Electrophoretic characterization of North American potato cultivars

A total of 112 named cultivars and advanced breeding lines were assayed through horizontal starch electrophoresis to test the utility of isozyme loci as a means to objectively identify potato cultivars. Both leaf and tuber tissue were sampled in thirteen enzyme systems. Two buffer systems (Histidine-citrate, pH 5.7 and Lithium-borate, pH 8.3) were used to resolve 16 isozyme loci, of which 14 were scorable without progeny testing. A total of 43 scorable allozymes were detected. All cultivars or advanced breeding lines that were the result of hybridization were discriminated by their sum electrophoretic pattern, whereas, sports (i.e., Russet Burbank vs. Burbank) or line selections (i.e., Norgold Russet “M1” vs. “M2”) have patterns that are identical to the original mother clone. The allelic diversity within and among cultivars indicate that horizontal starch electrophoresis offers an objective means to discriminate sexually-derived potato cultivars.     

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.     

Breeding progress for potato chip quality in North American cultivars

Forty-four potato cultivars, released in the period between 1876 and the present were grown concurrently in field trials, stored simultaneously in three different environments, then evaluated for chip quality. They represented cultivars historically used and/or bred for potato chip production. Quality factors measured were tuber solids, chip color, reducing sugar levels, sucrose levels, and percent of defect-free chips. Tuber solids tended to increase in the late period cultivars, but trends were erratic. The release of Lenape marked the beginning of an increase in tuber solids that has continued to the present. There was a significant trend for lower reducing sugars and better chip color that corresponded to increasingly later cultivar release dates. Since about 1960, progress toward lower reducing sugars and better chip color has been constant, regardless of whether tubers were stored at 4.4 C, stored at 4.4 C and reconditioned, or stored at 10 C. Late period cultivars tended to have a greater percentage of defect-free chips in comparison to those released earlier, with most of the improvement coming during the last few years. This study provided evidence that potato breeders have made significant progress in developing cultivars with good chip quality. Evidence was also found that Lenape was a landmark cultivar and has been an important contributor to the observed breeding progress     

Response of three potato cultivars to inoculation withAzotobacter

Summary When the potato cultivars Arran Banner, Bintje, and Compagnon were inoculated withAzotobacter chroococcum in Libya, only Arran Banner responded significantly; plant growth was stimulated and the yield of marketable tubers increased by 8.5–42.6% above the untreated control. The very large yield increase in one season was associated with unfavourable growing conditions.

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Zusammenfassung Im Herbst 1975, im Frühjahr und im Herbst 1976 wurden in Tripolis. Libyen, drei Versuche durchgeführt, um den Einfluss der Inokulation von Pflanzkartoffeln mitAzotobacter auf das Wachstum und den Ertrag von drei Kartoffelsorten (Arran Banner, Bintje und Compagnon) zu untersuchen. Nur bei der Sorte Arran Banner ergab sich eine Beeinflussung durch die Inokulation mitAzotobacter (Tabelle 1 und 3). Der Ertrag war in den drei Versuchen um 42.6% 17.4% bzw. 8.5% gesteigert. Die st?rkste Reaktion ergab sich im ersten Versuch. bei dem niedrige Temperaturen und Bew?lkung vorherrschten und die Wachstumsbedingungen für die Kartoffeln im allgemeinen ungünstig waren. Die Sorten Bintje und Compagnon zeigten keine signifikante Steigerung des Ertrages nach der Inokulation. Die Inokulation erh?hte die Stengell?nge, hatte aber keinen signifikanten Einfluss auf die Stengelzahl pro Pflanze (Tabelle 2). Z?hlungen im Boden der Rhizosph?re zeigten. dass nach Inokulation des Pflanzgutes mitAzotobacter die Population in der Wurzelzone anstieg (Tabelle 4). Die Ertragssteigerung nach der Inokulation scheint durch eine Anreicherung vonAzotobacter in der Rhizosph?re intokulierter Pflanzen hervorgerufen zu sein.

