Tuber Blight Research Articles

Superior resistance to Phytophthora infestans in new pre-breeding potato clones under different nitrogen fertilisation regimes used in organic agriculture

ABSTRACT Late blight caused by Phytophthora infestans is the most devastating disease for cultivated potatoes, causing considerable financial loss annually due to loss of yield and costs of fungicide applications. For organic farming especially, the strict limitations on the use of fungicides makes research necessary to investigate factors that influence disease severity. Therefore, effects of nitrogen fertiliser rates on leaf and tuber blight in organically grown potato cultivars and pre-breeding clones were evaluated in the present study. It was found that the foliage of the pre-breeding clones was little, or not at all, affected by P. infestans, irrespectively of the nitrogen application rate, while the cultivars reacted differently with mild to strong late blight symptoms. Only some of the clones and cultivars showed increased infection of tubers at the higher nitrogen application rates, whilst most showed no significant differences between the N rates. Overall, the present study showed that the use of new resistant cultivars could be a suitable approach to reduce late blight in organic farming, where soil nitrogen levels may vary due to the use of different forms of nutrient inputs with varying mineralisation rates.

Foliar Application of Fungicides Registered Against Late Blight Influences Main Potato Tuber Diseases and Key Quantitative Characteristics of Tubers

Adequate integrated management of potato leaf diseases can have an influence on pathogens which are challenging to control and cause main potato tuber diseases. Deriving from this hypothesis, an experiment was designed to evaluate the efficacy of foliar application of twelve fungicides on late blight in tubers, common scab, black scurf and silver scurf. In the period of 2013 to 2017, the fungicides were equally applied six times in registered doses during the growing seasons. Eight tuber disease indicators and eight yield characteristics were then evaluated in harvested tuber samples. Significant differences were found among the fungicides used. In comparison to the negative control (n. c.), the application of Infinito, Ranman Top and Revus Top reduced the quantity of tubers infected by late blight by 72% on average. The incidence of common scab increased by 65% of n. c. under the effect of copper oxychloride, while an average reduction by 19% of n. c. was observed with the use of Acrobat MZ WG, Curzate Gold and Consento. The occurrence of silver scurf was significantly enhanced by Curzate Gold and Consento (105% of n. c.), while it was suppressed by Revus Top and Revus (85% of n. c.). All fungicides were ineffective on black scurf yet had a positive influence on the potato yield and quality, with the choice of fungicide having a great impact on the quality of tubers. The application of any safe fungicide is important, especially in years similar to 2015, which was the most devastating recent year for potato production in terms of structural changes in yield of tubers.

Resistance to Phytophthora infestans Clonal Lineage US-23 in Potato Cultivars and Its Relationship with Early Blight Resistance and Tuber Yield.

Resistance to late blight caused by Phytophthora infestans clonal lineage US-23 in 217 old and modern potato cultivars was evaluated in field trials in 2016 and 2017 in Pennsylvania. Significant differences in resistance were found among these cultivars (P < 0.0001). Significant interaction between cultivars and environments was found (P < 0.0001). The values of relative area under the disease progress curve ranged from 0 to 0.5841 in 2016 and from 0 to 0.5469 in 2017. Broad-sense heritability of late blight resistance was estimated to be 0.91, with a 95% confidence interval of 0.88 to 0.93. Cluster analysis classified the cultivars into five groups: resistant, moderately resistant, intermediate, moderately susceptible, and susceptible. Thirty cultivars showing resistance and 32 cultivars showing moderate resistance were identified. The 217 cultivars were also evaluated for foliar maturity, tuber yield, and resistance to early blight caused by Alternaria solani. A few cultivars with late blight resistance independent of late maturity were found. Late blight resistance and early blight resistance were positively correlated, and 17 cultivars possessed resistance to both diseases. Yield trade-off associated with late blight resistance was not observed among the cultivars in the absence of disease pressure.

