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1.
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2.
Poinsettia plants growing in ebb-and-flow irrigation systems developed wilting and root rot during the summer growing seasons of 2010 in Gifu Prefecture and 2011 in Aichi Prefecture. Pythium species were isolated from roots with rot symptoms. The isolates were identified as P. helicoides and P. myriotylum on the basis of morphological characteristics and sequence homologies in the rDNA internal transcribed spacer regions. In pathogenicity tests, these isolates caused severe wilting and root rot. This is the first report of poinsettia root rot disease caused by P. helicoides and P. myriotylum, although P. aphanidermatum was reported as a pathogen of poinsettia root rot. To better understand these diseases, we performed an epidemiological study of three high-temperature-tolerant Pythium species, P. aphanidermatum, P. helicoides and P. myriotylum. Disease incidence as a percentage of diseased plants was greatest at 35 °C for all three species. Disease severity using the rating scale of root rot was also highest at 35 °C, particularly with high zoospore inoculum densities (100.0 zoospores/mL). Although the disease incidence and severity were reduced at lower temperatures, the three Pythium species were able to cause disease at temperatures as low as 20 °C.  相似文献   

3.
Monilia yunnanensis was recently identified as a new species causing brown rot of peach in China. Sterol 14α-demethylase inhibitors (DMIs) continue to be important in the management of brown rot of Monilinia spp. worldwide. Tebuconazole and triadimefon are two kinds of DMI fungicides that may be used for brown rot control in China. To establish the baseline sensitivity of M. yunnanensis to these two DMI fungicides, 203 M. yunnanensis single spore isolates were collected. Measurements of sensitivity to the two fungicides were based on inhibition of mycelial growth. For both fungicides, the sensitivity distribution was a unimodal curve, with an EC50 range (the effective concentration to inhibit mycelial growth by 50 %) of 0.0001–0.0644 μg/ml for tebuconazole and 0.2311–1.7477 μg/ml for triadimefon. The M. yunnanensis isolates were obtained from orchards where DMI fungicides have not been used for peach brown rot control, thus the fungicide sensitivity distribution established in this study can be considered as the baseline for monitoring the resistance development in M. yunnanensis once the DMI fungicides are used to control peach brown rot.  相似文献   

4.
Maize seed that was either treated with the fungicide Cruiser Extreme 250 ® (fludioxonil + azoxystrobin + mefenoxam + thiamethoxam) or not treated was planted at two Iowa locations in 2007. Root, mesocotyl and crown rot severity, incidence of Fusarium spp. colonisation and chlorophyll florescence (CF) were assessed at growth stages V2, V4 and V6, and stalk rot severity at R6. At both locations, seed treatment reduced disease severity and incidence of Fusarium spp. infection at all growth stages assessed. Measurements of CF decreased significantly with increased disease severity and incidence of Fusarium spp. at V2 and V4 at both locations, indicating that seedling disease negatively affected photosynthetic performance. Mesocotyl rot severity at V4 predicted crown rot severity at V6 at both locations, as well as crown rot at V6 and stalk rot at R6 at one location.  相似文献   

5.
A new boll rot disease of cotton (Gossypium hirsutum L.) cv. MCU 9 was observed in Tamil Nadu, India, in 1988. The causal organism was isolated in pure culture and identified asCorynespora cassiicola (Berk. & Curt.) Wei. The isolate, which on cotton is pathogenic only to bolls, is considered to be different from a strain ofC. Cassiicola known elsewhere causing leaf spot of cotton. The pathogenicity of this fungus on several other important crops was also tested. The fungus produced leaf spot and stem rot diseases on, respectively, eight and six host plants. Root rot, after inoculation, was observed only inVigna sinensis, Arachis hypogaea andSesamum indicium.  相似文献   

6.
The effect ofPhytophthora infestans on foliage growth and senescence of three potato cultivars was studied in two field experiments. Inoculum or fungicide was applied in different frequencies to establish a range of levels of disease. At weekly intervals leaf numbers were determined as well as vertical canopy profiles of senescent and lesion covered leaf and stem area. P. infestans reduced appearance of new leaves on the main stem only at the highest level of disease. The cultivars differed more in rate of primary infection of healthy leaves than in the subsequent increase in percentage lesion coverage of the infected leaves. Differences between cultivars in stem lesion coverage resembled the differences for leaf lesions, but in every cultivar stem lesions were most prominent in the top of the canopy, contrary to leaf lesions.P. infestans stimulated leaf senescence similarly in the different cultivars.  相似文献   

