Morphological changes and yield enhancement of superior potatoes by AC 243,654

AC 243,654, 1-(m)-methoxybenzyl)-3-nitroguanidine, represents a new family of plant growth regulators with cytokinin-like activity. This compound was tested at 1 and 4 kg/ha on greenhouse-grown potatoes (Solanum tuberosum L.), cultivar Superior. The treatments were applied two weeks after emergence. Morphological and yield effects of AC 243,654 were determined at 4, 7, 11, 14, 21, 42 and 70 days after treatment (DAT). Shortly after treatment, AC 243,654 stimulated plant height, branch number and stolon number. Plant weights were initially stimulated. At the final harvest, 70 DAT, the dry weight of treated plants was greater than that of the check plants; this is attributed to the anti-senescence effect of this compound on vine tissue. AC 243,654 induced tuber initiation at 14 DAT, whereas checks did not have tubers until one week later. Between 14 and 70 DAT, treated plants produced greater yield than check plants; the yield increases were primarily due to larger tubers. The yield of smaller tubers was decreased by the treatments. Although the number of larger tubers increased, total tuber number was decreased by AC 243,654. Observations on tuber number over time suggested that the check plants initiated more tubers than treated plants but most of these aborted. In treated plants, less tubers were initiated.     

Sunrise: An early maturing,golden nematode resistant,round, white potato variety

The Sunrise potato variety is an early maturing variety with round to oblong, moderately smooth, white skinned tubers with medium-shallow eyes. Its characteristics are closely parallel to those of Superior, except Sunrise is resistant to race A of the golden nematode (Globodera rostochiensis). Sunrise is primarily a table potato; however, in southern areas it can be used for chips when processed without prolonged storage at low temperatures. Sunrise is resistant to virus X and does not show the net necrosis symptoms caused by leafroll virus. Its parents are Wauseon and B 6563-2, a selection from the USDA breeding program.     

St. Johns: A round white potato variety for fresh market

The St. Johns potato variety is high-yielding and late-maturing with attractive, round to oblong, white-skinned, white-fleshed tubers with mediumshallow eyes. Its major use is expected to be as a maincrop tablestock variety. Taste panels rated St. Johns better than or equal to Katahdin in texture, color, mealiness, and flavor. St. Johns tubers do not show the net necrosis caused by potato leafroll virus, and are resistant to golden nematode, corky ringspot, hollow heart, and blackspot bruising. St. Johns is also moderately resistant to greening, shatter bruise, verticillium wilt, early blight, common scab, the common race of late blight, leafroll,Fusarium sambucinum (dry rot) andErwinia carotovora (soft rot), although some breakdown has been reported in commercial storages. Symptoms of leafroll virus infection are somewhat difficult to detect.     

Portage: A new early-maturing,round white table potato variety

The Portage potato variety is high-yielding and early-maturing with attractive, round to oblong, white-skinned, white-fleshed tubers with medium-shallow eyes. Its major use is expected to be as an early tablestock variety in areas where Superior suffers yield reductions caused by verticillium wilt. Portage tubers do not show the net necrosis caused by potato leafroll virus, and are susceptible to skinning, but are fairly resistant to hollow heart, blackspot and shatter bruise. Portage is moderately resistant toVerticillium alboatrum, andRhizoctonia solani, but its seed-pieces are sensitive to dry soil conditions; therefore, cut seed should be suberized before planting. Symptoms of leafroll virus infection are difficult to recognize.     

Quaggy Joe: A high-yielding, round, white potato variety for fresh market

The Quaggy Joe potato variety is high-yielding and medium to medium-late maturing with attractive, round-oval, white-skinned, white-fleshed tubers with medium-shallow pink eyes. Its major use is expected to be as a maincrop tablestock variety. Quaggy Joe is resistant to the potato leafroll virus, and is also moderately resistant to early blight (Alternaria solani), dry rot (Fusarium sambucinum), and soft rot (Erwinia carotovora subsp.carotovora). Quaggy Joe tubers have shown very little shatter or blackspot bruising, but sprout earlier than Atlantic. Young plants have shown sensitivity to the herbicide metribuzin.     

