The RAPD procedure was used to establish genetic diversity of 28 potato genotypes including siblings and genotypes with no immediate relationship. In addition amplified DNA from three parents and Solanum chacoense were compared with that from six progeny to determine the genetic relationships. Amplification of genomic DNA from the 28 genotypes using PCR and 12 decamer primers yielded 158 amplified DNA fragments, ranging in size from 490 to 3200 bp. A total of 128 unique RAPD fragments were observed among the 28 potato genotypes. Similarity measures and principal coordinate analysis generally reflected the expected trends in relationships of the full and half-sib potato genotypes. However there were important exceptions to this general trend and it appears that related varieties can be as genetically different as varieties with no immediate relationship. The data suggest that RAPD analysis used in conjunction with pedigree information can provide a superior measure of genetic divergence than analysis based solely on pedigree information.

Based on work conducted for the project "Preservation of sweet-potato biodiversity in Indonesia", this paper proposes a few conclusions, and discusses the significance of this research. The focus is on Irian Jaya where sweetpotato is a staple crop and cultivation has developed to high levels of sophistication. Beginning with a short overview of the components of sweet potato knowledge among local farmers, it is shown that many aspects of IK [indigenous knowledge] are rational and effective tools in crop management and the use of genetic variability. More specifically, selection for perceptual difference in varieties has been an important factor in the development of varietal diversity. Local communities need continuous access to genetic diversity for future use and development of their sweetpotato genetic resources. Different types of approach may be envisaged to achieve this "dynamic conservation", one of them being community-based conservation. Action research has been undertaken within project to look into the potential of local conservation and has brought some steps further in understanding of "on-farm conservation". The concluding section of the paper tries to evaluate the significance of the research in a wider political and institutional context, and looks at some policy implications for Irian Jaya.

Several Streptomyces species cause common scab of potato. The predominant pathogenic species, S. scabies, is associated with shallow, raised, and deep-pitted scab lesions. This species displays more diversity than one would expect in a conventional species. In spite of common morphological and physiological traits, S. scabies isolates vary considerably in fatty acid and protein composition. Furthermore, DNA-DNA hybridization studies reveal that S. scabies isolates can be divided into at least three genetic groups. In addition to S. scabies, other species such as S. acidiscabies and a species related to S. albidoflavus can induce scab symptoms in potato. S. acidiscabies is characterized by its ability to cause common scab in acidic environments. The species related to S. albidoflavus usually induces deep-pitted lesions and is associated with infected tubers grown in well-irrigated soils. Virulence factors of plant pathogenic streptomycetes are still unknown but the ability to produce phytotoxins called thaxtomins is a physiological property shared by most pathogenic strains.

This publication reports the workshop on in situ conservation and sustainable use of plant genetic resources for food and agriculture. The workshop was the continuation of an initiative which began in May 1990 when the Council for Tropical and Sub-Tropical Agricultural Research (ATSAF) and the International Board for Plant Genetic Resources (IBPGR), now International Plant Genetic Resources Institute (IPGRI), organized the first workshop in which German and IBPGR scientists met to ”strengthen the relationship between IBPGR and German scientists by establishing research contacs and collaboration”. This workshop resulted in a number of complementary funded projects including Refinement of Cryopreservation Techniques for Potato, Effective Pollination Control Methods in the Regeneration of Germplasm, and Spatial and Temporal Distribution of Genetic Diversity in Wild Forage Species under Stress Conditions. The convention on Biological Diversity emphasizes the importance of in situ conservation of plant genetic resources referring to the evolutionary process which sustains and develops genetic resources. Explicitly included is the in situ conservation of cultivated species in agricultural areas where farming systems and landraces were developed. The objective of the workshop was to contribute to conservation and sustainable use of plant genetic resources for food and agriculture, including forestry, through: increased understanding of in situ (including on-farm) conservation, integration of conservation strategies (in situ and ex situ), increased cooperation between IPGRI and parties in Germany and initiation of joint (IPGRI/German) Projects.