7.
Field trials conducted on a yellow-red latossol (pH 6.0), replicated in 2010 and 2011, sought to examine the effect of silicon, phosphite minerals, synthetic fungicides and genetic resistance for wheat blast management (Magnaporthe grisea) in Central Brazil. Disease intensity was measured on cvs. BRS 264 and BR18 subjected to the following Si treatments: pre-plant furrow application of Ca & Mg silicate (300 kg ha-1); post-plant scattered application of Ca & Mg silicate on top of the soil (1 ton ha-1); multiple foliar SiO2 applications (30 g l -1); and non-treated control. Blast incidence and severity were scored. Further experiments were conducted on cv. BR-264, for examination of the effect of potassium phosphite and synthetic fungicides on wheat blast intensity, with the following treatments: K2HPO3 (1ml l -1); epoxinazole + pyraclostrobin (700 ml ha-1); tebuconazole (600 ml ha-1); tebuconazole + trifloxystrobin (750 ml ha-1); and non-treated control. In 2010, disease intensity was lower than in 2011. In the silicate experiments, disease was significantly lower when plants were treated with foliar or furrow silicate. Si applications significantly reduced disease in BRS-264. While BR-18 consistently demonstrated lower disease levels, cv. BRS-264 generally responded more markedly to silicon applications. In the phosphite/fungicide experiment of 2010, all treatments reduced disease when compared with the control, and in 2011 phosphite efficiency was not significantly different from some fungicide treatments. Synthetic fungicides demonstrated an average blast control of 55% by severity values. Yields were increased in the phosphite-treated plots (by 9–80%), in the Si treatments (by 26–92%), and more so, and more consistently, with synthetic fungicides (by 90–121%). Combined results of all field studies, carried out under environmental conditions highly conducive to disease, indicated that control of wheat blast necessitates the joint integration of several alternatives for efficient disease management.  相似文献   

8.
Fusarium proliferatum has been identified as the main causal agent of bulb rot of garlic (Allium sativum L.). This disease occurs after the drying process and can rot almost 30 % of the bulbs. Few studies are available regarding the effectiveness of chemical treatments to reduce F. proliferatum incidence in garlic. The efficacy of three commercial fungicides of different chemical groups to reduce seven strains of F. proliferatum mycelial growth was tested in vitro. These three fungicides were also evaluated by foliar spreading of aqueous suspension in a field crop. Fluopyram 20 % + tebuconazole 20 % and tebuconazole 50 % + trifloxystrobin 50 % were highly effective at reducing mycelial growth in F. proliferatum with EC50 values <2 ppm. In general, the effectiveness of the fungicides was enhanced with increasing dosage. Our results indicate that the fungicides evaluated in this study may lead to a risk of resistance appearing in F. proliferatum at low concentrations and this risk is maintained at higher doses for the fungicide dimethomorph 7.2 % + pyraclostrobin 4 %. Although several of the fungicides affected in vitro mycelial growth of F. proliferatum, as a part of an strategy to measure the efficacy of resistance management it is necessary to monitor the ongoing efficacy of fungicides under commercial conditions. All fungicidal treatments tested in field application failed to control garlic bulb rot during storage.  相似文献   

9.
Modifying crop canopies can suppress plant diseases in some crops. For example, in carrot, lateral trimming of the canopy by 30–40 % after canopy closure reduced sclerotinia rot (Sclerotinia sclerotiorum) to zero under moderate disease pressure without the use of fungicides. Trimming reduced relative humidity within the carrot canopy and increased air and soil temperature, inhibiting the formation of apothecia of S. sclerotiorum. Trimming also severed infected petioles, which reduced the opportunity for infection to progress to the carrot crown. Trimming combined with application of foliar fungicide was even more effective. Trimming reduced carrot leaf blights (Alternaria dauci, Cercospora carotae) in 1 of 3 years, when disease pressure was low. However, there was no advantage of combining trimming and fungicide sprays for leaf blight control. Canopy modification also reduces disease in legume crops. Soybean cultivars with reduced height and lodging, and early maturity, had up to a 74 % reduction in apothecia of S. sclerotiorum within the crop, and up to an 88 % reduction in disease incidence at harvest. In field pea, artificially supporting plants to reduce lodging, in combination with fungicide application, reduced the severity of mycosphaerella blight (Mycosphaerella pinodes) on pods by 67 % and increased seed yield by 54 %. In chickpea, paired-row planting that opened the canopy increased seed yield by 12 %, likely by increasing fungicide deposition. Modifications of the crop canopy can reduce disease, the need for fungicide sprays, and sometimes improve fungicide efficacy, but the results are often pathosystem-specific.  相似文献   

