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1.
Summary The viability of five pathogens was decreased by treatment with hot water when tested in vitro.Polyscytalum pustulans was most sensitive andRhizoctonia solani least sensitive.
Potato tubers were exposed to 55°C for 5 min in a commercial continuous hot water treatment plant using naturally contaminated
seed tubers and tubers which had been inoculated by dipping in comminuted cultures. The frequency of eyes colonised byP. pustulans, Helminthosporium solani, andR. solani was reduced to virtually zero and the effect persisted on tubers subsequently stored at 4°C and at 15°C for up to 16 wk.
Results withColletotrichum coccodes were inconclusive. Treatment suppressedPenicillium spp. which, however, rapidly recolonised the eyes during storage, leading to higher contamination levels in the treated than
in the untreated tubers. With tubers inoculated withPhoma foveata, good control was achieved when the incubation period before treatment was 10 d but not when the period was 42 d. 相似文献
2.
Summary Seed tubers, cv. Désirée, derived from stocks treated annually with thiabendazole were infected with thiabendazole-resistant
strains ofHelminthosporium solani andPolyscytalum pustulans. Samples of seed tubers were either untreated or immersed for 5 min in fungicide suspensions of thiabendazole, imazalil or
thiabendazole plus imazalil and planted on four farms in 1988 and 1989. After harvest, tuber samples from each treatment were
treated with thiabendazole and stored for 6 months.
Applying imazalil or thiabendazole plus imazalil to seed tubers decreased the severity of silver scurf and skin spot on stored
progeny tubers. Thiabendazole applied to seed tubers or to progeny tubers after harvest did not affect the severity of either
disease, but post-harvest treatment decreased the incidence of black scurf after storage. 相似文献
3.
Summary Survival of the pathogen causing silver scurf of potato (Helminthosporium solani) in Alberta soils was studied by evaluatingH. solani infection in the progeny ofH. solani-free nuclear seed potato tubers planted in fields where potatoes had never been grown or were grown 1, 2, 3, or 4 years previously.
Daughter tubers from all the fields developed silver scurf lesions, andH. solani was isolated from infected tubers. This is the first report of survival ofH. solani in Alberta soils. Soil-borne inoculum appears to have a role in the epidemiology of the disease and in the introduction of
the pathogen into silver scurf-free potato seed stock. Of 31 plant species tested, only potato was found to be a host ofH. solani. Most of theH. solani isolates from north central Alberta were more sensitive to thiabendazole than those from southern Alberta, where thiabendazole
is much more commonly used. 相似文献
4.
Summary Field-grown tubers of 22 progenies ofSolanum tuberosum L. generated in a crossing programme involving seven parents differing in resistance toFusarium coeruleum Lib. ex Sacc. andF. sulphureum Schlect. (=F. sambucinum Fuckel, teleomorphGibberella pulicaris (Fr.) Sacc.) were wound-inoculated with a cornmeal + sand culture of each pathogen. Parental genotypes were also included.
The mean lesion size of each progeny was compared in 2 years of tests, as well as with published data on glasshouse-grown
tubers. ForF. coeruleum there was a high correlation between years as well as with the glasshouse data, but no such correlations were apparent withG. pulicaris. Furthermore, parental and GCA values, as well as progeny means and mid-parent scores, also correlated highly forF. coeruleum but not forG. pulicaris.
Glasshouse-grown tubers of 11 wildSolanum spp. were also inoculated with both pathogens. Some resistance to one or other, or both, was apparent, particularly inS. chacoense. 相似文献
5.
Summary The resistance to gangrene (caused byPhoma exigua var.foveata) of progenies from two hybridisation schedules involving cultivars resistant, susceptible, or of intermediate reaction to
gangrene was assessed. Two methods of sampling tubers from field-grown single-plant plots of 18 clones representing each progeny
were used: one tuber was taken from each plant, and a bulk sample of 18 tubers was selected at random from the whole progeny.
