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.     

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.     

Castile: A multiple-purpose,high yielding full-season golden nematode resistant potato variety

Castile is a golden nematode Race A (Globodera rostochiensis) resistant potato variety with the potential to produce high marketable yields of attractive tubers suitable for tablestock and processing. Tubers are oblong to long, slightly flattened with a smooth white skin and moderately shallow eyes. Vines of this variety are large, providing a dense canopy, and require a full growing season similar to that needed for Katahdin. Timely irrigation produces high marketable yields, stress conditions can limit yields. Specific gravity in New York State averages 0.005 above Katahdin and 0.009 below Atlantic. Tuber flesh is bright white. Baking and french fry quality is good. Chip color, when tubers are stored at 10 C for 120 days, is equivalent to Atlantic. Castile is resistant to corky ring spot, pinkeye, and moderately resistant to Fusarium rot.     

Prestile: A new round white potato variety

Prestile is a late maturing potato variety with attractive, round to oblong, white-skinned, white-fleshed tubers with shallow eyes. Its major use is expected to be for tablestock in areas where Katahdin and Ontario are now grown. Prestile tubers are slow to sprout in storage and do not show the net necrosis caused by potato leafroll virus, but are quite susceptible to heat necrosis. This variety is immune to potato virus X, and is moderately resistant to common scab (Streptomyces scabies), verticillium wilt (Verticillium albo-atrum), and early blight (Alternaria solani). Prestile is susceptible to skinning and shatter bruise, and is difficult to kill, particularly when heavily fertilized.     

Progress report: Resistance to the Colorado potato beetle and potato leafhopper inSolanum tuberosum subsp.andigena

An extensive collection of 1527 clones ofS. tuberosum subsp.andigena was screened in 1973 in unreplicated plots to test for resistance to the Colorado potato beetle and potato leafhopper. All clones were susceptible to the beetle. Of 17 clones selected in the 1973 tests for resistance to the potato leafhopper, 7 selections were significantly more resistant than the control (Katahdin) in a replicated experiment in 1974.     

Glycoalkaloid contents in tubers fromSolanum tuberosum populations selected for potato leafhopper resistance

Solanum tuberosum L. Gp. Tuberosum populations that had been improved for resistance to potato leafhopper,Empoasca fabae (Harris), by recurrent selection, were analyzed for tuber contents of the glycoalkaloids α-solanine and α-chaconine. The mean content of both glycoalkaloids was significantly higher in the more resistant populations compared with the unselected population. In a population generated from seven cycles of selection for resistance, the mean content of solanine + chaconine was 9.5 mg/100 g fresh weight compared with 4.0 mg/100 g in the original, unselected population; a 137% increase. Kennebec, in the same experiment, averaged 10.9 mg/100 g; Katahdin averaged 4.6 mg/100 g.     

Identification of stem soft rot (Erwinia carotovora subspeciesatroseptica) resistance in potato

Development of potato cultivars resistant to Erwinia species (Erwinia carotovora subspeciesatroseptica, E. carotovora subspeciescarotovora, andErwinia chrysanthemi) causing soft rot of stems and tubers involves identification and transfer of the resistance to breeding lines possessing desirable agronomic traits. In total, 363 accessions of six wildSolanum species, three somatic hybrids and nine sexual progeny of somatic hybrids were screened for stem soft rot resistance. Thirty-one, 50, and 67 percent of accessions ofSolanum boliviense, Solanum chacoense, and Solanumsanctarosae, respectively, were resistant or highly resistant, whereas, 100, 97, and 95 percent of accessions ofSolanum canasense, Solanum tarijense, andSolanum spegazzinii were susceptible or highly susceptible, respectively. Two tuber soft-rot resistant somatic hybrids, A937 and T355-11 produced earlier by the fusion ofSolanum brevidens (PI 218228) andSolanum tuberosum (PI203900) orS. tuberosum cv. Russet Burbank, respectively, and the sexual progeny of A937 andS. tuberosum cv. Katahdin were also highly resistant. Transfer of resistance fromS. brevidens to somatic hybrid (A937) and subsequently to the progeny suggests that the resistance is simply inherited. In addition to the identification of 65 resistant or highly resistant clones of wildSolanum species, this study has identified three tuber soft rot-resistant clones that are also resistant to stem soft rot. Potato cultivars showed a range of responses to the pathogen.     

Approaches to control of potato early dying caused byVerticillium dahliae

Potato early dying disease, caused byVerticillium dahliae, may be either suppressed or controlled by a variety of procedures. These methods include the growing of resistant cultivars, attention to cultural management, utilization of pesticides, and solar heating of soils. The greatest successes in control of Verticillium wilt have been achieved with the use of either soil fumigants or clonal resistance, but these approaches have been restricted. Widespread use of fumigants has been limited by cost, and the lack of commercial acceptance has often restricted the utilization of resistant potato cultivars. The Katahdin and Targhee cultivars are currently available with resistance and/or tolerance to this disease. The Russet Burbank potato also possesses a limited degree of resistance to the fungus, and with this resistance, the disease appears to be suppressed by optimal growing conditions. In potato fields that have been cropped for several years, disease suppression in Russet Burbank was found to be related to methods of irrigation and increased nitrogen availability. It is suggested that improved utilization of resistant germplasm and effective use of biological control strategies may ultimately lead to economical control of this disease.     