10.
Late wilt, a severe vascular disease of maize caused by the fungus Harpophora maydis, is characterized by relatively rapid wilting of maize plants before tasseling and until shortly before maturity. In Israel, the disease has become a major problem in recent years. The pathogen is currently controlled using cultivars of maize having reduced sensitivity. In an earlier work, we modified a molecular method for use as a diagnostic tool to evaluate disease progression in field-infested plants and showed that several fungicides suppressed H. maydis in vitro. Here, we examine the effect of different fungicides on disease progression in a contaminated maize field in the spring and summer of 2009 and 2010. The field was watered using a drip irrigation line for each row and the fungicides were injected directly into the drip line. One of the four fungicides tested, azoxystrobin, was highly effective compared with the control, inhibited the development of wilt symptoms and recovered cob yield by 100%. Although this is the first success in preventing disease symptoms in infested fields in Israel, the azoxystrobin treatment did not reduce the amounts of pathogen DNA in host tissues or delay its spread. Attempts to reduce concentrations of this fungicide or to apply it by spraying were less effective than the triple full dosage treatment. The presence of the pathogen in the host tissues of the successfully treated plants and its ability to undergo pathogenic variations are increasing the risk of pathogen resistance and the urgent need to develop new ways of controlling late wilt.  相似文献   

11.
The F2 population derived from a cross between isolates pRx (Avr1c-Avr1c) and ps1 (avr1c-avr1c) of Phytophthora sojae, fungal agent of soybean stem and root rot, was used to determine the genetic basis of avirulence towards Rps1c gene in soybean. The results indicated that this avirulence is dominant and controlled by a single locus, as expected for a simple gene-for-gene model. Segregation of Avr1c in the F2 progeny of this cross fits a 3:1 ratio. Four of 80 AFLP primers effectively distinguished the avirulent pRx from the virulent ps1. Among the 5 specific markers, band C was amplified from the avirulent pRx by primer set EGC/MAT, then recovered and cloned. This AFLP marker was successfully transfered to a SCAR marker through sequencing, primer design and specific amplication of the DNA of the avirulent pRx. Results of validity and specificity experiments with 50 individuals of the F2 progeny and 50 field isolates demonstrated that this SCAR marker (a 616-bp fragment) can be successfully and specifically amplified from the P. sojae isolates that have Avr1c gene.  相似文献   

12.
The introduced cultivar ‘Schwarz-21’, a source of resistance, was crossed with the large-podded local cultivar ‘Virginia Bet Dagan No. 4’. Selection of the progeny for larger pods led to reduced resistance levels. The combination of intermediate resistance and use of the inexpensive biocide metham (Vapam) led to low pod rot incidence.  相似文献   

13.
To evaluate the effect of conidial density of Monilinia spp. on the fruit surface on the incidence of latent infection and brown rot in peaches, eleven field surveys were performed in commercial orchards located in Cataluña, Spain over four growing seasons from 2002 to 2005, and nine surveys were conducted to determine the sources of overwintered Monilinia spp. inoculum. There was a significant positive relationship (r?=?0.69) between the numbers of conidia of Monilinia spp. on the fruit surface and the incidence of latent infections, but not with brown rot at harvest. Although mummified fruit, twigs and pits have been identified as being able to carry the pathogen from year to year in peaches grown in Spanish orchards, no relationships between any of these sources and the numbers of conidia on the fruit surface, or incidence of latent infection or brown rot were found. The effect of temperature (T), solar radiation (SR), rainfall (R) and wind speed (WS) on the area under the number of conidia of Monilinia spp. curve (AUncC) on peach surfaces was analysed. Regression analysis revealed that T, SR, R, and WS could account for 99% of the total variation in the area of the AUncC on peach surfaces. Thus, in order to reduce the incidence of latent infection and brown rot it is essential not only to remove the sources of primary inoculum but also to reduce the number of Monilinia spp. conidia on the fruit surface. Furthermore, the sources of airborne conidia of Monilinia spp. should be taken into consideration in disease management programmes in Spain.  相似文献   

14.
In pot experiments the fungicides benomyl and thiophanate-methyl controlledVerticillium wilt of strawberry when applied as a soil drench after planting. Both compounds were ineffective as foliar sprays and as root dips prior to planting. Soil drenches applied to commercially grown runner plants in the waiting field (August) and to the same plants in the greenhouse (December or January) increased the yield. On infested ground, a soil drench with thiophanate-methyl promoted the occurrence of crown rot caused byPhytophthora cactorum.  相似文献   