Cultivar response to Fusarium storage rot as affected by two methods of seed origin propagation; Clonal selection andin vitro culture

Progeny tubers from seed potatoes originating from either a traditional clonal selection method or the more modernin vitro tissue culture method of propagation were tested for storage rot response following inoculation of three tuber sites with twoFusarium species. Significant differences were found among disease responses for the twoFusarium species and for the four cultivars tested. Disease symptoms were less severe forF. solani var.coeruleum than forF. sambucinum. Fusarium sambucinum caused less disease in Superior than Kennebec, Russet Burbank and Sebago. Seed propagation method did not significantly affect disease response except for one case;in vitro culture of Kennebec had less disease due toF. sambucinum at the tuber side inoculation site than clonal selection. Kennebec and Superior inoculatedF. sambucinum had significant differences with respect to the number of years of field propagation for the tuber side inoculation site and for the tuber mean rot index. Significant differences in number of years of field propagation were also found for eye-ends of Superior tubers and stem ends of Russet Burbank tubers inoculated withF. solani var.coeruleum.     

Ac chaleur: a new early-maturing cultivar with excellent table quality

AC Chaleur is adapted as a second early cultivar in Eastern Canada. It has smooth, bright round-oval tubers with excellent table quality. When harvested at 70-80 days from planting, AC Chaleur tends to outyield Superior. This yield advantage decreases at later harvest times. AC Chaleur has resistance to PVYand moderate resistance to common scab.     

Resistance of tubers from different potato cultivars to soft rot caused byErwinia carotovora subsp.atroseptica

Mechanically harvested tubers of 14 potato cultivars grown on both loamy sand and silt loam soils were evaluated for resistance to bacterial soft rot caused byErwinia carotovora subsp.atroseptica. Cultivars were also assayed for calcium and dry matter content to determine possible correlations with soft rot resistance. Resistance of potato tubers to bacterial soft rot was assayed after harvest by inoculating tubers and determining percent surface area decayed after four days in a mist chamber. Tubers of the cultivars differed widely in resistance to bacterial soft rot. The ranking of the resistance of tubers from different cultivars to bacterial soft rot was similar for both soils, although disease severity in tubers from a particular soil type varied with the season. Of the cultivars tested, tubers of Butte, Russet Burbank, and Nor-gold Russet were ranked as the most resistant, whereas tubers of Redsen, Norchip, Norland and Belchip were rated as the most susceptible. Tubers of Rhinered, Red La Soda, Superior, Pontiac, Atlantic, and Nooksack were intermediate in resistance. Neither calcium concentration in medullar tissues nor dry matter of potato tubers alone could be correlated with ranking of the cultivars with respect to severity of bacterial soft rot. However, a multiple linear regression model incorporating both variables indicated that tubers with a high content of both calcium and dry matter were likely to be less susceptible to bacterial soft rot than were tubers with lower percentages of these variables.     

Effects of substituted nitroguanidine seed treatments on the potato variety Superior

In earlier reports, foliar applications of AC 243,654, a substituted benzyl nitroguanidine with cytokinin-like activity, increased yields of larger tubers and altered plant morphology of potatoes (Solanum tuberosum L.) in greenhouse tests. AC 243,654 was applied as seed tuber treatments to the potato variety Superior. Applications were 0.2 to 10% active ingredient (ai) dusts and 0.04 to 5% ai dips. All seed treatments increased the number of sprouts per tuber. The higher concentrations of seed treatments decreased stem height, and increased stem/branch number, plant dry weight and the number of tubers. Dust and dip treatments of 0.2 and 1% increased the yield (11 to 33%) of tubers < 38 mm in greenhouse tests. Higher rates decreased yields. In field trials, dust applications of AC 243,654 and its analog AC 89,470, the unsubstituted benzyl nitroguanidine, at 0.1 and 0.4% ai increased total and US #1 (< 47 mm diameter) yields between 10 and 18%; and 8 to 18%, respectively. The high rate of 10% ai of either compound decreased yield. AC 239,604, a substituted phenyl nitroguanidine, as a 0.1 % ai dust increased yields 21% while higher rates decreased them. Based on combined greenhouse and field data, AC 243,654 dust applications > 2% ai increased yields while greater application rates decreased yields.     

