Potato (Solanum tuberosum L.) is an important staple food and economic crop in many countries.  China has led world potato production in recent years.  To understand the genetic diversity of potato germplasms and to enrich the current gene pool for potato improvement, we made a global collection consisted of 288 potato germplasms from eight countries and the International Potato Center (CIP).  Using SSR and AFLP techniques, we evaluated the genetic diversity and population structure of these 288 potato accessions.  A total of 190 alleles on 20 SSR loci were detected and all of the SSR alleles were polymorphic among these potato germplasms with an average of 9.5 alleles per SSR locus ranging from 2 to 23.  The effective number of alleles per locus (Ne*), Nei’s genetic diversity (H*), and Shannon’s information index (I*) was from (0.1709±0.3698) to (1.6166±0.3414), (0.076±0.1388) to (0.3812±0.1886), and (0.1324±0.1970) to (0.5347±0.1440), respectively, and the mean polymorphic information content (PIC) value was 0.7312.  A total of 988 AFLP alleles were detected by 10 AFLP primer combinations with 983 polymorphic alleles, and 99.49% alleles was polymorphic with an average of 98.3 polymorphic alleles per primer combination ranging from 91 to 116.  The values of Ne*, H* and I* were from (1.5162±0.311) to (1.6423±0.3278), (0.3114±0.145) to (0.3675±0.1121), and (0.4761±0.1792) to (0.547±0.1322), respectively, and the average PIC value was 0.9871.  Bayesian analysis discriminated the accessions into seven subgroup and an admix group.  The majority of accessions from CIP and China were assigned into SG1, SG5, SG6, SG7 and admix group.  Accessions in SG3 were mainly from CIP and two small groups SG2 and SG4 were mainly from northeastern China.  In general, the results obtained from Bayesian statistical analysis, cluster analysis and principal coordinate analysis consistently revealed the lack of geographical differentiation among country-wide collections, indicating germplasm introduction was common for the countries out of potato origin center.  The polymorphic markers and the differentiate genetic lineages found in this study provide useful information for potato improvement and conservation programs.  

Triticum aestivum-Hayaldia villosa translocation line V3 has shown effective all-stage resistance to the seven dominant pathotypes of Puccinia striiforms f. sp. tritici prevalent in China. To elucidate the genetic basis of the resistance, the segregating populations were developed from the cross between V3 and susceptible genotype Mingxian 169, seedlings of the parents and F2 progeny were tested with six prevalent pathotypes, including CYR29, CYR31, CYR32-6, CYR33, Sun11-4, and Sun11-11, F1 plants and F3 lines were also inoculated with Sun11-11 to confirm the result further. The genetic studied results showed that the resistance of V3 against CYR29 was conferred by two dominant genes, independently, one dominant gene and one recessive gene conferring independently or a single dominant gene to confer resistance to CYR31, two complementary dominant genes conferring resistance to both CYR32-6 and Sun11-4, two independently dominant genes or three dominant genes (two of the genes show cumulative effect) conferring resistance to CYR33, a single dominant gene for resistance to Sun11-11. Resistance gene analog polymorphism (RGAP) and simple-sequence repeat (SSR) techniques were used to identify molecular markers linked to the single dominant gene (temporarily designated as YrV3) for resistance to Sun11-11. A linkage map of 2 RGAP and 7 SSR markers was constructed for the dominant gene using data from 221 F2 plants and their derived F2:3 lines tested with Sun11-11 in the greenhouse. Amplification of the complete set of nulli-tetrasomic lines of Chinese Spring with a RGAP marker RG1 mapped the gene on the chromosome 1B, and then the linked 7 SSR markers located this gene on the long arm of chromosome 1B. The linkage map spanned a genetic distance of 25.0 cM, the SSR markers Xgwm124 and Xcfa2147 closely linked to YrV3 with genetic distances of 3.0 and 3.8 cM, respectively. Based on the linkage map, it concluded that the resistance gene YrV3 was located on chromosome arm 1BL. Given chromosomal location, the reaction patterns and pedigree analysis, YrV3 should be a novel gene for resistance to stripe rust in wheat. These closely linked markers should be useful in stacking genes from different sources for wheat breeding and diversification of resistance genes against stripe rust.