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1.
Trehalose metabolism is related to the sclerotial development of Rhizoctonia solani AG-1 IA, the causal agent of rice sheath blight (RSB). Here, we further elucidated the functions of three genes Rstre, Rstps1 and Rstpp that encode three key enzymes trehalase (TRE), alpha, alpha-trehalose- phosphate synthase (TPS1) and trehalose 6-phosphate phosphatase (TPP) in the sclerotial development of R. solani AG-1 IA. Due to the lack of a stable genetic transformation system for R. solani, the heterologous expression of these three genes in Pichia pastoris GS115 was performed. The results showed that reactive oxygen species (ROS) contents and enzyme activities in R. solani decreased significantly in the treatments of the fermentation broths of Rstps1 and Rstpp transformants, and that in the treatment of the fermentation broth of Rstre transformant visibly increased. Furthermore, the fermentation broths of the transformants of all the three genes were added to potato dextrose agar (PDA) medium for the cultivation of R. solani, as a result, the dry weight of sclerotia in each PDA plate containing the fermentation broths of Rstps1 and Rstpp transformants significantly increased compared with the control, and that of Rstre transformant obviously decreased. Finally, 178 proteins were found to interact with RSTPS1, and 16 of them were associated with ROS. Taken together, the findings suggest that all these three genes related to trehalose metabolism play important roles in the sclerotial development of R. solani AG-1 IA, and can be used as new targets for the development of novel high-efficiency fungicides for the controlling of RSB.  相似文献   

2.
Two tillage practices, chisel plowing (30 cm) and deep moldboard plowing (22 cm), and five rotation crops (oats, lupine, buckwheat, broccoli and peas) were studied for their effects on the soil population ofRhizoctonia solani AG-3 and on Rhizoctonia disease on potato. All rotation crops were harvested except buckwheat, which was treated as a green manure crop. Chisel plowing significantly reduced (p = 0.05) the incidence and severity of stem lesions on potato caused byR. solani AG-3. In 1990, oats after moldboard plowing significantly increased disease when compared to other crops and broccoli after chisel plowing decreased disease severity. Soil populations ofR. solani AG-3 were significantly lower with chisel plowing. No interactions between tillage and rotation crops were observed. Rhizoctonia solani Kühn is a soil inhabiting plant pathogen found worldwide that affects many plant species including white potato (Solanum tuberosum L.).R. solani attacks potato at one or more stages in development resulting in distinct disease symptoms (25) often termed the Rhizoctonia disease complex of potato. In Maine, only strains AG-3 and AG-5 ofR. solani (4, 5) have been identified as attacking potato and causing four distinct types of symptoms: 1) black scurf (sclerotia) on tubers, 2) stem cankers, 3) aerial tubers and top rosetting, and 4) killing of sprouts. Crop rotation has been reported to reduce the incidence and severity ofR. solani on potato, but no single rotation method controls completely or to a high degree of reliability (11, 23, 24, 26). Deep moldboard plowing has been shown to reduce diseases caused byR. solani andSclerotium rolfsii Sacc. in crops other than potatoes (2, 7, 15, 19, 20). However, Gudmestadet al. (6) reported that deep moldboard plowing increased the severity ofR. solani on stems and stolons of potatoes. The reduction of diseases caused byR. solani andS. rolfsii by moldboard plowing is attributed to low inoculum densities in the upper soil layer by the burial of sclerotia to depths where germination and infection were prevented (14, 15, 19, 20). However, disking to a depth of 5–7 cm did not affect disease as the inoculum remained in the root zone (14, 15). Gurkin (7) states that the rationale for deep moldboard plowing is to promote decay of organic matter, remove organic matter from the infection court and to bury the sclerotia below the infection court. Cultural control techniques are largely preventive and are designed to reduce the quantity or the activity of inoculum by means of crop rotation, tillage practices, green manure crops, etc. (22). This study was conducted to determine individual effects and possible interactions of deep moldboard plowing versus chisel plowing in various rotation crops on the presence ofR. solani AG-3 in the soil and on the incidence of Rhizoctonia disease complex of potato.  相似文献   

3.
Canola seedling blight, caused by Rhizoctonia solani, and Fusarium spp., can result in large yield losses to canola (Brassica napus) at high inoculum pressure. The effect of inoculum density was studied by mixing different amounts of R. solani AG-2-1 and Fusarium avenaceum into a sterilized natural soil and soil-less mix (2:1, v:v) separately, and recording seedling emergence, damping-off and seedling height within ten days after seeding; root rot severity at 12 days after seeding and seed yield at harvest on canola cultivars ‘45H29’ and ‘73-77RR’. Root rot severity increased and emergence, plant height and seed yield decreased with increased inoculum density of both R. solani and F. avenaceum. For quantification of R. solani AG-2-1, a primer and TaqMan probe set (Rs21F/Rs21R/Rs21P) was designed based on the nuclear ribosomal internal transcribed spacer (ITS) region of R. solani AG-2-1. From a conventional PCR amplification, an 88-bp product was amplified from all isolates classified as AG-2-1 with the primers Rs21F and Rs21R. No product was amplified with DNA from isolates belonging to other anastomosis groups of R. solani, other pathogens or the host plant. By using quantitative PCR, DNA amounts as low as 100 fg of R. solani AG-2-1 were detected. The quantity of DNA from soil samples with different inoculum densities estimated using qPCR was highly correlated to the number of colony-forming units (cfu) obtained from the same soil samples for both R. solani AG-2-1 and F. avenaceum.  相似文献   

