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1.
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 相似文献
2.
Summary
Phytophthora infestans isolates collected in Poland in 1987–1995 were evaluated on detached leaflets of a differential series consisting of potato
genotypes possessing resistance genes R1–R11. On the same differentials was evaluated over three years a highly virulentP. infestans isolate MP 245.
Isolate MP 245 and those from natural populations ofP. infestans were seldom or inconsistently pathogenic to R5, R8 and R9. When leaflets of the differentials were infected with MP 245 the
lesions were often small and sporulation weak. A statistically significant interaction was found between years and pathogenicity
of MP 245 to individual differentials. Attempts to train the isolate MP 245 for pathogenicity to R9 were unsuccessful.
The variation in specific resistance of potato genotypes may complicate the evaluation of their resistance toP. infestans, as well as the evaluation of the virulence spectrum of natural fungus populations. This variation may be due to changes
in specific pathogenicity of the fungus or in specific resistance of the potato. Some differentials have a possibly useful
resistance toP. infestans. 相似文献
3.
Summary A single blighted tuber released on average 1.39 mg ofP. infestans mycelia and sporangia during simulated washing. In subsequent experiments up to 100% of tubers were infected when healthy
tubers were washed in a suspension ofP. infestans equivalent to a concentration of 1.65 μg ml−1, i.e. that calculated to be in a commercial washing plant after washing a potato stock with approximately 1% of tubers infected
with blight for 4 hours. Immature tubers were more prone to infection during washing than mature tubers. Damaging tubers,
irrespective of their maturity, increased the incidence of tuber infection. The viability ofP. infestans isolates was significantly reduced byin vitro immersion in water at 44°C for 5 minutes. The infection of daughter tubers dipped in a suspension ofP. infestans for 3 minutes was prevented when the suspension temperature was 44°C. There was no indication of tuber damage at this temperature. 相似文献
4.
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. 相似文献
5.
Summary In 1983 and 1984 there were reports in Norway of more severe late blight infection than usual on tubers of cv. Pimpernel,
a cultivar without R-genes known to be somewhat resistant to both haulm and tuber infection. Results from routine tests confirmed
earlier experience that cv. Pimpernel shows stable resistance to tuber late blight, although the ranking of cultivars may
vary between years.
In experiments during three harvest seasons tubers of different cultivars were inoculated with isolates ofP. infestans obtained from stocks of cv. Pimpernel with severe tuber late blight and with other isolates. In these experiments the isolates
from cv. Pimpernel caused more rot on tubers of Pimpernel than did other isolates. 相似文献
6.
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
7.
Summary Available information has been reviewed on tuber resistance toP. infestans, its inheritance and breeding procedures used to obtain potato cultivars superior in this character.
P. infestans is worldwide the most destructive potato pathogen. Tuber resistance is an essential component of potato resistance as this
pathogen is often responsible for tuber rot in storage, and infected tubers of susceptible cultivars provide an important
way for its overwintering.
In Europe many cultivars and advanced breeders selections have been obtained with tuber resistance toP. infestans, but in the last decades no progress is noted in the mean level of this resistance in cultivars. The expression of tuber
resistance depends to a large extent on testing conditions and therefore it can be difficult to evaluate. Consequently making
progress in breeding is not easy, and also cultivar assessment data from various countries sometimes differ considerably.
It is concluded from published data that it should be easier to make progress in breeding potato cultivars with resistant
tubers if more attention is paid to combining the various types of resistance which are already known, and if the genetic
determination of durable resistance toP. infestans is better understood.
Professor Dr. K.M. Świeżyński passed away on 27th July 2000 相似文献
8.
Summary Laboratory experiments and observations in commercial stores showed that viable sporangia ofPhytophthora infestans can be produced on infected potato tubers of different cultivars. Infection was also found to spread from diseased to healthy
tubers during handling. 相似文献
9.
Summary Formulae which determined tuber surface area from tuber dimensions and weight were tested by using samples from three potato
cultivars. Surviving populations of a labelled isolate ofErwinia carotovora ssp.atroseptica following planting, and populations of a fluorescent pseudomonad following dusting with a bacterial powder formulation were
used to demonstrate the application of these formulae to the calculation of bacterial density on the tuber surface. Results
obtained by washing whole tubers using the formulae to calculate the surface area were shown to be comparable in sensitivity
with those obtained by dilution-plating of periderm discs of 1cm2. 相似文献
10.
