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1.
Three potato cultivars (Russet Burbank, Norchip, and Gemchip) grown with nitrogen applied at three rates were stored at two temperature regimes (Treatment 1: 13 months at 10 CTreatment 2: 1 month at 10 C; followed by a 1 C decrease per week until tubers were 4 C; followed by 6 months at 4 C; followed by a 1 C increase per week until tubers were 10 C; followed by 3 months at 10 C). Tuber chemical components and potato chip appearance were measured at harvest and after 3, 6, 9, 11, 12, and 13 months; these measurements were performed within 24 hours of the time potatoes were removed from storage. Sugar responses (tuber glucose, fructose, sucrose) and potato chip appearance were affected by cultivar over time in both years and storage temperatures. Russet Burbank tubers displayed a significantly higher glucose forming potential and produced darker appearing chips, regardless of storage temperature or time in storage, compared to Norchip and Gemchip. Potatoes receiving a cold-storage treatment contained less sugar and produced lighter appearing chips after 12 months storage compared to tubers stored at a constant 10 C for 12 months. The linear association between tuber chemical components and potato chip appearance varied with storage temperature.  相似文献   

2.
Models which simulate the development of potato early blight, potato late blight and fungicide dynamics were used to analyze the effects of host resistance, fungicide and weather on individual and combined epidemics of these diseases. Fungicide and host resistance effects were based on (and accurately reflected) products and cultivars available to commercial potato growers in northeastern USA. Moderate resistance to early blight had a 2-3 fold greater effect than did moderate resistance to late blight in suppressing early and late blight, respectively. Analysis of simulation experiments indicated that replacement of an early blight susceptible cultivar with a cultivar moderately resistant to the disease would permit a reduction in the fungicide application frequency from once every week to once every two weeks without loss of disease suppression. Fungicide effect in suppressing late blight was 2-3 fold greater than in suppressing early blight. Variation in seasonal weather (typical of northeastern USA) influenced late blight development more strongly than it affected early blight development, and it affected epidemics of individual diseases more than combined epidemics.  相似文献   

3.
D.E. Groth   《Crop Protection》2008,27(7):1125-1130
The increased number of sheath blight (Rhizoctonia solani)-resistant rice (Oryza sativa) cultivars available will allow producers to use less fungicide and avoid significant reductions in grain and milling yields. Among cultivars currently in cultivation in the southern United States, sheath blight resistance levels range from very susceptible to moderately resistant. A study was conducted to determine the response of cultivars, with different levels of susceptibility, to sheath blight inoculations and fungicide application and to determine the impact of sheath blight disease development on rice yield and quality. Sheath blight epidemics in field plots were initiated by inoculation at the panicle differentiation growth stage in 2006 and 2007. Azoxystrobin at 0.17 kg a.i. ha−1 was applied at mid-boot. Inoculation significantly increased sheath blight severity and incidence and caused yield losses of 8% in moderately resistant cv. Jupiter to 40% in very susceptible cv. Trenasse. Milling yields were affected to a lesser extent. Fungicide treatments reduced sheath blight incidence and severity, regardless of cultivar except in Jupiter. Single azoxystrobin applications were effective in minimizing yield loss due to sheath blight in all cultivars.  相似文献   

4.
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5.
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6.
Three potato cultivars differing in degree of susceptibility to early blight were grown under crop management practices typical for Pennsylvania in 1987 and 1988. There were three experimental treatments: no fungicides, mancozeb with weekly applications initiated at 7 or 8 weeks after planting (early treatment), and weekly applications initiated at first symptoms of disease (late treatment). The no-fungicide control treatment had significantly higher AUDPC values than either treatment with fungicides and the no-fungicide treatment had significantly lower yield in 1987 but not in 1988. Tubers from the no-fungicide control had lower specific gravity. Norchip, the cultivar most susceptible to early blight examined in this study, responded the most in yield increases by the increased fungicide applications.  相似文献   

