We generated triploid hybrids of I. trifida and I. tabascana, providing insights into sweetpotato evolution and bridge germplasm for genetic improvement. Sweetpotato [Ipomoea batatas (L.) Lam.] (2n = 6x = 90) is an important root crop whose genomic polyploidisation process remains incompletely understood and highly complex. Its wild relatives are favoured for the study of genome formation, polyploidy processes and genetic improvement in sweetpotato. In this study, we obtained two triploid hybrids via reciprocal crosses between the closest diploid (I. trifida, 2n = 2x = 30) and the closer tetraploid (I. tabascana, 2n = 4x = 60) wild relatives of sweetpotato. To verify the authenticity of these two hybrids, molecular marker analysis, flow cytometry analysis, chromosome counting, morphological characterisation, pollen viability testing and meiotic observation were performed. Through InDel marker analysis, nine primer pairs consistently amplified parent-specific bands in the hybrids. Ploidy characterisation showed that both hybrids were triploid with 45 chromosomes. Morphologically, the two hybrids inherited many traits from both parents whilst producing some variation, such as both round and pentagonal corollas and purple stigmas with two or three lobes. Some pollen grains from the hybrids were fertile. The hybrids showed many abnormalities during meiosis, such as lagging chromosomes and uneven chromosome distribution. The triploid hybrids produced in this study can be used to infer early triploid genomic events during the origin and evolution of sweetpotato and to develop bridge germplasm for its genetic improvement.

The lack of genomic and genetic research on wild sweetpotato species has hindered the advancement of sweetpotato variety development through modern crop improvement techniques. To facilitate the use of genomic and genetic approaches in sweetpotato variety development, we conducted a comprehensive assessment of the genome size and ploidy of six closely related wild sweetpotato species using flow cytometry and chromosome counting. Additionally, we acquired insights into their genomic characteristics through high-throughput sequencing. Based on the 17-mer frequency distribution, the genome sizes of these species ranged from 518.47 Mb to 1,505.04 Mb. Notably, most diploid species exhibited genome sizes of approximately 500 Mb, with the diploid wild species I. purpurea standing out as having a significantly larger genome size compared to other diploid species. A substantial proportion of repeats (ranging from 57.47 to 81.07

Background Sweetpotato is an important vegetable and food crop that is bred through sexual crosses and systematic selection. The use of in vitro germination of sweetpotato pollen to test its viability has important theoretical and practical implications for improving the efficiency of sweetpotato crossbreeding by controlling pollination and conducting research on sweetpotato pollen biology. Results In this study, we observed the morphological structure of sweetpotato pollen under a scanning electron microscope (SEM), developed an effective method for the in vitro germination of sweetpotato pollen, and examined the viability of sweetpotato pollen after treating plants at different temperatures before blossoming. Sweetpotato pollen grains are spherical, with an average diameter of 87.07 ± 3.27 μm (excluding spines), with multiple germination pores and reticulate pollen surface sculpture. We applied numerous media to sweetpotato pollen germination in vitro to screen the initial medium and optimised the medium components through single-factor design. The most effective liquid medium for in vitro sweetpotato pollen germination contained 50 g/L Sucrose, 50 g/L Polyethylene glycol 4000 (PEG4000), 100 mg/L Boric acid and 300 mg/L Calcium nitrate, with a pH = 6.0. The optimum growth temperature for pollen development in sweetpotato was from 25 to 30 °C. Neither staining nor in situ germination could accurately determine the viability of sweetpotato pollen. Conclusions In vitro germination can be used to effectively determine sweetpotato pollen viability. The best liquid medium for in vitro germination of sweetpotato pollen contained 50 g/L Sucrose, 50 g/L Polyethylene glycol 4000 (PEG4000), 100 mg/L Boric acid and 300 mg/L Calcium nitrate, with the pH adjusted to 6.0. This study provides a reliable medium for the detection of sweetpotato pollen viability, which can provide a theoretical reference for sweetpotato genetics and breeding.

Adverse environmental stress is a major environmental factor threatening food security, which is why improving plant stress resistance is essential for agricultural productivity and environmental sustainability. The NAC (NAM, ATAF, and CUC) transcription factors (TFs) play a dominant role in plant responses to abiotic and biotic stresses, but they have been poorly studied in Ipomoea pes-caprae . In this research, 12 NAC TFs, named IpNAC1–IpNAC12, were selected from transcriptome data. The homologous evolution tree divided IpNACs into four major categories, and six IpNACs were linearly associated with Arabidopsis ANAC genes. From the gene structures, protein domains, and promoter upstream regulatory elements, IpNACs were shown to contain complete NAC-specific subdomains (A–E) and cis-acting elements corresponding to different stress stimuli. We measured the expression levels of the 12 IpNACs under abiotic stress (salt, heat, and drought) and hormone treatment (abscisic acid, methyl jasmonate, and salicylic acid), and their transcription levels differed. IpNAC5/8/10/12 were located in the nucleus through subcellular localization, and the overexpressing transgenic Arabidopsis plants showed high tolerance to salt stress. The cellular Na + homeostasis content in the mature and elongation zones of the four IpNAC transgenic sweetpotato roots showed an obvious efflux phenomenon. These conclusions demonstrate that IpNAC5/8/10/12 actively respond to abiotic stress, have significant roles in improving plant salt tolerance, and are important salt tolerance candidate genes in I . pes-caprae and sweetpotato. This study laid the foundation for further studies on the function of IpNACs in response to abiotic stress. It provides options for improving the stress resistance of sweetpotato using gene introgression from I . pes-caprae .