Gangrene resistance was assessed after incubating tubers which had been rolled in cornmeal-sand inoculum ofP. exigua var.foveata, and was expressed as a percentage of tubers infected. Results from the two methods of sampling correlated closely, and agreed
well with tests in a subsequent year on 10-tuber samples of each individual clone.
It is concluded that an 18-clone sample adequately represented each progeny, and that the mid-parent gangrene score satisfactorily
predicted the resistance of the resulting progeny. There are indications that susceptibility tended to be dominant. The implication
of these findings to breeding for resistance to gangrene is discussed. 相似文献
6.
Summary The highlands of South America are the probable geographic origin for the potato gangrene fungusPhoma exigua var.foveata (Foister) Boerema which was found parasitizing plants ofChenopodium quinoa in the Altiplano area of Peru. In vitro studies showed no dissimilarities between it and the antibiotic ‘E’ producing virulent
European isolates ofP. exigua var.foveata. It is as pathogenic to potatoes as the virulent European isolates but onC. quinoa andC. album it is more pathogenic than the European isolates. So far the fungus has not been found on potato tubers in South America
and the reasons why gangrene problems have not arisen there are discussed. 相似文献
7.
Summary Seed tubers were immersed in suspensions of thiabendazole (Storite) or thiabendazole plus imazalil (Extratect) at different
concentrations and planted in a field experiment. During the following 2 years samples of the produce were planted after treatment
with the same fungicide formulation used on the seed.
Silver scurf on daughter tubers decreased as concentrations of fungicide increased and Extratect gave better disease control
than Storite applied at the same thiabendazole concentration. Isolates ofH. solani resistant to thiabendazole were found on seed tubers 6 weeks after treatment with Storite, and also on daughter tubers after
the first application of the higher rates of Storite; their incidence increased with further annual treatments. In 3 years
no thiabendazole-resistant isolates were found after treatment with Extratect. Chlamydospores ofH. solani developed when sensitive isolates were subcultured onto agar containing thiabendazole. Isolates sensitive to thiabendazole
were slightly more sensitive to imazalil than resistant ones. 相似文献
8.
Ulla Bång 《Potato Research》1989,32(1):101-112
Summary Various haulm treatments and harvest times differentially influenced the incidence of storage rots in potato tubers (Solanum tuberosum L.) in field experiments in Sweden performed over 4 years. The incidence of gangrene caused byPhoma foveata Foister (Phoma exigua var.foveata (Foister) Boerema) increased in cv. Bellona after spraying haulms with diquat as did the amount of infection caused byFusarium avenaceum (Corda ex. Fr.) Sacc. in all three cultivars (Bintje, Bellona, and Magnum Bonum). The lowestP. foveata infection levels occurred after pulling haulms. Late harvesting increased the frequency ofP. foveata in cvs Bintje and Bellona both at 2 and 4 wks interval between haulm treatment and harvest. Tuber and visible stem infection
caused byP. foveata were correlated for cvs Bintje and Bellona, but not for cv. Magnum Bonum. The possible relation between tuber and stem infection
is discussed. 相似文献
9.
Ulla Bång 《Potato Research》1991,34(4):429-441
Summary The incidence ofP. foveata in soil and tuber samples from field experiments often increased significantly as the harvest season progressed and temperatures
fell. Mean levels of tuber and soil infestation were significantly higher in irrigated rows compared with those artificially
sheltered from precipitation, both at normal and late harvest dates.
Soil infestation was most frequently detected within 10 cm of the parent tuber. No pycnidia were visible on the haulm, and
very few latently infected stem segments and leaves were detected using various methods.
In three out of four years, the incidence ofP. foveata in tubers after wounding was reduced by washing them gently in tap water immediately after harvest. 相似文献
10.
