父本的776个标记位点构建了80个连锁群,共有252个标记位点构建在连锁图谱上,占标记总数的32.5％,每个连锁群上有2-24个标记位点,连锁群长度在2.0-156.8 cM,图谱总长为3 955.0 cM,标记间平均距离为15.7 cM.以F1杂交群体构建的遗传连锁图谱,结合2012年、201 3年2个环境,利用QTL作图软件MapQTL5.0,采用区间作图法进行分析,共检测到17个与淀粉含量性状相关的QTL,贡献率在8.4％-40.5％.其中qWsc-1、qWsc-2、qWsc-3 3个QTL位于母本万薯5号连锁群上,且在2年环境中均可检测到;14个QTL位于父本商丘52-7连锁群上,qSsc-1、qSsc-2、qSsc-3、qSsc-4、qSsc-8、qSsc-10、qSsc-11、qSsc-12是在2个环境均检测到的QTL.qSsc-5、qSsc-6、qSsc-7、qSsc-9、qSsc-1 3、qSsc-14是只在1个环境检测到的QTL.标记GDAAS0603在双亲中和2个环境中均同时检测到,这些环境稳定QTL可用于分子标记辅助选择.[结论]分别构建了亲本EST-SSR分子标记连锁群图谱,丰富了构建甘薯图谱的标记类型,定位了1 7个与淀粉含量相关的QTL位点.

Sweet potato (Ipomoea batatas L.) is a nutritious food crop and, based on the high starch content of its storage root, a potential bioethanol feedstock. Enhancing the nutritional value and starch quantity of storage roots are important goals of sweet potato breeding programs aimed at developing improved varieties for direct consumption, processing, and industrial uses. However, developing improved lines of sweet potato is challenging due to the genetic complexity of this plant and the lack of genome information. Short sequence repeat (SSR) markers are powerful molecular tools for tracking important loci in crops and for molecular-based breeding strategies; however, few SSR markers and marker-trait associations have hitherto been identified in sweet potato. In this study, we identified 1824 SSRs by using a de novo assembly of publicly available ESTs and mRNAs in sweet potato, and designed 1476 primer pairs based on SSR-containing sequences. We mapped 214 pairs of primers in a natural population comprised of 239 germplasms, and identified 1278 alleles with an average of 5.972 alleles per locus and a major allele frequency of 0.7702. Population structure analysis revealed two subpopulations in this panel of germplasms, and phenotypic characterization demonstrated that this panel is suitable for association mapping of starch-related traits. We identified 32, 16, and 17 SSR markers associated with starch content, β-carotene content, and starch composition in the storage root, respectively, using association analysis and further evaluation of a subset of sweet potato genotypes with various characteristics. The SSR markers identified here can be used to select varieties with desired traits and to investigate the genetic mechanism underlying starch and carotenoid formation in the starchy roots of sweet potato.

