The cultivar Cooperation-88 (C88), developed from the International Potato Center’s germplasm, bred in the Philippines and selected in Southwest China, has resistance to late blight, PVY, and PLRV. It is, however, a short-day cultivar and unsuitable for growing conditions in Canada. In 2015 the Canadian Private Potato Breeders Network (CPPBN) made reciprocal crosses between C88 with long day cvs Prospect and Shepody. C88 functioned as both male and female in the trial. Evaluations of progeny of the crosses indicated that some clones inherited resistance to late blight while producing high yields of tubers under long days. This finding reveals the acceptable heredity of resistance in a potato breeding program when a short-day cultivar is crossed with two different long day cultivars. This study meets the collaborative goal of the CPPBN to develop new potato varieties with durable resistance to late blight.

Potato late blight, caused by the oomycete Phytophthora infestans, is one of the most devastating diseases in the agricultural sector around the world.Many genes (R genes) conferring resistance to late blight have been identified in various potato species and most of these R genes have been used in potato breeding.The aim of this study was to develop and validate PCR-based assays for the R genes Rpi-blb1, Rpi-blb2, Rpi-blb3 and Rpi-bt1, to distinguish between late blight resistant and late blight susceptible potato progeny in the given breeding background.A total of 100 breeding progeny were screened for the presence of these R genes and tested for resistance against P. infestans mating type A2, genotype US-8 strain, using detached leaf and tuber rot assays.PCR products for the Rpi-blb1 and Rpi-bt1 resistance genes were identified in the resistant progeny but were absent in the susceptible ones; therefore these PCR assays could differentiate between late blight resistant and susceptible plants.Genotypic data from the DNA markers derived from the Rpi-blb1 and Rpi-bt1 genes was found to correlate with the phenotypic data for foliar late blight but not with data for tuber rot.Our results demonstrate that markers derived from these two R genes could be useful for marker-assisted selection (MAS) for foliar late blight resistance in potato breeding programs.

His thesis title was " Plant configurations, tolerant cultivars and carrot root exudates in relation to etiology and epidemiology of rusty root disease in muck grown carrots. " Robert is considered to be a potato guru in Eastern Canada. During his 31 year career, he has worked on a wide range of potato issues, including: potato breeding; resistance to cold temperature sweetening; potato viruses; evaluations of genetically modified potatoes; irrigation practices; storage management and evaluations of efficacy of new pesticides. Robert's work addresses problems or issues that directly affect potato growers and through his work gives growers practical solutions that they could apply directly to benefit their farms. Down to earth and practical, Robert is a favourite among growers. As a speaker, he is in high demand by potato growers' organizations across Canada and in the United States. Robert has been repeatedly invited to speak to grower groups in each of Canada's 10 provinces. His enthusiastic and animated speaking style engages growers (and scientists). Robert has an innate talent to present the sound science of his work in a way that growers can understand and trust. Robert has the respect of his peers and industry stakeholders. While working as a potato breeder at the University of Guelph, in a collaborative program with Agriculture Canada, he released the new potato cultivars 'Eramosa', 'Red Gold', 'Rose Gold' and 'Saginaw Gold'. In collaboration with Professor Rickey Yada (Food Scientist, University of Guelph), numerous scientific publications resulted from his research on varieties/seedlings with resistance to cold temperature sweetening. He has published more than 50 refereed journal articles, and 130 plus technical articles and abstracts. Robert is an active adjunct faculty member of the Biology As an adjunct faculty member, he is involved in the training of graduate students. Robert worked at Cavendish Farms, Prince Edward Island, Canada for 19 years as a research biologist and extension specialist to provide education to potato growers. Since his retirement in 2009, Robert continues to be intimately involved with potatoes. Robert works with his wife, Joyce Coffin (potato breeder) on their farm managing a private potato breeding project (Privar Farm Inc.). The cultivar 'Pros-pect' was developed in their breeding program and is commercially grown in Canada and USA for processing into French fries. Currently, Joyce and Robert's breeding program is focusing on late blight resistance.