Reaction of potato tuber slices toPhytophthora infestans in relation to physiological age

Tuber resistance toPhytophthora infestans was studied in relation to physiological age in tubers of the cultivars Atzimba, Katahdin, Kennebec, and Sebago. Resistance to race1,2,3,4 was evaluated in freshly harvested tubers, and tubers stored at 5 C for up to 215 days. Atzimba tubers were highly resistant when freshly harvested but became increasingly susceptible as they aged physiologically. Tubers of the other three cultivars were susceptible when freshly harvested and also when aged. Further, 57 tuber selections from among 11 crosses initially gave resistant reactions. However, after storage for six months at 5 C, 26.3% of the selections remained resistant, 22.8% were moderately resistant, 31.6% moderately susceptible, and 19.3% fully susceptible.     

Tolerance to potato leafhopper inSolanum tuberosum L. gp. Tuberosum clones

We identified clones inSolanum tuberosum L. gp. Tuberosum breeding populations that, although susceptible to infestation by potato leafhopper,Empoasca fabae (Harris), exhibited a tolerance which was manifested by the ability to produce higher than expected tuber yields when heavily infested with leafhoppers. Such tolerance was noted in a number of clones in varying degrees, but one, B6930-1, was exceptional. It sustained only a 19% loss in tuber yield compared to ‘Katahdin,’ a susceptible cultivar, that averaged 33% lower tuber yields under similar infestation levels. We studied the seasonal growth patterns of this clone and compared them to those of Katahdin, and B6705-10, a breeding clone with known resistance to leafhopper infestation. We found that much of B6930-l’s tolerance results from its early, vigorous vine growth and its early and rapid rate of tuber bulking, enabling this clone to escape some of the effects of leafhopper feeding, whereas Katahdin was usually just beginning to tuberize at the height of leafhopper infestation.     

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.     

Resistance of potato clones to the green peach aphid and potato leafroll virus

During 1980 and 1981 potato cultivars and breeding selections, including cultivated species and their hybrid derivatives, were evaluated for resistance to the green peach aphid (GPA),Myzus persicae (Sulzer), and to potato leafroll virus (PLRV). Criteria used were the number of aphids which colonized the clones in free choice field experiments and the number of plants derived from these experiments which showed symptoms of PLRV infection. Generally, greater resistance to GPA was found inSolarium tuberosum gp.andigena selections and hybrids than in gp.tuberosum cultivars. There were approximately fourfold differences in season-mean GPA levels among the clones tested each year. Forty-two families, representing a cross-section of the USDA breeding populations at the University of Idaho Research and Extension Center, Aberdeen, showed a similar range in colonization levels. Resistance to GPA colonization appeared to be more prevalent in gp.andigena, gp.phureja, and gp.stenotonum derivatives. There was a weak positive correlation (r² = .34, P = .01) between foliar total glycoalkaloids and season-mean GPA colonization levels for six clones representing the range of observed resistance to GPA. Resistance to GPA colonization was apparently not directly related to resistance to PLRV infection. Katahdin, for example, was relatively susceptible to GPA colonization but very resistant to PLRV infection whereas selection A69657-4 (gp.andigena) was among the most resistant to GPA colonization but among the more susceptible to PLRV infection. Breeding for resistance to GPA colonization therefore may not be as promising for PLRV control as developing PLRV resistant cultivars.     

Maintenance and growth ofHelminthosporium solani

We have found that by using water agar as an isolation medium, V-8 juice agar as a growth substrate, and sterilized rye grains as a storage medium we can: 1) produce copious amounts ofHelminthosporium solani conidia that were successfully used as inoculum and: 2) the sterilized rye grains could be used to maintain viable cultures of the five isolates ofH. solani used in this study for 16 months. All of the isolates were pathogenic on tubers of the potato cultivars Katahdin and Superior.     

Incidence and severity of powdery scab on potatoes in Pennsylvania

Studies were conducted in Potter Co., Pennsylvania to investigate the effect of powdery scab (Spongospora subterranea) on five potato cultivars (Norchip, Rosa, Kennebec, Katahdin, and Monona) at two planting dates. Soil temperature was within the range of 15–18 C and soil moisture was within 15–19% based on dry weight throughout the season. The effect of planting date was significant at each disease assessment, except for the severity on the fourth assessment. By the end of the season, incidence of scab was 66% or more for all cultivars. Rosa, Kennebec and Katahdin had a greater scab incidence over both planting dates and a greater severity at the first planting date than Monona and Norchip.     

