The genetic diversity of 123 potato clones, consisting of 103 clonal accessions from the International Potato Center (CIP) and 20 Chinese cultivars, was assessed using amplified fragment length polymorphism (AFLP) markers. Ten polymorphic primer combinations were selected to analyse and compare the diversity of the two sources of clones. A total of 521 reproducible bands were amplified, of which 488 were polymorphic. These AFLP markers were analysed to estimate the genetic distance (GD) and genetic similarity (GS) coefficient of all clones. The GD between pairs of clones ranged from 0.03 to 0.48. Nei’s gene diversity index was between 0.236 and 0.387, with an average of 0.330. The index of Shannon’s information varied from 0.361 to 0.567 with an average of 0.498. A high degree of polymorphism was observed with an average of 93.6% loci found to be polymorphic. Cluster analysis showed that the CIP accessions were grouped together at the GS 0.59 clustering line, whereas most Chinese cultivars grouped at the GS 0.82 clustering line. The diversity in CIP potato resources was found to be higher than that of the Chinese cultivars, indicating that the genetic base of Chinese potato cultivars is narrow and may benefit from broadening.

The present study was conducted to assess the genetic divergence (Mahalanobis D2) in 29 potato genotypes(parental lines) based on 20 characters and to find out relationship between genetic diversity and heterosis for tuber yield. Results showed that the parental lines though morphologically diverse had narrow genetic base and could be grouped into four clusters. Observed morphological diversity was not related to geographical as well as taxonomic diversity. Genetic divergence(D values) had a positive relationship with heterosis for tuber yield in the 120 progenies derived from 24 x 5 (line x tester)matings of the parents. Selection of parents based on genetic divergence followed by progeny test is suggested for effective exploitation of heterosis in potato breeding programmes

Sweet potato (Ipomoea batatas (L.) Lam.) is a crop of economic and social importance with nutritive values, high energy yield, wide adaptability and high level of genetic diversity. It is an important source of dietary fibre, minerals, vitamins and bioactive compounds such as  Î²-carotene, phenolic acid and anthocyanin. Sweet potato clones possess diversity in skin and flesh colors (white, cream, yellow, orange and purple) of tubers. Random amplified polymorphic DNA (RAPD) analysis using 21 Indian and exotic cultivars of sweet potato comprising of diversified skin and flesh colour including orange fleshed sweet potatoes with arbitrary 15 decamer primers showed 164 polymorphic bands which fell into three major clusters  viz., clusters A, B and C. Clusters A and B included both Indian and exotic orange-fleshed sweet potato cultivars, whereas cluster C included mostly white-fleshed cultivars of Indian origin. The predictive linkages will lead to a valuable breeding programme for the genetic improvement of sweet potato and verification of pedigree records.

The evolutionary diversity of wild potato species makes them excellent materials for improving the narrow genetic basis of the cultivated potato Solanum tuberosum. Understanding their genetic diversity is important not only to choose the best parents for breeding, but also to design proper crossing schemes and selection strategies. The objectives of this study were to determine the resistance response to Ralstonia solanacearum, Potato virus Y and low temperatures of 21 clones of 12 potato species, and to determine their genetic diversity through simple sequence repeat (SSR) markers. Sources of resistance have been found for all the investigated traits, with high resistance variability not only between but also within species. Combined resistances were also identified, with positive implications for efficient breeding. SSR analysis allowed the detection of 12 loci and 46 alleles across all genotypes, with an average value of 3.8 alleles per locus. Both unique and rare alleles useful for marker-assisted selection were found. SSR-based cluster analysis revealed that resistant genotypes were distributed among all clusters, suggesting that genetically different resistant genotypes were identified. The information obtained in this study is discussed from a breeding perspective.

Bolivia has a huge diversity of cultivated potato and its wild relatives for being part of the center of origin of this crop; however, that genetic diversity in the Bolivian potato collection is not well known, preventing its more efficient use. With the aim to better understand the collection diversity, a study was conducted using a set of 22 simple sequence repeats (SSR) for molecular characterization of six species of cultivated potato: Solanum tuberosum Subsp. andigena (991accessions), S. x ajanhuiri (56 accessions), S. x curtilobum (78 accessions), S. x juzepczukii (116 accessions), S. stenotomum (228 accessions) and S. goniocalyx (7 accessions). Results show that genetic diversity varíes with the species, presenting from highest to lowest diversity to Solanum tuberosum ssp. andigena, S. stenotomum, S. x curtilobum, S. x juzepczukii, S. x ajanhuiri and S. goniocalyx. Based on molecular data, about 60 potentially duplícate accessions were also found and SSRs STM 5114, STG0010, STM 0037 and STM1104 were identified as the most polymorphic, with PIC valúes from 0.74, 0.73, 0.72 and 0.69, respectively.

