The objective of this study was to compare the genetic divergence pattern in potato (Solanum tuberosum L.) under in vitro and in vivo conditions. Twenty two potato genotypes were evaluated for ten morphological characters under four in vitro conditions, and for 20 characters under four in vivo seasons. Mahalanobis' generalized intra- and inter-group genetic distances, and the distribution of genotypes into different clusters, led to the same conclusions under both in vitro and in vivo conditions: (1) genetic diversity was not related to geographic diversity, (2) genetic distances were higher between Tuberosum and Andigena than within Tuberosum and Andigena, and (3) present-day Indian varieties have more resemblance to Tuberosum than to the Andigena group. The in vitro approach was more effective than the in vivo approach for differentiating the genotypes per se, although its effectiveness for cross prediction is known to be low.

PCR-based markers were developed from mononucleotide simple-sequence repeats in the chloroplast genome of Nicotiana tabacum and applied to the analysis of genetic diversity. These markers were found to detect high levels of polymorphism at three taxonomic levels in Solanaceous plants. Of 36 chloroplast loci examined, 26 show some degree of polymorphism among potato accessions. Among a set of 30 tetraploid potato cultivars it is apparent that a single chloroplast haplotype is prevalent, presumably a result of the widespread use as a female parent of the imported US cultivar Rough Purple Chili in the latter half of the 19th century. Nonetheless, there is considerable chloroplast diversity in the cultivated potato, and it is clear that a large proportion of this variability has arisen through the use of wild or primitive cultivated species of potato in introgression programmes. This variability should be used in future breeding programmes. An examination of single accessions from 24 potato species, as well as representatives from tobacco and other members of the Solanaceae, reveals high levels of inter-specific chloroplast DNA variation. These data, and the ease of use and potential for multiplexing of these markers, suggest that cpSSRs will be of great utility in population genetics, germplasm management, evolutionary and phylogenetic studies as well as in, the analysis of material from introgression and somatic-fusion experiments. Interestingly, the polymorphism arising from one of the more-polymorphic chloroplast loci examined, does not originate solely from the SSR, and is due to variation in the copy number of two tandemly arrayed sequence elements.

The potato crop originated in the Andean highlands where numerous farmer's varieties and non-cultivated wild species exist. An Andean potato collection is held in trust at the International Potato Center (CIP) to preserve the biodiversity of this crop and ensure the supply of germplasm for potato improvement worldwide. A core collection representing the biodiversity of the Andean potato germplasm is under construction using morphological, molecular, and geographic data. One of the eight cultivated potato species, Solanum phureja, has been genotyped using the RAPD technique. A protocol suitable for large germplasm collection genotyping has been developed to process numerous samples at reasonable costs. From 106 RAPD primers evaluated, we have selected 12 primers yielding 102 polymorphic markers, which unambiguously discriminated all 128 accessions but 2 that are possible duplicates. The S. phureja germplasm collected throughout the Andean countries appears to have a homogeneous genetic constitution. There was no clear geographic pattern as indicated by cluster analysis of the RAPD data. A sub-group of 20 accessions has been identified on the basis of the marker data and selected to maximize molecular (RAPD) variance and polymorphism. The probability of capturing equal amounts of marker polymorphism in this sub-group of 20 accessions by random sampling is less than 40%. This set accessions represents our first group of accessions that may constitute a core of the S. phureja collection. This tentative core will be challenged for diversity content by alternate markers and agronomic traits. Hence, the methodology for sampling less than 10% of the base collection, proposed for core collections by Brown (1989), can be based on molecular marker data provided cost-efficient fingerprints are developed.

Genetic diversity analysis was performed in sweetpotato genotypes from the Philippine highlands and Discorea germplasm from Nigeria, Kenya and Philippines. Genomic DNA from seven potato genotypes selected from those which produced storage roots under drought conditions in the Northern Philippine highlands was subjected to Random Amplified Polymorphic DNA (RAPD) analysis. Twenty decamer primers were tested and 16 yielded DNA-amplification products. Among the 97 scored bands, 77 were polymorphic (79.38 percent) and genotype specific DNA markers were also identified. The pairwise marker difference between genotypes ranged from 0.378 to 0.936 indicating a broad range of genetic diversity. RAPD analysis was likewise done in 16 clones belonging to 3 species of yam, D. bulbifera, D. rotundata and D. alata. Twelve primers yielded DNA-amplification products in all yam species and clones. Of the 84 bands generated, 98.8 percent were polymorphic. Coefficient of similarity ranged from 0.45 to 0.98 for closely related clones into three separate groups show that RAPD markers can efficiently discriminate the different clones in a yam germplasm of diverse origin. The D. bulbifera group originated in Kenya, the D. rotundata group in Nigeria and "Sampero" in the Philippines

Microsatellite or simple-sequence repeats (SSRs) has been identified as an ideal molecular marker because of their hypervariability, abundance and uniform distribution in plant genomes. The use of radioisotopes such as 32P and 33P is the most commonly used detection system for SSRs. Under Philippine conditions, the use of radioactive detection system presents problems on waste disposal and procurement and could severely limit the widespread and routine applications of SSR technology. In this study, protocol for SSR analysis coupled with a silver staining detection technique has been developed for a number of important crops. Examples of various applications of SSR analysis in linkage map construction, genetic diversity studies and hybridity testing in coconut, corn, potato, banana and/or abaca will be presented

