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1.
Calonectria pseudonaviculata causes lesions on boxwood leaves and twigs. Controlled-environment experiments were conducted to determine the effects of temperature and leaf wetness period on C. pseudonaviculata sporulation on diseased (cv. Suffruticosa) leaves and of dryness periods and high temperature on conidial survival. Infected leaves were incubated in moist chambers and subjected to six temperatures (9, 13, 17, 21, 25, and 29°C) and six leaf wetness periods (0, 12, 24, 40, 48, and 72 h). Spore production was influenced significantly by wetness period, temperature, and their interaction. Increasing duration of leaf wetness and increasing temperature generally increased sporulation, with no sporulation occurring at 29°C or 9 and 13°C, except at 72 h of wetness exposure, while it was optimal at 21°C. Detached leaves with profuse conidia were subjected to a range of drying (relative humidity at 65%) times (0, 2, 4, 6, and 8 h) at two temperatures of 21 and 29°C. Conidia were then harvested and plated on water agar. Germinating conidia were counted to measure the spore viability. Spore mortality increased with increasing dryness duration at both temperatures but occurred more quickly and severely at 29 than 21°C. Overall, this study extended biological knowledge of conditions required for crucial stages of the C. pseudonaviculata disease cycle and the obtained results will be vital for developing boxwood blight forecasting and management tools.  相似文献   

2.
Early blight caused by Alternaria solani is a highly destructive disease of potatoes. Control of early blight mainly relies on the use of preventive fungicide treatments. Because of their high efficacy, azoxystrobin and other quinone outside inhibitors (QoIs) are commonly used to manage early blight. However, loss of sensitivity to QoIs has previously been reported for A. solani in the United States. Two hundred and three A. solani field isolates collected from 81 locations in Germany between 2005 and 2011 were screened for the presence of the F129L mutation in the cytochrome b gene; of these, 74 contained the F129L mutation. Sequence analysis revealed the occurrence of two structurally different cytb genes, which differed in the presence (genotype I) or absence (genotype II) of an intron, with genotype I being the most prevalent (63% of isolates). The F129L mutation was detected only in genotype II isolates, where it occurred in 97%. Sensitivity to azoxystrobin and pyraclostrobin was determined in conidial germination assays. All isolates possessing the F129L mutation had reduced sensitivity to azoxystrobin and, to a lesser extent, to pyraclostrobin. Early blight disease severity on plants treated with azoxystrobin was significantly higher for A. solani isolates with reduced fungicide sensitivity in the conidial germination assay compared with sensitive isolates. Data suggest an accumulation of F129L isolates in the German A. solani population over the years 2009–2011. It is assumed that the application of QoIs has selected for the occurrence of F129L mutations, which may contribute to loss of fungicide efficacy.  相似文献   

3.
Calonectria pseudonaviculata, the causal agent of the disease of Buxus spp. known as ‘box blight’, was first detected in the mid‐1990s in the UK and New Zealand. Since then, the geographic range of box blight has rapidly expanded to at least 21 countries throughout temperate regions of the world, causing significant losses in nurseries, gardens and wild boxwood populations. This study determined the genetic diversity in a collection of 234 Calonectria isolates from diseased Buxus plants, originating from 15 countries and four continents. Two genetic clades, G1 and G2, were identified within this sample using multilocus phylogenetic analysis. The application of genealogical concordance phylogenetic species recognition criteria using four independent nuclear loci determined that the Calonectria isolates in these two clades are separate phylogenetic species. The isolates in the G1 clade were upheld as C. pseudonaviculata sensu stricto. Based on phylogenetic distinctiveness and the lack of mating, a new species is proposed, Calonectria henricotiae sp. nov., for the Calonectria isolates in the G2 clade. A PCR‐RFLP assay and real‐time PCR assays were developed to easily and reproducibly differentiate these species. To assess the practical implications of the identification of the two species, their physiology, fungicide susceptibility and pathogenicity were compared. No differences in pathogenicity were observed. However, C. henricotiae isolates exhibited greater thermotolerance and reduced sensitivity to specific triazole as well as strobilurin fungicides. The identification of a second phylogenetic species causing box blight may have a substantial impact on the epidemiology and control of this destructive disease.  相似文献   

