首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Alternaria solani Sorauer (Ellis) is a causal agent of early blight of potato (Solanum tuberosum L.). Sensitivity to chlorothalonil, triphenyl tin hydroxide (TPTH), and mancozeb was determined for field isolatesof A. solani in 1998 and 1999. Specifically, the relative sensitivity ofA. solani to foliar fungicides in field populations collected from several commercial fields was evaluated over the course of two growing seasons. Sensitivity to these foliar fungicides was determined with anin vitro spore-germination assay method. The fungicide concentration that inhibited conidial germination by 50% (EC50) was estimated for each isolate. Sensitivity ofA. solani isolates to TPTH and mancozeb varied little during the growing season, possibly because there were few TPTH and mancozeb applications made to the fields studied. At several locations, however, repeated exposure ofA. solani populations to chlorothalonil resulted in considerable variability in sensitivity, frequently causing isolates to have decreased sensitivity to this fungicide at the end of the growing season. In five of seven fields, isolates of A.solani collected at the end of the season were significantly less sensitive to chlorothalonil than isolates collected at the beginning of the season.  相似文献   

2.
A host resistance factor was integrated into the FAST (Forecaster ofAlternariasolani onTomatoes) system to initiate and to schedule fungicide applications for three levels of potato cultivar susceptibility while maintaining disease control and yield. Four cultivars ranging from susceptible to moderately resistant were each treated with the fungicide chlorothalonil during two field seasons. The five fungicide treatments were a 7-day schedule initiated after 50% flowering; a non-sprayed control; and three FAST application schedules based on combinations of critical levels of cumulative severity (CS, the disease severity values as a function of leaf wetness and temperature) and cumulative rating (CR, the disease rating values as a function of average temperature and hours of relative humidity greater than 90%) values. The FAST system predicted the onset of early blight and subsequent periods conducive for disease development in 1993 and 1994. There were cultivar-by-spray-schedule interactions for both disease severity and yield, suggesting that differences in early blight sus-ceptibility exist between cultivars. Use of the recommended schedules for the cultivar’s targeted level of susceptibility reduced early blight severity and minimized fungicide use while maintaining yield. These results indicate that a host-resistance factor can be incorporated into the FAST system.  相似文献   

3.
The Kennebec variety of potato was exposed toAlternana solani inoculum during the 1970 and 1971 seasons to determine the effects of differential rates of nitrogen and phosphorus on the incidence of early blight. Both high nitrogen and low phosphorus treatments significantly reduced the incidence of early blight and the combination of high nitrogen and low phosphorus consistently gave the lowest incidence of the disease during both years. The data suggest that this combination of nutrients may be related to early blight resistance in the plant by extending the period of meristematic activity permitting the plant to wall off infection. Yield data indicated that there was too great a yield difference between fertilization for optimum early blight control and fertilization for optimum yield. Therefore, in Maine, potatoes should be fertilized for optimum yield with a reasonable specific gravity, and early blight should be controlled by the application of fungicides and sanitation measures.  相似文献   

4.
Copper oxychloride at three dosage rates, nickel chloride at two rates and a combination of the two at three rates were tested against blister blight of tea (caused by Exobasidium vexans Massee) at six different treatment intervals from June to November, 1981. Under severe monsoon weather conditions, disease incidence exceeded the critical economic threshold limit with both fungicides when applied at intervals longer than 3 days. Only with the combination of copper and nickel was blister blight infection below the critical limit at 5-day spray intervals. When weather conditions were mild in October and November the treatment interval could be safely extended to 11 days with either copper or nickel alone, or both used together. The eradicant nickel chloride was superior to the protectant copper fungicide under severe weather conditions. A strong interaction was evident between dosage, treatment interval, the mode of action of the fungicide and weather conditions in blister blight disease control. The results point to the need in practice for short spray intervals with a copper-nickel combination at 210 g/ha of each from June to September and longer intervals thereafter, for maximum economic control.  相似文献   

5.
A species specific forward primer was designed in order to identify the phytopathogenic fungus Alternaria solani, which causes early blight on potato. The reverse primer came from another survey of the American population of A. solani. The combination of these two primers can be used both as molecular identification of A. solani as well as sending the PCR product for sequencing in search for the F129L substitution associated with loss of sensitivity toward fungicides based on strobilurins. The diagnostic method has been successfully used when identifying the causal agent of lesions on potato leaflets during large field assays.  相似文献   