A TaqMan real-time reverse transcription-PCR (real-time RT-PCR) procedure was developed, optimized, and compared with other routine methods to detect Potato virus Y (PVY) in dormant potato tubers. Three pairs of primers and probes were designed and evaluated for their suitability to facilitate the real-time RT-PCR detection of PVY for all strain groups including PVYO, PVYN, PVYN:O (= PVYN-Wi) and PVYNTN. Among the primer and probe combinations tested, the combination PVY-1 produced the lowest threshold cycle (Ct) value of 25.75. The procedure was further optimized by adjusting various parameters including primer/probe concentration, reaction volume, amplification cycles, and master mixes from different sources. The real-time RT-PCR was then employed to detect PVY from dormant tubers of different cultivars and potato fields, and the results were compared with those obtained from conventional RT-PCR, enzyme-linked immunosorbent assay (ELISA) on sprouts and grow-out testing. Out of 1,069 single-virus infected (PVY only) tubers tested, both formats of RT-PCR detected PVY in 52 samples, ELISA on sprouts in 45, ELISA on leaves in 54 and visual observations in 53. However, in 61 multiple-virus infected tubers tested, both formats of RT-PCR, and ELISA on both sprouts and leaves detected a similar number of positives, thus, making all the methods equally sensitive. Considering that ELISA requires sprouting of dormant potato tubers for PVY testing, grow-out testing takes approximately 6–8 weeks to obtain results, and conventional RT-PCR needs post-PCR processing, real-time RT-PCR offers a speedy alternative for large scale detection of PVY from dormant tubers. The method is therefore recommended for testing of PVY in potato tubers on a commercial scale in a diagnostic laboratory.

This chapter discusses the various factors that affect the quality of potatoes during post-harvest storage such as maturity stage of crop (early/late), intended use (table stock/processing/seed), preharvest conditions of crop, harvest and handling conditions, health of the crop such as incidence of pests and diseases, biochemical changes, storage preparations and conditions, and management of storage environment. The potato crop can be separated into late- or early-crop based on their maturity at harvest. Maturity is a complex physiological and morphological condition, which is influenced by several factors including respiration, carbohydrate changes, dry matter content, moisture loss, dormancy, and sprouting. The quality of the potato crop that is stored ultimately determines the quality of the stored product. A good storage management cannot enhance quality out of storage if the health of the tubers is compromised during preharvest conditions. Harvesting immature tubers, when the soil conditions are too wet or dry, and during too-warm weather conditions can affect the quality of tubers. Maintenance of post-harvest quality is critical for both growers and processors.

Common scab is an important disease of potato caused by Streptomyces scabies and other closely related species. In this study, the genetic diversity of Streptomyces spp. causing common scab of potato in eastern Canada was for the first time investigated. Forty-one Streptomyces spp. isolates were retrieved from necrotic lesions of potato tubers harvested from different regions of the Canadian provinces New-Brunswick, Nova Scotia and Prince-Edward-Island. Most isolates were closely related to known pathogenic S. scabies strains on the basis of partial 16S ribosomal (r) RNA and rpoB gene sequence analyses. Two isolates were identified as pathogenic species of Streptomyces acidiscabies. To our knowledge, this species has never been previously isolated in these areas. Genome fingerprinting studies using repetitive elements (rep) polymerase chain reactions (PCR) revealed 10 distinct genetic groups in eastern Canada. The geographical distribution of the genetic groups was region-dependant. Pathogenicity- and virulence-related genes (txtA, txtC, and tomA) were PCR-amplified from each isolate, and nucleotide sequence analysis of partial gene fragments revealed slight polymorphisms in both txtA and txtC genes. No genetic variation was noted in the partial tomA gene sequences.

Alternative sprout inhibitors were tested for their efficacy in retaining processing quality of potatoes during long term storage. Carvone, dimethylnaphthalene and ethylene were compared to the commercial standard, CIPC, (isopropyl N-(3-chlorophenyl) carbamate) and an air control, for their effects on sprout development, fry color and sugar content of potato tubers, during 25 weeks of storage at 9C. All treatments reduced sprouting although the amount of sprouting varied among treatments. At the end of the 25 week storage period the amount of sprouting based on total sprout weight and maximum sprout length was, in order from least to most, CIPC, carvone, ethylene, DMN and air. Poorer processing quality due to darker fry color and higher levels of reducing sugars and sucrose occurred in the ethylene-treated potatoes. If properly applied, these sprout inhibitors could be commercially acceptable, although each may have practical advantages and disadvantages.

