Sweet potato (Ipomoea batatas L.) is the fifth most important crop in the developing countries after rice, wheat, maize and cassava. The amplified fragment length polymorphism (AFLP) method was used to study the genetic diversity and relationships of sweet potato accessions in the germplasm collection of Sokoine University of Agriculture, Morogoro and Sugarcane Research Institute, Kibaha, Tanzania. AFLP analysis of 97 sweet potato accessions using ten primer combinations gave a total of 202 clear polymorphic bands. Each one of the 97 sweet potato accessions could be distinguished based on these primer combinations. Estimates of genetic similarities were obtained by the Dice coefficient, and a final dendrogram was constructed with the un-weight pair-group method using arithmetic average. AFLP-based genetic similarity varied from 0.388 to 0.941, with a mean of 0.709. Cluster analysis using genetic similarity divided the accessions into two main groups suggesting that there are genetic relationships among the accessions. Principal Coordinate analysis confirmed the pattern of the cluster analysis. Analysis of molecular variance revealed greater variation within regions (96.19%) than among regions (3.81%). The results from the AFLP analysis revealed a relatively low genetic diversity among the germplasm accessions and the genetic distances between regions were low. A maximally diverse subset of 13 accessions capturing 97% of the molecular markers diversity was identified. We were able to detect duplicates accessions in the germplasm collection using the highly polymorphic markers obtained by AFLP, which were found to be an efficient tool to characterize the genetic diversity and relationships of sweet potato accessions in the germplasm collection in Tanzania.

Wild potato species (genus <i>Solanum</i>, section <i>Petota</i>) represent a tremendously diverse gene pool which is traditionally utilized as a source of diverse traits for potato breeding. Abiotic and biotic stress tolerance and resistance belong to the most frequently utilized traits of wild species in potato breeding programs. This review provides an introduction to the taxonomy, centre of diversity, genetic characteristics, evolution and important tolerance and resistance traits of wild potatoes and their use for potato breeding. The review has been written for readers who are interested in the problems of finding and utilization of new resistance genes from the wild genetic resources.

Decisions that improve genebank management depend on understanding patterns of diversity in the genetic resources being conserved. In potato, populations of the wild Mexican species S. verrucosum (ver) collected from the north (N) of the natural range had been shown to be genetically distinctive from those in the south (S). But this geographic association with genetic diversity was noted to be confounded with proximity of other wild potato species, suggesting introgression as a possible cause. RAPD bands that distinguished N and S ver were generated. When their association with nearby populations of other wild potato species was assessed, the hypothesis of introgression was not supported. We conclude that the apparently distinctive genetics of N ver are not explained by common alleles introgressed from proximal populations of other species. Thus, N ver germplasm populations, although less numerous, should be represented in samples of species ver with regard to collection, preservation and evaluation.

Fourteen microsatellite markers covering various genome regions were used to investigate a genetic diversity of the potato varieties. The set of varieties represents 37 varieties including Belarus breeding varieties and introduced varieties. The SSR primers generated a varying degree of polymorphisms. A total of 79 alleles were observed. Potato varieties were identified and their phylogenetic similarity was established by NJ cluster analysis. The method can be used for an identification and certification of potato varieties

In this paper, we describe the assessment of linkage disequilibrium and its decay in a collection of potato cultivars. In addition, we report on a simple regression based association mapping approach and its results to quality traits in potato. We selected 221 tetraploid potato cultivars and progenitor lines, representing the global diversity in potato, with emphasis on genetic variation for agro-morphological and quality traits. Phenotypic data for these agro-morphological and quality traits were obtained from recent trials performed by five breeding companies. The collection was genotyped with 250 AFLP® markers from five primer combinations. The genetic position of a subset of the markers could be inferred from an ultra dense potato map. Decay of linkage disequilibrium was estimated by calculating the squared correlation between pairs of markers using marker band intensities. Marker-trait associations were investigated by fitting single marker regression models for phenotypic traits on marker band intensities with and without correction for population structure. The paper illustrates the potential of association mapping in tetraploid potato, because existing phenotypic data, a modest number of AFLP markers, and a relatively simple statistical analysis, allowed identifying interesting associations.

Common scab is an important disease of potato caused by Streptomyces scabies and other closely related species. In this study, the genetic diversity of Streptomyces spp. causing common scab of potato in eastern Canada was for the first time investigated. Forty-one Streptomyces spp. isolates were retrieved from necrotic lesions of potato tubers harvested from different regions of the Canadian provinces New-Brunswick, Nova Scotia and Prince-Edward-Island. Most isolates were closely related to known pathogenic S. scabies strains on the basis of partial 16S ribosomal (r) RNA and rpoB gene sequence analyses. Two isolates were identified as pathogenic species of Streptomyces acidiscabies. To our knowledge, this species has never been previously isolated in these areas. Genome fingerprinting studies using repetitive elements (rep) polymerase chain reactions (PCR) revealed 10 distinct genetic groups in eastern Canada. The geographical distribution of the genetic groups was region-dependant. Pathogenicity- and virulence-related genes (txtA, txtC, and tomA) were PCR-amplified from each isolate, and nucleotide sequence analysis of partial gene fragments revealed slight polymorphisms in both txtA and txtC genes. No genetic variation was noted in the partial tomA gene sequences.