Linking crop traits to transcriptome differences in a progeny population of tetraploid potato

BackgroundPotato is the third most consumed crop in the world. Breeding for traits such as yield, product quality and pathogen resistance are main priorities. Identifying molecular signatures of these and other important traits is important in future breeding efforts. In this study, a progeny population from a cross between a breeding line, SW93–1015, and a cultivar, Désirée, was studied by trait analysis and RNA-seq in order to develop understanding of segregating traits at the molecular level and identify transcripts with expressional correlation to these traits. Transcript markers with predictive value for field performance applicable under controlled environments would be of great value for plant breeding.ResultsA total of 34 progeny lines from SW93–1015 and Désirée were phenotyped for 17 different traits in a field in Nordic climate conditions and controlled climate settings. A master transcriptome was constructed with all 34 progeny lines and the parents through a de novo assembly of RNA-seq reads. Gene expression data obtained in a controlled environment from the 34 lines was correlated to traits by different similarity indices, including Pearson and Spearman, as well as DUO, which calculates the co-occurrence between high and low values for gene expression and trait. Our study linked transcripts to traits such as yield, growth rate, high laying tubers, late and tuber blight, tuber greening and early flowering. We found several transcripts associated to late blight resistance and transcripts encoding receptors were associated to Dickeya solani susceptibility. Transcript levels of a UBX-domain protein was negatively associated to yield and a GLABRA2 expression modulator was negatively associated to growth rate.ConclusionIn our study, we identify 100’s of transcripts, putatively linked based on expression with 17 traits of potato, representing both well-known and novel associations. This approach can be used to link the transcriptome to traits. We explore the possibility of associating the level of transcript expression from controlled, optimal environments to traits in a progeny population with different methods introducing the application of DUO for the first time on transcriptome data. We verify the expression pattern for five of the putative transcript markers in another progeny population.

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.

New Records of Mealybugs on Sprouted Potatoes in Storage at Kulumsa, Southeast Ethiopia - A Potential Future Threat for Potato Production

Potato has lived with several diseases and insect pests such as late blight and potato tuber moth for several decades. However, newly emerging insect pest known by the name 'mealybugs' is recorded as a new threat for potato production in the highlands of Arsi, Southeast Ethiopia. This pest has never been observed in the area in the history of potato culture in which potato has been grown for many years. Therefore, awareness creation should be the primary step by which any respective stakeholders including potato growers, research institutions, ministry of agriculture; NGOS, etc. are informed about the importance of the pest. This will help to look for appropriate management options and take the necessary precautions before the pest becomes important in other areas in the country.

Characterization of tuber blight‐suppressive soils from four provinces of the Ecuadorean Andes

Late blight, caused by the oomycete Phytophthora infestans, is a threat to potato‐cropping systems worldwide. In the Ecuadorian Andes, despite a high late blight incidence in foliage, tuber blight is rare. In this work, the hypothesis that Ecuadorian Andean soils are naturally suppressive to P. infestans tuber infection was evaluated. Soils from four potato‐growing regions were assessed for disease suppressiveness by determining the effects of soil heat treatment on P. infestans sporangia and their ability to infect potato slices after 1, 8, 15 and 30 days of exposure to soils. Tuber infection after inoculation with P. infestans‐infested soils was consistently lower during the evaluation period compared with heat‐treated soils. Fresh, untreated soils affected germination and viability of P. infestans sporangia in a site‐dependent manner. In addition, the effect of heat treatment on soil bacterial communities was assessed through terminal restriction fragment length polymorphism analysis of the 16S rDNA gene region. Heat treatment disrupted bacterial community composition, and a subset of terminal restriction fragments (TRF) was either positively or negatively correlated with tuber infection. Bacterial TRF negatively correlated with tuber infection corresponded in fragment size to taxa with known ability to inhibit pathogens and promote plant growth. Finally, bacterial isolates obtained from untreated soils, which inhibited P. infestans growth in vitro, represented 22–47% of isolates recovered, and matched classes predicted by the TRFs. This work represents a first step in understanding the mechanisms behind the low incidence of tuber blight in Andean potato‐cropping systems.

Study on Biological and Economic Considerations in the Control of Potato Late Blight and Potato Tuber Blight