The effect of ethylene on tuber sprout growth and quality in potato ( Solanum tuberosum L. `Russet Burbank') was tested in laboratory and commercial studies for 6 and 3 years, respectively, in comparison with untreated (laboratory study) and CIPC-treated tubers (laboratory and commercial studies). In both studies, ethylene was applied continuously at 166 μmol·m -3 for at least 25 weeks, beginning in early December (laboratory study) or early December to early January (commercial study). In the laboratory study, ethylene delayed the appearance of sprouts for 5 to 15 weeks, compared with untreated tubers. In the ethylene-treated tubers in both studies, sprouts appeared on many eyes but most of them remained very small (<5 mm long). Longer sprouts (>5 mm) appeared after 15 weeks but did not exceed 12 and 59 mm in the laboratory and commercial studies, respectively. Sprouts on ethylene-treated tubers were more easily detached up to 6 weeks after ethylene treatment ended, compared with untreated tubers. In both studies, ethylene treatment was not associated with decay, disorder or internal sprouting problems. In both studies, the Agtron fry color [or U.S. Dept. of Agriculture (USDA) color grade] of ethylene-treated tubers was darker than CIPC-treated tubers at almost all sampling times. Continuous exposure to ethylene was an effective sprout control agent but it produced a darker fry color, compared with CIPC-treated potatoes.

Ozone and 1,8-cineole were investigated as alternatives to isopropyl-n-(3-chloro-phenyl)carbamate (CIPC) to control sprout development of potato (Solatium tuberosum) tubers cv Russet Burbank during long-term storage. Sprout development was similar in ozone-treated and air-stored tubers, but both had much larger and more numerous sprouts than CIPC-treated tubers. Sucrose and reducing sugars in ozone-treated tubers were similar to levels in air-stored potatoes. Fry color was not different among potatoes stored in ozone, air and CIPC. Conversely, potatoes treated with 1,8-cineole did not produce any sprouts during the 25 week study. The fry color of tubers exposed to cineole was darker than either air-stored or CIPC-treated tubers. Sucrose and reducing sugar levels were higher in cineole-treated tubers than in tubers treated with CIPC.

The free amino compound profiles, total nitrogen and dry matter content of tubers from five summer potato cultivars grown at Harrow and Simcoe, Ontario were monitored for four weeks commencing 3 July, about 80 days after planting in an attempt to determine the contribution of these factors to differences and changes in chipping performance which could not be accounted for by tuber sugar levels. In general: 1) tubers of the best chipping cultivars contained more dry matter and less amino compounds and total nitrogen than the poorer chipping cultivars at each harvest; 2) growth location differences were noted for corresponding cultivars and harvests; 3) larger proportions of the more intense Maillard colour forming amino compounds were found in tubers of the poorer chipping cultivars; and 4) tuber amino compound and total nitrogen levels decreased, and dry matter contents increased over the harvest period. Thus, the level and distribution of amino acids and the total nitrogen and dry matter content of tubers may be important factors contributing to the intensity of chip colour.

The effect of an 8 h light/day or total darkness photoperiod on thein vitro microtuberization of cultivars “Red Pontiac”, “Shepody”, “Kennebec” and “Yukon Gold” was investigated using a medium consisting of Murashige and Skoog salts, vitamins, high sucrose and high benzylamino purine levels and cultured at 16°C for 12 weeks. Percent tuberization of the singlenode leaf cuttings averaged over all 4 cultivars was initially lower, with the 8 h photoperiod at 4 weeks, but later was similar to the total darkness photoperiod at 8 and 12 weeks. Microtubers from all cultivars had a higher mean fresh weight when treated with an 8 h photoperiod as compared with total darkness, though the difference was not significant with “Yukon Gold.” ldRed Pontiac” and “Shepody” produced microtubers that were well over twice the fresh weight of those produced in the total darkness treatment. Delayed leaf senescence, microtuber greening, and nodal rooting were evident with the 8 h light treatment.

A potato chipping selection F58050 with high specific gravity and low sugar content and a non-chipping cultivar Sable with low specific gravity and high sugar content were each autografted and cross-heterografted to assess source-sink relationships on specific gravity, sugar content and chip color of potatoes. Heterografting of Sable scions onto F58050 stocks reduced the specific gravity of F58050 tubers compared to autografts of F58050 (P<.05). Grafting of F58050 scions onto Sable stocks did not significantly increase the specific gravity of Sable tubers compared to autografts of Sable. Heterografting of Sable scions onto F58050 stocks resulted in significantly (P<.05) darker chip color but no significant increases in reducing sugar content of potatoes as compared to potatoes from autografts of F58050, both at harvest and after 3 months’ storage at 12 C. On the other hand, potatoes from heterografting of F58050 scion onto Sable stock showed a slight improvement in chip color and significantly (P<.05) lower reducing sugar content than potatoes from autografts of Sable.