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Résumé Trois expérimentations ont été menées à Tripoli en Libie afin d'étudier l'effet de l'inoculation de tubercules de semence avecAzotobacter sp. sur la croissance et le rendement de 3 variétés de pomme de terre (Arran Banner, Bintje et Compagnon). Ces essais se sont déroulés durant l'automne 1975, le printemps et l'automne 1976. Il n'y a eu que la variété Arran Banner qui a répondu de manière conséquente à l'inoculationd'Azotobacter sp. (tableaux 1 et 3). L'augmentation de rendement a été respectivement de 42.6%, 17.4% et 8,5% dans les 3 expériences. La meilleure réponse a été obtenue dans la première expérimentation où des températures basses et des jours couverts ont dominé et où les conditions de végétation ont été généralement défavorables à la pomme de terre. Les variétés Bintje et Compagnon n'ont pas montré d'augmentation significative du rendement avec inoculation. L'inoculation parAzotobacter sp, augmente la longueur des tiges, mais n'a pas d'effet significatif sur le nombre de tiges par plante (tableau 2). Les comptagesd'Azotobacter sp. dans la rhizosphère ont indiqué que l'inoculation de la semence augmentait la populationd'Azotobacter au niveau de la zone racinaire (tableau 4). Cela est probablement d? au fait que l'augmentation du rendement grace à l'inoculation résulte d'une meilleure adaptationd'Azotobacter sp. au niveau de la rhizosphère des plantes inoculées.

     

Response of two sweet potato cultivars to weed interference

Field experiments were conducted at the U.S. Vegetable Laboratory, Charleston, SC, U.S.A in 2000, 2001, and 2004 to assess the effect of different durations of weed interference on two sweet potato cultivars with different shoot growth habits. The cultivars were Beauregard, which has a spreading growth habit that is typical of U.S. sweet potato cultivars and Carolina Bunch, with an erect growth habit. Weed interference treatments included control plots that were maintained weed free throughout the growing season and plots that were maintained weed free for 0, 10, 20, and 30 days after transplanting. In general, Carolina Bunch was more tolerant of weed interference than was Beauregard. In two of three years Carolina Bunch storage root yields were higher than Beauregard yields in plots that received no weeding; whereas, yields of the two cultivars in weed free plots were not different. Weed interference affected shoot growth to a greater extent than it affected storage root production. At the end of the growing season, Carolina Bunch shoot biomass was greater than Beauregard shoot biomass in plots receiving no weeding and in plots that were maintained weed free for 10 days in all three years. Shoot biomasses of the two cultivars were not different in weed-free plots. Weed shoot biomasses were greater in Beauregard plots than in Carolina Bunch plots in several instances. These results demonstrate that sweet potato cultivars with a vigorous, erect shoot growth habit (with shorter stems, greater branching, and a denser and taller canopy early in the growing season) may be less susceptible to weed interference than cultivars with spreading shoot growth. This study also confirmed previous observations that sweet potato productivity is not greatly affected by moderate weed interference; thus, it may not require intense weed management to produce high yields.     

Founding clones, major contributing ancestors, and exotic progenitors of prominent North American potato cultivars

Neither founding clones nor major genetic contributors to modern North American potato cultivars have been systematically identified. Available pedigrees, through 12 generations, were used to identify founding clones and major contributing ancestors (MCAs), to outline relationships among these clones, to determine the genetic contribution of MCAs and exotic germplasm to prominent cultivars, and to draw conclusions about the gene base of prominent North American cultivars. Based on 1996 certified seed acreage, 46 cultivars were identified as prominent, of which 44 had published pedigrees. Using this pedigree data, 12 MCAs consisting of four types were identified: land race types including Daber and Sutton’s Flourball; immediate descendants of land race types including Busola, Early Rose, Garnet Chili, Imperator, Richter’s Jubel, and Triumph; early USDA releases including Chippewa, Earlaine, and Katahdin; and one derivative of a GermanSolanum demissum ×S. tuberosum population designated Germ. No. 3895-13. These clones appeared in the pedigrees of from 61 to 100% of the 44 most prominent North American cultivars. Some MCAs appeared numerous times in the pedigrees of the cultivars with the maximum being Busola, which appeared in the pedigree of NorDonna 94 times. Across the 44 cultivars, the genetic contribution of MCAs averaged from 1.4% for Daber to 23.2% for Katahdin. A positive genetic contribution by exotic germplasm was present in 34 of the 44 cultivars. Krantz, Russet Nugget, Conestoga, and Yukon Gold had exotic germplasm contributions of 49.5, 34.1, 32.3, and 31.3%, respectively.     

