Potato Genetic Resources Research Articles

Screening for Resistance Resources against Bacterial Wilt in Wild Potato.

Potato is an important crop, used not only for food production but also for various industrial applications. With the introduction of the potato as a staple food strategy, the potato industry in China has grown rapidly. However, issues related to bacterial wilt, exacerbated by factors such as seed potato transportation and continuous cropping, have become increasingly severe in the primary potato cultivation regions of China, leading to significant economic losses. The extensive genetic diversity of Ralstonia solanacearum (R. solanacearum), which is the pathogen of bacterial wilt, has led to a lack of highly resistant potato genetic resources. There is a need to identify and cultivate potato varieties with enhanced resistance to reduce the adverse impact of this disease on the industry. We screened 55 accessions of nine different wild potato species against the bacterial wilt pathogen R. solanacearum PO2-1, which was isolated from native potato plants and belongs to phylotype II. Three accessions of two species (ACL24-2, PNT880-3, and PNT204-23) were identified with high resistance phenotypes to the tested strains. We found these accessions also showed high resistance to different phylotype strains. Among them, only PNT880-3 was capable of flowering and possessed viable pollen, and it was diploid. Consistent with the high resistance, decreased growth of R. solanacearum was detected in PNT880-3. All these findings in our study reveal that the wild potato PNT880-3 was a valuable resistance source to bacterial wilt with breeding potential.

Screening for Resistance Against Ralstonia Solanacearum in Commercially Available Colombian Potato Varieties

Ralstonia solanacearum, the causal agent of bacterial wilt, is one of the most devastating bacterial diseases worldwide. In potatoes and many other commercial species such as tomato, banana, plantain, and eggplant, among others, there is a lack of efficient strategies to control this pathogen. Therefore, using resistant cultivars might be the best strategy to prevent this disease. However, breeding for bacterial wilt resistance is challenging since latent infections pose a significant limitation when evaluating resistance to this disease in plant germplasm. Part of the diversity of potato genetic resources is maintained in the Colombian Central Collection (CCC) of potatoes, Corporación Colombiana de Investigación Agropecuaria (Agrosavia). With its 2069 accessions, the CCC is a good source for plant breeding programs. As a first attempt to identify bacterial wilt resistant/tolerant potato sources, 11 commercially available potato varieties were evaluated, representing Andigena and Phureja materials from the CCC. To this end, plants were drench-inoculated with R. solanacearum. This strain was able to cause severe disease in six of the 11 accessions tested. Thus, five highly R. solanacearum-resistant accessions were identified. These results represent a preliminary assessment for identifying bacterial wilt resistance sources that will contribute to establishing a potato breeding program to face this devasting pathogen before it arrives 70 Colombia.

Breeding accession value of potato genetic resources as sources of resistance to fungal diseases

Aim. To select sources and donors of resistance to fungal diseases late blight and fusarium (Phytophthora infestans (Mont.) de Bary and Fusarium sambucinum Fuck) among the gene pool accessions and available potato forms. Results and Discussion. Among wild species accessions, sources of resistance both to late blight of tubers and to Fusarium dry rot were identified. Solznum vernei, S.ocadae, S.dodsii, S.venturii, and S.boliviense accessions had tubers with high resistance to P.infestans. In addition, 31 accessions of wild species with high resistance to F.sambucinum were identified. Among newly created backcrosses of multispecies hybrids, 31 accessions were distinguished due to high or very high resistance of tubers to the pathogen. Backcrosses G13.45s14, G14.4s11, G15.7s105, G15.10s14, G15.24s17, G15.31s3, G15.32s50, G15.32s54, G15.15.36, 38s14, G17.16s8, G17.17s12, G17.17s13, G17.19s2, G17.22s50, and G17.28s8 were noticeable for the highest resistance. Six backcrosses of multispecies hybrids with high resistance of leaves to P.infestans were obtained. ccessions of the collection of potato genetic resources stored at the Institute of Potato Growing of NAAS of Ukraine are donors of resistance to Phytophthora infestans (Mont.) de Bary: 04.20s116 (UM0101669), 86.685s56 (UM0101705), 88.1425s1 (UM0101706), 88.1450s2 (UM0101595), Santarka (UM0102819), Podoliia (UM0102818), Hurman (UM0102878), Zarevo (UM010018). Sources of resistance to Fusarium sambucinum Fuck were found among backcrosses of multispecies hybrids. Backcrosses G13.49s45, G15.36s22, G17.10s1, G17.22s12, G17.22s50, and G17.28s8 were characterized by high individual resistance. Backcrosses G15.36s22, G17.10s1, G17.22s12, and G17.22s50 are of high breeding value, as they are their resistance score is 7-9 points, both to P. infestans and to F. sambucinum. Backcross G17.28s8 stood out due to its high resistance to late blight of leaves and tubers as well as to Fusarium dry rot. Conclusions. In the potato gene pool, sources of resistance to fungal diseases late blight and fusarium (Phytophthora infestans (Mont.) de Bary and Fusarium sambucinum Fuck) were identified. Both among wild species accessions and among backcrosses of multispecies hybrids, sources of potato resistance to late blight and Fusarium dry rot were found; they are valuable starting material to breed new varieties that would be highly resistant to biotic and abiotic factors.

