Advanced Breeding Clones Research Articles

Evaluation of Genetic Resources in a Potato Breeding Program for Chip Quality

The objective of this study was to assess the ability of experimental advanced breeding clones as parental genotypes to transmit agronomic and quality traits to their progenies in breeding programs. A half diallel set of crosses (excluding reciprocals) with six parents was assayed in field trials for three years; four of the parents were Solanumtuberosum subsp. tuberosum cultivars, and two of them were advanced breeding clones that included genes from S. tuberosum subsp. andigenum with immunity to PVY virus and good agronomic performance. However, no information was available about the behavior of these clones as parental materials for quality traits, such as potato chip quality. The diallel mating design allowed us to discover their ability to transmit agronomic and quality traits to their offspring. Significant effects on general combining ability and specific combining ability were found for plant maturity, only general combining ability effects for specific gravity were found, and interactions of both general combining ability and specific combining ability with the environment for the chip color trait were found. However, no genetic effects were detected for yield. Where general combining ability significant effects were found, additive genetic effects are predominant; thus, so for those traits, it would be possible to use these genotypes as parents to obtain improved progenies. Such abilities were not found in the advanced breeding clones.

Identification of superior parental lines based on BLUP breeding values in potato (Solanum tuberosum L.)

Identification of superior parental lines require phenotypic or genotypic characterization of the germplasm, which is time consuming and laborious. The advanced potato breeding clones including control varieties were evaluated under field conditions to identify the suitable parental lines for tuber yield, late blight and specific gravity based on estimated breeding values using historical data as training population during 2008-09 to 2019-20. Pedigree of all the clones was searched to a depth of 5-6 generations. The mixed model fitting using REML was true. The minimum and maximum values for total tuber yield, late blight area under disease progress curve (AUDPC) and specific gravity were 28.33-732.2, 0-1846.25, 1.043-1.087, respectively. Pedigree had 161 founders out of total 759 individuals and the pedigree matrix showed relationship in 1,09,057 pairs. Heritability estimate was highest for specific gravity (0.77) followed by late blight AUDPC (0.49) and total tuber yield (0.24). The estimate of the BLUP breeding values (EBVs) for total tuber yield were highest for Kufri Mohan, Kufri Pukhraj, Kufri Khyati, SM/14-342 and Kufri Pushkar while SM/10-05, SM/09-99, Kufri Girdhari, SM/11-120 and Kufri Karan for late blight resistance, and Kufri Chipsona-1, SM/14-225, SM/14-229, SM/10-220 and SM/09-153 for specific gravity were the best genotypes. The prediction accuracy measured as correlation between EBV and observed phenotype score for specific gravity (0.97) was near perfect, very high for late blight AUDPC (0.75), and high for total tuber yield (0.55). The prediction bias measured as regression coefficient and scatter plots of observed phenotype values on EBVs was nil to low for specific gravity andlate blight AUDPC, while underestimation was observed for total tuber yield. Overall, the prediction accuracies for all the three traits were very good and selection of parental lines using Best Linear Unbiased Prediction breeding values could result in enhanced genetic gain in potato breeding

Public potato breeding progress for the Nordic Region of Europe: evidence from multisite testing of selected breeding clones and available released cultivars

ABSTRACT The breeding of new cultivars is a powerful approach to increase both the quantity and quality of potato harvest per land unit. The aim of this research was to determine using multi-site testing the progress made by the genetic enhancement of potato in Sweden in the last 1.5 decades by comparing advanced breeding clones (T4 upwards) bred in Sweden (Svensk potatisförädling hereafter) versus available released cultivars in Europe and grown in its Nordic Region. The multi-site testing results show that potato breeding based in Scandinavia offers to the growers of the Nordic Region of Europe cultivars for prevailing farming environments and end-user needs rather than relying, as happens today in the market, on foreign cultivars. These cultivars bred elsewhere are not always very suitable for the challenging Nordic agroecosystems, as shown by the results of the multi-site testing herein. Such an approach on relying on foreign cultivars may be advocated for not funding potato breeding in, and for Fennoscandia by those ignoring the results shown by this research.