Summary Of 250 isolates ofPhytophthora infestans obtained from Northern Ireland potato crops between 1981 and 1993, only six proved to be of the A2 mating type, the remainder
being A1. The first A2 isolate was obtained from a tuber in 1987. The frequency of A2 isolates from 1987 onwards was 3%, a
lower incidence than has been reported for England and Wales and the Republic of Ireland. There was no association between
phenylamide resistance and mating type. 相似文献
11.
D. Andrivon 《Potato Research》1994,37(3):279-286
Summary Nineteen races were found among 116 isolates ofPhytophthora infestans recovered from French potato and tomato crops during 1991–1993. The most common races were 1.3.4.7.11. 1.3.4.7.8.11 and 1.3.4.7.10.11
in 1991, race 1.3.4.7.11 in 1992, and race 1.3.4.7.10.11 in 1993. None of the isolates was virulent to either R2 or R6, and
only one to R5. The mean number of virulences per isolate was 5.78 in 1991, 4.35 in 1992 and 4.53 in 1993. TheP. infestans population from Brittany showed mainly quantitative changes in the frequencies of major races over the period investigated,
but races identified were almost the same in all 3 years. No geographical substructure was apparent, since variation between
locations accounted for only 13–22% of the total racial diversity within the Brittany population. This is interpretated as
evidence for limited gene flow in this population, which is believed to have evolved from a few founding genotypes. 相似文献
12.
C. B. Wegener 《Potato Research》2001,44(4):401-410
Summary Four potato lines of cv. Désirée that express the pectate lyase (PL) isoenzyme 3 ofErwinia carotovora subsp.atroseptica were examined in a 4-year field experiment with respect to plant development, tuber yield and resistance of tuber tissue
toErwinia soft rot. The PL3 degrades plant cell wall pectin into unsaturated oligogalacturonates eliciting plant defence responses.
In one line, enzyme expression was controlled by the CaMV 35S promoter (C) and in three lines it was driven by the potato
patatin B33 promoter (D). Plant development of the D-lines in field plots was not distinguishable from that of the non-transgenic
counterpart. Also tuber yield was not too different. By contrast, plants of the C-line were smaller than those of the nontransformed
counterpart and also showed reduced tuber yield. There were no significant differences in dry mass, starch and protein content
of tuber tissue between PL transgenic and non-transgenic potatoes. But compared with the latter, field-grown tubers expressing
the PL displayed an enhanced resistance toErwinia soft rot. Thus, average rotting caused byEc-bacteria was diminished in tubers of PL-transgenic lines by 34.1%. The resistance of tubers toEc soft rot was significantly correlated with the PPO activity in tuber tissue. 相似文献
13.
The goal of these studies was to evaluate the influence of tuber age on the expression of resistance to Phytophthora infestans in five selected potato genotypes (three cultivars and two clones) varying in tuber resistance and maturity type, and also
to select the best time for testing potato tubers for resistance to blight. Resistance was evaluated by inoculating whole
tubers at 13 different times as they progressively aged during growth and storage. Tuber age was expressed as weeks after
planting. Tubers were rated from week 13 (late July) until week 43 (late February) for tubers planted on 27–28 April, over
three consecutive seasons (2001–2003). Analysis of variance performed on tuber resistance data showed significant effects
of genotype, year and tuber age. Significant contributions of genotype × year, genotype × tuber age, year × tuber age and
year × genotype × tuber age interactions were also detected. A slight increase in tuber resistance with tuber age was observed
for cvs Bzura, Sokół and Irga, while the opposite trend was observed for the clones 97-A-63 and DG 92-227. Changes in tuber
resistance with age of tested genotypes were not related to their maturity type. The period of most stable expression of tuber
resistance was observed when tubers were tested between the 16th and 28th week after planting. 相似文献
14.
Outbreaks of late blight occurred in commercial potato fields in northwestern Washington in 1989 and reached epidemic proportions in 1990. Since most blighted fields reportedly had received 2–4 late-season applications of metalaxyl, the possibility existed that pathogenic strains ofPhytophthora infestans had developed resistance to this systemic fungicide. In testing this hypothesis,P. infestans was isolated consistently from diseased leaves, stems, and tubers of potato when small tissue pieces were surface-disinfected in 0.5% NaOCl for 3 min. Virulence of isolates was assessed on detached leaflets of eight differential (R-gene) potato genotypes. Although simple races (single and double) were recovered, there was also a high frequency of complex race combinations. When tested in metalaxyl-amended media, 81% of the 73 isolates recovered from diseased tissues were highly resistant to 10 μg metalaxyl/ml and 19% yielded intermediate resistance. Sensitive isolates were not recovered. Fifty-five percent of 40 isolates sporulated on potato tuber disks in the presence of ≥10 ug metalaxyl/ml. On leaf tissues, 85% of 20 isolates sporulated in the presence of 10 μg metalaxyl/ml, and 50% sporulated in the presence of 100 μg/ml. This is the first report ofP. infestans resistance to metalaxyl in the U.S. 相似文献
15.