通过使用20％聚乙二醇(PEG)-6000模拟干旱环境验证光合参数对于甘薯抗旱评价的适用性,并优化甘薯抗旱评价方法.结果表明,通过丙二醛(MDA)含量和相对含水量(RWC)变化值鉴定了3个甘薯栽培种的耐旱性,24、72 h干旱胁迫下甘薯抗旱性表现一致,均为潮薯1号抗旱性最强,徐薯18居中,福薯7-6最弱.分别测量3、24 h干旱胁迫处理下净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和胞间CO2浓度(Ci)4个光合参数的变化值,24 h干旱胁迫下光合参数的变化与MDA含量和RWC变化一致.相关性分析结果表明,4个光合参数与MDA含量、RWC均有极显著相关性,其中Ci与MDA含量、RWC的相关系数均最大,证明了4个光合参数均可作为抗旱评价指标.对24 h干旱胁迫下4个光合参数的变化值进行主成分分析,第1主成分的特征值为3.90,累计贡献率达到97.39％,基于主成分分析方法利用光合参数建立了甘薯抗旱性综合评价指数模型.

Sweetpotato (Ipomoea batatas (L.) Lam.), whose roots are rich in starch, is widely grown around the world and plays a prominent role in ensuring food security. At present, there are no reports on the genetic diversity of sweetpotato germplasm revealed by InDel markers. In this study, we developed a set of 30 InDel markers to evaluate the genetic diversity and relationships of 240 accessions, comprising 77 landraces, 80 introduced accessions, 82 improved varieties released in China, and a diploid wild relative Ipomoea trifida. A total of 94 reliable loci were obtained, with a mean of 3.13 loci per primer, and the PIC value ranged from 0.143 to 0.821. The whole population could be divided into three sub-populations according to a structure analysis based on the Bayesian model, which was consistent with the results of principal component analysis (PCA). A neighbor-joining tree was constructed based on Nei’s genetic distance ranging from 0 to 0.556 and discriminated the panel of the population into three main groups (Ⅰ, Ⅱ, Ⅲ). Group Ⅲ was further split into seven subgroups (ⅢA–ⅢG). The clustering pattern of the 240 accessions was unrelated to their geographic origins. Most of the accessions, whether landraces, improved varieties released in China or introduced germplasm, were mixed, which revealed the high level of genetic similarity among accessions from different regions. There was little difference in the level of genetic diversity between landraces and improved varieties, which was probably due to the exchange and utilization of accessions from different regions. More efforts should be made to collect and utilize sweetpotato germplasm resources and further broaden the genetic basis of sweetpotato cultivars.

To elucidate nutritional components in sweet potato cultivars for table use and to compare the phytochemicals of cultivars from different countries, ‘Kokei No. 14′ and ‘Xinxiang’ were selected. The physiological parameters and metabolites were determined using the colorimetric method and widely targeted metabolomics, respectively. Transcriptomic analysis was performed to explain the mechanism that resulted in phytochemical differences. ‘Xinxiang’ showed higher flavonoid and carotenoid contents. Metabolomics showed five upregulated flavonoids. Two essential amino acids (EAAs) and one conditionally essential amino acid (CEAA) were upregulated, whereas four EAAs and two CEAAs were downregulated. Unlike lipids, in which only one of thirty-nine was upregulated, nine of twenty-seven differentially accumulated phenolic acids were upregulated. Three of the eleven different alkaloids were upregulated. Similarly, eight organic acids were downregulated, with two upregulated. In addition, three of the seventeen different saccharides and alcohols were upregulated. In ‘other metabolites,’ unlike vitamin C, 6′-O-Glucosylaucubin and pantetheine were downregulated. The differentially accumulated metabolites were enriched to pathways of the biosynthesis of secondary metabolites, ABC transporters, and tyrosine metabolism, whereas the differentially expressed genes were mainly concentrated in the metabolic pathway, secondary metabolite biosynthesis, and transmembrane transport functions. These results will optimize the sweet potato market structure and enable a healthier diet for East Asian residents.

