China is the world’s leading country for potato production but potato is not native to China. To gain insights into the genetic diversity of potato germplasm various studies have been performed but no study has been reported for potato landraces in China. To improve the available genepool for future potato breeding programs, a diverse population containing 292 genotypes (including foreign elite lines, local landraces and cultivars) was developed and genotyped using 30 SSR markers covering the entire potato genome. A total of 174 alleles were detected with an average of 5.5 alleles per locus. The model-based structure analysis discriminated the population into two main sub-groups, which can be further subdivided into seven groups based on collection sites. One sub-group (P1) revealed less genetic diversity than other (P2) and contained a higher number of commercial cultivars possibly indicating a slight reduction in diversity due to selection in breeding programs. The P2 sub-group showed a wider range of genetic diversity with more new and unique alleles attained from wild relatives. The potato landraces, clustered in sub-population P1 may be derived from historical population imported from ancient European and International Potato Center genotypes while sub-population P2 may be derived from modern populations from International Potato Center and European genotypes. It is proposed that in the first step, the potato genotypes were introduced from Europe to China, domesticated as landraces, and then hybridized for modern cultivars.

David Ellis et al., 'Ex Situ Conservation of Potato (Solanum Section Petota (Solanaceae)) Genetic Resources in Genebanks', The Potato Crop, pp.109-138, Springer International Publishing, 2019 | Conserving the genetic diversity of potato is critical for the long-term future of potato improvement programs. Further, it is the social and ethical responsibility of the present generation to ensure future generations have the same opportunities to use, exploit, and benefit from the genetic diversity that exists today. Genebanks and the ex situ conservation of potato genetic resources are the only way to ensure this happens; in situ conservation plays a complementary role, but it can never ensure that the vast diversity that exists on earth today is still there for use in the future. Material in ex situ genebanks not only serve as a reservoir of ready-to-use genetic material when needed but also provide invaluable tools for research now and in the future of cultivated potato and its wild relatives

Potato, tomato, pepper, and eggplant or aubergine are key food security and commercial crops. Making their genetic diversity more widely available will support the livelihoods of farmers and other enterprises around the world. This project aims to streamline access to the extensive genetic resources of these crops | International Potato Center, 'Sharing the genetic diversity of solanaceous food crops. Project profile', p.2, International Potato Center, 2019

Sweet potato (Ipomoea batatas L. Lam) is an important food crop widely cultivated in the world. In this study, nine chloroplast simple sequence repeat (cpSSR) markers were used to analyze the genetic diversity and relationships of 558 sweet potato accessions in the germplasm collection of the National Agrobiodiversity Center (NAC). Eight of the nine cpSSR showed polymorphisms, while Ibcp31 did not. The number of alleles per locus ranged from two to four. In general, the Shannon index for each cpSSR ranged from 0.280 to 1.123 and the diversity indices and unbiased diversity ranged from 0.148 to 0.626, and 0.210 to 0.627, respectively. Results of the median-joining network showed 33 chlorotypes in 558 sweet potato accessions. In factor analysis, 558 sweet potato accessions were divided into four clusters, with clusters I and II composed only of the sweet potato accessions from Korea, Japan, Taiwan, and the USA. The results of this study confirmed that the genetic diversity of the female parents of sweet potato accessions conserved at the NAC is low and therefore more sweet potato accessions need to be collected. These results will help to establish an efficient management plan for sweet potato genetic germplasms at the NAC.

John Bamberg, Shelley Jansky, Alfonso del Rio, Dave Ellis, 'Ensuring the genetic diversity of potatoes', Achieving sustainable cultivation of potatoes Volume 1, pp.57-79, Burleigh Dodds Science Publishing, 2019 | Preserving genetic diversity lies at the heart of improvements in breeding and resilience in potato cultivation. This chapter discusses the challenges, opportunities and recent accomplishments of potato gene banks in the areas of acquisition, classification, preservation, evaluation and distribution of genetic stocks and information, as well as offering a legal perspective on access to genetic materials. The chapter reviews routes for acquisition of potato genetic material, together with methods for its classification and preservation. The chapter also discusses the evaluation and enhancement of potato genetic material, before looking at issues of control and assess to minimise problems such as transmission of disease

Potato leaf blight disease caused by Ulocladium atrum (Syn. Stemphylium atrum) is an important and epidemic disease in potato-growing regions of Iran. In this study, 30 isolates of the disease were collected from the main potato-growing regions of Iran and were analyzed on the basis of morphological characterization and pathogenicity. Based on morphological characteristics, all isolates were identified as U. atrum. Pathogenicity studies indicated that all 30 isolates were pathogenic on potato “Agria” to varying degrees. Five U. atrum isolates causing potato leaf blight disease, obtained from the Plant Pathology Laboratory, Isfahan Research Center for Agriculture and Natural Resources, Isfahan, Iran, were also examined in this study. A total of 35 isolates were genetically analyzed using random amplified polymorphic DNA (RAPD) and inter-simple sequence repeats (ISSR) markers. Cluster analysis using the un-weighted pair group method with the arithmetic average (UPGMA) method for RAPD marker revealed no clear grouping of the isolates obtained from different geographical regions. The groupings, based on morphological characteristics, virulence variability and RAPD analysis, were not correlated. Cluster analysis using Jaccard’s coefficient for ISSR divided the U. atrum isolates into four main groups, in which there was no significant correlation between the isolate groupings regarding their geographic location and pathogenicity. Using molecular techniques genetic variability was detected among the accessions, with cophenetic correlation coefficients (CCC) of 0.80 for RAPDs and 0.89 for ISSRs. The RAPD and ISSR marker results corresponded well, with a correlation of 0.55.