7.
In both 1981 and 1982, 51 potato fields were surveyed every 7–10 days for early blight severity and fungicide use. Early blight severity data from each field were used as input to a regression model to estimate yield loss in that field. The model for early maturing potato cultivars was Percent Yield Loss=0.8183+0.6441* (% blight increment between days 56 and 66)+0.6102* (% blight increment between days 66 and 76)+1.3480* (% blight increment between days 76 and 86). The model for late maturing cultivars was Percent Yield Loss=2.1846-4.7734* (% blight on day 56)+0.7440* (% blight on day 76)+ 0.5676* (% blight on day 96). In both 1981 and 1982, early blight was found to be present in all fields of the survey. In 1981, early blight was estimated to have caused mean losses of 6.5% (Red River Valley), 3.7% (Central sands) and 2.3% (Southern muck). In 1982, losses from the same areas were 5.4%, 3.7% and 2.6% respectively. In 1981, individual county losses ranged from 2.3% for Freeborn to 12.9% for Marshall while in 1982 losses were from 2.0% for Freeborn to 6.7% for Clay. Although fungicide use data were incomplete, the county with lowest yield loss had the most fungicide applications.  相似文献   

8.
The effect of early blight on tuber yield of two potato (Solanum tuberosum L.) cultivars (Russet Burbank and Norland) was evaluated using number and timing of applications of three chemicals to generate different disease epidemics in 1981 and 1982. Under the non-irrigated farming conditions in Minnesota, there were no significant differences among captafol, triphenyltin hydroxide and maneb-Zn in blight control to increase yield. Of the five spray schedules tested, a 7–10 day spray schedule initiated when blight severity exceeded 0.01%, and a 7–10 day schedule initiated when blight was found above the lower third of the plant, generally gave significant, positive yield responses with all three chemicals. At Rosemount in 1982, the greatest yield increases (relative to unsprayed) obtained were 34.9% and 48.6% in total tuber yields for Norland and Russet Burbank, respectively. At Rosemount in 1982, the highest yield increases (relative to unsprayed) obtained were 92.2% and 56.6% in total tuber yields for Norland and Russet Burbank respectively. At Grand Forks in 1981, the highest yield increases were 126.8% and 34.6% in total tuber yields for Norland and Russet Burbank respectively. Across all three experiments, maximum yield losses (percentage of [[yield of ‘healthy’—yield of unsprayed check]/yield of ‘healthy’’]) were 58.4% (US #1 tubers) and 55.9% (total tubers) for cv. Norland and 34.4% (US #1 tubers) and 36.2% (total tubers) for cv. Russet Burbank.  相似文献   

9.
Summary Potato cultivars of different maturity classes and levels of resistance toPhytophthora infestans were grown under several disease intensities in three field trials. Seasonal courses of ground cover by green foliage and final tuber yields were determined. Light use efficiencies (LUE) were calculated from regression analyses of yield on cumulative light interception. Late blight reduced tuber yields by decreasing cumulative light interception without affecting LUE. No differences in LUE between cultivars or cultivar classes were detected. Therefore, the maintenance of green leaf area is important when breeding potatoes for optimal performance in the presence of late blight. The results support the hypothesis that the correlation between lateness and reported resistance of potato cultivars is due to the vigorous foliage growth of late cultivars.  相似文献   