KASP markers validation for late blight, PCN and PVY resistance in a large germplasm collection of tetraploid potato (Solanum tuberosum L.)

Molecular markers are important and valuable tools in crop breeding programmes to help in the discovery and manipulation of important genes governing resistance reaction. In potato, several biotic stresses hamper quantity and quality of tuber production. Availability of molecular markers and high throughput screening method provide an excellent opportunity to practice marker assisted selection for potato improvement without waiting for phenotypic screening. In this study, we developed 20 KASP markers related to late blight, PVY and PCN resistance traits to facilitate the screening at earlier stages of potato breeding programmes. Out of these 20 markers, nine KASP assays were validated and associated with the phenotype data on respective traits for reliability in their wider application. The validation was done in a panel of 1447 potato germplasm accessions including varieties from diverse provenience and advanced breeding clones. Among traits, the best association found related to KASP markers for late blight, namely markers snp ST00106, snp ST00020 and snp ST00023. Overall, the allele calls were conclusive for all the nine markers, and the results demonstrate the usefulness of SNP KASP markers in high throughput cost effective marker assisted selection (MAS) for important biotic stress traits in potatoes.

Genome-Wide Association Study of Resistance to Potato Common Scab

Potato common scab caused by bacterial pathogen Streptomyces scabies (Thaxt.) Waksman & Henrici is one of the most important diseases of potato (Solanum tuberosum L.) worldwide. Currently, the most effective and desirable method to control common scab is through the use of resistant cultivars. In order to decipher the genetic control of resistance to common scab disease in Canadian potato germplasm, an association panel of 143 clones including advanced breeding clones and commercial cultivars was genotyped with 12K SolCAP SNPs and phenotyped for potato common scab resistances in multiple years. By conducting a genome-wide association analysis (GWAS) using GWASpoly R package, three resistance QTLs were identified on potato chromosomes 2, 4, and 12, respectively. The phenotypic variation explained by these QTLs was 21%, 19%, and 26%, respectively. The QTL on chromosome 2 was simplex-dominant whereas duplex-dominant QTLs were identified on chromosomes 4 and 12. These findings will be useful to design marker-assisted selection and breeding strategies to improve resistance to common scab in new potato cultivars.

Effects of Field Selection Parameters and Specific Gravity on Culinary Evaluation Traits in a Potato Breeding Programme

Potato culinary evaluation is an integral component of a breeding programme to determine suitability of new cultivars to specific end-uses. In most breeding programmes, quality assessment is conducted after a few generations of field selection on tubers collected from the field or from storage conditions. In order to optimize selection procedures, we analysed the relationship between specific gravity of potato tubers and quality evaluation traits as well as the effects of field selection parameters in clones that are intended for fresh market and processing uses. A total number of 237 advanced breeding clones were analysed over three consecutive years in the potato breeding programme at Agriculture and Agri-Food Canada (AAFC). Principal component analysis (PCA) and linear mixed-effects model fit by maximum likelihood indicated that parameters used in field selection significantly contributed to specific gravity and culinary components. Specific gravity also contributed significantly to culinary traits related to acceptable quality of baked, boiled and French-fried products. However, such relationship was not observed for chip quality. Significant associations were found between field selection parameters, such as maturity, early vigour, top vigour, early harvest, tuber size and tuber appearance and culinary components related to French fry and chip quality, but not for quality of baked and boiled products. Broad-sense heritability estimates for various culinary evaluation traits ranged from 57 to 92%. The results suggest that specific gravity and culinary traits should be incorporated in early or intermediate generation selection parameters in order to optimize selection gains for specific end-uses.

