Characterization ofSolanum tuberosum simple sequence repeats and application to potato culiwar identification

With the continued introduction of new potato cultivars, accurate identification is becoming difficult but is essential for maintaining cultivar integrity and Plant Breeders’ Rights. Hypervariable DNA sequences, referred to as simple sequence repeats (SSRs) or microsatellites, have been reported to be an excellent source of genetic markers. To determine the abundance, distribution, and composition of SSRs withinSolanium tuberosum, 252 sequences were searched for tetranucleotide and smaller SSRs with a minimum length of 20 nucleotides and a maximum discrepancy of two nucleotides. In total, 40 unique SSRs were observed in the 252S. tuberosum sequences examined and occurred at a frequency of one SSR every 8.1 kb. To assess the ability of site-specific amplified SSRs to identify potato cultivars, a simple (TCAC)_m and compound (TCAC)_m ? (CTT)_n SSR 5’ to the starch synthase gene and a compound (C)_p ? (CT)_q ? (AT)_r ? (G)_s SSR 5’ to the sequence encoding mature proteinase inhibitor I, were examined and shown to produce unique DNA profiles for 73 of 95 tetraploid cultivars. In total, 24 alleles were observed at these loci and the accurately sized amplified DNA products can be used to establish a database for cultivar identification. Site-specific amplified alleles were somatically stable and have been conserved in clonal variants of Russet Burbank independently maintained for almost seven decades, a characteristic essential for cultivar identification. As genetic markers, the abundant, informative, and easily examined site-specific amplified alleles of SSRs are ideal for quickly and accurately determining cultivar identity of S.tuberosum ssp.tuberosum.     

Assessment of PCR-based simple sequence repeats to fingerprint North American potato cultivars

Seven primer pairs flanking di- and tri-nucleotide repeat sequences, identified from previously sequenced regions of the potato genome, were examined for their potential use in DNA-fingerprinting of thirty-nineSolanum tuberosum subsp. tuberosum cultivars (released between 1861 and 1988) and one diploidS. phureja breeding line. Of the simple sequence repeats (SSRs), the primers for six SSRs amplified DNA sequences within the potato genome between cultivars for a total of 14 bands. The polymerase chain reaction (PCR)based amplification products generated from each primer pair consisted of 1 to 2 bands per cultivar but band variation among cultivars demonstrated up to 4 bands per SSR. A similarity matrix generated from five SSRs was able to distinguish 24 of the 40 cultivars. However, when the potato cultivars were grouped by tuber type (round white-skinned, long white-skinned, russetskinned, red-skinned, and yellow flesh) only five pairs of cultivars remained indistinguishable: Atlantic/Katahdin, Belchip/Wauseon, Red LaSoda/Bliss Triumph, Red Pontiac/Norland, and Burbank/Spunta. Although SSRs did not generate unique fingerprints for all of the North American genotypes examined, the potential to discriminate most cultivars should increase as additional SSRs are identified in potato.     

Potato cultivar identification using simple sequence repeats markers (SSR)

Summary Identification of potato cultivars is currently based on phenotypic characters. Crop inspections are needed at different stages and the increasing number of cultivars means the process is becoming more and more complex. Molecular markers are a possible complementary tool to identify potato cultivars and to rapidly check the identity of seeds lots. In this study 286 potato cultivars produced in France were characterized by Polymerase Chain Reaction (PCR) using Simple Sequence Repeats (SSR) markers. Sequential amplifications with 4 to 5 of the chosen SSR markers enabled complete discrimination between all the cultivars. The patterns were registered in a database and the procedure is now used routinely in France.     

A simple assay system incorporating monoclonal antibodies for the detection of potato virus T

Summary Two monoclonal antibodies (McAbs) which react specifically with potato virus T (PVT) were produced and tested for cross reactivity with potato viruses (A, S, X, Y^o, Y^N, leaf roll), apple stem grooving virus (ASGV) and against healthy sap. They were found to be highly specific for PVT. These two McAbs form the basis of an enzyme-linked immunosorbent assay (ELISA) for the detection of PVT in infected plant material which is of key significance for potato quarantine.     

Detection of tobacco rattle virus in potato tubers using a simple RT-PCR procedure

Summary A simple assay for detection of tobacco rattle virus in infected tubers involving RT-PCR was developed. The assay detected a wide range of strains, including nonparticle NM variants. RNA extraction methods were compared, and a simple method was found to give reliable results. The method enabled detection of at least 1 ng of tobacco rattle particles in 100 mg tuber extract.     

An educational computer-based multimedia system for enhancing crop yield through improved potato planting

A multimedia software package was developed to present appropriate potato planting techniques necessary to increase crop yields. Resource material used included research and extension articles, video and photographs. Topics discussed are seed storage, seed cutting, planter management, plant spacing, and plant development. The intended audience for the software package includes extension staff and potato growers. The authoring software used for the development of the program was Toolbox, supported by several other software programs. The presentation runs on an IBM compatible 486 PC under MS-Windows.     

An agenda for future potato research

Summary The world is changing, and the rate of change is accelerating, nowhere moreso than in the pace of scientific discovery and the advance of technology. The last thirty years have also seen substantial global changes in potato production which are likely to continue if current projections are correct. Climate change is bound to affect local weather patterns, which will influence both the epidemiology of pests and pathogens and broaden their geographic range. An agenda for future research will of necessity include much of the current agenda; research into more sustainable systems; research into new and novel resistances to biotic and abiotic constraints, combining modern cell and molecular-based technologies with classical breeding approaches and research into the genetic and biochemical bases of low temperature sweetening and dormancy control, that should lead to varieties with superior storage characteristics, particularly for processing. However, a future agenda has to retain some flexibility and a component of speculative research. Perhaps potatoes could become a source of industrial feedstock or pharmaceuticals, perhaps there is a place for cultivars produced by botanic seed in Europe? The exciting thing about research is that we cannot always predict where it will lead, and a future agenda must not curb the enthusiasm of any young scientist by too rigidly adhering to that suggested here. it is essential that scientific options are kept open.     