Summary A study was carried out on eightF. oxysporum f.sp.tuberosi isolates from northern Italy. Six were from rotten tubers and two were from weak, but not wilted plants from seed-growing
areas. Greenhouse and laboratory tests were done to assess the pathogenicity and potential spread of the fungus within the
plant. All isolates caused dry rot on inoculated tubers. They were also able to infect vascular tissues through roots and
leaves, but none caused wilt, stemend rot or other symptoms.F. oxysporum is often not visible in the field, but its propagules can increase under favourable conditions. It may therefore become a
potential danger during potato storage. 相似文献
16.
Kenneth L. Deahl Frances M. Perez Jonathan M. Thompson Caoimhe Fleming-Archibald Stephen Thompson Rosemary Collier Steven Kildea Louise R. Cooke 《Potato Research》2009,52(4):341-354
Potato production on the island of Jersey, in the English Channel, is dominated by Jersey Royal, a selection of the early
cultivar International Kidney. Jersey Royal is very susceptible to Phytophthora infestans, the cause of potato late blight, and Jersey’s climate is frequently conducive to infection. During 2004–2006, isolates of
P. infestans were obtained from Jersey Royal plant samples from 41 different sites (24 crops, one infected tuber, 16 volunteers) and from
five outdoor tomato crops and characterised by mating type, mtDNA haplotype, Gpi and Pep allozyme genotype, metalaxyl resistance and RG57 fingerprint. A subset of 17 isolates was additionally characterised by simple
sequence repeat (SSR). All but one isolate from potato belonged to a single A1 multilocus genotype or a variant. The five
isolates from tomato represented three distinct genotypes, none of which was found on potato and included one which was A2
mating type. The populations of P. infestans on potato and tomato in Jersey appear distinct, with that on potato being highly clonal. 相似文献
17.
Summary A total of 37 single-lesion isolates ofPhytophthora infestans were collected during 2000 from different potato growing regions in the central part of Serbia. They were paired in Al and
A2 matings to determine their mating types. Of these 37 isolates, 28 were found to belong to the A2 mating type, eight to
the Al type and one was found to be self-fertile (A1/A2). Using the in vitro mycelial radial growth method no metalaxyl resistantP. infestans isolate could be found. The rate of occurrence of intermediate isolates was not high, on the average 2.70%. All other isolates
were sensitive to metalaxyl. There was no correlation between mating type and the intermediate metalaxyl resistance found. 相似文献
18.
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
19.
Summary The kinetics of accumulation of phytoalexins, glycoalkaloids and phenolics was studied in two potato cultivars differing in
their degrees of field resistance when infected withPhytophthora infestans. Tuber slices and leaves of cvs Pampeana INTA (high degree of field resistance, free of R genes) and Bintje (susceptible)
were infected with race C (complex race 1, 3, 5, 7, 11) ofPhytophthora infestans. Phytoalexins and phenolics accumulated in tuber and leaf tissues which had been inoculated. The levels of these compounds
in the susceptible cv. Bintje were relatively low and similar to those found before inoculation. Leaves of cv. Pampeana INTA
had a very high glycoalkaloid content, suggesting that glycoalkaloids may play a role in protection of leaves against the
fungus. However, we could find no correlation between resistance and glycoalkaloid content of tubers. Our results suggest
a major role of phytoalexins, phenolics and glycoalkaloids in the complex mechanisms of field resistance. 相似文献
20.
Geert J. W. Janssen Arend Van Norel Brigitte Verkerk-Bakker Richard Janssen 《Potato Research》1995,38(4):353-362
Summary Various methods of screening for resistance to root-knot nematodes were compared and evaluated. Seedling populations ofSolanum spp., grown in clay pots and plastic tubes with silver sand and inoculated with juveniles ofMeloidogyne chitwoodi andM. hapla, showed large differences in the number of egg masses on roots 7 weeks after inoculation. The differences were reproducible
when re-testing was done with cuttings and plants from tubers. No resistance toMeloidogyne spp. was observed with ten potato cultivars when grown in clay pots, plastic tobes or closed containers. Plants from tubers
in growth pouches developed a large two-dimensional root system, and after inoculation with juveniles the infection process
could be observed over 8 weeks.
A method of infecting potato tuber tissue withMeloidogyne is described, using tuber slices in Petri dishes as a potential screening test for tuber resistance. 相似文献