An economic analysis was made of old results from 1993-1996 (22 field trials) and new results from 2010-2013 (12 field trials) obtained in field trials with different doses of fungicides to control potato late blight (PLB) and potato tuber blight (PTB) caused by Phytophthora infestans. The objective was to determine the economically optimal dose for effective control. In 1993-1996, the economic net return was highest for long intervals of about two weeks between treatments and a dose of 60% of the recommended level. The difference between the experimental treatment with the highest net return and the untreated control was 1587 € per hectare (ha-1) in susceptible cultivars, but only 531 € ha-1 in moderately resistant cultivars. In addition, the mean difference in net return between all treated susceptible and all treated moderately resistant cultivars was 874 € ha-1. In the half of the field trials with the lowest maximum attack of PLB, the difference between the experimental treatment with the highest economic income and untreated control was 547 € ha-1, while it was 1571 € ha-1 in the half of the trials with the highest maximum attack. The results for 2010-2013, which were all based on a short treatment interval of about one week between treatments, showed that in table potato the economic net return was highest at 100% and 75% of the recommended dose, whereas in starch potato cultivars it was highest at 50% and 25% of the recommended dose. The net financial result was calculated for 13 different scenarios. As expected, potato price and potato crop yield and quality were of the greatest importance. The price of fungicides affected net profits by between 167 and 656 € ha-1 depending on treatment intervals and dose. These results challenge the way in which late blight is controlled in conventional potato farming today, especially in starch potatoes. We therefore propose investment in future years be based on the dose-range response in cultivars with differing host resistance to both PLB and PTB, and on forecasting and warning with respect to PLB- and PTB-control in different potato cultivars. We believe that such investment could be very valuable in optimizing the use of fungicides in potato cultivation.

Stem blight, foot rot and storage tuber rot of sweet potato caused by Plenodomus destruens in China

In September 2014, severe stem blight, foot rot and storage tuber rot on sweet potato were observed in experimental fields in Sanmen County, Zhejiang Province, China. The causal agent was identified as Plenodomus destruens on the basis of morphological characteristics and molecular identification. In pathogenicity tests, P. destruens caused severe wilting, stem rot, and storage tubers rot symptoms similar to those observed in the field. This is the first report of P. destruens causing stem blight, foot rot and storage tuber rot on sweet potato in mainland China where sweet potato is a main crop.

Potassium phosphite combined with reduced doses of fungicides provides efficient protection against potato late blight in large-scale field trials

Potato late blight caused by the oomycete Phytophthora infestans is a devastating disease of potato worldwide. Most of the potato cultivars grown in conventional agriculture are susceptible, or at best moderately resistant, and require frequent applications of fungicides to avoid heavy yield losses.In field trials spanning four years, we have investigated the effect of potassium phosphite, an inorganic salt on potato late blight. Potassium phosphite is known to induce defence responses in potato and to also have direct toxic effects on oomycetes, which in turn counteract late blight and tuber blight development. However, the use of this salt is not yet implemented and approved in European potato cultivation. We compared the effect of phosphite alone with fungicides currently used in Swedish potato cultivation. We also investigated the combined use of potassium phosphite and reduced doses of fungicides. Table potato cultivars and starch potato cultivars with different levels of resistance were used.We found that potassium phosphite in combination with reduced doses of fungicides results in the same level of protection as treatments with the recommended full dose of fungicides. These combined treatments reduce the need of traditional fungicides and may also decrease the selection pressure for fungicide resistance development in the pathogen. In relatively resistant starch potato cultivars using phosphite alone gave sufficient protection against late blight. Furthermore, in starch potato a combination of phosphite and fungicides at two-week intervals provided similar protection to weekly applications of fungicide at the recommended dose. Foliar treatment with phosphite also gave protection against tuber blight at similar levels to that of the best-performing fungicide. Our data suggests that potassium phosphite could be used in potato cultivation in temperate regions such as in Sweden, at least in combinations with reduced rates of fungicides. The implementation of the use of phosphite in practical potato crop protection as part of an IPM strategy is discussed. Doses, intervals and combinations could be adjusted to the level of cultivar resistance.

Potato Tuber Blight Resistance Phenotypes Correlate with RB Transgene Transcript Levels in an Age-Dependent Manner.

Plants have evolved strategies and mechanisms to detect and respond to pathogen attack. Different organs of the same plant may be subjected to different environments (e.g., aboveground versus belowground) and pathogens with different lifestyles. Accordingly, plants commonly need to tailor defense strategies in an organ-specific manner. Phytophthora infestans, causal agent of potato late blight disease, infects both aboveground foliage and belowground tubers. We examined the efficacy of transgene RB (known for conferring foliar late blight resistance) in defending against tuber late blight disease. Our results indicate that the presence of the transgene has a positive yet only marginally significant effect on tuber disease resistance on average. However, a significant association between transgene transcript levels and tuber resistance was established for specific transformed lines in an age-dependent manner, with higher transcript levels indicating enhanced tuber resistance. Thus, RB has potential to function in both foliage and tuber to impart late blight resistance. Our data suggest that organ-specific resistance might result directly from transcriptional regulation of the resistance gene itself.

