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1.
Summary Data from five long-term field experiments on sandy and sandy peat soils were analyzed for the effect of soil type on damage
caused by potato cyst nematodes to potato crops. It was shown that the water retention of the topsoil and the subsoil largely
determined the potential yield level in the different fields. According to Oostenbrink's equation the slopes of the curves
are steeper with increasing yield level, indicating that the higher the potential yield level, the higher the absolute yield
loss. However, when yield was expressed as percentage of maximum yield, yield reduction related to potato cyst nematode density
did not differ significantly, except when tolerant cultivars were grown. Increasing tolerance of cultivars to nematode damage
was reflected in less steep slopes of the yield/nematode density curves. 相似文献
2.
Summary The sandy and sandy peat soils of the northeast of The Netherlands are mineralogically very poor and acid. Independently of
potato cyst nematode infestations, there is a considerable negative effect of increasing soil pH on potato tuber yield. Potato
cyst nematode infections aggravate the effect of soil pH in depressing yield. It was shown that both potato cyst nematode
infection and increasing soil pH values reduce the buffering capacity of the root system. Testing for yield as well as for
tolerance to potato cyst nematode infection should be made at a range of soil pH values, similar to those found in the target
area. This refers to active breeding programmes as well as to the selection of cultivars for yield trials. 相似文献
3.
M. S. Phillips 《Potato Research》1981,24(1):101-103
Summary The resistance expressed by progenies of potato seedlings to the white potato cyst nematode (Globodera pallida) has been assessed on bulk sowings of seedlings and on individual plants raised from tubers, and a positive correlation between
the seedling and plant tests has been established. The use of such a seedling test as an addition to other methods of screening
is discussed. 相似文献
4.
5.
Summary The tolerance toGlobodera pallida of 15 potato genotypes with a high level of resistance toG. pallida was assessed by measuring their tuber yield in heavily infested fields and in nematicide treated strips in the same fields.
Tolerance was also assessed in pots in the glasshouse by measuring the total biomass after 35 and 70 days growth in heavilyG. pallida infested soil and in uninfested soil. Large differences in tolerance between the genotypes were observed. High correlations
were observed between tolerance assessments made in the field experiments and between field and pot experiments. No relationship
was found between tolerance and maturity. Shoot and root dry weight were about equally affected by the nematode. 相似文献
6.
Summary The effect of soil pH on yield losses due to potato cyst nematodes (Globodera pallida) was investigated in experiments in the field and in a semi-controlled environment. Through annually liming a reclaimed peat
soil with about 22% organic matter, plots with pH levels of 4.5, 5.0, 5.5, 6.0 and 6.5 were obtained. In 1990 potato yields
in these plots decreased from 45 t/ha at pH 4.5 to 33 t/ha at pH 6.5, whereas the nematode densitites decreased from about
18 to 9 juveniles per g soil. In a container experiment a strong interaction was recorded between soil pH and the presence
of nematodes. Tuber yields were about 11% lower at pH 6.5 than at pH 4.5 in the absence of nematodes, but about 44% lower
when an initial population of 27 juveniles per g soil was present. 相似文献
7.
Summary To describe the relationship between nematode density and yield, four equations of increasing complexity are found in the
literature. They concern a linear regression curve, a log linear regression curve, a regression curve based on an exponential
relation and an inverse linear regression curve. The yield to PCN density responses of these equations are shown on a linear
and on a logarithmic scale. Considerable differences are shown in the way they respond to the same data. None of these equations
is able to explain or forecast yield decrease caused by potato cyst nematodes. 相似文献
8.
Summary Potato clones and cultivars differ in their ability to tolerate damage by the potato cyst nematodes:G. rostochiensis andG. pallida. This paper reports a simplified field assessment whereby single, spaced plants are grown in heavily infested soils. These
trials identified those clones which are either very sensitive to damage or those that grow and yield well in the presence
of nematodes. The use of such a screening procedure in a breeding programme is discussed. 相似文献
9.
Summary Tests for systemic induced resistance (SIR) to late blight were performed with different potato cultivars in field trials
and in growth chamber experiments.
The non-pathogenPhytophthora cryptogea (Pc) and salicylic acid (Sa) were used as inducer agents. In the field, plants were naturally infected byPhytophthora infestans while the indoor plants were inoculated. The degree of SIR obtained varied with the cultivar used and also with the type
of inducer. For example in the field the susceptible cv. St. Cecilia had enhanced resistance with Pc whereas Sa caused increased
susceptibility. Inbred resistant cvs acquired increased resistance after treatment with Sa.
In a separate pilot experiment in a growth chamber, Sa at two different concentrations was injected into potato seed tubers
before planting. The higher Sa concentration increased resistance in genetically resistant cultivars while the lower Sa concentration
brought about increased susceptibility. 相似文献
10.