4.
Dothistroma needle blight (DNB), caused by Dothistroma septosporum, is the most important disease currently affecting pine plantations in Britain. Intraspecific variation in susceptibility to DNB has been observed in several pine species, but it is not clear if similar variation occurs in Pinus sylvestris (Scots pine), Britain's only native pine. In three separate experiments 2‐ and 3‐year‐old Scots pine saplings from six native Scottish populations were artificially inoculated with D. septosporum conidial suspensions and incubated under conditions optimal for disease development. Conidial suspensions were produced using a single isolate from northeast Scotland. In one experiment, plants were also treated with various spore suspension concentrations to assess the impact of inoculum load on disease severity. There were no significant interactions between host population, plant height, and experiment/inoculum load (anova , P > 0·05), but population, height and inoculum load all significantly affected disease severity (anova , P < 0·05). Among the 2‐year‐old trees, those from Amat were less susceptible than those from Glen Loyne and Glen Cannich (anova , P < 0·05). Among the 3‐year‐old trees, those from Beinn Eighe were less susceptible than those from Abernethy. Plant height and DNB susceptibility had a slightly negative relationship. The use of a spore suspension with a concentration of 1·6 × 106 spores mL?1 was optimum for disease development. In an in vitro experiment, production of conidia was greater when cultures were incubated in darkness. This paper is the first to report intraspecific variation in DNB susceptibility within Scots pine.  相似文献   

5.
The control of seedborne rice seedling diseases in the seed beds is important to avoid epidemics in rice nurseries and paddies, which may result in severe yield loss. Recently, irradiation with plasma containing electrons, creating positive or negative ions and neutral species, has been shown to have an antimicrobial effect, probably via generation of reactive oxygen species. This study examines whether two seedborne rice seedling diseases, bakanae disease caused by the fungal pathogen Fusarium fujikuroi, and bacterial seedling blight caused by Burkholderia plantarii, are suppressed by irradiation of infected rice seeds with atmospheric plasma. Seed germination and seedling growth were not inhibited in plasma‐treated healthy seeds. When F. fujikuroi‐infected rice seeds were irradiated with plasma after being immersed in sterile distilled water, bakanae disease severity index and the percentage of plants with symptoms were reduced to 18.1% and 7.8% of non‐irradiated control, respectively, depending on the duration of plasma irradiation. The bacterial seedling blight disease index was also reduced by plasma irradiation in vacuum‐inoculated seeds to 38.6% of the non‐irradiated control, and in infected seeds harvested from spray‐inoculated heads of rice plants to 40.1% of the control. Therefore, plasma irradiation seems to be effective in controlling two independent seedborne rice seedling diseases.  相似文献   

6.
Boxwood blight is an emerging disease of ornamental as well as native boxwood. The disease became widely established in Europe at the beginning of the 21st century, prior to its more recent discovery in North America and Asia. Two sister-species of fungi cause the disease, Calonectria pseudonaviculata (Cps) and C. henricotiae (Che). Prior efforts to quantify intraspecific genetic polymorphisms of Cps and Che have yielded little information, limiting the ability to understand the evolution and migration of these pathogens. This study describes the development and implementation of simple sequence repeat (SSR) markers to analyse genetic diversity from a global collection of Cps and Che isolates, representing major blight outbreaks since the disease was first identified in the UK in the late 1990s. Analysis of the Cps CB002 genome sequence identified 180 single copy SSR loci using stringent search criteria, 11 of which were polymorphic and used to screen a global sample of 306 isolates. Fourteen multilocus genotypes of Cps and two multilocus genotypes of Che were identified. Twelve of the 14 Cps genotypes differed from each other by a single allele. The most common Cps genotype was found on all continents where boxwood blight is confirmed. Based on measurement of linkage disequilibrium, Cps showed no evidence of sexual recombination. Further in silico analysis identified 1594 SSRs using relaxed SSR definition criteria. Comparison of these SSR-containing loci with Cps and Che genome sequences representing three different genotypes demonstrated that single nucleotide polymorphisms might serve as informative genetic markers for future studies.  相似文献   