Response of four potato cultivars to rate and timing of nitrogen fertilizer

The release of three new potato (Solarium tuberosum L.) cultivars, Bannock Russet, Gem Russet, and Summit Russet, with unique plant growth characteristics, necessitates the development of appropriate N fertilizer recommendations. These three new cultivars, along with the standard cultivar, Russet Burbank, were treated with four N rates (0, 100, 200, and 300 kg N ha^?1) using two different application timing procedures (“early,” with two-thirds N applied preplant, and “late,” with one-third applied preplant). Measurements included total and U.S. No. 1 yields, petiole NO₃-N concentrations, and net returns derived from economic analysis using a processing-based contract. Each of the four cultivars showed a unique response to N application treatments. Bannock Russet achieved maximum yield and net returns with relatively small amounts of N fertilizer. It also showed no response to N application timing and had moderate NO₃-N sufficiency concentrations early in the season, that decreased markedly late in the season. Gem Russet N requirement for maximum yield was similar to that of Russet Burbank, but required a higher amount of N for maximum net returns. Gem Russet also showed no response to application timing and had NO₃-N sufficiency concentrations similar to or slightly higher than those of Russet Burbank. Summit Russet showed a strong trend for improved N use-efficiency when most of the N was applied early. On the other hand, analysis of net returns revealed a trend for greater profitability for Summit Russet when the majority of N was applied during tuber bulking. Petiole NO₃-N sufficiency concentrations for Summit Russet were generally higher than those for the other three cultivars. In comparison with some earlier studies with Russet Burbank, this research suggested lower optimal N rates and petiole NO₃-N sufficiency concentrations.     

Response of ten potato cultivars to temperature as measured by chlorophyll fluorescencein vivo

Forty-day-old plants of ten cultivars of potato,Solanum tuberosum L. (Alpha, Atlantic, Bintje, Caribe, Kennebec, Red Pontiac, Russet Burbank, Sebago, Shepody and Superior), were placed into a controlled environment chamber held continuously at 35 C and their growth (Plastochron Index) and several chlorophyll fluorescence parameters (O, P, T, Fv and Fr) were measured after 1, 14, 21 and 28 days’ exposure. The cultivars were grouped according to heat tolerance based upon survival of three of four plants. The least heat tolerant group, surviving 14 days, included Atlantic, Bintje and Superior. The medium heat tolerant group, surviving 21 days’ exposure, included Kennebec, Red Pontiac and Sebago. The best heat tolerant group, surviving 28 days’ exposure, included Alpha, Caribe, Russet Burbank and Shepody. In addition, chlorophyll fluorescence parameters of six plants of each cultivar were also measured after 1 h at 5, 15, 25 and 35 C exposure in a second experiment. In all cases plants in the group with the least tolerance displayed less fluorescence than the medium or high heat tolerance plants, suggesting that plants with the least tolerance to high temperature exposure had less energy transfer through PSII (Photosystem II). These plants also had a rise in T at temperatures aboveca. 15 C. A decrease in Fv during growth at 35 C was a good indicator of foliar heat damage. Chlorophyll fluorescence of plant tissue in all three groups increased after short exposure of 1 h to temperatures below 15 C and also after continuous exposure to 35 C. At both ranges of temperature, damage was probably occurring to the thylakoid membranes which inhibited re-oxidation of PSII. Since the rate of response was different, chilling and high temperature apparently differ in how they alter the thylakoid membranes.     

Differential susceptibility of potato cultivars to four herbicides

Greenhouse and field studies were conducted to evaluate the susceptibility of six potato (Solatium tuberosum L.) cultivars to injury by four herbicides. The White Rose cultivar was the most susceptible to injury, especially from metribuzin {4-amino-6-tert-butyl-3-(methylthio)-s-triazin-55 (4H) one}, and linuron {3-(3,4-dichlorophenyl)-l-methoxy-l-methyl-urea}. Injury was attenuated by decreasing the rate of herbicide in the range of 4.5 to 0.5 kg/ha (4 to 0.5 1b/A) and by increasing the seed piece size. Injury seemed to be associated with soil texture and was greater in a sandy loam than in a sandy clay loam soil. Greenhouse studies provided valuable leads on cultivar susceptibility to herbicides but reductions in foliar weight of 15 to 20% are required to justify any suspicion that field injury will occur.     