Genetic Diversity and Population Structure of Potato Germplasm in RDA-Genebank: Utilization for Breeding and Conservation.

Potato (Solanum tuberosum L.) is an important staple food and economic crop in many countries. It is of critical importance to understand the genetic diversity and population structure for effective collection, conservation, and utilization of potato germplasm. Thus, the objective of the present study was to investigate the genetic diversity and population structure of potato germplasm conserved in the National Agrobiodiversity Center (NAC) of South Korea to provide basic data for future preservation and breeding of potato genetic resources. A total of 24 simple sequence repeat (SSR) markers were used to assess the genetic diversity and population structure of 482 potato accessions. A total of 257 alleles were detected, with an average of 10.71 alleles per locus. Analysis of molecular variance showed that 97% of allelic diversity was attributed to individual accessions within the population, while only 3% was distributed among populations. Results of genetic structure analysis based on STRUCTURE and discriminant analysis of principal components revealed that 482 potato accessions could be divided into two main subpopulations. Accessions of subpopulation 1 mainly belonged to cultivars and breeding lines. Accessions of subpopulations 2 basically corresponded to wild relatives of potatoes. Results of this study provide useful information for potato improvement and conservation programs, although further studies are needed for a more accurate evaluation of genetic diversity and phenotypic traits of potatoes.

Innovation and the commons: lessons from the governance of genetic resources in potato breeding

This article explores the relation between innovation and resources that are governed as commons by looking at the governance of potato genetic resources, especially in the context of the emergence of hybrid diploid potato breeding that will enable potato propagation through true seeds. As a new breeding tool, hybrid diploid potato breeding may not only revolutionize traditional potato breeding practices, it may also strongly affect current governance modes of potato genetic resources as a commons. Contrary to conventional accounts of the commons that treat technological innovation mainly as an exogenous factor, we argue that technological innovation can better be understood as an endogenous factor. In particular, we develop a co-production framework of innovation and the commons that draws attention to the different ways in which innovation, commons and its governance interact. Using this framework, we demonstrate that the constitution of potato genetic resources as a commons cannot be understood without considering the various ways in which technological innovation affects resources and mediate how these are governed. While reversely, technological innovations themselves are also enabled and constrained by users who govern potato genetic resources as a shared resource. We argue that changes in the governance of genetic resources can be understood as a change from one socio-technical constellation to another, whereby innovations, resources, and institutions are continuously co-produced.

Composition of the collection of primitive cultivated species within the Solanum L. section Petota Dumort. and contemporary trends in their research