7.
The antifungal activities of hyoscyamine and scopolamine, major alkaloids extracted from the desert plant Hyoscyamus muticus, against two rice pathogens, Magnaporthe oryzae and Rhizoctonia solani, were studied. The minimum inhibitory concentration of hyoscyamine that resulted in distinctive inhibition (MIC50) was 1 μg/ml for both fungi. Exposure to hyoscyamine caused the leakage of electrolytes from the mycelia of both fungi. Hyoscyamine (>1 μg/ml) irreversibly delayed or inhibited conidial germination and appressorium formation in M. oryzae grown on polystyrene plates. Hyoscyamine effectively inhibited the attachment of conidia to the surface of rice (Oryza sativa) leaves and inhibited appressorium formation on the leaves. A high concentration of scopolamine (1000 μg/ml) also delayed or inhibited conidial germination in M. oryzae, but conidial germination was restored after washing the conidia with water. Antifungal activity of hyoscyamine was reduced by scopolamine. Magnaporthe oryzae infection was significantly suppressed (by >95%) in leaves of intact rice plants treated with hyoscyamine (10 μg/ml). Moreover, 10 μg hyoscyamine/ml significantly reduced the disease severity index for sheath blight to ≤0.2, when compared with the disease index of control plants (>7.0). Hyoscyamine (>20 μg/ml) completely inhibited sclerotial germination and development of R. solani by delaying the initiation, maturation, and melanization of the sclerotia. These results suggest that tropane alkaloids may be useful for controlling blast and sheath blight diseases of rice and for studying the mechanisms that regulate conidial germination in M. oryzae and sclerotial germination and development in R. solani.  相似文献   

8.
The effect of hot water treatment (HWT) to control peach brown rot was investigated. Peaches were dipped in water at 60°C for 60 s and artificially inoculated with Monilinia fructicola conidia. HWT failed to control brown rot if applied before inoculation and microscopic observations revealed a stimulatory effect on germ tube elongation of M. fructicola conidia placed immediately after HWT on the fruit surface, compared to the control. The influence of fruit volatile emission due to HWT was performed on the pathogen conidia exposed to the headspace surrounding peaches. The results showed an increase of M. fructicola conidial germination ranging from 33 to 64% for cultivars Lucie Tardibelle and Red Haven heat‐treated peaches, respectively, compared to the control. The volatile blend emitted from heat‐treated fruit was analysed by solid‐phase microextraction/gas chromatography‐mass spectrometry (SPME/GC‐MS) and proton transfer reaction‐time of flight‐mass spectrometry (PTR‐ToF‐MS). Fifty compounds were detected by SPME/GC‐MS in volatile blends of cv. Lucie Tardibelle peaches and significant differences in volatile emission were observed among heated and control fruit. Using PTR‐ToF‐MS analysis, acetaldehyde and ethanol were detected at levels 15‐ and 28‐fold higher in heated fruit compared to unheated ones, respectively. In vitro assays confirmed the stimulatory effect (60 and 15%) of acetaldehyde (0·6 μL L?1) and ethanol (0·2 μL L?1) on M. fructicola conidial germination and mycelial growth, respectively. The results showed that volatile organic compounds (VOCs) emitted from heat‐treated peaches could stimulate M. fructicola conidial germination, increasing brown rot incidence in treated peaches when the inoculation occurs immediately after HWT.  相似文献   

9.
Anthracnose fruit rot of blueberries caused by Colletotrichum acutatum is a serious problem in humid blueberry‐growing regions of North America. In order to develop a disease prediction model, environmental factors that affect mycelial growth, conidial germination, appressorium formation and fruit infection by C. acutatum were investigated. Variables included temperature, wetness duration, wetness interruption and relative humidity. The optimal temperature for mycelial growth was 26°C, and little or no growth was observed at 5 and 35°C. The development of melanized appressoria was studied on Parafilm‐covered glass slides and infection was evaluated in immature and mature blueberry fruits. In all three assays, the optimal temperature for infection was identified as 25°C, and infections increased up to a wetness duration of 48 h. Three‐dimensional Gaussian equations were used to assess the effect of temperature and wetness duration on the development of melanized appressoria (R2 = 0·89) on Parafilm‐covered glass slides and on infection incidence in immature (R2 = 0·86) and mature (R2 = 0·90) blueberry fruits. Interrupted wetness periods of different durations were investigated and models were fitted to the response of melanized appressoria (R2 = 0·95) and infection incidence in immature (R2 = 0·90) and mature (R2 = 0·78) blueberry fruits. Additionally, the development of melanized appressoria and fruit infection incidence were modelled in relation to relative humidity (R2 = 0·99 and 0·97, respectively). Three comprehensive equations were then developed that incorporate the aforementioned variables. The results lay the groundwork for a disease prediction model for anthracnose fruit rot in blueberries.  相似文献   