Resistance of advanced cassava breeding clones to infection by major viruses in Uganda

Cassava brown streak disease (CBSD) and cassava mosaic disease (CMD) are two viral diseases that cause severe yield losses in cassava of up to 100%, thereby persistently threatening food and income security in sub-Saharan Africa. For effective management of these diseases, there is a critical need to develop and deploy varieties with dual resistance to CBSD and CMD. In this study, we determined the response of advanced breeding lines to field infection by cassava brown streak viruses (CBSVs) and cassava mosaic begomoviruses (CMBs). This aim helped in identifying superior clones for downstream breeding. In total, 220 cassava clones, three in uniform yield trials (UYTs) and 217 in a crossing block trial (CBT), were evaluated for virus and disease resistance. Field data were collected on disease incidence and severity. To detect and quantify CBSVs, 448 and 128 leaf samples from CBSD symptomatic and symptomless plants were analyzed by reverse transcription PCR and real-time quantitative PCR, respectively. In addition, 93 leaf samples from CMD symptomatic plants in the CBT were analyzed by conventional PCR using CMB species-specific primers. In the CBT, 124 (57%) cassava clones did not express CMD symptoms. Of the affected plants, 44 (55%) had single African cassava mosaic virus infection. Single Cassava brown streak virus (CBSV) infections were more prevalent (81.6%) in CBT clones than single Ugandan cassava brown streak virus (UCBSV) infection (3.2%). Of the three advanced clones in the UYT, NAROCASS 1 and NAROCASS 2 had significantly lower (P < 0.05) CBSD severity, incidence, and CBSV load than MH04/0300. In the UYT, only 22% of samples tested had CBSVs, and all showed a negative result for CMBs. The low disease incidence, severity, and viral load associated with NAROCASS 1 and NAROCASS 2 is evidence of their tolerance to both CBSD and CMD. Therefore, these two cassava clones should be utilized in CBSD and CMD management in Uganda, including their utilization as progenitors in further virus resistance breeding.

Progress and Successes of the Specialty Crop Research Initiative on Acrylamide Reduction in Processed Potato Products

Acrylamide, a suspected human carcinogen, is a Maillard reaction product that forms when carbohydrate-rich foods are cooked at high temperatures. Processed potato products, including French fries and potato chips, make a substantial contribution to total dietary acrylamide. Health safety concerns raised by acrylamide in food increased financial risks to the potato industry and encouraged industry to take a proactive approach toward acrylamide mitigation. The USDA National Institutes of Food and Agriculture Specialty Crop Research Initiative (SCRI) on acrylamide reduction in potato was a cooperative endeavor in which industry partners worked at a systems level with university and government researchers to develop acrylamide mitigation strategies. Short-term goals focused on identifying advanced breeding clones and recently released varieties that have lower acrylamide-forming potential than standard potato varieties. Research was also directed at developing more efficient potato breeding methods, including marker-assisted breeding, genome wide selection, and improved phenotyping methods. Data from the National Fry Processing Trial (NFPT) and SCRI agronomic trial have shown that dramatic reductions in acrylamide are achievable through the use of new varieties that maintain low concentrations of tuber reducing sugars. Chipping potato trials coordinated by Potatoes USA and data from breeding populations suggest that maintaining low tuber reducing sugars through extended storage and lowering tuber asparagine content are options for decreasing acrylamide content in potato chips. To have an impact, new varieties must have exceptional agronomic performance and must produce finished products that meet requirements for consumer attributes including color, texture and taste. Data consistently show that this is more easily achievable in chipping potatoes than in fry processing potatoes.

Genetic bases of tomato and sweet pepper marker-assisted selection in Belarus

Molecular markers are important and valuable tools in crop breeding programmes to help in the discovery and manipulation of important genes governing resistance reaction. In potato, several biotic stresses hamper quantity and quality of tuber production. Availability of molecular markers and high throughput screening method provide an excellent opportunity to practice marker assisted selection for potato improvement without waiting for phenotypic screening. In this study, we developed 20 KASP markers related to late blight, PVY and PCN resistance traits to facilitate the screening at earlier stages of potato breeding programmes. Out of these 20 markers, nine KASP assays were validated and associated with the phenotype data on respective traits for reliability in their wider application. The validation was done in a panel of 1447 potato germplasm accessions including varieties from diverse provenience and advanced breeding clones. Among traits, the best association found related to KASP markers for late blight, namely markers snp ST00106, snp ST00020 and snp ST00023. Overall, the allele calls were conclusive for all the nine markers, and the results demonstrate the usefulness of SNP KASP markers in high throughput cost effective marker assisted selection (MAS) for important biotic stress traits in potatoes.