Mary J. Frazier Kiran K. Shetty Gale E. Kleinkopf Phillip Nolte 《American Journal of Potato Research》1998,75(3):129-135
Thiabendazole insensitive strains ofHelminthosporium solani, the causal agent of silver scurf, make controlling the disease with seed treatment difficult. Potato tuber seed treatments and environmental storage management practices were investigated as means to minimize silver scurf. Fungicide seed treatments were evaluated for control ofH. solani; disease was evaluated during the growing season, at harvest, and after 5 months of storage. Silver scurf was observed on progeny tubers eleven weeks after planting. Fungicides that reduced silver scurf incidence and severity on the seed resulted in reduced incidence and severity of the disease in the progeny tubers at harvest and significantly lower disease ratings after storage. Only small increases in disease incidence (0-8%) were seen after storage. Thiophanate-methyl with mancozeb, Captan with mancozeb, and fludioxonil were among the most effective in reducing the incidence and severity of silver scurf on seed and in progeny tubers (Incidence on progeny tubers at harvest for these three treatments were 3%, 9%, and 8% respectively). Thiophanatemethyl alone was not effective for control of silver scurf (48% incidence compared to 43% incidence for the untreated control). Environmental conditions in storage affected disease development. Reduced humidity (85%) during the curing period (0–3 weeks after harvest) significantly reduced (11%) the surface area of tubers infected with silver scurf. Free moisture on the tuber surfaces during storage significantly increased (15%) tuber surface area infection.H. solani was shown to survive in soil and on some potato storage building materials for up to 9 months. The silver scurf disease of potatoes can be suppressed using effective seed treatment and storage management. 相似文献
11.
H. W. Platt 《American Journal of Potato Research》1992,69(3):179-186
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. 相似文献
12.
The occurrence, pathogenicity (1997 isolates only) and fungicide sensitivity of pathogens causing dry tuber rots in Scottish
seed potatoes was investigated over three storage seasons between 1997 and 2000 in relation to region of production, cultivar,
class and generation of seed potatoes, type of temperature control in store and earthiness of tubers. A total of 156 samples,
each comprising up to ten rotted tubers, was received over the three seasons. The relative importance of each pathogen in
causing rots was summarised by calculating a mean rot index that combined the prevalence of a pathogen in the samples with
the incidence of tubers affected by the pathogen within those samples. Phoma foveata (gangrene) had the highest rot index, which was five times greater than for P. exigua and ten times greater than for P. eupyrena. This relationship was mirrored by the relative pathogenicities of P. foveata and P. eupyrena, as measured by size of rots developing at inoculated wounds in test tubers. Fusarium avenaceum appeared to be the greatest cause of Fusarium dry rots, having a rot index at least twice as great as that for F. solani var. coeruleum. Infection by F. sulphureum was relatively uncommon. In the pathogenicity test, F. avenaceum, F. solani var. coeruleum and F. sulphureum produced rots of similar depths and widths and larger than those of F. culmorum. The mean rot index for Cylindrocarpon spp. was slightly more than that for F. avenaceum, whereas C. destructans produced smaller rots in the tuber pathogenicity test. Region of production affected the prevalence of P. foveata and F. avenaceum, but only the occurrence of P. foveata was affected by class and generation of seed potatoes. Isolate sensitivity to thiabendazole and imazalil was examined in
vitro over 2 years. Six out of seven isolates of F. sulphureum were resistant to thiabendazole, with the remaining isolate being partially resistant. The growth of two out of 34 isolates
of F. avenaceum was inhibited by more than 50% only at 100 mg thiabendazole l−1. All isolates, except those of F. avenaceum,, were inhibited in their growth by more than 50% at either 1 or 10 mg imazalil l−1. However, the growth of 40% of isolates of F. avenaceum was inhibited only at 100 mg l−1. The various changes in pathogen prevalence and isolate sensitivity to fungicides recorded in this study highlight the need
for regular monitoring programmes to be conducted in order that disease-control strategies can remain effective. 相似文献
13.