Different plant species and potato cultivars differed in nutrient use efficiency . Potassium efficiency was lowest for potato followed by wheat and sugar beet. Potato had a similar total K requirement as wheat. Wheat and sugar beet were similarly K efficient. Wheat had a lower K requirement than sugar beet but more roots, therefore, a small influx was sufficient. Sugar beet had a high K requirement and fewer roots. Maize was less Zn-efficient than potato and sunflower. The low Znuptake efficiency of maize was associated with a low Zn influx which nullified the effect of its high root-DMA ratio. Potato cv. Kufri Chandramukhi had a higher K uptake efficiency than Kufri Badshah and Kufri Jyoti. Kufri Chandramukhi maintained higher K influx by utilizing more non-exchangeable soil K than Kufri Jyoti and Kufri Badshah. However, potato cv. Kufri Chandramukhi had a lower Zn uptake efficiency than cv. Kufri Badshah due to its lower root-DMA ratio than Kufri Badshah because Zn influx was similar in both the cultivars. Kufri Chandramukhi was more P efficient than Kufri Badshah and Kufri Pukhraj. Roots of P- efficient genotypes had the capacity to keep more applied P in available form than inefficient genotypes. Comparison of DNA finger prints of these genotypes revealed the genetical variation in the genotypes, responsible for different nutrient use efficiency. Potassium efficient species and cultivars maintained higher K influx by using higher amount of less mobile soil K (non-exchangeable K) whereas phosphorus efficient cultivars had shown higher P influx due to the capability of their roots to reduce fixation of applied P in the soil. Higher root growth (root-shoot/DMA ratio) was responsible for higher zinc efficiency of potato cultivars.

Spongospora subterranea f. sp. subterranea (Sss) causes two diseases on potato (Solanum tuberosum), lesions on tubers and galls on roots, which are economically important worldwide. Knowledge of global genetic diversity and population structure of pathogens is essential for disease management including resistance breeding. A combination of microsatellite and DNA sequence data was used to investigate the structure and invasion history of Sss. South American populations (four countries, 132 samples) were consistently more diverse than those from all other regions (15 countries, 566 samples), in agreement with the hypothesis that Sss originated in South America where potato was domesticated. A substantial genetic differenciation was found between root and tuber-derived samples from South America. Estimates of past and recent gene flow suggested that Sss was probably introduced from South America into Europe. Subsequently, Europe is likely to have been the recent source of migrants of the pathogen, acting as a "bridgehead" for further global dissemination. Quarantine measures must continue to be focussed on maintaining low global genetic diversity and avoiding exchange of genetic material between the native and introduced regions. Nevertheless, the current low global genetic diversity of Sss allows potato breeders to select for resistance, which is likely to be durable.

Microsatellite markers or simple sequence repeat (SSR) were used to determine the genetic diversity of sixty four sweet potato accessions of National Plant Genetic Resources Laboratory, Institute of Plant Breeding in the University of the Philippines, Los Baños. Ten SSR markers based on three different crops (Ipomoea batatas-based, Musa-based and Allium-based markers) were used. Eight of these ten primer pairs amplified a range of 2 to 8 polymorphic fragments per primer. Resulting unique banding patterns for the 10 SSR markers ranged from 1 to 21. The resolving power of the SSR markers used, measured as polymorphism information content (PIC), ranged from 41.14% to 83.90%, which indicates high genetic diversity. Highest PIC was observed in marker mMaC1R1-69, as well as the most number of banding patterns. Profiles of the markers used were subjected to cluster analysis using Jaccard's coefficient at 0.51 which showed high genetic diversity among accessions. The resulting dendrogram generated five distinct clusters. Grouping based on geographic location was observed. Knowledge about sweet potato germplasm diversity could be an important aide in crop improvement strategies.

One hundred potato genotypes were grown under rain-fed condition at Dharwad and evaluated for presence of genetic diversity using Mahalanobis D2 analysis. The D2 analysis grouped all genotypes into 8 clusters. Source of the genotypes had no relation with genetic diversity. Average tuber weight per plant registered the maximum relative contribution to total divergence followed by number of main stems per plant.