The diversity of potato genetic resources in the VIR genebank harbors one of the world’s first collections of primitive cultivated species. These accessions are native potato varieties cultivated by the indigenous population of South America. The oldest accessions in the collection are traced back to 1927. Approximately one fifth of the collection (106 accessions out of 573) is the unique material procured by VIR’s collecting missions to Bolivia, Colombia, Ecuador, and Peru. According to S. Bukasov’s potato classification, the diversity of South American highland potatoes explored by VIR’s collectors belongs to spp. Solanum ajanhuiri Juz. et Buk., S. × chaucha Juz. et Buk., S. mammilliferum Juz. et Buk., S. phureja Juz. et Buk., S. rybinii Juz. et Buk., S. goniocalyx Juz. et Buk., S. stenotomum Juz. et Buk., S. tenuifilamentum Juz. et Buk., S.× juzepczukii Buk., and S. × curtilobum Juz. et Buk. Within this group of species, S. × ajanhuiri, S. phureja and S. stenostomum are the closest in their characteristics to ancient domesticated forms of tuber-bearing Solanum spp. This publication is an analytical review of the current composition of the primitive cultivated potato species collection and the results of its earlier studies. Ecogeographic descriptions of the sites native for cultivated potatoes and information on the sources of the accessions are presented. A large-scale evaluation of primitive cultivated potato accessions by a set of characters, carried out in field and laboratory experiments, uncovers their breeding potential and serves as the primary information platform for further indepth research. Studying S. phureja and closely related cultivated potato species is important for finding solutions of fundamental problems in plant biology. The data arrays accumulated today would facilitate targeted selection among accessions to identify most promising ones for molecular genetic studies into the gene pool diversity of potato species.

Development of a fast and user-friendly cryopreservation protocol for sweet potato genetic resources

Sweet potato (Ipomoea batatas) is one of the ten most important staple crops and provides a livelihood for many people around the globe. To adapt to ever-changing circumstances farmers and breeders need to have access to a broad diversity of germplasm. This study focuses on the development of a cryopreservation protocol that allows the long term storage of different sweet potato cultivars. For this, a droplet vitrification protocol was optimized, comparing several parameters; preculture method (0.3 M sucrose vs no preculture); meristem position (axillary vs apical); plant age (3 to 9 weeks); regeneration medium (MS + 2.22 µM BA, Hirai and MS); and length of loading solution treatment (20 to 360 min). Two months after cryopreservation, the regeneration rates of the meristems were compared, which resulted in significant differences for the preculture method, meristem position and loading solution. With these new insights an optimized droplet vitrification protocol was developed with the following parameters: use of 3–9 week old axillary meristems, no preculture phase, 20 min LS treatment, 30 min PVS2 treatment, exposure to liquid nitrogen by droplet vitrification, warming treatment in RS for 15 min, 1 day 0.3 M sucrose recuperation culture, 1 month MS + 2.22 µM BA followed by 1 month of MS cultures. This protocol was subsequently tested on 10 representative accessions resulting in a post cryopreservation regeneration rate of more than 40% for 70% of the tested cultivars, showing that this protocol could be implemented for a large portion of existing sweet potato collections.

The collection of potato varieties as a reserve of source material for breeding for high yield, earliness, and resistance to diseases and pests

Background. Information is provided about the results obtained by screening the VIR collection of improved potato varieties for main commercial traits: earliness, high yield, high starch content, and resistance to late blight (Phytophthora infestans (Mont.) de Bary), viruses, and pests, such as cyst nematode (Globodera rostochiensis Woll. (Ro1)), and Colorado beetle (Leptinotarsa decemlineata Say).Materials and methods. Potato accessions representing domestic and foreign varieties from the VIR collection served as the material for this research. The screening was performed according to the techniques developed at the Potato Genetic Resources Department of VIR.Results and conclusion. Potato varieties with valuable commercial traits were identified as breeding sources promising for earliness: ‘Bashkirskiy’ (k-25338), ‘Charoit’ (k-25221), ‘Colleen’ (k-25224), ‘Lagun’ (k-25294), etc.; for high yield: ‘Ametist’ (k-25336), ‘Banba’ (k-25222), ‘Bastion’ (k-25198), ‘Nur-Alem’ (k-25253), ‘Senim’ (k-25306), etc.; for high starch content: ‘Charaўnik’ (k-25139), ‘Darnitsa’ (k-25179), ‘Lad’ (k-25180), ‘Maksimum’ (k-25136), etc.; for resistance to late blight: local variety (Georgia) (k-25298, k-25326), ‘Sunkar’ (k-25258), ‘Udovitskiy’ (k-25260), ‘Vektor’ (k-25200), ‘Zvezdochka’ (k-25209); for resistance to viruses: ‘Azart’ (k-25196), Gala (k-25270), ‘Nadezhda’ (k-25213), Utro (k-25219), ‘Volat’ (k-25263), etc. Varieties combining resistance to gold potato cyst nematode with other valuable commercial traits were selected. Varieties with relative resistance to Colorado potato beetle were isolated under favorable conditions for the pest’s development. As a result of the research, new source material was identified, with a potential to improve major commercial traits of potato: earliness, high yield, high starch content, resistance to late blight, viruses, and pests (cyst nematode and Colorado beetle).