10.
Narrow brown leaf spot (NBLS) of rice (Oryza sativa L.) is caused by Cercospora janseana (Racib). O. Const. (Synonyms: Cercospora oryzae Miyake, Passalora janseana Racib. U.). Experimental studies were conducted at Rice Research Station, Louisiana State University, and Agricultural Center, Crowley, to manage NBLS by fungicide application of propiconazole at different growth stages of rice cultivars having different susceptibility levels to NBLS in different planting dates. Results of these studies revealed that April (early) had less NBLS severity as compared to May (late) planting. Very susceptible cultivars, CL131 and Cheniere, had the highest and resistant cultivars, Della and Presidio, had the lowest NBLS severity at both the planting dates. Propiconazole application significantly reduced the NBLS severity in comparison to untreated. Fungicide application at panicle initiation was the most effective time to manage NBLS on the very susceptible and susceptible cultivars at both planting dates. NBLS on moderately susceptible cultivars was best managed by applying fungicide either at panicle initiation or early boot stage in early planting but panicle initiation was the best time to apply fungicide in late planting. Resistant cultivars did not need fungicide in April planting but did need in May planting. Rice yield was determined to be higher in April than May planting. Fungicide application at early boot stage protected the yield by 9.4% in April planting and 34.2% when applied at panicle initiation in May. Susceptible cultivar, Cheniere, exhibited the greatest yield and resistant cultivars had lowest yield in both the planting dates regardless of its susceptibility level to NBLS. Yield of very susceptible to susceptible cultivars was reduced in late planting but no effect was observed on yield of moderately susceptible and resistant cultivars.  相似文献   

11.
Three soybean [Glycine max (L.) Merr.]cultivars (Samsoy 1, TGx 1025-12E and TGx 996-26E) were evaluated for yield losses resulting from frogeye leaf spot caused by Cercospora sojina Hara. Replicated field plots were established at two locations in Nigeria that have a high natural infestation of C. sojina. The cultivars were either not sprayed, sprayed once or sprayed twice during the growing season with the fungicide benomyl. Disease spread early in the season was from border rows of a susceptible soybean cultivar into the plots. Mean disease severity (DS) for unsprayed cultivars ranged from 0.6 to 4.5 on a scale of 0–5. Plots receiving two sprays had lower DS values, ranging from 0.5 to 2.4. Differences between unsprayed and double-sprayed plots for yield and 300-seed weight ranged from 2.5 to 58.8 and 0.6 to 28.6%, respectively. Seed weight was negatively correlated with DS.  相似文献   

12.
Nipigon is a high-yielding, early sizing, table potato with good boiling and baking quality and is specifically adapted to northern Ontario. It has some resistance to late blight, rhizoctonia and viruses X and Y. The Nipigon potato was bred and initially selected within the Potato Breeding Project at the Fredericton Rcsearch Station of Agriculture Canada. This variety has been under test as seedling F61051 since 1965 throughout eastern Canada, but mostly in Ontario. Nipigon was selected from the progeny of a cross between two Fredericton seedlings; F53026 an early, scab-resistant seedling with very good tuber type and F51043, which has good processing quality and resistance to the common races of late blight,Phytophthora infestans (Mont.) de Bary. The pedigree is as follows:   相似文献   

13.
The purpose of this study was to identify when the critical period for control of early blight occurs and thus the need to initiate a spray schedule of protectant fungicides. The initiation of weekly fungicide spray schedules was staggered to identify the critical period. The accumulation of 400 P-Days, environmental conditions favorable for sporulation, spore dissemination and plant infection and airborne spores ofA. solani were detected prior to the critical period each year. Since early blight is a disease of old plants, host susceptibility appeared to be involved in the timing of the critical period in addition to favorable weather and the presence of the pathogen. A measure of potato plant development, and therefore susceptibility toA. solani, is needed to adequately predict the critical period. The accumulation of 400 P-Days may aid in the prediction of the critical period by estimating the time of plant susceptibility and therefore the timing of the first necessary fungicide spray.  相似文献   

14.
The goal of this research was to evaluate the management techniques of cultivar selection, fungicide application number, fungicide spray timing, and nitrogen rate management. Cultivars of Superior, Shepody, and Russet Burbank were observed to differ in disease severity and yield. White mold was observed to be a yield limiting factor for Superior with r2 values of 0.65 and 0.66 for the relationship between white mold severity and total and marketable yield, respectively. In contrast, Russet Burbank and Shepody had only 2 % to 4 % of yield variation explained by white mold severity. Superior showed significant yield responses to two boscalid applications as opposed to one or zero, and was the only cultivar to show a response to fungicide application number. Analysis of fungicide application timing showed discrepancies between responses of severity (quadratic effect) and yields (linear effect). Lowest severity was modeled to be at applications made at peak flowering, while highest yields were modeled to be at applications made prior to. Nitrogen rates were observed to affect white mold incidence whereby disease counts were elevated at nitrogen application rates below 134 kg/ha as compared to application rates in excess of 134 kg/ha.  相似文献   