Zusammenfassung Zur routinem?ssigen Resistenzbestimmung von Kartoffelgenotypen gegenüberGlobodera pallida (Stone) Behrens (Pa3) wurde ein monoxenischesin vitro-Verfahren entwickelt, dessen Grundlage die keimfreie Kultivierung der Testgenotypen in einem N?hragarmedium unter definierten
Bedingungen war. Dadurch konnte die vollst?ndige Entwicklung der Nematoden sowie die Dimension ihres N?hrzellensystems in
den transparenten Kartoffelwurzeln kontinuierlich beobachtet werden. Der Test erm?glichte die Selektion resistenter Genotypen
anhand geringer quantitativer Unterschiede in der vermutlich polygen-vererbten Resistenzreaktion. Für die Anzucht keimfreier
Pflanzen aus Kartoffelsamen und- knollen wurden spezielle Verfahren entwickelt und an mehreren Genotypen geprüft. Die dabei
festgestellte Variabilit?t, insbesondere bei der Wurzelbildung, erforderte für den geeigneten Zeipunkt der Nematodenzugabe
die Ausarbeitung eines Wurzelboniturschemas. Die Genotypen konnten nach dem Test in T?pfen weiterkultiviert werden.
Summary A monoxenic resistance test for routine use was developed to determine the resistance of potato genotypes to the cyst nematodeGlobodera pallida (Stone) Behrens. The basis of the procedure is the aseptic cultivation of the genotypes under test in a nutrient medium in defined conditions. It was possible with it to observe invasion, the development of the nematodes, as well as the dimensions of their feeding cells in the transparent potato roots. Small, quantitative differences, due presumably to the polygenically determined resistance reactions of the genotypes, could be distinguished, and selection for resistance was feasible. For routine trials special procedures were developed using surface sterilisation of potato seed and etiolated sprouts which gave high levels of sterility. The genotypes from seeds could be tested directly, but those from etiolated sprouts had to be prepared by stem cutting. A root system was obtained which correlated with known ratings. Each genotype established from seed and etiolated shoots, developed at different rates, as did their root systems, and no definite timespan could be set before nematode introduction. Growing the cultivars under light before the test resulted in faster root development (Table 2), and a higher nematode infestation than in darkness (Figure 4). The time for nematode inoculation was determined by a rating system based on the location of the perimeter of the root system (Figure 5). In this way physiological factors and the individual growth rate of each genotype were allowed for, with the aim of assessing possibly high levels of nematode infection. At the end of the test the seedling genotypes can be removed from sterile culture and grown on in pots. Where genotypes form minitubers (Table 1) it is possible to proceed early to the next stage in cultivation or to store them trouble-free.相似文献
11.
N. Ioannou 《Potato Research》1989,32(1):33-47
Summary The infection pressure of two viruses, potato leafroll (PLRV) and potato virus Y (PVY), both common in seed potatoes grown
in Cyprus, was determined in three experiments in 1982–83. Virus-free bait plants, of potato and four other species, were
exposed weekly to field infection during the growing season (March–June), and then returned to an aphid-free glasshouse for
symptom expression. Only tobacco plants produced clear symptoms enabling reliable assessment of PVY infection pressure. When
assessed with ELISA or by tuber indexing, the potato plants were efficient baits for both viruses whose infection period commenced
at emergence (mid March to early April) and ended within 6–7 weeks. The seasonal trend of aphid populations, determined with
Moericke traps or 100-leaf counts, correspond to that of virus spread. Correlation and regression analysis of aphid and virus
data implicated the alate form ofMyzus persicae as the principal vector of both viruses. 相似文献
12.
Summary Synergism between fungicides could be used to reduce the application dosage. Synergism between cymoxanil and mancozeb was
studied using potted potato plants under field conditions. In three experiments the preventive efficacy of the fungicides
and fungicide mixtures in the treatments were studied using a bio-assay. Potato plants were sprayed with the fungicides or
fungicide mixtures. Leaves were picked from the potato plants with regular intervals after fungicide application. The efficacy
of the fungicides was studied in a bioassay by inoculating the leaves withPhytophthora infestans zoosporangia. The Abbot method was used to show synergistic effects of the cymoxanil/mancozeb mixtures tested. In two of
three experiments synergy of the fungicide mixtures was found. 相似文献
13.
Effect of haulm treatments on the formation of microsclerotia ofVerticillium dahliae Kleb. on potato
Summary In four pot experiments, potato plants of cv. Element were artificially infected withV. dahliae. At an early and a late harvest haulms were killed chemically, by burning or by various other treatments, including cutting
them into pieces of different lengths and keeping the debris on the soil surface or covering with soil. After 4 weeks the
plant material was air-dried and the number of microsclerotia per mg was determined.
At the early harvest, in two experiments, the chemical treatment yielded more microsclerotia than the cutting treatments.
Covering colonised haulm tissue with non-sterilised soil was effective in inhibiting microsclerotia formation. Shorter haulm
pieces led to fewer microsclerotia at the later harvest if the material was kept on the soil surface. The variation in microsclerotial
yield and in treatment effects among the different experiments was large. 相似文献
14.
J. F. J. M. van den Heuvel J. A. A. M. Dirven G. J. van Os D. Peters 《Potato Research》1993,36(2):89-96
Summary The acquisition of potato leafroll virus (PLRV) byMyzus persicae nymphs from the top leaves of potato plants was studied throughout a growing season in relation to the antigen titre in those
leaves and the feeding behaviour of the aphid. Secondarily-infected plants of eight potato genotypes with different levels
of field resistance served as virus sources. Early in the growing season, plants were efficient sources for virus acquisition.