In 2011–2014, ELISA or nucleic acid spot hybridization (NASH) testing for common potato viruses or Potato spindle tuber viroid (PSTVd) was performed on 500 leaf samples collected in potato fields in the northeast provinces Heilongjiang and Inner Mongolia, China. The results revealed that 38.4% (Heilongjiang) and 27.7% (Inner Mongolia) were positive for Potato virus Y (PVY). To unveil the strain composition and population structure of PVY in the region, the multiplex RT-PCR described by Chikh-Ali et al. was performed on all of the ELISA-PVY-positive samples. Of the 158 samples whose PVY strain scenarios could be determined, PVYᴺᵀᴺ⁻ᴺᵂ-SYR-II and PVYᴺ⁻ᵂⁱ were the most abundant strains, occurring in 58.9 and 47.5% samples, followed by PVYᴺᵀᴺ⁻ᴺᵂ-SYR-I (31.0%), PVYᴺ:ᴼ (19.6%), Eu-PVYᴺᵀᴺ (7.6%), NA-PVYᴺ (1.3%), and PVYᴼ (0.6%). In the 84 single-strain-infected samples, PVYᴺ⁻ᵂⁱ accounted for 41.7%, PVYᴺᵀᴺ⁻ᴺᵂ-SYR-II for 40.5%, PVYᴺᵀᴺ⁻ᴺᵂ-SYR-I for 14.3%, and PVYᴺ:ᴼ and Eu-PVYᴺᵀᴺ for 3.6% each. Seven isolates representing PVYᴺᵀᴺ⁻ᴺᵂ-SYR-I (HLJ-6-1 and HLJ-9-4), PVYᴺᵀᴺ⁻ᴺᵂ-SYR-II (INM-W-369-12 and SC-1-1-2), PVYᴺ:ᴼ (HLJ-30-2), and PVYᴺ⁻ᵂⁱ (HLJ-BDH-2 and HLJ-C-429) were sequenced and analyzed molecularly. Whereas the sequence identities for isolates belonging to the same strain group were >98.5%, they fell for isolates belonging to different strain groups to 92.7–98.1% at the genome level and 96.1–98.4% at the polyprotein level. Interestingly, the exact location of the recombination events varied among isolates within a strain group. Phylogenetic analysis of all 42 full length PVY sequences from China indicated that most clustered to various recombinant groups, despite the fact that the PVY isolates were isolated from at least five host species. Pathological analysis of four isolates representing PVYᴺ:ᴼ, PVYᴺ⁻ᵂⁱ, PVYᴺᵀᴺ⁻ᴺᵂ-SYR-I, and PVYᴺᵀᴺ⁻ᴺᵂ-SYR-II revealed that the PVYᴺᵀᴺ⁻ᴺᵂ-SYR-II isolate incited the most severe symptoms on potato cultivar Kexin 13, followed by PVYᴺᵀᴺ⁻ᴺᵂ-SYR-I, PVYᴺ:ᴼ and PVYᴺ⁻ᵂⁱ. The PVYᴺᵀᴺ⁻ᴺᵂ-SYR-I and PVYᴺᵀᴺ⁻ᴺᵂ-SYR-II isolates also caused necrotic ringspots on the tubers of Kexin 13, indicating their ability to induce the potato tuber necrotic ringspot disease in potato.

The peach potato aphid, Myzus persicae (Sulzer), is a worldwide pest of many crops, and the most important aphid pest of peach and potato crops in Tunisia, mainly due to virus transmission, for which insecticides are frequently applied. We studied the genetic structure of M. persicae populations in Tunisia, in order to further our understanding of the biotic and abiotic factors shaping populations and to predict their evolutionary responses to the present management practices. We monitored peach orchards and seed potato crops in different seasons and regions from 2011-2013 and in 2016 (19 populations), assessing the genetic diversity of M. persicae at six microsatellite loci. Temporal and spatial changes in the frequency and distribution of 397 genotypes in 548 sampled aphids were studied. Only 37 genotypes were found more than once (clonal amplification), as most genotypes were found only once (91.60% in peach; 88.73% in potato crops). A similarly high genetic diversity was observed in aphids sampled from peach (G/N = 0.76; Ho = 0.617) and potato (G/N = 0.70; Ho = 0.641). Only a weak genetic differentiation among populations was found, mainly between geographic locations. Clustering analysis revealed genotypes to be grouped mainly according to host plant. The availability of the primary host, high proportion of unique genotypes, high genetic diversity and lack of structuring suggest that the aphid reproduces mainly through cyclical parthenogenesis in Tunisia. On the other hand, we provide a farm-scale study that shows how easily M. persicae can colonize different areas and hosts, which may have important implications in relation to plant virus vectoring.