Potato Late Blight and Tuber Yield: Results from 30 Years of Field Trials

During 1983–2012, three field trials per year were performed in each of the three southernmost counties in Sweden to test different fungicide programmes aiming to control late blight, primarily in the very susceptible potato cultivar Bintje. A dataset with results from these field trials was used (i) to examine possible changes in the appearance and behaviour of late blight attack over the years, (ii) to investigate the relationship between late blight in foliage and tuber blight, (iii) to investigate the relationship between late blight and tuber yield and (iv) to identify any correlations between different variables in the dataset. Late blight reached epidemic proportions, i.e. 75% disease severity in the untreated control, in the majority of the field trials. The estimated first attack of late blight was earlier in many field trials after 1998. Differences between years and regions were great in terms of date of the first attack and how the attack developed during the season. For example, in 2002–2005 and 2007, the first attack occurred 40–55 days after planting (DAP), compared with 95–108 DAP in 1994 and 1996. In 1994, 2006 and 2009–2011, the attacks increased from first symptoms to 65% disease severity in the untreated control within 16–21 days, compared with 35–40 days in 1995, 1999 and 2002. The relationship between foliage late blight and tuber blight was weak with the best match found at high disease severity late in the growing season (r = 0.33; p < 0.001). The relationship between blight-free tuber yield and start of the first attack indicated a yield increase of 287 kg/day (R 2 = 0.27) for every day’s delay in first attack. Using the DAP for 65% disease severity in the untreated control improved the correlation (R 2 = 0.64) and indicated a yield increase of 534 kg/day for every day’s delay in first attack. The later the onset of attack, the higher the blight-free tuber yield in treated plots. In general, significant correlations were found between blight-free tuber yield, size fractions of tuber yield, date of first late blight attack, date of different degrees of disease severity, disease severity, date of treatment, treatment measures and maintenance.

Tuber Blight Development in Potato Cultivars in Response to Different Genotypes of Phytophthora infestans

Migrations or introduction of new genotypes of Phytophthora infestans to a specific region imposes a different perspective for potato production. During 2009–2010, a late blight epidemic affected the Northeastern United States, which quickly spread through several states. The epidemic was characterized by the appearance of a new genotype of P. infestans designated US-22, which was isolated from tomato and potato. Potato tubers are an essential component of late blight epidemics where the pathogen cannot overwinter on Solanaceous plants. Six potato cultivars were inoculated with 12 isolates of P. infestans (five different genotypes), including isolates of the genotype US-22. Tuber blight development was characterized in terms of tissue darkening expressed as area under the disease progress curve values and lenticel infection. The responses indicated that US-8 was more aggressive than US-22, but US-22 isolates obtained from potato were more aggressive on potato than those acquired from tomato. Tuber periderm responses to infection were limited, yet US-8 isolates infected the periderm more often than US-22 isolates. There were significant differences among the cultivars tested but cv. Jacqueline Lee was the most resistant overall. Although isolates of P. infestans genotype US-22 were less aggressive in comparison with US-8 isolates, US-22 isolates still infected potato tubers and were as aggressive us US-8 isolates on some cultivars. Management of late blight caused by isolates of US-22 through host resistance may be feasible but imposes a different set of criteria for consideration from those that US-8 imposed.

Determination of Resistance to Phytophthora infestans on Potato Plants in Field, Laboratory and Greenhouse Conditions

An experiment was conducted to determine the host resistance of potato against Phytophthora infestans for twenty-five potato genotypes in 2010 and 2011 at Khumaltar, Lalitpur, Nepal using four assays: three for foliage resistance (field, whole-plant and detached leaf) and one for tuber resistance (tuber slice). An isolate of P. infestans collected from Lalitpur (LPR-1) was used for inoculation at a concentration of 3 x 103 sporangia ml-1 in all assays. Infected foliage area in the field and whole-plant assays, lesion size on detached leaves, and colony growth on tuber slice were all individually converted to 0-9 interval scale for susceptibility. Field assessment, considering the most robust measure of resistance, was used as benchmark for comparing the other assays. Sixteen of the genotypes had very little disease in the field (scale value <1) indicating they were probably expressing race-specific resistance, which has historically been short lived. Susceptibility levels measured in the whole-pant assay were highly correlated (r = 0.90) with converted field scale values, although the correlation was lower for the detached leaf assay (r = 0.63) and least for tuber-slice assay (r = 0.46). Low correlation in the detached leaf assay was assumed to represent lower resolution of the single-cycle assay. Low correlation in the tuber assay may have also reflected genetic differences as foliage and tuber blight resistance are not always correlated. Genotypes with extreme resistance in the field were frequently identified as having partial resistance in the other assays, which could mistakenly be interpreted as more durable field resistance. The consequences for selecting durable resistance are discussed.