The effect of Dual® on the flavor of riced baked potatoes

Samples of Katahdin potatoes (Solanum tuberosum) from untreated and Dual 8E-treated plots (4 lb. ai/A applied at the first hilling) were evaluated for flavor by a sensory panel of 21 members. No off-flavor was associated with the Dual-treated baked potatoes.     

Influence of slitted polyethylene mulch,nitrogen rates,and trickle irrigation on potatoes

In 1974, potatoes(Solanum tuberosum L.) were grown on unmulched, clear, and black slitted polyethylene. Production and tuber specific gravity of the potatoes were determined at four nitrogen rates (0, 75, 150 and 225 lb/A) and with two varieties (Superior and Katahdin). In 1975, potatoes were grown on unmulched and clear slitted polyethylene with and without trickle irrigation. Nitrogen increased marketable yields up to 150 lb/A on the unmulched potatoes. Irrigation increased the marketable yields of potatoes on both unmulched and mulched plots. However, no advantage was found in marketable yields, specific gravities or tuber sizes of the potatoes grown on either clear or black slitted polyethylene mulch over conventional unmulched soil for the ‘Superior’ or ‘Katahdin’ varieties.     

Resistance toPseudomonas solanacearum in potato: Infectivity titrations in relation to multiplication and spread of the pathogen

When several wilt-resistant potato clones were tested against a highly virulent strain from Mexico (No. 276) by standard stem inoculation methods, only one clone ofSolanum phureja was resistant. When different inoculum concentrations were introduced quantitatively for infectivity titrations, however, different levels of resistance were clearly defined among clones previously rated as susceptible. Linear regression was used to estimate the ED₅₀ values (dosage required to wilt 50% of the population) for each of seven clones. These values ranged from 3 and 100 colony-forming units (CFU) for Katahdin and Russet Burbank, respectively, to 2.1 x 10⁶ CFU for S.phureja clone 1386.15. The distribution of bacteria in stems of Russet Burbank plants inoculated with the compatible strains 276 and K-60 and the incompatible strains B1 and S-210 was very different. In all cases, incompatible bacteria were not detected 10 cm above the inoculation point in the stem, even by 12 days after inoculation, whereas compatible strains multiplied rapidly at this site by 6 days. At the inoculation site and at sites immediately adjacent to it, however, incompatible bacteria attained populations that only differed by one order of magnitude from those of compatible bacteria. Similar results were obtained when a resistant clone (MS 118.24) was inoculated with the virulent strain K-60. Thus, resistance was characterized both by reduced acropetal spread and by tolerance to large numbers of the bacterium.     

Influence of chemical seed and soil treatments onVerticillium-induced yield reduction and tuber defects

Experiments were conducted in 1969 and 1970 to determine the influence of chemical treatments of seed pieces and soil on the development ofVerticillium wilt as measured by tuber yield increases and reduction in severity of tuber defects. The influence of storage onVerticillium-induced tuber defects was evaluated. Seed treatment chemicals tested included zinc ion maneb, maneb, maneb-chloroneb, Polyram, benomyl, and thiabendazole. Soil treatment chemicals included O-Diethyl (O-methyl-sulfinyl) phenyl phosphoro-thioate, disulfoton, phorate, carbofuran, aldicarb, ethyl 4 (methyl- thio)-m-tolyl isopropyl phosphor amidate, benomyl, and thiabendazole. Inoculated seed pieces and artificially infested plot areas were used the first year while the second year natural inoculum from a previous crop was the source of infection. Kennebec and Katahdin cultivars were tested in 1969 and Kennebec alone in 1970. Verticillium-induced yield reductions and tuber defects were more severe in all respects with Kennebec than with Katahdin. With Katahdin the only significant evidence of infection was stem end discoloration. Seed treatments, with the exception of benomyl or thiabendazole, which were erratically phytotoxic, resulted in consistent yield increases and reduction in pink eye severity. In 1969 seed treatment reduced stem end browning in Kennebec. Soil treatment with disulfoton, carbofuran, and aldicarb, both alone and in combination with seed treatments resulted in consistent yield increases with Kennebec. The seed piece and soil treatment combinations tested in 1970 appeared to have an additive effect on yield increase from combination treatments equivalent to the gain from soil treatment alone plus seed treatment alone. The nematicide soil treatment materials did not influence yield. Tuber stem-end browning and pink eye defects in Kennebec did not increase in severity over a five month storage period.     

Some storage characteristics of potato cultivar Atlantic

The cultivars Atlantic, Kennebec and Katahdin were compared as to their storability and cooking qualities for the storage seasons 1974–75 and 1975–76. The studies show Atlantic was equal to Katahdin and Kennebec with regard to storability, except that at storage temperatures above 40°F (4.5°C) for 6 months, sprouting was excessive. Storage losses due to Fusarium tuber rots from natural infection were higher in Atlantic than either Katahdin or Kennebec. The processing quality for chips and French fries of Atlantic was equal or slightly better when compared to the other varieties tested.     

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.