6.
Three different rates of soil-applied nitrogen were combined in all possible combinations with different schedules of fungicidal sprays for early blight (Alternaria solani) control in field experiments for three consecutive years. The nitrogen was applied with a constant rate of phosphorus. Yield response to fungicidal sprays was more pronounced when potato plants had received nitrogen and phosphorus. Both spraying and fertilizer application reduced the percentage of leaflets infected by early blight. However, the effect of the fungicide was greater than that of fertilizers. Estimates based on the cost and price assumptions indicated that $1.00 investment in the optimum number of fungicidal sprays at the adequate rate of fertilizer returned $8.34, $9.71 and $1.89 in 1970, 1971 and 1972, respectively.  相似文献   

7.
The use of azoxystrobin (Quadris) for early blight control often results in potato vines remaining greener later in the growing season. This observation has lead to the suggestion that nitrogen (N) fertilizer could be applied at lower rates when azoxystrobin is used in a fungicide program since high N rates are sometimes used to help manage early blight. The objectives of this study were to evaluate the effectiveness of azoxystrobin for control of early blight under various N fertility management regimes and to determine if azoxystrobin affected plant N fertilizer requirements. Plots were established in 1999 and 2000 at Becker, MN, on a Hubbard loamy sand as a complete factorial, split-plot arrangement using a randomized complete block design with four replications. Fungicide treatments were used as the whole plot factor and included an untreated control, chlorothalonil, and azoxystrobin rotated with chlorothalonil. Fertility treatments were used as the sub-plot factor and included N applied at three levels (170, 250, and 340 kg ha?1) and two timings (all prehilling or pre- and post-hilling). Early blight was problematic in 1999 and both early and late blight were severe in 2000. Significant interactions were observed between fungicide and fertility treatments for disease control. Control of diseases with fungicides was generally more effective at higher N rates regardless of N application timing. When azoxystrobin was used in the fungicide program, N rate was not as critical in managing foliar disease. In 1999, an interaction was not observed between N rate and fungicide treatment for yield. Yields increased with increasing N rate regardless of fungicide program. However, a significant interaction did occur between N rate and fungicide treatment in 2000 where yields decreased linearly in the control with increasing N rate, increased linearly with N rate using chlorothalonil, and did not respond significantly to N rate using azoxystrobin/chlorothalonil. Results of this study indicate that interactions between the incidence of early/late blight disease and N requirement for potato may depend on the rate of vine death and conditions affecting tuber maturity. At equivalent N rates, post-hilling N tended to depress yield regardless of fungicide program, suggesting that under the conditions of this study late season N is not an effective practice for managing foliar diseases such as early or late blight.  相似文献   

8.
Sprinkler application of four fungicides, Du-Ter 47.5% W.P. (0.70 kg/ha), Difolatan 4F (3.51 1/ha), Bravo W-75 (1.68 kg/ha) and Bravo 500 (1.17 1/ha, 1.761/ha and 2.341/ha) were evaluated in Colorado for control of potato early blight caused byAlternaria solani (Ellis & G. Martin) L.R. Jones and Grout and compared to the conventional method of airplane application. Fungicides applied through center pivot irrigation systems generally achieved disease control equal to airplane application. Application of fungicides through both center pivot sprinklers and by airplane effectively reduced early blight infection. Control of early blight by airplane or sprinkler application of fungicides significantly (P = 0.05) increased potato yields in 1978. In other years (1977, 1979 and 1980) fungicide applications which reduced disease severity generally increased tuber yields but the increases were not significant when compared to the control.  相似文献   

9.
A field study was undertaken to ascertain the effects of elicitors viz. benzothiadiazole (BTH) and salicylic acid (SA) on defense related enzymes viz. peroxidase, phenylalanine ammonia lyase, superoxide dismutase, chitinase and β-1,3-glucanase, and phenols in rice (Pusa Basmati I) plants. First foliar spray of BTH (50 mg/kg) and SA (50 mg/kg) was done at the maximum tillering stage and inoculation with Rhizoctonia solani was carried 24 h after elicitor treatment. Elicitors were further sprayed at every growth stage. Time course analysis showed peak accumulation of defense related enzymes and phenols in the rice leaves treated with BTH and SA, and accumulation was the highest at the flowering stage. Higher enzymatic activity was observed in elicitor treated plants inoculated with R. solani. Compared to the untreated control plants, application of elicitors before R. solani inoculation significantly elicited the defense related enzymes and phenols. Moreover, application of elicitors had a positive effect on yield and disease reduction. It is suggested that pretreatment of rice leaves with BTH and SA could be used to enhance the level of protection against sheath blight and to improve rice yield in the fields.  相似文献   