15.
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.  相似文献   

16.
Regression analyses were performed on field data from 1981 and 1982 to determine models for estimating yield loss caused by early blight in potato cvs. Norland and Russet Burbank. Percent yield loss (total tubers and US# 1 tubers) caused by early blight could not be satisfactorily explained by any regression model using only a single disease assessment as the input variable. Several multiple point models, which explained more than 70% of the variation in yield loss due to early blight, were determined for each cultivar. The models for cv. Norland used either early blight severity assessments on days 56, 66, 76 and 86 after sprout emergence, or blight severity increments for 10-day periods among days 46–86, as the input variables. The models for cv. Russet Burbank used the same input variables as for cv. Norland and additionally, blight severity on day 96. Yield loss in US#1 tubers was a more stable variable than loss in total tubers for estimating early blight effect.  相似文献   

17.
For organic potato producers the two main challenges are disease and nutrient management. Both factors are limited by regulations that on the one hand prohibit the use of chemical fertilisers, especially nitrogen and, on the other hand, most synthetic pesticides. Late blight, caused by Phytophthora infestans is commonly thought to be the factor most limiting yield. However, because there is no really effective fungicide available to control late blight, there are virtually no yield loss data available for organic farming conditions. In this paper the state of the art of organic potato management with respect to disease and nutrient management is summarised. In a second part, the interactive effects of N-availability in the soil, climatic conditions and late blight were studied in the presence and absence of copper fungicides from 2002–2004 for the mid-early main-crop potato cv. Nicola. From the experimental work it became clear that copper fungicides in most cases do slow down epidemics adding an average of 3 days to the growth duration. However, only 30% of the variation in yield could be attributed to disease reduction. A model including disease reduction, growth duration and temperature sum from planting until 60% disease severity was reached, and soil mineral N contents at 10 days after emergence could explain 75% of the observed variation in yield. However, the model failed when N-supply was extremely high. The implications of the results on the management of organic potatoes with respect to cultivar choice, nutrient and disease management are discussed. In conclusion, several points emerge from the results: In organic farming, yields are foremost limited by nutrient availability in spring and early summer. The effects of late blight on yields may often be overestimated and cannot be deducted from results in conventional farming because of the strong interaction with nutrient status. Resistance clearly remains the most important strategy against late blight in organic potato production. However, as important or even more important than resistance is the early development and bulking behaviour and the ability of a cultivar to make use of organic nutrients efficiently. In the absence of efficient organic pesticides it is possible to reduce blight pressure to a certain extent by arranging the crop in small narrow fields perpendicular to the main wind direction neighboured either by non-hosts or completely resistant potatoes.  相似文献   

18.
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19.
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.  相似文献   

20.
Elicitors of systemic acquired resistance are well known to reduce severity of several plant pathogenic diseases caused by fungi, bacteria and viruses. Their field applications for management of plant diseases are, however, limited because of yield penalties. Our studies on affect of Benzo (1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), an elicitor of systemic acquired resistance, on chickpea blight caused by a fungal pathogen Didymella rabiei showed that multiple foliar applications of the chemical were effective in management of the disease under economic threshold levels. Multiple applications, however, affected chickpea grain yield adversely. The BTH induced yield penalties could be prevented by foliar spray schedule comprised of BTH and a contact fungicide mancozeb. One spray of BTH (50 ppm) followed by another of mancozeb (0.2%) was less effective (8.3% severity) than three sprays of BTH (4.2% severity) in blight control, however, this treatment enhanced grain yield significantly (1.241 t ha−1) over three sprays of BTH (0.922 t ha−1).  相似文献   

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