10.
The effects of post‐harvest curing and storage temperature on severity of black dot, caused by Colletotrichum coccodes, were investigated for potato crops grown for different crop durations (days from 50% emergence to harvest) in soils that posed a low, medium and high risk of disease. In field trials over four growing seasons (2005–8), black dot severity at harvest increased with increasing crop duration, within the range 103–146 days from 50% emergence to harvest (P < 0.05). In field trials over three growing seasons (2006–8), black dot severity on tubers at harvest increased significantly with increasing soil inoculum in each year, within the range 43–4787 pg C. coccodes DNA/g soil (P < 0.05). Storage trials were conducted to measure the influence of accumulated post‐harvest temperature on black dot. In 2005, no difference in black dot severity was observed on tubers stored for 20 weeks at 2.5 and 3.5 °C. In 2006 (but not 2007), increasing the duration of curing after harvest from 4 to 14 days increased black dot severity on tubers from 8.9 to 11.2% (P < 0.01) in long duration crops (>131 days after 50% emergence) grown under high (>1000 pg C. coccodes DNA/g soil) soil inoculum. The number of days of curing did not affect disease severity for shorter duration crops grown at high soil inoculum, or on crops grown at medium or low (100–1000 and <100 pg C. coccodes DNA/g soil, respectively) soil inoculum concentrations. Soil inoculum and crop duration together provided a reasonable prediction of black dot severity at harvest and after a 20‐week storage period.  相似文献   

11.
Late blight, caused by the oomycete Phytophthora infestans, is a threat to potato‐cropping systems worldwide. In the Ecuadorian Andes, despite a high late blight incidence in foliage, tuber blight is rare. In this work, the hypothesis that Ecuadorian Andean soils are naturally suppressive to P. infestans tuber infection was evaluated. Soils from four potato‐growing regions were assessed for disease suppressiveness by determining the effects of soil heat treatment on P. infestans sporangia and their ability to infect potato slices after 1, 8, 15 and 30 days of exposure to soils. Tuber infection after inoculation with P. infestans‐infested soils was consistently lower during the evaluation period compared with heat‐treated soils. Fresh, untreated soils affected germination and viability of P. infestans sporangia in a site‐dependent manner. In addition, the effect of heat treatment on soil bacterial communities was assessed through terminal restriction fragment length polymorphism analysis of the 16S rDNA gene region. Heat treatment disrupted bacterial community composition, and a subset of terminal restriction fragments (TRF) was either positively or negatively correlated with tuber infection. Bacterial TRF negatively correlated with tuber infection corresponded in fragment size to taxa with known ability to inhibit pathogens and promote plant growth. Finally, bacterial isolates obtained from untreated soils, which inhibited P. infestans growth in vitro, represented 22–47% of isolates recovered, and matched classes predicted by the TRFs. This work represents a first step in understanding the mechanisms behind the low incidence of tuber blight in Andean potato‐cropping systems.  相似文献   

12.
Botrytis cinerea, the main pathogen of strawberry, has the ability to remain quiescent in unripe tissue and develop disease symptoms in ripe fruit. As strawberry ripening is characterized by an increase of aroma compounds, the role of volatile emission in the development of infection was investigated. Thirty‐five strawberry volatile organic compounds (VOCs) were tested on B. cinerea in vitro and volatile emission was analysed in strawberry harvested at four ripening stages by headspace solid‐phase microextraction/gas chromatography–mass spectrometry and proton transfer reaction–time of flight–mass spectrometry. The coupling of such data sets made it possible to conclude that key strawberry aroma compounds stimulate B. cinerea conidial germination and some typical wound‐volatiles stimulate pathogen conidial germination or mycelial growth. This study is the first report of fungal stimulation by some VOCs naturally occurring in strawberry: the esters ethyl butanoate, cis‐3‐hexenyl acetate, trans‐2‐hexenyl acetate, methyl butanoate and hexyl butanoate, the furanones furaneol and mesifurane, and the alcohol trans‐2‐hexenol. The results of this work provide advances in understanding the functional role of fruit VOCs and suggest, for the first time, that fruit VOCs may influence the development of B. cinerea from the latent phase and that they could favour the invasive growth of B. cinerea after wounding. In particular, ethyl butanoate and furaneol could signal strawberry ripening, and the green leaf volatiles trans‐2‐hexenol, trans‐2‐hexenyl acetate and cis‐3‐hexenyl acetate could signal the presence of damaged tissues that are easier sites for penetration by B. cinerea.  相似文献   