Summary The sesquiterpenes 2-(1',2'-dihydroxy-1'-methylethyl)-6,10-dimethyl-spiro-[4,5]dec-6-en-8-on (1) and its 2'-O-β-d-glucopyranoside (2) were isolated from the stress zones of potato tubers infected withPhoma foveata andFusarium spp., and rishitin and solavetivone from tuber slices inoculated withErwinia carotovora. The influence of these compounds, and of the naturally occurring plant sesquiterpenoids abscisic acid, cedrol and farnesol,
on the mycelial growth ofPhytophthora infestans were tested on agar plates using a defined medium. All sesquiterpenoids suppressed the growth of the pathogen, except for1 and its glucoside2 which induced a slight, however significant, growth stimulation. Compounds1 and2 could not be isolated fromE. carotovora orP. infestans-inoculated tuber tissue. 相似文献
14.
Summary An interaction betweenP. infestans andE. carotovora subsp.atroseptica (Eca) in rotting tubers was confirmed and the biochemical basis for its occurrence investigated. The pH of tissue infected
withP. foveata became alkaline whereas tissue infected withP. infestans orF. coeruleum did not rise above neutrality, which could promote pathogenicity of Eca by maintaining pH closer to the optimum for polygalacturonase
activity. Polygalacturonase, pectate lyase and galactanase were detected in cultures of all three fungi grown on media containing
cell wall material or pectin from tubers. AsP. infestans produced more polygalacturonase than the other two fungal tuber rot pathogens the possibility was investigated that oligogalacturonide
products of enzymatic degradation of pectin byP. infestans stimulates pathogenicity of Eca. However, while tubers soft-rotted after infiltration with supernatant from fungal cultures
grown on tuber cell wall material, controls showed that rotting resulted from infiltration rather than the products contained
in the infiltrated water. 相似文献
15.
Enrichment techniques and serological strain typing methods were used to determine the source of stem and progeny tuber populations ofErwinia carotovora (Ec) in 1980 and 1981. Plots were established in a field that had been planted with potatoes since 1972. Seed tubers of cultivars Russet Burbank and Norgold Russet were assayed forErwinia carotovora pv.carotovora (Ecc) andErwinia carotovora pv.atroseptica (Eca) by tuber peeling and direct plating and plating following enrichment in a pectate-based broth. Levels of seed tuber infestation ranged from undetectable to 2.4 × 104 colony-forming units per g peel tissue. Prior to planting Ecc was detected in soil samples from field plots by enrichment in a pectate-based broth. Ec was isolated from symptomless plants with increasing frequencies from 8 weeks following planting regardless of the level of Ec populations in seed tubers. At harvest progeny tuber recontamination was low and not related to levels of seed tuber Ec populations. In 1980, serological typing of representative Ecc isolates indicated serogroups III, XXIX, and unknown strains isolated from the soil but not the seed tubers prior to planting were isolated from stems and progeny tubers. Serogroup XXIX was isolated from soil, seed, stems and progeny tubers in 1981. Throughout both years, Ecc was isolated more frequently than Eca from seed, soil, stems, and progeny tubers. These data emphasize the potential for reinfestation of seed stocks and infection of plants by populations of Ecc that overwinter in soil under Wisconsin conditions. 相似文献
16.
S. H. De Boer J. D. Janse D. E. Stead J. Van Vaerenbergh A. R. McKenzie 《Potato Research》1992,35(2):207-216
Summary An indirect sandwich enzyme-linked immunosorbent assay (ELISA) was used to monitor potato stems of three cultivars for the
presence of the ring rot pathogen,Clavibacter michiganensis subsp.sepedonicus, during the growing season and in progeny tubers after harvest. The highest ELISA values were obtained with the highest concentration
of bacteria used to inoculate seed pieces in all cultivars tested. Low ELISA values were obtained for stems and progeny tubers
selected from plants grown from seed inoculated at lower bacterial concentrations. Estimates of bacterial densities in stems
and progeny tubers by immunofluorescence indicated that low ELISA values were most probably caused by low bacterial numbers.