Growth of early potatoes from different portions of seed tubers II. Yield

Several of the recently released early-potato (Solanum tuberosum L.) cultivars used in Ontario have produced uneven stands which have been shown to be a result of delayed emergence from basal end seed pieces. A study was conducted to evaluate the effects of seed portions on the yield of three early potato cultivars, Jemseg, Superior and Yukon Gold. Yield of plants from basal seed pieces was lower than that from apical seed pieces or whole tubers for Jemseg and Yukon Gold during several sequential harvests. With Superior, cut seed portions yielded less than whole seed. Number of stems per plant was lower for basal plants of Jemseg. Tubers with strong apical dominance or dormancy such as Jemseg and Yukon Gold are prone to differences in yield among seed portions.     

Mainestay: A high-yielding, round white potato variety for fresh market

The Mainestay potato variety is high-yielding and late-maturing producing attractive, round, white-skinned, white-fleshed tubers with medium-shallow eyes. Its major use is expected to be as a maincrop tablestock variety. Mainestay appearance ratings are similar to those of Katahdin, and greening in Mainestay tubers is less than in Kennebec. Most boil and bake qualities were rated equal to Katahdin in at least half of the tests, and Mainestay usually has a low incidence of internal defects. However, purple streak, heat necrosis, vascular discoloration, and heat sprouts have been seen on occasion. Mainestay tubers do not show the net necrosis caused by potato leafroll virus, and have shown very little hollow heart or blackspot bruising. Mainestay is susceptible to common scab and acid scab, but moderately resistant to verticillium wilt (Verticillium, albo-atrum andV. dahliae), early blight (Alternaria solani), rhizoctonia (Rhizoctonia solani), dry rot (Fusarium sambucinum), and pink rot (Phytophthora erythroseptica). It is moderately susceptible to the common race of late blight (Phytophthora infestans). Mainestay tubers are slow to mature after vine kill, and additional time is required prior to harvest in order to allow for proper periderm development and to reduce storage losses.     

First report ofPythium sylvaticum causing potato tuber rot

Leak is a post-harvest disease of potato tubers manifested by a wet, spongy rot that can quickly lead to complete tuber decay. In North America, leak is most commonly caused byPythium ultimum var.ultimum Trow, although a number of otherPythium spp. have been found to be pathogenic to potato tubers. We report that an isolate identified by DNA sequencing asP. sylvaticum Campbell & Hendrix was pathogenic to potato tubers. The organism produced a dark, hollow cavity in tubers that was much drier in texture than typical symptoms of leak. Symptomology was similar in tubers of the cultivars Yukon Gold, Green Mountain, and Russet Burbank. Studies to complete Koch’s postulates confirmed thatP. sylvaticum could be reisolated from diseased tissue and produced the same disease symptoms when isolates were subsequently re-inoculated into healthy tubers. This is the first report ofP. sylvaticum causing rot in potato tubers.     

Red Pearl: A new gourmet red potato variety

Red Pearl is a medium-late variety with round tubers of stable dark red skin and white flesh. It is an ideal gourmet and canning variety due to its high tuber set and high proportion of tubers less than 4.76 cm diameter (up to 71% of the total yield). Red Pearl has good boiling and baking qualities. Its specific gravity is slightly higher and the tuber dormancy is longer than Dark Red Norland. Red Pearl yields only 54% to 77% of Red Norland because of its small tuber size. Red Pearl is less susceptible to common scab (Streptomyces scabiae < than Dark Red Norland, significantly more resistant to corky ring spot (tobacco rattle virus) than Dark Red Norland and is resistant to bacterial wilt and brown rot (Ralstonia solanacearum). Red Pearl showed similar susceptibilities to several other diseases, including early blight, late blight, pink rot, and tuber soft rot, compared to Dark Red Norland. Red Pearl is more susceptible to shatter bruise and blackspot than Dark Red Norland when handled from storage at 7.2 C.     