13.
Rhizopus rot, caused by Rhizopus stolonifer, is one of the main postharvest diseases in stone fruits, but there is little known about the processes of disease development during transport and postharvest storage. The objective of this study was to characterize temporal progress and spatial distribution of the disease in peach fruit. Rhizopus rot development was evaluated using two different fruit arrangements. Only one fruit of each arrangement was inoculated with a R. stolonifer spore suspension. Disease incidence and severity were assessed daily for all the fruit. Nonlinear models were fitted to the quantity of fruit and to the area of fruit that became infected over time and distance in relation to the source of inoculum. Disease‐free fruit placed next to the artificially inoculated peaches showed disease symptoms due to pathogen dissemination by mycelial stolons. The disease incidence and severity progress rates varied from 0.33 to 0.53 day?1 and from 0.30 to 0.49 day?1, respectively. The spatial spread of the disease followed a dispersive wave pattern with increasing speed over time, but decreasing speed with disease severity. For disease severity y = 0.5, the velocity at day 3 varied from 0.14 to 0.32 fruit diameter day?1, while it ranged from 0.38 to 1.46 fruit diameter day?1 at day 12.  相似文献   

14.
The order Coryneliales includes several fungi such as Corynelia spp. that are pathogenic to trees in the Podocarpaceae. The aim of this study was to assess the spatial pattern and temporal progress of disease caused by Corynelia uberata on Podocarpus falcatus in Ethiopian forests and to evaluate the germination potential of seed retrieved from fruit infected by C. uberata. Corynelia uberata was found on leaves, young stems and/or on fruit of P. falcatus in Ethiopian forests. Spatial analysis in the Adaba‐Dodola forest showed that disease intensity of C. uberata was significantly higher in non‐‘WAJIB’ blocks (disturbed forest) than ‘WAJIB’ blocks (sustainably managed forest) (P < 0·0001). In the temporal disease progress study, a significantly higher incidence and severity of disease on fruit was recorded during the wet season relative to dry season (P < 0·0001). The green milk stage of fruit exhibited significantly higher mean incidence (P < 0·0001) and severity (P < 0·0001) of disease compared to other growth stages of fruit. The disease incidence and severity in general, as well as on different fruit growth stages, were highly correlated (P < 0·0001, R2 ≥ 0·95). Germination rate of seed decreased significantly with an increase in the level of fruit infection by C. uberata (P < 0·0001). Thus, C. uberata can apparently influence germination of seed and may pose a threat to the regeneration of P. falcatus from seeds in Ethiopian forests.  相似文献   

15.
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16.
The aim of this 4‐year study was to characterize temporal development of brown rot blossom blight and fruit blight (caused by Monilinia spp.) and their sporulating areas in sour cherry orchards; and to determine the relationships amongst incidence and sporulating area of blossom blight, fruit blight and fruit rot. The study was performed in integrated and organic orchard blocks on two cultivars (Újfehértói fürtös and Érdi b?term?). On both cultivars, disease progress on flowers and fruits was 2–10 times slower in the integrated than in the organic management system. The peak incidence values were 9 and 31 days after petal fall for blossom blight and fruit blight, respectively. After these dates, no new blight symptoms on flowers and/or fruits appeared and the disease was levelling off. Final blossom blight incidence ranged from 1 to 5% and from 12 to 34%, and fruit rot incidence from 2 to 6% and from 11 to 26% in the integrated and the organic orchards, respectively. The sum of fruit blight incidence ranged from 9 to 22% for the organic system, but was below 5% for the integrated system, while the final sporulating area was 5–16 mm2 and <3 mm2, respectively. Among the five highest Pearson's correlation coefficients, relationships between blossom blight and early fruit blight stage (r = 0·845, P = 0·0087 integrated; r = 0·901, P = 0·0015 organic), and between sporulating area and fruit rot (r = 0791, P = 0·0199 integrated; r = 0·874, P = 0·0039 organic) were the most significant relationships from an epidemic standpoint as they indicated a connection between different brown rot symptom types.  相似文献   