10.
Both sheath blight and blast are important rice diseases worldwide. The exploration of environmentally sound practices to control these diseases will help to reduce fungicide application. Effects of rice (Oryza sativa) intercropping with water chestnut (Eleocharis dulcis) on rice sheath blight and rice blast disease as well as the extracts of different plant parts and root exudates from water chestnut on pathogens of rice sheath blight (Rhizoctonia solani) and rice blast disease (Magnaporthe oryzae) were investigated using pot experiments and bioassay tests. The results from pot tests showed that rice-water chestnut intercropping system suppressed sheath blight and blast and improved land equivalent ratio (LER). The results from bioassay tests indicated that extracts and root exudates from water chestnut had significant effects to inhibit the expansion of these pathogens. The scales of these inhibitions were time and concentration dependent. The antifungal activities of the extracts from aboveground parts and pulp of water chestnut were significantly higher than the extracts from other parts and root exudates. The water extracts of aboveground parts showed the highest antifungal activity on both pathogens according to EC50 values. The antifungal activities of the same extracts from water chestnut on R. solani were significantly higher than on M. oryzae. The result suggests that water chestnut possesses bioactive substances to suppress rice sheath blight disease and rice blast disease. The rice-water chestnut intercropping system can be used as an environment-friendly method for diseases control in rice field.  相似文献   

11.
A series of clonal variants of common potato varieties which had been selected for different maturities were screened in the field for their resistance to early blight caused by the fungusAlternaría solani. Maturity of these cultivars was also rated in the field. A strong correlation was found between cultivar maturity and resistance to early blight. Earlier-maturing cultivars were more susceptible, and later-maturing cultivars were more resistant. Starch gel electrophoresis of the tuber enzymes of these cultivars indicated that the maturity variants did not differ with respect to the isozymes tested. This is consistent with the hypothesis that variants of the same cultivar, differing only in maturity, had been selected. These results therefore suggest that it may be difficult to select cultivars which are both early-maturing, and resistant to early blight.  相似文献   

12.
Root and crown rot is the major soil-borne fungal disease in sugar beet. In Europe, the disease is mainly caused by the anastomosis group (AG) 2-2IIIB of the basidiomycete Rhizoctonia solani (Kühn). No chemical fungicide to control the disease has been registered in Europe. Therefore, agronomic measures must be optimized to keep the disease severity below an economic damage threshold and to minimize white sugar yield losses. R. solani AG 2-2IIIB infects many other crops besides sugar beet, including maize, where it causes root rot. Sugar beet and maize are frequently grown in the same crop rotation. The proportion of cultivated maize in several European sugar beet growing areas is expected to rise due to a projected increase in demand for renewable resources over the next few years. Although the susceptibility to and tolerance of the disease varies among cultivars in both crops, little is known about the effects of cultivar susceptibility in the pre-crop on a subsequent susceptible crop. The cultivation of R. solani-resistant maize genotypes in rotation with resistant sugar beet might therefore be a useful tool in an integrated control strategy against R. solani, eliminating the need to restrict the desired crop rotation for phytosanitary reasons. A crop rotation experiment with artificially inoculated R. solani was conducted in the field to investigate the pre-crop effects of maize cultivars which differed in their susceptibility to R. solani on a susceptible sugar beet cultivar. We hypothesized that the maize genotype would influence the inoculum potential and performance of a susceptible sugar beet genotype grown after a maize pre-crop, and that this would correlate with the susceptibility of the maize genotype. The results demonstrate that the susceptibility of maize genotypes is consistent over a period of years and that cultivated maize genotypes influenced the inoculum potential measured as disease severity in sugar beet. However, disease severity in sugar beet did not correlate with the disease susceptibility of the genotype of the maize pre-crop. Possible reasons for this missing relationship might be differences in the quality of maize residues for the saprophytic survival of the pathogen or a genotype-specific alteration of the antagonistic microbial community. However, our findings showed that in the presence of maize- and sugar beet-pathogenic R. solani, the most favourable maize cultivar for a crop rotation cannot be determined solely on the basis of its resistance level against Rhizoctonia root rot.  相似文献   