Late blight and virus host-plant resistances, crossing ability and glycoalkaloids in Nordic potato germplasm

ABSTRACTOld potato cultivars from the Nordic Genetic Resource Center (NordGen) and advanced breeding clones from the Swedish University of Agricultural Sciences (SLU) were evaluated for susceptibility to Potato Virus Y (PVY) and Potato Leafroll Virus (PLRV), foliar and tuber resistance to late blight – caused by Phytophthora infestans – as well as for glycoalkaloid content and crossing ability. Enzyme-Linked Immunosorbant Assay (ELISA) tests were used for PVY and PLRV screening during two years that were characterized by intensive virus incidence and severity in the field, while foliar and tuber resistances to late blight were assessed under artificial inoculation with an aggressive Swedish isolate of P. infestans. Hybrid seeds were obtained by crossing cultivars such as ‘Kiva’, ‘Sarpo Mira’, ‘Rosamunda’ and ‘Superb’ with SLU advanced breeding clones and a selected clone of Solanum tuberosum Group Andigena. Some cultivars (‘Hårek’, ‘Sarpo Mira’) and breeding clones (04-2662, 04-2085) with late blight resistance did not show virus infection. The α-solanin and α-chaconin contents of some of the old Nordic potato cultivars and breeding clones were similar to the known Dutch table cultivar ‘Bintje’ after 3 years of testing. This research allows identification of promising Nordic potato cultivars and SLU breeding clones for further use in developing germplasm aiming at organic and conventional farming systems.

Genetic Diversity and Relationship of Ethiopian Potato Varieties to Germplasm from North America, Europe and the International Potato Center

Potato is an increasingly important crop in Ethiopia, but the origin of local cultivars grown throughout the country is unknown. To evaluate the genetic diversity of Ethiopian potato cultivars, and to assess their relationship with germplasm from North America, Europe and the International Potato Center (CIP), 8303 SNP markers were used to characterize 44 local Ethiopian cultivars, as well as 26 CIP, 22 American and 17 European potato cultivars and advanced breeding clones. The marker data revealed that most of the local cultivars were duplicates; among the 44 cultivars tested, only 15 unique genotypes were observed. Principal component and neighbor-joining dendrogram analyses showed that American, European and CIP germplasm form three distinct clusters, with older Ethiopian cultivars overlapping the European cultivars, suggesting that the oldest local cultivars are of European descent. Local cultivars overall separated into two distinct clusters, suggesting that at least two distinct introductions gave rise to current local cultivars in Ethiopia. Ethiopian germplasm harbors comparable levels of genetic diversity to American, European, and CIP germplasm and could provide the foundation for a national potato breeding program.

Identification and reproducibility of diagnostic DNA markers for tuber starch and yield optimization in a novel association mapping population of potato (Solanum tuberosum L.).