Genetic variability of yellow potato cyst nematode G. rostochiensis from three Russian populations (Karelia, Vladimir oblast, and Moscow oblast) was investigated using two types of nuclear markers. Using RAPD markers identified with the help of six random primers (P-29, OPA-10, OPT-14, OPA-11, OPB-11, and OPH-20), it was possible to distinguish Karelian population from the group consisting of the populations from two adjacent regions (Moscow oblast and Vladimir oblast). Based on the combined matrix, containing 294 RAPD fragments, dendrogram of genetic differences was constructed, and the indices of genetic divergence and partition (P, H, and G ₛₜ), as well as the gene flow indices N ₘ between the nematode samples examined, were calculated. The dendrogram structure, genetic diversity indices, and variations of genetic distances between single individuals in each population from Karelia and Central Russia pointed to genetic isolation and higher genetic diversity of the nematodes from Karelia.Based on polymorphism of rDNA first intergenic spacer ITS1, attribution of all populations examined to the species G. rostochiensis was proved. Small variations of the ITS1 sequence in different geographic populations of nematodes from different regions of the species world range did not allow isolation of separate groups within the species. Possible factors (including interregional transportations of seed potato) affecting nematode population structure in Russia are discussed.

This edition of New Agriculturist focusses on the potato, examining&nbsp;the challenges and opportunities facing producers worldwide. Among the articles includes in the edition are a report from Bolivia&nbsp;looking at&nbsp;efforts to improve access for rural potato growers to high-value urban markets, and the work to conserve the vast genetic diversity of potato in the highlands of Peru. Also covered are attempts to revamp potato production in famine-stricken North Korea, the emerging market for processed potato chips in East Africa, the challenge of climate change for potato-growing areas, and the ever-present danger of the devastating late blight fungus. A&nbsp;full list of articles is as follows: <strong>Ever-present danger - late blight:</strong> Late blight is still a formidable enemy of potato growers worldwide, able to wipe out entire crops in just a few weeks. Over 150 years since it triggered the Irish Potato Famine, scientists and farmers are still fighting the ever-mutating fungus. <strong>Climate change - can potato stand the heat?</strong>&nbsp; Rising temperatures, changes in rainfall distribution and concentrations of greenhouse gases will affect where potato is grown in the future. But scientists are hopeful it will weather the storm. <strong>Rooting for tubers:</strong> In the face of rising food prices, the potato is being promoted in Bangladesh and Peru as a nutritious alternative to more expensive staple foods such as rice and wheat. <strong>Going native: the sweet success of Bolivia's bitter potato:</strong> An initiative to improve sales of a processed potato product in Bolivia has been a runaway success, transforming a traditional "folk" food into a sophisticated, high-value product. <strong>Popular revolution in potato production in North Korea:</strong> North Korea has the potential to make substantial gains by restructuring its potato industry. An FAO-led project has been helping farmers access improved varieties, clean seed and better storage facilities. <strong>Protecting potato diversity in Peru:</strong> A pioneering project to document indigenous potato varieties in the highlands of Peru has made some promising discoveries, as well as protecting against biodiversity loss and bio-piracy. <strong>Cashing in on chips:</strong> The demand for potato chips (French fries) is booming in East Africa. Policy and financial support for in-country, commercial processing of potatoes into chips, combined with improved supply of suitable potato varieties, could bring about a strong regional chip trade. <br /><br />

【目的】检测不同马铃薯产区晚疫病菌基因型的特征,揭示马铃薯晚疫病菌群体的进化潜能和演替。【方法】用已开发出来的微卫星标记（SSR）对云南省23个马铃薯产区的晚疫病菌群体的遗传结构进行研究。【结果】在两个SSR位点Pi4B和Pi4G上共检测到8个等位基因,占优势的等位基因是218和161,基因频率分别为84.02%、32.52%。在分析的235个云南晚疫病菌菌株中,检测到18个不同的SSR基因型,其中8个新的SSR基因型谱系H-03、H-04、H-05、H-06、H-07、I-01、J-01和K-01被首次检测到;SSR基因型D-03、D-05、H-01和H-05是云南马铃薯晚疫病菌群体的优势谱系,在云南的群体中所占的比例分别为20.85%、22.98%、15.32%和19.57%,分布于云南的大部分马铃薯产区。【结论】云南马铃薯晚疫病菌群体遗传多样性在地理分布上差异明显,滇中多季作种植区晚疫病菌群体显示了较高的遗传多样性,滇南冬播作一季种植区群体结构单一。有证据表明中国云南晚疫病菌群体与其它国家20世纪80年代后出现的晚疫病菌群体在遗传上存在关联。 | [ Objective] This study was performed to detect the genotypic characteristics ofPhytophthora infestans populations and reveal the evolutionary potential and replacement of pathogen. [Method] The population genetic structure of P. infestans of potato collected from twenty three potato regions in Yunnan was analyzed based on the developed microsatellite markers （SSR）. [Result] Eight alleles were detected on two SSR loci, Pi4B and Pi4G, from Yunnan populations. The 218 and 161 alleles were predominant SSR ones among eight alleles and the gene frequency was 84.02% and 32.52%, respectively. Total eighteen different SSR genotypes were determined among 235 isolates and eight new SSR genotypic lineages, H-03, H-04, H-05, H-06, H-07, ]-01, J-01 and K-01, were firstly detected worldwide. The SSR genotypes, D-03, D-05, H-01 and H-05, were main lineages among populations, which spread out most potato production regions, having genotypic ratio 20.85%, 22.98%, 15.32% and 19.57%. [ Conclusion ] The geographical distribution of genotypic diversity of P infestans populations is different significantly in Yurman. The genetic diversity of P infestans populations in middle multiple cropping zones is high, however, that in south winter planting zones is low. The strong genetic evidence shows that the populations of P. infestans in Yunnan are related to those of other countries occurred after the second worldwide migration of P infestans.