13.
MicroRNAs(miRNAs) are about 22 nucleotides regulatory non-coding RNAs that play versatile roles in reprogramming plant responses to biotic and abiotic stresses. However, it remains unknown whether miRNAs confer the resistance to necrotrophic fungus Rhizoctonia solani in rice. To investigate whether miRNAs regulate the resistance to R. solani, we constructed 12 small RNA libraries from susceptible and resistant rice cultivars treated with water/pathogen at 5 h post inoculation(hpi), 10 hpi and 20 hpi, respectively. By taking the advantage of next-generation sequencing, we totally collected 400–450 known mi RNAs and 450–620 novel miRNAs from the libraries. Expression analysis of mi RNAs demonstrated different patterns for known and novel miRNAs upon R. solani challenge. Thirty-four mi RNA families were identified to be expressed specifically in rice, and most of them were involved in plant disease resistance. A particular Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway analysis result revealed that a great majority of target genes of regulated miRNAs belonged to the pathway of plant-pathogen interaction. Moreover, miR444 b.2, miR531 a, mir1861 i, novel_miR1956 and novel_miR135 conferred response to R. solani infection confirmed by Northern blot. Our global understanding of miRNA profiling revealed that the regulation of mi RNAs may be implicated in the control of rice immunity to R. solani. Analysis of the expression of miRNAs will offer the community with a direction to generate appropriate strategies for controlling rice sheath blight disease.  相似文献   

14.
Early blight, caused byAlternaria solani Sorauer, is a serious disease of potatoes that occurs in most potatogrowing regions in the world. There is little resistance to early blight among commercial potato cultivars. However, resistance to early blight in diploid (Solanum phureja-S. stenotomum) potatoes has been identified, and was found to be highly heritable and readily transferred to the tetraploid level via4×-2× crosses. The purposes of this study were to identify good levels of early blight resistance in open-pollinated4×-2× (Solanum tuberosum×S. phureja-S. stenotomum) hybrids selected for horticultural characteristics, to estimate broad-sense heritability for early blight resistance in these hybrids, and to investigate the general and specific combining ability for resistance to early blight from some of these early blight resistant tetraploid selections. Four early blight resistant clones were crossed as female parents with four different male parents in a design II mating scheme to generate 16 families. Approximately 20 randomly chosen offspring per family were visually evaluated for early blight resistance in 1995 and 1996 in a randomized complete block design in Pennsylvania. Broad-sense heritability for early blight resistance among the open-pollinated4×-2× hybrids which were originally selected for horticultural characteristics was 0.91 with a 95% confidence interval of 0.80, 0.94. There were significant differences among female and male parents for area under the disease progress curve, indicating the importance of general combining ability for early blight resistance in this germplasm. The female x male source of variation was not significant, indicating that specific combining ability was not important. The greatest number of resistant progeny were observed in families where both parents were derived from the early blight resistant population; however, at least one highly resistant progeny was produced in all families. These results suggest that the early blight resistance in these clones can be readily incorporated into the commercial tetraploid breeding population.  相似文献   

15.
Under environmental conditions favorable for wound healing, potato tubers became significantly (P = 0.05) more resistant toA. solani infection during a two-day interval between wounding and inoculation. This period coincided with the time required for wounded tubers to completely seal wounded surfaces by suberization at 15.6°C/98% RH. Suberization of the wounded surfaces provided tubers significant (P = 0.05) protection againstA. solani invasion but wound periderm development was also essential for total exclusion of the pathogen. Wound healing takes place faster at high temperatures and relative humidities. The effect of temperature is more critical in the wound healing process.  相似文献   

16.
Sunflower (Helianthus annuus L.) is an important oilseed crop in China and is grown in rotation with potato in the northern parts of China, including Inner Mongolia, Hebei, Shaanxi, Shanxi, Gansu, Jilin, Liaoning and Heilongjiang provinces. In 2014, diseased samples of sunflower (variety 3638C) with black sunken lesions on bracts and stems of sunflower were collected in Wuchuan, Hohhot (41°05′ N, 111°27′ E) and Chahaeryouyihouqi, Wulanchabu (41°52′ N, 113°0′ E), Inner Mongolia, China. We used morphological and molecular techniques to identify the causal agent of Alternaria leaf blight. Phylogenetic analysis based on a combined phylogenetic dataset using the glyceraldehyde-3-phosphate dehydrogenase (gpd) and Alternaria major allergen gene (Alt a1) was done to support the morphological identification. In addition, PCR was performed with specific primers targeted on Alt a1 and calmodulin genes of A. solani and A. tomatophila. The results showed that HaAs7 gave an amplicon of the expected size (164 bp) with A. solani-specific primers, however, no band was observed with the A. tomatophila-specific primers. The opposite pattern of PCR result (483 bp) was obtained with DNA of HaAt4 as template, indicating that HaAs7 is A. solani and HaAt4 is A. tomatophila. Furthermore, evaluation the pathogenicity of the recovered Alternaria isolates and their potential as causal agents of Alternaria leaf blight of sunflower was done. Pathogenicity tests showed that A. solani and A. tomatophila tested could be capable of causing Alternaria leaf blight of sunflower. Till now, nine species of Alternaria have been reported causing Alternaria leaf blight of sunflower, this is the first report that A. solani and A. tomatophila as causal pathogens for Alternaria leaf blight on sunflower.  相似文献   