Background Sweetpotato ( Ipomoea batatas [L.] Lam.) is an important food crop. However, the genetic information of the nuclear genome of this species is difficult to determine accurately because of its large genome and complex genetic background. This drawback has limited studies on the origin, evolution, genetic diversity and other relevant studies on sweetpotato. Results The chloroplast genomes of 107 sweetpotato cultivars were sequenced, assembled and annotated. The resulting chloroplast genomes were comparatively analysed with the published chloroplast genomes of wild species of sweetpotato. High similarity and certain specificity were found among the chloroplast genomes of Ipomoea spp. Phylogenetic analysis could clearly distinguish wild species from cultivars. Ipomoea trifida and Ipomoea tabascana showed the closest relationship with the cultivars, and different haplotypes of ycf1 could be used to distinguish the cultivars from their wild relatives. The genetic structure was analyzed using variations in the chloroplast genome. Compared with traditional nuclear markers, the chloroplast markers designed based on the InDels on the chloroplast genome showed significant advantages. Conclusions Comparative analysis of chloroplast genomes of 107 cultivars and several wild species of sweetpotato was performed to help analyze the evolution, genetic structure and the development of chloroplast DNA markers of sweetpotato.

以来自不同育种单位的54份橘肉甘薯和52份紫肉甘薯品种资源为材料,测定块根中淀粉、可溶性糖、还原糖、粗蛋白、β-胡萝卜素和花青苷的含量.结果表明,橘肉甘薯的可溶性糖和还原糖含量通常高于紫肉甘薯,淀粉含量低于紫肉甘薯,粗蛋白含量与紫肉甘薯类似;橘肉甘薯的β-胡萝卜素含量为0.4～280.7μg/g,紫肉甘薯的β-胡萝卜素含量最高为31.8μg/g,花青苷含量为15.0～20.0μg/g.相关性分析结果表明,淀粉含量和可溶性糖含量、还原糖含量呈极显著负相关.基于6种营养物质的含量,分别将橘肉甘薯和紫肉甘薯品种资源聚为5个和4个类群;其中,二者均为第II类群种质资源综合品质较好.本研究结果为这些甘薯品种资源的加工利用及品种改良提供理论参考和材料基础.

为了解紫肉甘薯中花青苷的组分构成及多样性分布,以来自国内外多家培育单位的68份紫肉甘薯品种资源为试验材料,利用液质联用技术测定了 6类共计68种花青苷的含量.结果表明,6类花青苷中,矢车菊类和芍药类花青苷的含量较高,分布范围较广,天竺葵类花青苷的含量整体最低,分布范围最狭窄.相关性分析结果表明,检测到花青苷的总含量和矢车菊类、芍药类及矮牵牛类花青苷的含量均呈极显著正相关.系统聚类分析结果表明,68份紫肉甘薯品种资源被聚为6个类群,其中第Ⅱ类群6类花青苷的含量均较高,第Ⅳ类群各类花青苷的含量均较低.68种花青苷在68份紫肉甘薯品种中的检出情况表明,有7种花青苷能够在全部的紫肉甘薯品种中检出,10种只能在少于50份的材料中检出.68种花青苷含量的相关性分析结果表明,每类花青苷中均有几种花青苷的含量相等或呈极显著正相关.本研究通过对紫肉甘薯品种资源花青苷组分构成及多样性的分析与评价,筛选出6类花青苷含量较高的紫肉甘薯品种3份,单类花青苷含量较高的品种7份,为优质甘薯的推广和后续优质品种的选育提供了材料基础.

利用流式细胞术,以大豆Williams 82为内参,对甘薯近缘野生种Ipomoea cordatotriloba进行基因组大小测定,结合染色体压片技术进行倍性鉴定,并利用二代高通量测序技术对测定结果进行验证.结果表明:利用流式细胞术测得I.cordatotriloba基因组大小为(539.69±13.76)Mb;染色体压片结果显示其染色体数目为30条,由于其基数x=15,从而获知I.cordatotriloba为二倍体;经K-mer计算并修正后得出的C值为560.70 Mb,与流式细胞分析结果相近;同时,测序结果显示其基因组杂合率为0.40％;重复序列比率为57.93％;GC含量为38.10％.以上结果为此物种全基因组精细图谱绘制打下基础,同时为甘薯近缘野生种的利用提供参考.

对有性杂交获得的三浅裂野牵牛人工合成四倍体(6x×2x)进行倍性鉴定和减数分裂行为研究,以期在细胞学水平揭示这个物种的遗传信息,为其在育种上的利用提供借鉴.对10个分散良好的有丝分裂中期的染色体进行计数,人工合成四倍体的体细胞染色体数目为2n=4x=60.流式细胞术预估人工合成四倍体的基因组大小为(790.45±12.52)Mb,约为二倍体三浅裂野牵牛I.trifida(2x)基因组大小的1.7倍.共观察770个人工合成四倍体的花粉母细胞,其减数分裂过程完整,但染色体存在异常行为;中期Ⅰ、中期Ⅱ、后期Ⅰ和后期Ⅱ的异常率分别为10.11％、68.42％、42.86％和54.55％,存在板外染色体、滞后染色体、染色体桥和分裂不同步等异常现象.本试验合成的材料为有性杂交创制的桥梁物种,或将成为甘薯分子细胞遗传学研究的基础材料.