Key messageSNPs in candidate genesPain-1,InvCD141(invertases),SSIV(starch synthase),StCDF1(transcription factor),LapN(leucine aminopeptidase), and cytoplasm type are associated with potato tuber yield, starch content and/or starch yield.Tuber yield (TY), starch content (TSC), and starch yield (TSY) are complex characters of high importance for the potato crop in general and for industrial starch production in particular. DNA markers associated with superior alleles of genes that control the natural variation of TY, TSC, and TSY could increase precision and speed of breeding new cultivars optimized for potato starch production. Diagnostic DNA markers are identified by association mapping in populations of tetraploid potato varieties and advanced breeding clones. A novel association mapping population of 282 genotypes including varieties, breeding clones and Andean landraces was assembled and field evaluated in Northern Spain for TY, TSC, TSY, tuber number (TN) and tuber weight (TW). The landraces had lower mean values of TY, TW, TN, and TSY. The population was genotyped for 183 microsatellite alleles, 221 single nucleotide polymorphisms (SNPs) in fourteen candidate genes and eight known diagnostic markers for TSC and TSY. Association test statistics including kinship and population structure reproduced five known marker–trait associations of candidate genes and discovered new ones, particularly for tuber yield and starch yield. The inclusion of landraces increased the number of detected marker–trait associations. Integration of the present association mapping results with previous QTL linkage mapping studies for TY, TSC, TSY, TW, TN, and tuberization revealed some hot spots of QTL for these traits in the potato genome. The genomic positions of markers linked or associated with QTL for complex tuber traits suggest high multiplicity and genome wide distribution of the underlying genes.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-016-2665-7) contains supplementary material, which is available to authorized users.

Nutritional contents of advanced breeding clones of Solanum tuberosum group Phureja

Nutritional contents of seven advanced breeding clones (AC) of potato (Solanum tuberosum group Phureja) and two commercial cultivars, Criolla Colombia and Criolla Galeras, of S. tuberosum group Phureja as control were evaluated. Fat, protein, ash, dietary fibre, and mineral contents were determined in whole boiled tubers. The AC-04 had the highest levels of protein (9.7 g/100 g dried weight, DW) and magnesium (107.0 mg/100 g DW) as compared to Criolla Colombia (4.0 g of protein/100 g DW and 99.5 mg of magnesium/100 g DW) and Criolla Galeras (3.1 g of protein/100 g DW and 95.0 mg of magnesium/100 g DW). The highest contents of fat (0.7 g/100 g DW), soluble dietary fibre (4.9 g/100 g DW), and manganese (0.8 mg/100 g DW) were found in AC-09, values that represented 3.9, 1.7, and 1.2 fold increase as compared to Criolla Colombia, respectively, and 3.9, 1.8, and 1.1 fold increase as compared to Criolla Galeras. The AC-51 had the highest content of insoluble dietary fibre (13.8 g/100 g DW). Among all genotypes the AC-52 had the highest contents of iron (1.3 fold increase), zinc (1.2 fold increase), and calcium (1.3 fold increase) as compared to Criolla Colombia.

Validation of candidate gene markers for marker-assisted selection of potato cultivars with improved tuber quality

Tuber yield, starch content, starch yield and chip color are complex traits that are important for industrial uses and food processing of potato. Chip color depends on the quantity of reducing sugars glucose and fructose in the tubers, which are generated by starch degradation. Reducing sugars accumulate when tubers are stored at low temperatures. Early and efficient selection of cultivars with superior yield, starch yield and chip color is hampered by the fact that reliable phenotypic selection requires multiple year and location trials. Application of DNA-based markers early in the breeding cycle, which are diagnostic for superior alleles of genes that control natural variation of tuber quality, will reduce the number of clones to be evaluated in field trials. Association mapping using genes functional in carbohydrate metabolism as markers has discovered alleles of invertases and starch phosphorylases that are associated with tuber quality traits. Here, we report on new DNA variants at loci encoding ADP-glucose pyrophosphorylase and the invertase Pain-1, which are associated with positive or negative effect with chip color, tuber starch content and starch yield. Marker-assisted selection (MAS) and marker validation were performed in tetraploid breeding populations, using various combinations of 11 allele-specific markers associated with tuber quality traits. To facilitate MAS, user-friendly PCR assays were developed for specific candidate gene alleles. In a multi-parental population of advanced breeding clones, genotypes were selected for having different combinations of five positive and the corresponding negative marker alleles. Genotypes combining five positive marker alleles performed on average better than genotypes with four negative alleles and one positive allele. When tested individually, seven of eight markers showed an effect on at least one quality trait. The direction of effect was as expected. Combinations of two to three marker alleles were identified that significantly improved average chip quality after cold storage and tuber starch content. In F1 progeny of a single-cross combination, MAS with six markers did not give the expected result. Reasons and implications for MAS in potato are discussed.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-012-2035-z) contains supplementary material, which is available to authorized users.