Effects of in-season crop-protection combined with postharvest applied fungicide on suppression of potato storage diseases caused by oomycete pathogens

The effects of fungicides and biofungicides applied during the growing season in combination with storage applications to control potato storage diseases caused by oomycete pathogens were evaluated. The in-season treatments included in-furrow and foliar application of mefenoxam or phosphorous acid and foliar application of Bacillus subtilis. Storage treatments included phosphorous acid, B. subtilis and a 3-way mixture of azoxystrobin, fludioxonil and difenoconazole. These products were tested for control of tuber late blight, Pythium leak and pink rot at 10 °C (cv. FL1879) or 4 °C (cv. Goldrush). The combination of phosphorous acid in the field and during storage significantly reduced tuber blight development. Field treatment with B. subtilis, mefenoxam or phosphorous acid combined with the storage treatment of phosphorous acid significantly reduced Pythium leak development. Interaction of field treatments, mefenoxam or phosphorous acid, with storage treatments, phosphorous acid or the 3-way mixture of azoxystrobin, fludioxonil and difenoconazole significantly reduced pink rot incidence.

Efficacy of fungicide combinations, phosphoric acid and plant extract from stinging nettle on potato late blight management and tuber yield

Late blight caused by Phytophthora infestans is a major constraint to potato production. Inadequate control of the disease has often resulted in potato yield losses. We assessed the efficacy of fungicides, phosphoric acid and stinging nettle extract combinations for late blight control at two locations in Kenya. Disease severity, relative area under disease progress curves (RAUDPC), pathogen lesions and tuber yield were quantified during the 2008 and 2009 cropping cycles. The application of metalaxyl alternated with phosphate resulted in the greatest suppressive effects on late blight. The average late blight severity ranged from 3.5 to 34% in 2008 and 4.7 to 50% in 2009 at Tigoni location. RAUDPC for the same location ranged from 5 to 40% and 5 to 50% in 2008 and 2009, respectively. Similar levels of late blight severity were recorded at Marimba location in both years. Lesion growth and pathogen lesion numbers on potato plants differed significantly (p < 0.05) among treatments. Fungicides, phosphoric acid and stinging nettle extract varied in late blight control. Potato tuber yield varied among treatments. Phosphoric acid treatment had significantly (p < 0.05) greater tuber yield compared to metalaxyl at both locations. Field plots treated with plant extracts from stinging nettle resulted in the lowest tuber yield compared to other treatments with the exception of the untreated control. Fungicides, phosphoric acid, stinging nettle extract and their combinations can be readily effective in the suppression of late blight severity and pathogen lesions with moderate increases in tuber yield.

Evaluation of host susceptibility, pathogen aggressiveness and sporangial survival in soil as factors affecting incidence of potato tuber infection by Phytophthora infestans in Ecuador

Incidence of potato tuber infection by Phytophthora infestans is low in Ecuador. Factors considered to potentially affect the incidence of tuber infection include pathogen aggressiveness, host resistance, direct suppression from biological and chemical characteristics of soil acting on pathogen propagules, and exclusion resulting from soil structure and high ridging. In this study, we tested the hypothesis that low incidence could be due to reduced pathogen aggressiveness and/or low host susceptibility by comparing several pathogen isolates and commonly grown potato cultivars from Ecuador with isolates and cultivars from Europe, where tuber blight is known to be a problem. Additionally, in Ecuador, whole tubers and slices of common varieties were inoculated with local isolates of P. infestans to test for potential infection under Ecuadorian conditions. All isolates, regardless of origin, caused tuber infection. The aggressiveness of isolates varied, but this was both between and among Ecuadorian and Swedish isolates and it was not possible to establish a clear difference in the degree of infection based on isolate origin, or origin of potato variety. In general, we found no evidence to suggest that low aggressiveness of the pathogen or extreme resistance of the host explains low incidence of tuber blight in Ecuador. Therefore, we conclude that low incidence of tuber blight in Ecuador is probably caused by soil factors. Furthermore, exclusion due to soil structure and high hilling may play an important role as a preliminary soil infectivity study demonstrated that P. infestans sporangia were infective in six Ecuadorian field soils for at least 15 days.