A simple device for the determination of potato tuber specific gravity

A simple device consisting of a plastic rack with suspended wire basket was developed. This device when used in conjunction with a top loading balance greatly facilitates the determination of the specific gravity of individual tubers.     

A rapid and simple method for determination of potato chloroplast DNA type

A procedure for restriction enzyme analysis of the potato chloroplast DNA (ctDNA) is described. The advantages of this method are: 1) rapid determination of ctDNA type, 2) no ultracentrifugation, and 3) low cost of analyses. This method makes it easy to distinguish the ctDNA types of wild and cultivated potato accessions.     

An approach to field screening potato genotypes for potato leaf roll virus resistance

Eight potato cultivars and two advanced breeder selections were assessed for field resistance to the potato leaf roll virus (PLRV) following field exposures in which PLRV-infected Russet Burbank plants were used as inoculum sources within treatments. This screening protocol provided consistent PLRV resistance ratings despite year-to-year variation in PLRV pressure. Secondary disease incidence based on enzyme-linked immunosorbent assay (ELISA) of foliage from tuber progeny ranged from 0–87% in 1990 and 0–67% in 1991, and was consistent with reported PLRV resistance ratings for eight of ten genotypes. Agreement between visual assessment and ELISA on plants from harvested tubers was 94% in 1990 and 83% in 1991, for all genotypes. However, agreement data were inconsistent from year-to-year, with the exception of three genotypes. In both years, current season infection, based on ELISA of foliage, was detected in less than two percent of the plants and, was inadequate as a measure of secondary PLRV incidence. Green peach aphid (GPA) populations did not differ among genotypes at sampling times during the season, but the PLRV concentration in GPA colonizing Russet Burbank plots was significantly higher than in GPA colonizing any other genotype.     

A relational database system for potato breeding programs

Using a desktop database management system (DBMS), a relational database system was developed to replace outdated systems for data storage, retrieval and summary in a potato breeding research program. The new system allows for easy and efficient access, storage and interrelation of potato data, and automated reporting functions to support presentation and analysis requirements of the research program. DBMS tools and programmed functions provide summary information pertaining to such areas as potato plant genealogy and progeny performance in early selection, regional adaptation and disease resistance trials. Database structures have been implemented to facilitate the collection and verification of new data, interface to a hand-held data collection computer, and transfer report data and charts to standard word processing and presentation software. The concepts and techniques used in the construction of this database system can be applied to other potato and plant breeding programs     

Techniques for using sprouts for potato production in the tropics

A series of experiments were conducted in Vietnam to develop a system whereby detached sprouts from physiologically old green sprouted seed tubers could be used to grow potatoes. Three node segments from the mid or basal portion of the detached sprout produced the greatest percentage of shoots and roots. Growth was best in a medium of equal parts of sub-soil, pig manure and brick kiln ash. Sprout cuttings produced plantlets ready for transplanting in 14–20 days with mean daily temperatures of 22 to 24°C. When transplanted in mid-November, yields from sprout cuttings in field experiments were 10 to 18 t/ha which were 33% lower than from healthy seed tubers but more than the national average yield using degenerated seed tubers. Tubers produced by plants grown from sprout stored well and gave good yields when replanted the following year. Requests for reprints to International Potato Center, Box 933, Manila, Philippines.     

An efficient potato pollen extractor for bulk pollen collection

Commercial quantities of hybrid TPS production require bulk collection of pollen from male lines. Current usage of a buzzer system by the potato workers has proved inefficient needing frequent repairs with continuous usage. Described is a modified device utilizing battery operated portable stirrer that allows more efficient extraction of potato pollen in large quantities without the disadvantages of a buzzer system.     

A classification system for impact-related defects in potato tubers

The type of tuber bruise that occurs for a given severity of impact indicates the condition of that tuber in relation to its impact sensitivity. This article describes a system for classifying such bruises. Such information is important because sensitive tubers can be re-conditioned (e.g., temperature and/or hydration can be adjusted) to reduce risk of bruising during harvesting and handling. Each class of bruise is described, illustrated, and related to tuber condition. The literature review illustrates the inadequacies of previous bruise evaluation systems in relating bruise type to tuber condition. Growers, processors, storage operators and fresh packers can use this system to make informed decisions on adjusting modifiable factors such as temperature, hydration level, and impact velocity to reduce impact-related defects during harvesting and handling of potatoes.     

A simple non-destructive technique for healthy and diseased leaf area assessment of potato plants

Summary A method for assessing the leaf area of potato plants was based on the number of leaves coinciding with imaginary vertical lines descending from a horizontal grid of points above the plant or crop canopy. Leaves seen through each vertically aligned pair of holes in a perforated double table, covering the midpoint of the exposed area, were counted and moved aside one by one, until the ground was seen. For both green and diseased surfaces the leaf area, or its horizontal component, was calculated as the product of sum of records and the grid cell size. Tested against a destructive method, the technique worked equally well for healthy and diseased leaf area of potato plants infected byPhytophthora infestans. The theoretic estimate of the standard error for a single measurement was derived as the geometric mean of the leaf area and the grid cell size. The method is also suitable forLAI of crop stands.