Genetic diversity of tropical forest tree species was assessed by using two tropical trees as model species namely Scaphium macropodum and Fordia johorensis in fragmented forest of Jambi Province, Sumatra. Leaf samples or inner bark tissues of the two species were collected from three sites viz. two sites are located in Silvagaina concession in Kuamang Kuning representing fragmented forest, and a site in an area of a private company PT. IFA-Barito Pacific Timber Group located in Pasir Mayang representing site linked with continuous forest. The analysis of six isozyme systems i.e. IDH, MDH, ME, PGD, PGI and SDH was conducted using potato starch gel electrophoresis. Estimates of genetic diversity i.e. mean number of alleles per locus, effective number of alleles per locus, percentage of polymorphic loci observed and expected heterozygosyties for F. johorensis is were not significantly different, while that for S. macropodum were significantly different (P 0.05) between Pasir Mayang and one of the sites in Kuamang Kuning. This suggest that fragmentation, under certain conditions, affected genetic diversity of S. macropodum | Telah diteliti keragaman genetik pohon hutan tropis menggunakan Scaphium macropodum dan Fordia johorensis sebagai model pada hutan yang terfragmentasi di Propinsi Jambi di Pulau Sumatra. Analisis dilakukan berdasarkan marka (penanda) isoenzim. Enam sistem enzim yang dianalisis yaitu IDH, MDH, ME, PGD, PGI dan SDH diperoleh dengan teknik gel elektroforesis pati kentang. Sampel daun atau kambium batang dari kedua jenis diperoleh dari tiga lokasi yaitu Camp Silvagama di Kuamang Kuning dan di areal milik satu perusahan swasta (PT. IFA Barito Pacific Timber Group) Pasir Mayang. Estimasi keragaman genetik yaitu rata-rata jumlah alel per lokus, jumlah efektif alel per lokus, persentase lokus polimorfik, heterozigositas yang diamati dan yang diharapkan, pada F. johorensis tidak berbeda nyata sedang pada S. macropodum sangat berbeda nyata (P0,05) antara Pasir Mayang dan salah satu lokasi di Kuamang Kuning. Dengan demikian, fragmentasi pada kondisi tertentu, mempengaruhi keragaman genetik S. macropodum

El tizón tardío de la papa, causado por Phytophthora infestans, es la enfermedad más destructiva de este cultivo y la que mayores problemas económicos ha ocasionado durante muchos años. A través del análisis de isoenzimas y del DNA nuclear y mitocondrial, se ha demostrado la amplia diversidad en la estructura genética de las poblaciones de P. infestans, así como las variaciones que en ellas han ocurrido. Además, utilizando técnicas modernas de biología molecular, han sido puestos en evidencia caracteres específicos de las poblaciones del hongo. En Cuba han sido detectados los dos tipos de compatibilidad (A1 y A2), y se han observado además diferentes rangos de resistencia al metalaxyl, evidenciando diversidad fenotípica en las poblaciones del hongo. En este trabajo se resumen los aspectos más característicos de las poblaciones de P. infestans en los países donde ha sido estudiado, como un primer paso para comprender la estructura genética de este microrganismo, y así poder ser analizados en un futuro sus caracteres genéticos en nuestro país. | The late blight of the potato, caused by Phytophthora infestans, it is the most destructive disease of this cultivation and greater the one which economic problems has caused during many years. Through analysis of isoenzymes and of the nuclear DNA and mitocondrial, it has been demonstrated the wide diversity in the genetic structure of the populations of P infestans, as well as the variations that they have occurred in these. Furthermore, using modem techniques of molecular biology have been put in evidence specific characters of the populations of the fungi. In Cuba have been detected the two types of compatibility (A 1 and A2) and they have been observed furthermore, different resistance ranges to the metalaxyl, evidencing phenotypic diversity in P. infestans populations. In this work, is summary the most characteristic aspects of the populations of P. infestans in the countries where it has been studied, as a first step to understand the genetic structure of this microorganism and thus be able be analyzed their genetic characters, in a future in our country.

Bacterial communities in the phyllosphere of genetically modified potato plants carrying a T4-lysozyme gene and of control plants without the gene were compared in the greenhouse and in the field. The polyphasic investigation included characterisation of isolates by fatty acid analysis, community-level catabolic profiling in BIOLOG GN microplates and genetic community fingerprinting by denaturing gradient gel electrophoresis of 16S rDNA fragments amplified by PCR from community DNA (PCR-DGGE). The diversity and frequency distribution of species determined by fatty acid analysis of 190 isolates from a greenhouse experiment and 488 isolates from a field sampling, as well as PCR-DGGE fingerprints of phyllosphere samples from the field, indicated highly similar communities of T4-lysozyme plants and controls. In addition, effects on community-level catabolic profiles were detected neither in the greenhouse nor in the field trial. Differences in the percentages of culturable species were detectable for the T4-lysozyme plants, namely a higher percentage of isolates classified as Erwinia sp. and lower abundances of Gram-positive isolates and of Agrobacterium, but the observed effects were minor relative to the natural variability observed in several field samplings. The observed effect on Agrobacterium populations in the field was confirmed by PCR-DGGE.