Diversity Analysis of Sweet Potato Genetic Resources Using Morphological and Qualitative Traits and Molecular Markers.

The European Union (EU) market for sweet potatoes has increased by 100% over the last five years, and sweet potato cultivation in southern European countries is a new opportunity for the EU to exploit and introduce new genotypes. In view of this demand, the origins of the principal Italian sweet potato clones, compared with a core collection of genotypes from Central and Southern America, were investigated for the first time. This was accomplished by combining a genetic analysis, exploiting 14 hypervariable microsatellite markers, with morphological and chemical measurements based on 16 parameters. From the molecular analyses, Italian accessions were determined to be genetically very similar to the South American germplasm, but they were sub-clustered into two groups. This finding was subsequently confirmed by the morphological and chemical measurements. Moreover, the analysis of the genetic structure of the population suggested that one of the two groups of Italian genotypes may have descended from one of the South American accessions, as predicted on the basis of the shared morphological characteristics and molecular fingerprints. Overall, the combination of two different characterization methods, genetic markers and agronomic traits, was effective in differentiating or clustering the sweet potato genotypes, in agreement with their geographical origin or phenotypic descriptors. This information could be exploited by both breeders and farmers to detect and protect commercial varieties, and hence for traceability purposes.

Long-term conservation of potato genetic resources: Methods and status of conservation

Plant genetic resources (PGRs) play an important role in agriculture, environment protection, cultural property and trade; they need to be conserved. There are two fundamental approaches for the conservation of PGRs: in situ and ex situ. In situ conservation is the conservation of ecosystems and natural habitats and the maintenance and recovery of viable populations of species in their natural surroundings. Ex situ preservation is the storage of seeds or plant materials under artificial conditions to maintain their long term viability and availability for use. Genebanks employ seed storage, field collections of living plants and in vitro storage (tissue culture or cryopreservation) for ex situ preservation of PGR. Storage of orthodox seeds, which are tolerant to low moisture content and low temperatures at appropriate temperature and humidity, is the most convenient ex situ conservation method. Plants that produce recalcitrant seeds or non-viable seeds are conserved in field genebanks as well as in-vitro in slow growth media for short-to-medium term and cryopreservation in liquid nitrogen at -1960C for long-term periods. Cryopreservation is very expensive and needs trained personnel; this could explain why this method is rarely used for conservation of plant genetic resources in most developing countries. Potato tubers are bulky and highly perishable; the crop is generally conserved as clones either in field genebanks (with annual replanting), in-vitro conservation in slow growth media for short-to-medium term and cryopreservation for long term. Field genebanks are expensive to maintain and the crop is exposed to many dangers; hence, cryopreservation is the only feasible method for long term conservation. However, given the high cost of cryopreservation, long-term conservation of potato genetic resources is poorly developed in most resource-poor countries leading to high rates of genetic erosion. This paper looks into the various methods that that can be applied to conserve potato genetic resources and the status of conservation of potatoes in major genebanks and some countries.