It is suggested that the sensitivity of ELISA for detecting the ring rot pathogen in potato stems and progeny tubers is a
function of the concentration of bacteria in individual seed pieces. 相似文献
17.
Summary Potato seed tubers infected withHelminthosporium solani andColletotrichum coccodes were treated with prochloraz (as Omega 450 g a.i. l−1 EC) and/or prochloraz managanese chloride (as Octave 25 g/kg DP), and planted in two separate fields not previously cultivated
with potatoes. Dipping seed 28 d prior to planting in 2,4 or 6 g a.i. l−1 Omega, and dusting with 500 or 750 g Octave per 100 kg seed significantly reduced the incidence of silver scurf and black
dot on progeny tubers. In one field, the higher concentrations of Omega and Octave gave slightly better control than the lower
Omega concentrations. At the second site, postharvest application of 4 g a.i. l−1 Omega or 750 g Octave per 100 kg seed limited development of both diseases on progeny tubers, with slightly better control
when an additional Octave dusting was applied 14 d before planting. None of the prochloraz treatments adversely affected plant
stand or tuber yield. 相似文献
18.
Summary Tubers were obtained from 80 glasshouse-grown seedlings of each of twelve progenies, inoculated withPhoma foveata Foister, and the mean percentage of infected tubers recorded. There was a good correlation (r=0.798) between this assessment and that made previously on field-grown tubers of eleven of the progenies. A gangrene test
on glasshouse-grown tubers is suggested as a more rapid means of identifying progenies with useful levels of resistance. 相似文献
19.
Ulla B?ng 《Potato Research》2007,50(2):185-203
The potential utility of natural volatiles in various essential oils (EOs) from plants as fumigants to control potato tuber
(Solanum tuberosum L.) pathogens was assessed. The antifungal effects of the volatiles at various concentrations were studied at 10 °C both
in vitro using conidial suspensions of Helminthosporium solani, Fusarium solani var. coeruleum and Phoma foveata plated on agar, and in vivo by inoculating potato tubers. The effects of the volatiles on the mycelial growth of Rhizoctonia solani were also studied, but only in vitro. Vapours of many of the EOs tested exhibited some fungicidal activity but volatiles
of garlic, Allium sativum, were, with few exceptions, most effective on all four pathogens in all experiments. An exposure time of at least 2 weeks
was usually required for good control of disease development in vivo. Vapours of A. sativum never stimulated conidial germination, as was observed with some other oils, or damaged tubers, but those of Armoracia rusticana caused tuber collapse. Volatiles from thyme (Thymus vulgaris) EO showed antifungal activity in vitro on all four pathogens, but did not control F. solani, P. foveata or H. solani in vivo. In contrast, sage (Salvia officinalis) EO was ineffective against P. foveata and H. solani in the in vitro system, but controlled disease development in vivo at similar doses. The sometimes conflicting results obtained
in the two test systems show that screening in vitro only is insufficient for evaluation of potent antifungal substances to
be used in practice. 相似文献
20.
Summary High grade potato seed tubers of three cultivars were inoculated in Scotland by vacuum infiltration in suspensions ofErwinia carotovora subsp.carotovora and subsp.atroseptica in different combinations, and transported to Valencia, Spain. They were cut into two to three pieces and planted in January
1984, 1985 and 1986 in fields furrow irrigated before and after emergence. High incidences of blanking and blackleg were associated
with seed inoculated with high numbers ofE.c. atroseptica alone or together withE.c. carotovora and not with high or low numbers ofE.c. carotovora alone.E.c. atroseptica predominated at emergence in March in rotting seed pieces which failed to produce a plant, regardless of the seed treatment,
and in diseased stems in April but it was replaced byE.c. carotovora in May. The levels of blanking and blackleg after inoculating 16 cultivars with both erwinias were not correlated between
years nor were they significantly different within years among most of the cultivars. 相似文献