17.
Elicitors of systemic acquired resistance are well known to reduce severity of several plant pathogenic diseases caused by fungi, bacteria and viruses. Their field applications for management of plant diseases are, however, limited because of yield penalties. Our studies on affect of Benzo (1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), an elicitor of systemic acquired resistance, on chickpea blight caused by a fungal pathogen Didymella rabiei showed that multiple foliar applications of the chemical were effective in management of the disease under economic threshold levels. Multiple applications, however, affected chickpea grain yield adversely. The BTH induced yield penalties could be prevented by foliar spray schedule comprised of BTH and a contact fungicide mancozeb. One spray of BTH (50 ppm) followed by another of mancozeb (0.2%) was less effective (8.3% severity) than three sprays of BTH (4.2% severity) in blight control, however, this treatment enhanced grain yield significantly (1.241 t ha−1) over three sprays of BTH (0.922 t ha−1).  相似文献   

18.
Pesticide use in US fall crop potato production was surveyed for the years 1990 to 1994. The purpose of the study was to provide information about the relative importance of each pesticide and potential alternatives. The objectives were to: (1) inventory pesticides used on potatoes, (2) rank the target pests and (3) estimate the economic value of the major pesticides. Extension specialists working on potatoes in twelve states provided the main source of survey data. The most commonly used pesticides in four categories were: fungicide —chlorothalonil, insecticide —methamidophos, herbicide —metribuzin, and “other” -diquat. The most frequent target pests were: early blight (Alternaria solani), late blight (Phytophthora infestans), aphids (primarily Myzuspersicae), Colorado potato beetle (Leptinotarsa decemlineata), lambsquarter (Chenopodium album), and pigweed (Amaranthus spp.). The pesticides that provided the most annual value to potato growers were methamidophos ($281 million), diquat ($86 million), metribuzin ($81 million), CIPC ($56 million) and esfenvalerate ($52 million).  相似文献   

19.
In tomato crop, the induction of resistance emerges as an important alternative for achieving the reduction of chemicals in disease control. This study aimed to evaluate the ability of 28 Trichoderma isolates to promote the growth of tomato seedlings and to induce systemic resistance (ISR) against Xanthomonas euvesicatoria and Alternaria solani, the causal agents of bacterial spot and early blight, respectively. Twelve isolates promoted the increase of plant dry matter mass (DMM) above 100%, showing the great potential of these strains. All isolates were able to colonize the root system of tomato plants. The plant growth-promoting isolates were further evaluated for potential elicitation of ISR. Treatment of the soil with all Trichoderma isolates provided protection in tomato plants from 24.13 to 95.94% against X. euvesicatoria and 30.69 to 95.23% against A. solani. The most efficient isolates in reducing the severity of bacterial spot and early blight were the isolates IB 28/07, IB 30/07, IB 37/01 and IB 28/07, IB 30/07 and IB 42/03, respectively. The effect of different time intervals between Trichoderma application and inoculation with pathogens in inducing systemic resistance in tomato plants was evaluated for the isolate IB 28/07. IB 28/07 conferred protection against both diseases at all time intervals, confirming the ability of the isolate to reduce the severity of these diseases up to 21 days after treatment of tomato plants. In vitro assays revealed that all isolates of Trichoderma were able to degrade cellulose. Only the isolate IB 34/08 showed antagonistic activity against X. euvesicatoria and none caused reduction in the in vitro mycelial growth of A. solani. Trichoderma isolates were identified at species level by DNA sequencing.  相似文献   

20.
The heritability of resistance to early blight caused byAlternaria solani (Ell. & Martin) Son was estimated for field grown, diploid potatoes at Fletcher, North Carolina in 1981. Fourteen breeding lines, selected from a random mated hybrid population ofSolanum tuberosum, subsp.phureja andstenotomum, were used. Resistance was measured as the slope obtained by regressing the logit of the disease proportion Y, measured as % defoliation, on time. A wide range of resistance was found. Narrow-sense heritability, as determined by offspring-midparent regression, on an individual plant basis, was calculated to be 0.825.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号