Screening of wild potato genetic resources for combined resistance to late blight on tubers and pale potato cyst nematodes

The Leibniz Institute of Plant Genetics and Crop Plant Research maintains a diverse collection of wild potato germplasm with more than 2800 accessions from 139 botanical species, 19 Solanum series and 14 countries of origin. During the past two decades, almost half of the collection has been screened for resistance to late blight (Phytophthora infestans) and pale cyst nematode (Globodera pallida (Pa2/3)) infection under laboratory conditions. In particular, resistance to tuber blight was considered, which is an important component of P. infestans resistance and has not been investigated that detailed yet. Out of the 1055 accessions tested, 68 were very resistant and 311 were classified as partially resistant against tuber blight. Besides in accessions of species well-known for foliage resistance, resistance to tuber blight was also observed in previously less reported species such as S. acaule, S. fendleri, S. megistacrolobum, S. polytrichon, S. jamesii, S. trifidum, and S. tarnii. In regard to G. pallida infection, 78 out of 749 tested accessions were classified as resistant, belonging to the species S. acaule, S. circaeifolium, S. gourlayi, S. kurtzianum, S. oplocense, S. sparsipilum, S. spegazzini and S. vernei. New or previously less reported sources of G. pallida resistance were identified in accessions of S. brevicaule, S. demissum and S. microdontum. In various accessions of different species, combined resistance was observed and the relationship to their country of origin is discussed.

INFORMATIONAL RESOURCES ON POTATO GERMPLASM COLLECTIONS

The potato (Solanum tuberosum L.) is one of the most important food crops, the advantage of which is the ability to give a high yield in a wide range of agroecosystems, high specific production of dry weight per unit of cultivated area. Nowadays potato is considered a source of vitamins, minerals, dietary fiber and other nutrients. Potato cultivars are characterized by low genetic diversity, which reduces their potential to produce varieties with improved properties. Wild potato relatives retain a high degree of genetic diversity, which can be used to find the superior alleles and for their further transfer to cultural genotypes. To this end, there is an intense development of potato gene banks, with the help of the information technology to access the data. The present review is devoted to global information resources in potato. It describes the most relevant information portals and databases of genetic resources for potatoes. Analysis of information in the Internet shows that the main information resources on potato collections are concentrated in the United States and Europe. Information portals provide a wide variety of information useful to producers, consumers and breeders. On such portals, there is an intensive information support of the latest technologies in the field of potato growing and breeding. An interesting direction is the provision of services to determine the DNA prints (markers) of potato varieties, involvement of potato growers in the process of operational monitoring of diseases and pests of potatoes. Integration of data on potato collections plays an important role at the present stage. In line with this, European collections and databases are being developed. However, despite the existence of pan-European potato collection, national collections are still given support. An important collection-related trend in recent years has been inclusion of samples with a large number (more than a hundred) characteristics, which are evaluated by constantly testing varieties within the framework of foreign state breeding programs. As a result of access to such information, the breeder can effectively plan an experiment with the purpose of directed selection for key features of plants. These trends confirm the effectiveness of the use of the latest technologies (including information) in the maintenance and dissemination of potato genetic resources.

Mobilization, conservation and study of cultivated and wild potato genetic resources

Nowadays, the world’s largest Potato Genebanks, including VIR Potato Genebank, hold about 98 thousand accessions of potato and its wild relatives. This gene pool, which has been accumulated for almost a century, represents a huge genetic diversity of tuber bearing species of the genus Solanum L., which has a great importance for basic and applied research in general, and for human food security. The genebanks of potato and other crops have three highly important tasks such as permanent replenishment of collection material, ensuring its preservation by various storage and maintaining methods, including seed and vegetative propagation, its all-round use in basic and applied research, as well as the improvement of the efficiency of agricultural production. Analysis of performance of the above tasks in genebanks and research institutes in most countries concerned with storage, study and use of potato germplasm, shows great results and achievements, both in terms of its biology and its improvement as a food crop. However, the above three ways to perform tasks still need to be improved in connection with progress made over past decades, in particular in the field of basic and applied sciences. In this paper, a brief analysis of the status of conservation, study and use of potato genetic resources and its wild relatives in the domestic and foreign breeding, as well as solutions of problems in these areas are provided. A great leap forward today is the use of molecular genetic methods for genotyping collection material in gene banks to identify and itemize collection samples, as well as for using this material in basic and applied research, including breeding programs. Coordination of efforts for the collection of wild species that are not in the collections or are represented by a small number of samples, as well as the exchange of material and information about it, will help expand genetic diversity in genebanks and knowledge of the biological features of the potato.