15.
The protection of plants against bacterial disease is one of the important issues that need to be studied in agricultural applications. The application of a transgene, such as a gene that encodes plant ferredoxin-like protein (PFLP), to generate resistant plants is one possible strategy. Our previous reports have demonstrated that transgenic plants that express extracellular PFLP (ESF plants) are more resistant to bacterial pathogens. This protein intensifies the hypersensitive response (HR) in plants when they are infiltrated by a pathogen-associated molecular pattern (PAMP), harpin (HrpZ), from Pseudomonas syringae. In addition, this intensified HR is associated with the expression of membrane-bound NADPH oxidase. Thus, we attempted to determine the involvement of PFLP in intensifying PAMP-triggered immunity (PTI) to enhance disease resistance. First, we showed that transgenic Arabidopsis plants with the pflp gene were resistant to bacterial soft rot caused by Pectobacterium carotovorum subsp. carotovorum (Pcc). Then, the fliC gene which encoded flagellin from Pcc was cloned and expressed. The FliC protein was used in the functional study with PFLP in Arabidopsis Col-0 plants. The reactive oxygen species (ROS) generation and HR ratio were induced by the treatment with both PFLP and FliC together, but they were not induced by treatment with PFLP or FliC alone. Similar results were confirmed in ESF plants, where FliC elicited rapid ROS accumulation and callose deposition. Moreover, we demonstrated that the PFLP-intensified ROS generation and HR were related to Ca2+ influx and activation of NADPH oxidase. We concluded that the PFLP-intensified disease resistance is associated with the intensification of PAMP-triggered immunity.  相似文献   

16.
Six fungicides were evaluated under laboratory and field conditions for control of Phytophthora leaf blight of taro,Coloeasia esculenta, incited byPhytophthora colocasiae. Inin vitro tests Deraosan 65W was the most effective in inhibiting the mycelial growth of the test pathogen followed by Difolatan 80W, Fytolan (copper oxychloride), Apron 35F, Topsin-M 50W and Dithane Z-78 75W. Excellent control was obtained with Demosan 65W and Difolatan 80W, good control with Apron 35F, fair control with Fytolan, and poor control with Topsin-M 50W and Dithane Z-78 75W. Results ofin vivo tests were correlated with those of thein vitro tests. Roguing of infected leaves did not eradicate the pathogen but can only delay epiphytotics.  相似文献   

17.
From several greenhouse plants showing foot and root rot symptomsPhytophthora isolates were gathered. Isolates fromPeperomia, Saintpaulia andSinningia were identified asP. nicotianae van Breda de Haan var.nicotianae and an isolate fromBegonia asP. cryptogea Pethybr. & Laff. Cardinal temperatures for the various isolates were determined. The specific and non-specific pathogenicity of the isolates was studied by inoculating the different crops with the different isolates, including aP. cryptogea isolate fromGerbera and aP. nicotianae var.nicotianae isolate from carnation. TheP. nicotianae var.nicotianae isolates appeared to be morphologically identical. Some of the isolates were similar in host range, but others exhibited differences in host specificity at 20°C as well as 25, 30 or 35°C. The same applies for the twoP. cryptogea isolates.  相似文献   

18.
Sweet cherry is a major commercial crop in Turkey, the most important producer of the fruit worldwide. Sweet cherry decline was observed in an orchard in Ankara province of Turkey. Affected young trees exhibited reduced tree vigor, yellowing and wilting of leaves, and dieback symptoms resulted in tree death. A Phytophthora sp. was consistently isolated from necroses that appeared on taproots and crowns. The pathogen was identified as Phytophthora cryptogea based on several morphological features and DNA sequence of the internal transcribed spacer (ITS) region. P. cryptogea was pathogenic on excised shoots and 1-year-old cherry rootstocks. This is the first report of P. cryptogea causing disease of sweet cherry in Turkey.  相似文献   

19.
In September 2014, Phytophthora rot on wasabi plants [Wasabia japonica (Miq.) Matsum.] was found for the first time in the city of Okutama, Tokyo, Japan. A Phytophthora sp. strain was constantly isolated from brown stem bases and rhizomes of infected plants. The same symptoms as those observed in the field were produced in vitro through inoculation of test plants with the isolated Phytophthora sp. The fungus was identified as Phytophthora drechsleri based on morphological and DNA sequence comparison. Phytophthora rot, “eki-byo” in Japanese, is proposed for this disease common name.  相似文献   

20.
Essential oils from 14 species of Labiatae were steam-distilled and analyzed. Bean leaf discs freshly sprayed with different concentrations of the acetonic solutions of the oils caused mortality and induced repellency in adult females of the carmine spider mite,Tetranychus cinnabarinus (Boisd.), and egg-laying was reduced. Seven-day-old residues still had some activity. On the basis of EC-50s, the most effective oils were:Lavandula angustifolia xL. latifolia (0.09%);L. angustifolia (0.1%);Melissa officinalis (0.12%);Mentha piperata (1.3%);Salvia fruticosa (1.4%);Ocimum basilicum (1.4%); andRosmarinus officinalis (2.2%).  相似文献   

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