Freezing and Frost Damage of Potato Plants: a Case Study on Growth Recovery,Yield Response,and Quality Changes

The relationship between the severity of natural freezing and frost damage (FFD) and the observed growth recovery and field production of Superior potatoes (Solanum tuberosum L.) was investigated under screen house conditions. Potato plants were damaged by accidental freezing and frost during the early phase of shoot growth, 40 days after planting in highland summer crop areas in Korea. The observations of FFD were classified visually into “severe” (>75%), “moderate” (50%), “mild” (<25%), and “no FFD”, based on the percentage of the area of the shoots which was damaged. The early vegetative growth recovery, in terms of groundcover, was reduced as the level of FFD increased. At 28 days after a freezing and frost damage (DAFF), the potato plants with mild or no symptoms had produced more groundcover than the plants with moderate or severe symptoms. At 35 DAFF, groundcover was the same across all levels of severity, at nearly 100%. Despite the slower canopy development, plants with FFD achieved a higher fresh shoot weight and total chlorophyll content, whereas physiological growth indices such as photosynthetic rate and stomatal conductance of leaves were not different among levels of FFD at 60 DAFF. The number of lateral stems and days to tuberization increased significantly as the level of FFD increased; however, the harvest index, the number of tubers per plant, and seed tuber production were all reduced in plants with severe FFD. In addition, the tubers from plants with severe FFD had an increased ratio of length to width and 40% more tuber eyes than tubers from undamaged plants. The elongated tubers also showed an increase in cell division, demonstrated by higher numbers of cells in the cortical zones. The aforementioned measurements were obtained from natural event and led to a deduction that Superior has a capacity to recover from FFD, unless the plants were severely damaged (>75%) early in the season.     

Latent infection of potato tubers byPseudomonas solanacearum

Strains ofPseudomonas solanacearum differed in their ability to infect tubers of different resistant potato clones grown in infested soil. When eight resistant clones (Solanum phureja orS.phureja ×S. tuberosum hybrids) were grown at 24–28°C in soil infested with a race 1 or a race 3 strain of the bacterium, relatively few plants had wilt symptoms at harvest, but 26.7% and 9.2% of the tubers harvested from plants infected with the race 1 and race 3 strains, respectively, carried latent infections. Some infected clones never yielded diseased tubers, however. The development of symptoms above ground was not correlated with the incidence of tuber infection in any particular clone. No tuber infection occurred in tolerant or resistant clones grown in infested soil at cool (12–22°C) temperatures. Tubers were inoculated directly in an attempt to evaluate the ability of bacteria to multiply in these tissues at different temperatures. Highly virulent strains ofP. solanacearum survived in susceptible tubers in higher numbers and for longer periods than in resistant ones. Low temperature (4°C) had a deleterious effect on survival of the bacterium in tubers, but did not completely eliminate the pathogen even after 40 days.     