Aphid resistance in potato

The problem of aphid resistance of potato genetic resources is discussed. Generally, resistance to the green peach aphid (Myzus persicae Sulzer) and the potato aphid (Macrosiphum euphorbiae Thomas) is analyzed in all available literature sources. The Solanum tuberosum L. gene pool contains very few resistant forms. Accessions highly resistant to M. persicae were revealed among 36 of 86 examined wild potato species. The largest number of resistant forms was found among S. bulbocastanum Dun., S. tarijense Hawkes, S. infundibuliforme Phil., S. canasense Hawkes and S. stoloniferum Schlechtd. et Bche. The forms highly resistant to M. euphorbiae belong to 24 of 85 studied species, namely to 10 of 18 series; the species S. bulbocastanum, S. stoloniferum and S. demissum Lindl. include the maximum number of resistant forms. Wild species accessions with specific and group resistance to aphids were revealed. Glandular pubescence of leaves and stems in such species as S. polyadenium Greenm., S. tarijense and S. berthaultii Hawkes is considered as the main mechanism of resistance. Hybrids between S. tuberosum and S. berthaultii were widely used in breeding programs; however, the presence of glandular trichomes was linked to a number of undesirable characters. It is expected that association between the trichome conditioned insect resistance of S. berthaultii and undesirable agronomic traits could be overcome with the use of molecular genetic methods. Studies of the antifeedant activity of potato glycoalkaloids and their aglucons produced controversial results. In numerous works the aphid resistance of potato is connected with plant physiological state. Differences among wild potato accessions in the localization of resistance factors (leaf surface, epidermis, mesophyll, floema) were found that were indicative of differences of resistance mechanisms in the studied forms. Works on investigating induced aphid resistance in potato have great theoretical and practical significance.

A Toolbox of Potato Genetic and Genomic Resources

Access to genetic and genomic resources can greatly facilitate biological understanding of plant species leading to improved crop varieties. While model plant species such as Arabidopsis have had nearly two decades of genetic and genomic resource development, many major crop species have seen limited development of these resources due to the large, complex nature of their genomes. Cultivated potato is among the ranks of crop species that, despite substantial worldwide acreage, have seen limited genetic and genomic tool development. As technologies advance, this paradigm is shifting and a number of tools are being developed for important crop species such as potato. This review article highlights numerous tools that have been developed for the potato community with a specific focus on the reference de novo genome assembly and annotation, genetic markers, transcriptomics resources, and newly emerging resources that extend beyond a single reference individual.

Assessment of genetic diversity and relatedness in the Latvian potato genetic resources collection by DArT genotyping

Potato (Solanum tuberosumL.) has been cultivated in Latvia since the 17th century, and formal breeding programmes have been established since the start of the 20th century. The Latvian potato genetic resource collection consists of 83 accessions of Latvian origin, including landraces, old cultivars released starting from the 1930's, modern cultivars and breeding material. These are maintained in field andin vitrocollections. Pedigree information about the potato cultivars is often limited, and the use of hybrids of local cultivars as parents is common in the Latvian potato breeding programme. Ninety-four Latvian potato varieties and breeding lines and some commonly used foreign accessions were genotyped with the potato DNA diversity array technology. Analysis of the Latvian potato genetic resources collection revealed that the amount of genetic diversity has increased in the modern cultivars in comparison with the old cultivars.

Diversity of potato genetic resources.

A considerable number of highly diverse species exist in genus Solanum. Because they can adapt to a broad range of habitats, potato wild relatives are promising sources of desirable agricultural traits. Potato taxonomy is quite complex because of introgression, interspecific hybridization, auto- and allopolyploidy, sexual compatibility among many species, a mixture of sexual and asexual reproduction, possible recent species divergence, phenotypic plasticity, and the consequent high morphological similarity among species. Recent researchers using molecular tools have contributed to the identification of genes controlling several types of resistance as well as to the revision of taxonomical relationships among potato species. Historically, primitive forms of cultivated potato and its wild relatives have been used in breeding programs and there is still an enormous and unimaginable potential for discovering desirable characteristics, particularly in wild species Different methods have been developed to incorporate useful alleles from these wild species into the improved cultivars. Potato germplasm comprising of useful alleles for different breeding objectives is preserved in various gene banks worldwide. These materials, with their invaluable information, are accessible for research and breeding purposes. Precise identification of species base on the new taxonomy is essential for effective use of the germplasm collection.