17.
The Gram‐negative bacterium Erwinia amylovora, causal agent of fire blight disease in pome fruit trees, encodes a type three secretion system (T3SS) that translocates effector proteins into plant cells that collectively function to suppress host defences and enable pathogenesis. Until now, there has only been limited knowledge about the interaction of effector proteins and host resistance presented in several wild Malus species. This study tested disease responses in several Malus wild species with a set of effector deletion mutant strains and several highly virulent E. amylovora strains, which are assumed to influence the host resistance response of fire blight‐resistant Malus species. The findings confirm earlier studies that deletion of the T3SS abolished virulence of the pathogen. Furthermore, a new gene‐for‐gene relationship was established between the effector protein Eop1 and the fire blight resistant ornamental apple cultivar Evereste and the wild species Malus floribunda 821. The results presented here provide new insights into the host–pathogen interactions between Malus sp. and E. amylovora.  相似文献   

18.
This study investigated the use of cold plasma to reduce the in vitro growth of two postharvest fungal plant pathogens, Colletotrichum alienum and C. fioriniae, isolated from avocados. Cold plasma (CP) was used to treat pure cultures and conidial suspensions of both pathogens, for 180 or 360 s, in either open or sealed environments from varying distances. In an open environment, the 360 s treatment at a distance of 5 cm reduced the colony growth of freshly inoculated cultures to less than 2 mm/day compared to the control of more than 8 mm/day, and treatment of conidial suspensions resulted in almost 100% reduction of conidial germination. In the same environment, the 180 s CP treatment did not significantly reduce the colony growth of fresh or actively growing cultures, but did suppress the germination of conidia by up to 80%. In a sealed environment, the 360 s CP treatment also effectively reduced the growth of freshly inoculated cultures, with no growth for some isolates. Production of reactive oxygen and nitrogen species was observed during treatment, and these may have contributed to the reduction in growth and germination. These results demonstrate the potential of CP for the control of two Colletotrichum species.  相似文献   

19.
Germination and emergence are critical life stages for annual plants and so their full understanding is essential for managing arable plant populations. This study investigated the most important species‐specific environmental cues that regulate seed germination and emergence (temperature and light) of the arable Ranunculaceae species Consolida orientalis, Consolida pubescens, Delphinium gracile, Delphinium halteratum ssp. verdunense and Nigella gallica, to propose management strategies for their preservation in agro‐ecosystems. Growth chamber and outdoor pot experiments were conducted for two consecutive seasons to analyse light (complete darkness or 12 h light) and temperature (5/10, 5/15 and 10/20°C) requirements and emergence patterns. The relative light germination requirement (ΔGlight), which extends from ?100 (complete darkness) to 100 (light), was estimated. Weibull functions were fitted to observed emergence (%) in pots. For all species, germination was higher in complete darkness than with a light regime (?60 < ΔGlight < ?95). This dark requirement indicates better germination for buried seeds. A tillage operation just after seed shed is therefore recommended. Consolida spp. germinate and emerge almost exclusively in autumn–winter, while Delphinium spp. and N. gallica can also germinate in spring. These arable plants would be able to adapt to delayed sowings, an important strategy for avoiding early‐emerging competitive weeds. Facultative winter‐germinating species could face early herbicide treatments if sufficient emergence occurs in winter–spring. These results bring new information to help develop conservation strategies for these species in agro‐ecosystems.  相似文献   

20.
Growth room experiments were conducted to assess the interaction of soil type, biofungicides, soil compaction and pathotype/host on infection and symptom development caused by Plasmodiophora brassicae, the cause of clubroot on Brassica spp. In two initial experiments, four soil types (peat soil, mineral soil, non‐calcareous sand, soil‐less mix), two biofungicides (Bacillus subtilis, Clonostachys rosea), and two pathotypes (3 and 6, Williams’ differential set) were assessed. Differences in clubroot severity associated with soil type were unexpectedly small and variable. Prestop (C. rosea) was often more effective than Serenade (B. subtilis) at reducing clubroot levels on peat and mineral soils, but less effective than Serenade on sand. Inoculation with pathotype 3 often resulted in a slightly higher mean severity than pathotype 6. The interaction of soil type × biofungicide was similar on both canola (B. napus) and Shanghai pak choy (B. rapa subsp. chinensis), whether the soil was kept saturated or allowed to drain after inoculation. The impact of soil type on biofungicide efficacy might explain, in part, why biofungicides are more effective in one location than another. The observation that clubroot severity in soil‐less mix was affected by compaction led to an investigation of soil bulk density. Severity was higher in soil‐less mix that was more compacted than in the initial experiments, and was lower in peat and mineral soils when soil bulk density was reduced by adding soil‐less mix. In this study, soil bulk density had a larger impact on clubroot than soil type, organic matter or pathotype.  相似文献   

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