Growth and Tuberization of Hydroponically Grown Potatoes

Three hydroponic systems (aeroponics, aerohydroponics, and deep-water culture) were compared for the production of potato (Solanum tuberosum) seed tubers. Aerohydroponics was designed to improve the root zone environment of aeroponics by maintaining root contact with nutrient solution in the lower part of the beds, while intermittently spraying roots in the upper part. Root vitality, shoot fresh and dry weight, and total leaf area were significantly highest when cv. Superior, a medium early-maturing cultivar, was grown in the aeroponic system. This better plant growth in the aeroponic system was accompanied by rapid changes of solution pH and EC, and early tuberization. However, with cv. Atlantic, a mid-late maturing cultivar, there were no significant differences in shoot weight and leaf area among the hydroponic systems. The first tuberization was observed in aeroponics on 26–30 and 43–53 days after transplanting for cvs Superior and Atlantic, respectively. Tuberization in aerohydroponics and deep-water culture system occurred about 3–4 and 6–8 days later, respectively. The number of tubers produced was greatest in the deep-water culture system, but the total tuber weight per plant was the least in this system. For cv. Atlantic, the number of tubers <30 g weight was higher in aerohydroponics than in aeroponics, whereas there was no difference in the number of tubers >30 g between aerohydroponics and aeroponics. For cv. Superior, there was no difference in the size distribution of tubers between the two aeroponic systems. It could be concluded that deep-water culture system could be used to produce many small tubers (1–5 g) for plant propagation. However, the reduced number of large tubers above 5 g weight in the deep-water culture system, may favor use of either aeroponics or aerohydroponics. These two systems produced a similar number of tubers in each size group for the medium-early season cv. Superior, whereas aerohydroponics produced more tubers than aeroponics for the mid-late cultivar Atlantic.     

Ascorbic acid and glycoalkaloid content of Atlantic and Superior potato tubers as affected by supplemental irrigation and soil amendments

Atlantic and Superior potato (Solanum tuberosum L.) tubers were collected at harvest from two field experiments in Maine during 1993 and 1994. Tubers were analyzed for ascorbic acid (ASC) and total glycoalkaloid (TGA) concentration within one month of harvest and after 4 to 5 months of storage at 10 C. ASC concentration was significantly higher in Superior than Atlantic at harvest and after storage. TGA concentration was consistently higher in Atlantic than Superior. Irrigation tended to slightly reduce ASC and increase α-solanine concentrations when applied too late in the season for yield benefits. Storage decreased tuber ASC content, but no specific pattern was observed for TGA changes. Soil amendment programs using compost and manure (22 Mg ha^?1 potato compost + 45 Mg ha^?1 manure) did not dramatically affect tuber ASC or TGA concentrations. ASC content of the tubers declined dramatically in storage, but no consistent pattern was found for tuber TGA changes. We conclude that genotype, growing environment, and storage time play much stronger roles in determining tuber ASC and TGA levels than do irrigation and soil management programs. We observed a negative relationship between the average tuber size of the assayed samples and ASC concentration in fall samplings; however, this relationship was not observed from storage. Average tuber size and TGA content generally displayed a negative relationship.     

Steuben: a golden nematode resistant variety with wide adaptation

Steuben is a golden nematode resistant variety with wide adaptation and high yield potential. It has a mid to late season vine maturity but starts to size its crop of tubers as early as Superior. It has potential for tablestock as well as for chipping from the field and from 10°C storage. It is resistant to pitted scab but susceptible to superficial scab which can be severe enough to reduce its value for tablestock under some conditions. The maturity of the crop entering storage appears to be an important determinant for chip color out of storage.     

Somerset: A new chipping potato variety

The Somerset potato variety is a medium-maturing variety with attractive, round to oblong, white-skinned, white-fleshed tubers with shallow eyes. Its major use is expected to be as a chipping variety in areas where potatoes are stored for some length of time, since its sugar content is lower than most varieties during storage, and it can be chipped after six months in storage. Somerset does not show the net necrosis caused by potato leafroll virus, and is immune to race 0 of Phytophthora infestans (late blight). Somerset is also moderately resistant to infection by Alternaria solani (early blight), and is only moderately susceptible to Verticillium wilt. Somerset is more susceptible to both common and acid scab than Superior, but less susceptible than Kennebec and Katahdin. It also has shown susceptibility to skinning and shatter bruise, but does not have a strong blackspot bruise reaction.     

AC Ptarmigan: An early maturing potato cultivar with good chipping and fresh market quality

AC Ptarmigan is an early maturing, buff skin, cream flesh potato cultivar which has good, stable chip quality and can be processed directly from the field. The cultivar has uniform attractive tubers with shallow eyes. It is moderately resistant to common scab, early blight, potato virus Y and potato leafroll virus. It is susceptible to late blight and shows clear field symptoms when infected with bacterial ring rot.