[目的]甘薯病毒病(sweet potato virus disease,SPVD)是甘薯上的毁灭性病害之一,严重时可造成90％以上的产量损失.论文旨在对甘薯SPVD染病植株中甘薯羽状斑驳病毒(Sweet potato feathery mottlevims,SPFMV)和甘薯褪绿矮化病毒(Sweet potato chlorotic stunt virus,SPCSV)2种病毒的复合侵染情况进行研究,建立SPVD荧光定量RT-PCR快速检测方法,为SPVD的早期预警和流行学研究提供技术手段.[方法]选取重庆地区具有不同SPVD典型症状的甘薯品种(系)叶片作为试验材料,对其进行症状和SPFMV、SPCSV的硝酸纤维素膜酶联免疫吸附(NCM-ELISA)检测;对供试材料叶片中的SPFMV外壳蛋白CP和SPCSV热激蛋白HSP70核苷酸序列进行克隆和序列分析,根据保守核苷酸序列设计荧光定量RT-PCR检测引物.以甘薯泛素(ubiquitin,UBI)和组蛋白(histone,H2B)编码基因为内参对供试样品进行荧光定量RT-PCR检测,与感染SPVD典型症状和NCM-ELISA检测结果进行比较,并对取自不同甘薯品种(系)、相同品种(系)不同单株以及相同植株不同部位叶片检测结果进行比较,筛选可快速、精确、定量检测SPVD的荧光定量RT-PCR检测方法.[结果]症状学诊断表明不同甘薯品种(系)的感病叶片可能表现出不同的典型症状特点,同一品种(系)的不同感病植株感病症状相似但也存在差异.序列分析结果表明供试材料中SPFMV至少存在2个株系类型(RC和EA),SPCSV至少存在1个株系类型(WA).在15份供试材料中,10份材料由NCM-ELISA和荧光定量RT-PCR均检测到SPFMV和SPCSV的共同感染,且荧光定量RT-PCR检测结果与发病症状和NCM-ELISA检测结果相吻合,其检测结果可准确反映甘薯SPVD染病植株中2种病毒复合侵染情况.荧光定量RT-PCR检测结果还表明,不同品种(系)或相同品种(系)不同单株病叶中SPFMV CP与SPCSV HSP70转录水平存在差异;相同植株顶端幼嫩叶片和中部成熟叶片中SPFMV CP与SPCSV HSP70转录水平也存在差异.染病材料中SPFMV中CP转录水平均相对较高,是SPCSV的HSP70转录水平的3-556倍.4份材料经NCM-ELISA检测只有SPFMV而没有SPCSV感染,而荧光定量RT-PCR还可检测到其中2份材料中SPCSV HSP70转录水平,说明这2份材料中也存在SPFMV和SPCSV的共同感染,表明荧光定量RT-PCR比NCM-ELISA检测结果更灵敏、准确.[结论]筛选出可利用SPFMV CP与SPCSV HSP70转录水平进行检测的荧光定量RT-PCR检测引物,建立了SPVD荧光定量RT-PCR快速检测方法,为SPVD针对性地监测预警提供了极为有效的方法.在建立甘薯SPVD防御体系时,需综合考虑2种甘薯病毒的共侵染特性和甘薯品种差异,采取针对性的监测和预警机制.

In this experiment,shoot tips 0.22-0.35 mm in size derived from the tuberous root buds of sweet potato cv.Yushu-2infected by SPFMV with two protuberant,semi-closed or closed leaf primordia were used as explants and cultured on MS media supplemented with BAP and IAA or BAP and NAA at different concentrations to obtain virus-free plantlets.Then nitrocellulose membrane-ELISA(NCMELISA)was used for virus detection.The results indicated that the optimum combination of hormones for shoot tip culture was 0.8-1.4mg/L BAP+0.01mg/L NAA,and the regenerated sprouts were stronger and grew rapidly.The percentage of plantlet regeneration varied with explants,being 92.9%,88.9%and 46.7%form explants with closed,semi-closed and protuberant leaf primordial,respectively.At the same time,the percentage of virus-free plantlets also varied with explants,being 100%,83.9%and 71.9%for protuberant,semi-closed and closed leaf primordial,respectively.

Three sweet potato varieties,Yushu-2(high starch content),Nanshu-88(medium starch content)and Shangqiu52-7(low starch content)were used as trial materials.During tuberous root expanding,their corresponding photosynthetic changes with light intensity,diurnal changes of photosynthesis and yield-related characters were investigated.The results indicated that variety Yushu-2had higher net photosynthetic rate(Pn),stomatal conductance and intercellular CO2concentration than the other two varieties under different light intensity.During the period of rapid expanding of tuberous roots,mean diurnal variation in net photosynthetic rate was in positive correlation with fresh sweet potato yield and biomass yield,in non-significant negative correlation with dry matter yield and in highly significant positive correlation with starch yield.In addition,the phenomenon ofmidday depressionof photosynthesis was observed in sweet potato leaves,especially for varieties of high water use efficiency(WUE).Furthermore, the higher starch content a variety had,the lower its water use efficiency was.For sweet potato there was significant correlation between photosynthetic characteristics and yield-related traits such as Pn and WUE.

Seven different varieties of sweet potato were used to study their population yield advantage and economic benefit when they intercropped with maize through using randomized block design .The results showed that the yield of sweet potato under this intercropping mode was lower than that under monocropping mode .Under sweet potato-maize intercropping mode , there was a significant difference in the number of tubers per plant , tuber weight per plant , and tuber yield among different varieties of sweet po-tato.The tuber yield and starch yield of sweet potato were higher when maize intercropped with Nanshu 88, Xushu 22 and Yushu 2. When 7 sweet potato varieties intercropped with maize , the land equivalent ratios of complex populations were all more than 1, re-vealing that the intercropping advantage existed .The monocropping or intercropping of special sweet potato varieties ( Ning 4-6, Ji-heishu 1, E08101 and so on) with maize obtained a higher output value .