Validation of tuber blight ( Phytophthora infestans) prediction model

Potato tuber blight caused by Phytophthora infestans accounts for significant losses of tubers in storage. Despite research on infection and management of tuber blight, there is paucity of information on the prediction of the occurrence tuber blight or modelling of tuber infection by P. infestans under field conditions. A tuber blight prediction model was developed in New York in experiments conducted using cultivars Allegany, NY101, and Katahdin in 1998 and 1999. This model was validated using data collected from the potato cultivar Snowden in field experiments in Laingsburg, Michigan from 2000 to 2009. In both New York and Michigan experiments, disease was initiated by artificial inoculation of cultivars with a US-8 isolate of P. infestans. Mean leaf area affected ranged from 0 to 94% at New York, and 0 to 93% at Michigan. At New York and Michigan, mean tuber blight incidences ranged from 1 to 40% and 0 to 15%, respectively. In the validation of the model using data collected at Laingsburg, Michigan, the model correctly predicted tuber blight incidence in 7 out of 9 years. Comparison of observed with predicted values indicated that slopes of the regression line between observed and predicted germination and infection data were not significantly different ( P > 0.3547). Correlation coefficient between observed and predicted values was high ( r 2 > 0.65) and the coefficient of variation of the residuals of error was about 12%. Although inoculum availability is assumed in the model, incorporation of relationships of inoculum density, propagule survival in soil, and tuber blight incidence would greatly improve the prediction of tuber blight under field conditions.

Alta Crown: A New Russet Potato Cultivar with Resistance to Common Scab and A Low Incidence of Tubers Deformities

Alta Crown (CV92028-1) is a new russet potato cultivar with resistance to common scab and a low incidence of tuber deformities. It was selected at the Lethbridge Research Centre of Agriculture and Agri-Food Canada, from a cross made at Colorado State University, San Luis Valley Research Center between breeding clones AC83172-1RU and C086030-1RU. Alta Crown has semi-erect, short, and compact vines. The cultivar has uniform, oblong to long, medium to large tubers with a medium to dark russet skin, cream- colored flesh and shallow eyes. In trials across western Canada and Ontario, Alta Crown produced similar or lower total yields than did Russet Burbank and Shepody, but a higher percentage of marketable tuber yield at maincrop harvest, and at early harvest. The average weight of marketable tubers was superior to that of Russet Burbank at all sites, and to that of Shepody at some sites. Alta Crown exhibited resistance to tuber deformities, hollow heart and internal necrosis defects. Specific gravity of Alta Crown in western Canadian regional trials was similar to that of Shepody and Russet Burbank. Fry colour was also similar to Russet Burbank and Shepody in product quality evaluations. Alta Crown was identified as having resistance to common scab and was moderately resistant to late blight tuber rot and foliar early blight, but was susceptible to foliar late blight. It shows moderate foliar and tuber symptoms when infected with bacterial ring rot. A post-harvest laboratory testing is recommended to complement visual inspection.

Foliar and tuber late blight resistance in a Solanum tuberosum breeding population

With 2 figures and 2 tables AbstractThe purpose of this research was to identify the genetic basis of foliar and tuber resistance to Phytophthora infestans in a potato breeding population developed from a cross between two tetraploid Solanum tuberosum lines, NY121 and NY115. The parent with high foliar resistance, NY121, was highly susceptible to tuber blight. Foliar resistance was assessed in field trials, while tuber blight was assessed both in the field and in the laboratory. A quantitative trait locus (QTL) explaining ca. 50% of the phenotypic variance for foliar resistance was located on the lower arm of linkage group V, and was loosely associated with tuber blight resistance (significantly in one of two trials). This QTL was confirmed in a separate sample from the same population. Tuber blight detected via laboratory assays was not correlated with tuber blight incidence in the field. Most markers associated with tuber blight resistance were not associated with foliar resistance and most markers associated with foliar resistance were not associated with tuber blight resistance.