Relative resistance of potato cultivars to bacterial wilt

Fifty-one potato cultivars were evaluated for reaction to infection byPseudomonas solanacearum Sm. under high disease pressure in a field plot near Tifton, Georgia during the spring of 1978 and 1979. Plots were infested by clipping beds of thickly seeded tomato plants with a rotary mower contaminated with the wilt baterium in 1975, 1976, 1977 and 1978. The plants were incorporated into the soil following disease development. In addition to the use of infested soil, one stem on each potato plant was inoculated in late May by cutting with a knife blade dipped in a bacterial suspension. Most of the cultivars evaluated were highly susceptible to bacterial wilt. Ontario was the only cultivar highly resistant to the disease, with only 1% and 8% dead or dying plants in 1978 and 1979, respectively. Based on tuber infection, Ontario and Snowchip were the most resistant, with 9% and 14% infection, respectively, in 1978 and both 4% in 1979. Saco, Green Mountain and Sebago also showed some resistance.     

Differential interaction between two potato cultivars and two isolates ofPhoma exigua var.foveata

Summary In experiments carried out over two years at two sites, a differential interaction between two potato varieties and two isolates ofP. exigua var.foveata was demonstrated in the cortical tissue.     

The conservation of potato cultivars

Summary To prevent the loss of important genetic information cultivars are conserved in several collections of gene banks. In principal, there are two options for the medium to long-term storage of potato cultivars: storage as in vitro plantlets or microtubers and storage of meristems or shoot-tips in liquid nitrogen. In the Braunschweig potato cultivar collection, 360 cultivars are maintained under slow-growth conditions. Ten microplantlets of each cultivar are stored in test tubes containing filter paper bridges and 5 ml Murashige and Skoog (MS) liquid medium. The cultures were maintained at 10°C with a light intensity of 2 klux and 16 hours-day and can be stored under these conditions up to three years. Two hundred and forty-five cultivars are cryostored in liquid nitrogen. About 300 trimmed shoot-tips of each cultivar are incubated in MS-Towill-medium and then transferred into the cryoprotective solution. After an incubation time of about 2 hours trimmed shoot-tips fixed on an aluminium foil were put in cryo vials and stored in a container. The survival rate of the thawed, trimmed shoot-tips varies from 55%–100%. More important for a gene bank, however, is the plant regeneration. The average regeneration of all cultivars is about 40%.     

Response of tubers of five potato cultivars to co-inoculation with US-1 and US-8 genotypes ofPhytophthora infestans

Summary The severity of late blight tuber rot in five potato cultivars (Green Mountain, Sebago, Dorita, AC Brador and Island Sunshine) resulting from inoculation with US-1/US-8 combinations of Canadian isolates ofPhytophthora infestans was evaluated. In addition, the potential for mixed (A1∶A2) inoculations to result in oospore formation was examined. In studies conducted in 1996 and 1997, cv. Dorita (and Island Sunshine in 1997) developed the least amount of surface or internal necrosis relative to the other cultivars following co-inoculation with US-1 and US-8 isolates ofP. infestans. Differences also were revealed among isolate combinations used for inoculation. The combination of a US-1 isolate from Prince Edward Island with a US-8 isolate from New Brunswick consistently produced the least amount of necrosis in tubers of the various cultivars. There was no evidence of oospore production in any of the tubers examined. AAFC Contribution No. 919     

Variation in pathogenicity among isolates ofPhoma exigua var.foveata on potato cultivars differing in resistance

Summary The size of gangrene lesions on potato tubers was significantly affected by isolate ofPhoma exigua var.foveata and cultivar. Inoculation methods based on the introduction of a wheat-germ/sand culture into the peripheral tissues of the tuber revealed greater differences among isolates and cultivars than one involving a deeper insertion of a mycelium/potato dextrose agar plug. The method of testing influenced the order of ranking of certain isolates and cultivars. The relative pathogenicity of isolates was similar over two years, but no cultivar-isolate interactions were found.