Phenotypic Analyses of Multi-Environment Data for Two Diverse Tetraploid Potato Collections: Comparing an Academic Panel with an Industrial Panel

Phenotypic analyses of two different association panels of tetraploid potato cultivars are presented. Association panels are sets of variously related genotypes assembled for association analysis purposes. The aims of this research were to inspect, analyse and compare two phenotypic data sets, a first step in association mapping analysis. A first panel of 205 contemporary and historical cultivars, selected to represent the commercial potato germplasm pool, was evaluated in two trials in 2006, one on sandy soil and the other on clay soil, both with two replications. It was called the academic panel. Data for the second panel with 299 genotypes were compiled from contributions from five breeding companies and included 66 locations and 18 years. Each of the participating breeding companies contributed data from their clonal selection programmes for 38 advanced breeding clones and a series of standard cultivars. It was called the industrial panel. Variance components for genotypic main effects and genotype-by-environment interactions were calculated, and estimates for the random genotypic main effects were produced. The genotypic main effects for 19 agro-morphological and quality traits were used to study trait by trait correlations within each panel. In addition, for the genotypes shared by both panels, the correlation of genetic main effects between the panels was investigated. The heritability of all traits was high and no large differences were observed between panels. Coefficients of trait variation were highly correlated (r = 0.9) for both panels and trait by trait correlations in both panels showed highly similar patterns. These results demonstrate that a single-year balanced field trial as well as using breeders’ records yields robust phenotypic information that can be used in a genome-wide association study. Issues related to data management and definition of traits are discussed.

Candidate Gene Approach to Identify Genes Underlying Quantitative Traits and Develop Diagnostic Markers in Potato

ABSTRACTPotatoes (Solanum tuberosum L.) and humans (Homo sapiens L.) are both outcrossing species. The phenotypic variation of both is controlled by environmental factors and by natural DNA polymorphisms between individuals. Therefore we adopt similar approaches as used in human population genetics, such as association mapping, to identify loci and their alleles that are causal for complex agronomic characters such as quantitative resistance to pathogens or tuber sugar content. Functional analysis of genes operating in resistance to pests and pathogens or in carbohydrate metabolism, either in potato itself or in other plants including the model species Arabidopsis thaliana (L.) Heynh., provides many functional candidates for these complex agronomic traits. In our approach, functional candidate genes are tested for linkage to quantitative trait loci (QTL) for pathogen resistance or tuber quality traits, thereby selecting positional candidates (genes colocalizing with a QTL). DNA polymorphisms in or physically linked to positional candidate genes are then evaluated in populations of tetraploid potato genotypes and tested for association with phenotypes evaluated in the same populations. We have used the candidate gene approach to identify DNA‐based markers that are diagnostic for quantitative resistance to late blight caused by Phytophthora infestans (Mont.) de Bary, to the root cyst nematode Globodera pallida (Stone), and for chip color in tetraploid potato cultivars and in advanced breeding clones.

Resistance Behaviour of Potato Cultivars and Advanced Breeding Clones to Tuber Soft Rot Caused by Pectobacterium atrosepticum

Genetic resistance is one of the best methods to control bacterial soft rot of potato tubers. However, an extensive description of resistance levels in currently registered cultivars is not available, as the literature contains only scattered reports. Using a half-tuber test, we therefore investigated the resistance to Pectobacterium atrosepticum of 93 potato cultivars registered on the French National List between 1935 and 1987, and 157 candidates for registration between 1987 and 1997. The relative ranking in a set of 11 control cultivars was stable over the 11 test years, with Ackersegen, Daresa and Bintje being the most susceptible and Kerpondy, Sirtema and Kaptah Vandel being the most resistant. Both registered and candidate cultivars showed a wide distribution of mean rot volumes six days after inoculation, irrespective of cultivar type (ware, starch, or firm-flesh). Mean resistance was significantly higher in recently bred than in older cultivars.