The amount of viral antigen detected inM. persicae nymphs fed on the top leaves was strongly correlated with the titres of viral antigen in these leaves. Virus acquisition
from the top leaves of older potato plants was markedly impaired and could not be correlated with their virus titre. With
increasing age of the potato plants and the development of virus symptoms, the virus titre in the leaves declined and the
initial weak correlation between the virus titre and field resistance ratings disappeared. Thus, screening secondarily-infected
potato plants for field resistance to PLRV based on the concentration of viral antigen in leaves or in aphids fed on them
should be avoided later in the growing season. The feeding rate ofM. persicae, measured by the number of honeydew droplets excreted, did not account for the reduced uptake of virus from older plants
since it was not influenced by the age of the plant. Throughout the growing season, the feeding rate ofM. persicae nymphs on PLRV-infected plants was higher on genotypes with low levels of field resistance to PLRV than on genotypes with
high ones. 相似文献
15.
D. R. Lynch R. L. Wastie H. E. Stewart G. R. Mackay G. D. Lyon A. Nachmias 《Potato Research》1991,34(3):297-304
Summary The phytotoxic components of the culture filtrate of the fungusAlternaria solani Sor, which causes early blight in potato, were used in this study to differentiate between resistant and susceptible genotypes
selected to represent a range of reactions when screened in the field. Detached leaflet assays, using spores and toxic metabolites
from the culture filtrate, were compared with field ratings and a whole-plant glasshouse test. Rank correlations between several
detached leaflet tests were highly significant (P<0.01) but the correlations between these tests and the glasshouse and field tests were poor. The disease ratings obtained
in the various tests were clustered into four groups and assigned to resistance classes. For many of the genotypes there was
a good correspondence between resistance classes for all test methods. Divergent results between tests were associated with
foliage maturity characteristics of the genotypes.
Contribution no. 3879050 of the Lethbridge Research Station. 相似文献
16.
Summary Three in vitro bioassays (single-node cutting, root tip segment and microtuberization) gave similar results in ranking the
salinity (NaCl) tolerance of several potato genotypes (Solanum spp.) and were verified by tuber yield criteria in a field lysimeter trial with salinized irrigation water. Salinity stress
consistently depressed growth in the single-node cutting and root tip segment bioassays, reduced microtuber yield in the microtuberization
bioassay and decreased tuber yield in field lysimeters. The single-node cutting bioassay was simpler to perform than the root
tip segment and microtuberization bioassays and did not exclude certain genotypes as did the microtuberization bioassay. The
single-node cutting bioassay can be recommended as a substitute for more labour-intensive and costly field assessments of
salinity effects of yield. 相似文献
17.
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
18.
K. Scholte 《Potato Research》1989,32(1):65-73
Summary The effect ofStreptomyces spp. (netted scab) on the growth of potato was investigated in three pot experiments, in two of which the effect ofVerticillium dahliae was also assessed.
The netted scab organisms attacked all underground plant parts of susceptible potato cultivars early in the growing season;
the roots were especially seriously attacked, markedly reducing tuber yield and number but prolonging the duration of the
growing season. The nematicide oxamyl had little effect on the incidence of netted scab. Repeated growing of the susceptible
cv. Bintje greatly increased soil contamination with the netted scab pathogens.
V. dahliae reduced haulm growth before wilt symptoms were evident and it reduced tuber yield but not number. Oxamyl delayed infection
byV. dahliae by controlling parasiticPratylenchus nematodes (mainlyP. thornei). 相似文献
19.
M. S. Phillips 《Potato Research》1984,27(1):89-93
Summary The resistance toGlobodera pallida of individual potato seedlings from three progenies derived fromSolanum tuberosum ssp.andigena CPC 2802 was assessed using three inoculation treatments. Plants grown from tubers from the seedlings were used to reassess
resistance. All the seedling test inoculation treatments over-estimated the proportion of clones classified as resistant compared
to the results from tuber-grown plants. However, the mean relative resistance of progenies estimated by both tests showed
good agreement, and it is suggested that seedlings are best used for assessing the resistance of progenies of crosses to identify
promising combinations rather than individual clones. 相似文献
20.
Summary
Macrosiphum euphorbiae, collected in the field from potato plants infected with potato leafroll virus (PLRV), transmitted the virus to fewer potato
plants in a field trial than did laboratory-rearedMyzus persicae. In the laboratory,M. persicae was the only efficient vector of PLRV fromPhysalis floridana seedlings, potato sprouts or excised leaves toP. floridana. Two clones ofM. euphorbiae and one clone ofAulacorthum solani transmitted PLRV from infected potato plants toNicotiana clevelandii as effeciently asM. persicae but a clone ofAphis gossypii was an inefficient PLRV vector. An isolate of PLRV, whichM. persicae transmitted inefficiently from potato toN. clevelandii, was also transmitted inefficiently byM. euphorbiae andA. solani. 相似文献