Cryopreservation for preservation of potato genetic resources.

Cryopreservation is becoming a very important tool for the long-term storage of plant genetic resources and efficient cryopreservation protocols have been developed for a large number of plant species. Practical procedures, developed using in vitro tissue culture, can be a simple and reliable preservation option of potato genetic resources rather than maintaining by vegetative propagation in genebanks due their allogamous nature. Cryopreserved materials insure a long-term backup of field collections against loss of plant germplasm. Occurrence of genetic variation, in tissue culture cells during prolonged subcultures, can be avoided with suitable cryopreservation protocols that provide high regrowth, leading and facilitating a systematic and strategic cryo-banking of plant genetic resources. Cryopreservation protocols for potato reviewed here, can efficiently complement field and in vitro conservation, providing for preservation of genotypes difficult to preserve by other methods, wild types and other species decided as priority collections.

Three vitrification-based cryopreservation procedures cause different cryo-injuries to potato shoot tips while all maintain genetic integrity in regenerants

We previously reported successful cryopreservation of shoot tips of potato ‘Zihuabai’ by three vitrification-based protocols. In the present study, cryo-injury to shoot tips and genetic stability in regenerants recovered from cryopreserved shoot tips by the three vitrification-based protocols were further investigated. The results showed that sucrose preculture caused no obviously different injuries, while dehydration with plant vitrification solution 2 (PVS2) was the step causing major damage to cells of shoot tips, regardless of the cryogenic procedures. Compared with droplet-vitrification and encapsulation–vitrification, vitrification caused the most severe injury to cells of the shoot tips, thus resulting in much longer time duration for shoot recovery and much lower shoot regrowth rate. Cells in apical dome and the youngest leaf primordia were able to survive and subsequently some of them regrew into shoots following all three vitrification-based cryopreservation procedures. Analyses using inter-simple sequence repeat (ISSR) and amplified fragment length polymorphism (AFLP) markers in shoots regrown from all three vitrification-based protocols did not find any polymorphic bands. The results reported here suggest that vitrification-based cryo-procedures can be considered promising methods for long-term preservation of potato genetic resources.

Dynamics of on-farm management of potato (Solanum tuberosum) cultivars in Central Kenya

Studies to understand the dynamic nature of farmers’ management of potato and assess the extent of genetic erosion and farmers’ perceptions of genetic erosion in potato were conducted in Kiambu West district in 2006. A stratified random sampling procedure was used to draw a sample of 302 farmers for the study. Majority of the farmers interviewed obtained seeds from informal sources. Farmers identified 29 varieties which were once widely grown in the study area. Of these, only 9 are still grown while another 11 have been introduced. The most commonly grown varieties were Zangi (69.4%), Tigoni (41.4%), Thima Thuti (30.8%) and Karuse (20.9%). Twenty cultivars including Amin, Anett, Cardinal, Feldeslohn, Gituru, Kiraya, Kibururu, Kenya Baraka, Kenya Dhamana, Karora Iguru, Maritta, Mirka, Njae, Njine, Patrones, Romano, Roslin Bvumbwe, Roslin Gucha, Suzanna and Furaha were the most affected by genetic erosion. The most important causes for abandonment of varieties were low yields, rapid greening, susceptibility to late blight, strong dormancy, sensitivity to drought, and susceptibility to bacterial wilt, susceptibility to potato tuber moth, poor storability and poor cooking quality. The emergence of new and better varieties, lack of markets and lack of seed were the three most cited non-varietal reasons for abandoning varieties. Farmers were not bothered by the loss of varieties. When comparing varieties currently cultivated to formerly available varieties, a genetic erosion of 31.0% was computed suggesting that genetic loss has occurred in the study area. Results of this study suggested that it is necessary to initiate collection, characterization and conservation studies of potato varieties across the country. There is also the need for awareness creation on the importance of potato genetic resources and their conservation. Key words: Conservation, genetic erosion, farmers’ perceptions, Kenya, potato, seed sources, Solanum tuberosum, variety abandonment.