Half-sib progeny evaluation and selection of potatoes resistant to the US8 genotype of Phytophthora infestans from crosses between resistant and susceptible parents

The objectives of this study were to evaluate the use of potato (Solanum tuberosum L.) late blight (Phytophthora infestans (Mont.) de Bary) resistant parents in cultivar development and identify superior clones possessing moderate to high late blight resistance combined with acceptable maturity and tuber quality. Ninety-five crosses were made between eight unadapted parents with reported late blight resistance (B0718-3, Bertita, Bzura, Greta, Libertas, Stobrawa, Tollocan and Zarevo) and susceptible parents (cultivars or advanced breeding clones) adapted to North American growing conditions. A total of 408 field selected clones were assessed for late blight resistance in the greenhouse and in the field using a mixture of US8 P. infestans isolates (A2 mating type, metalaxyl resistant) that overcame all known R-genes except R8 and R9. Clones with ≤ 10% infected foliar area in the greenhouse test or ≤ 0.30 RAUDPC (relative area under the disease progress curve) value in the field in 1998 were re-tested in 1999. A total of 118 (29% of 408) putative late blight resistant clones were selected. The eight late blight resistant parents differed in both the ability to transmit late blight resistance and in the level of resistance transmitted to the progeny. The Tollocan and B0718-3 families (half-sib progeny) had the greatest degree of resistance and frequency of resistant clones. Scott-Knott cluster analysis ranked 79 clones (67% of 118) in the high and moderate late blight resistant groups. Among these 79 clones, 19 clones had vine maturity equal to or earlier than mid-season combined with acceptable tuber quality. Further selection in 2000 resulted in eight advanced selected clones (six from Tollocan and two from B0718-3 families) with the same level of resistance as the parent combined with vine maturity and tuber quality equivalent to Atlantic, a standard cultivar for chip processing in North America. The results indicate that this breeding approach can be used to select parents for late blight resistance breeding and to identify superior clones with high levels of late blight resistance and marketable vine maturity and tuber quality.

Sensory evaluation as a tool in breeding potatoes for French fries and flakes

Standardized sensory evaluation of advanced breeding clones developed in the research program of the Horticulture Department at North Dakota State University has been conducted annually since 1980. Procedures used by the USDA-ARS Potato Research Laboratory for processing tubers into partially fried french fries or flakes are described along with the procedures used for finish-frying of the fries and rehydrating the flakes in preparation for sensory evaluation in the Food and Nutrition Department at North Dakota State University. Following brief training, panelists evaluate the fries and flakes from each clone in triplicate for color, flavor, and texture. Procedures for determining length of fries and limpness of fry strips are described. Samples of 334 clones prepared as french fries and 135 clones prepared as flakes have been evaluated. Examples are given of types of data collected with interpretation of results in relationship to their use in the breeding program.

Outcrossing rate in cultivated autotetraploid potato

Outcrossing rates in potato were measured in an open-pollination field experiment at a location in the Peruvian Andes. Embryo spot, a dominant genetic seed marker, was used to measure outcrossing rate. The source of the dominant marker, the donor, was interplanted among recipient clones lacking the marker (recessive genotype), for which outcrossing was to be measured. Eight out of the 17 clones tested were advanced breeding clones which had wild species cytoplasm. Seven out of eight of these had outcrossing rates above 0.75, showing complete male sterility in one case and partial male sterility in six cases. Among the other clones tested, which were male-fertile, outcrossing estimates ranged from 0.10 to 0.74. Wide variability in outcrossing rate in autotetraploid potato suggests that it should be possible to select for higher outcrossing rate in production of open-pollinated true seed populations of potato for genetic or commercial purposes.