4.
Anastomosis group (AG) identity ofRhizoctonia solani isolates collected from potato plants growing near Leon, Guanajuato, in central Mexico was determined. In samples from 15 fields, we found AG-3 and AG-4 with a frequency of 73.5% and 26.5% respectively. AG-4 was found only during the flowering stage of plant growth, whereas AG-3 was present on plants at every stage of development. The efficacy againstR. solani, in vitro andin situ, of certain biocontrol agents (Bacillus subtilis, Gliocladium virens) and fungicides (Pencycuron, Tolcoflos-methyl, Fluazinam, Azoxystrobin) was assessed. CertainBacillus strains collected from the field inhibitedin vitro growth of isolates of certain AGs. Only Pencycuron and Tolcoflos-methyl inhibited AG-3 100%in vitro, whereas in the field, Azoxystrobin and Pencycuron showed the highest efficacy against development of sclerotia on tubers.  相似文献   

5.
From 2012 to 2015, a total of 226 isolates of Rhizoctonia solani were collected from the stem cankers on potato stems and sclerotia on tubers from different potato cultivation areas of Heilongjiang Province, China. These isolates were assigned to the anastomosis group (AG) by performing conventional PCR assays using previously published primers for ITS-rDNA regions, as well as by observing hyphal interactions where appropriate. Most of the isolates were assigned to AG-3PT (58.85 %), and several were assigned to AG-5 (21.68 %), AG-2-1 (7.08 %) and AG-4 (12.39 %). Pathogenicity tests showed that the AG-3 and AG-5 isolates had the highest virulence, and the disease indices were 1.96a and 2.47a for stem and 1.48a and 1.6a for root (P < 0.05) after analyzed by LSD multiple comparisons, respectively. Both two isolates consistently caused large brown lesions with sunken on the potato stems and roots in in vitro and greenhouse experiments. This is the first detailed report on the AG composition, variability and pathogenicity of R. solani isolates associated with stem cankers and black scurf found on potatoes cultivated in Heilongjiang Province.  相似文献   

6.
The soil-borne pathogen Rhizoctonia solani AG 8 causes major yield losses in wheat (Triticum aestivum. L) production worldwide. Plant tissues of Brassicaceae species contain glucosinolates that are hydrolyzed in the presence of the enzyme myrosinase into products with pesticidal properties. Growth chamber studies were conducted to determine the effect of the Brassicaceae seed meals (SMs) from Brassica juncea, Brassica napus and Sinapis alba on the suppression of the R. solani AG 8 infection of winter wheat. Pasteurized sandy soils were amended with intact and denatured SMs of rape seed and mustard at a rate of 0.5% by soil weight. Regardless of the glucosinolate type and content, all intact and denatured Brassicaceae significantly reduced the infection of winter wheat seedlings by R. solani AG 8 compared to the un-amended control. However, soils amended with S. alba SMs had the lowest severity of Rhizoctonia root rot relative to other amended soils. Phytotoxicity arising from the use of Brassicaceae SMs was observed particularly in soils amended with high glucosinolate-containing SMs. These studies demonstrate that Brassicaceae SMs can be used to manage disease caused by R. solani AG-8. However, future studies will need to focus on strategies for diminishing the crop growth-reducing effects associated with Brassicaceae SM amendment to fully maximize these fungicidal benefits.  相似文献   

7.
Laetisaria arvalis, a soil-inhabiting basidiomycete, reducedRhizoctonia solani infection of white potato. A greenhouse study that monitored population levels of both fungi showed that soil infested withL. arvalis suppressed the growth ofR. solani after eight wks. Populations ofL. arvalis andR. solani increased after 11 wks. when both fungi were infested simultaneously and whenL. arvalis was introduced to soil previously infested withR. solani. Five years of field studies showed that variousL. arvalis seed treatments and soil amendments reducedR. solani infection of stems and stolons and sclerotial formation on tubers equal to the standard chemical treatment of pentachloronitrobenzene (PCNB) + thiabendazole. No relationship was shown between populations ofL. arvalis andR. solani in field plot soils, but native or wild strains ofL. arvalis were shown to be present at detectable levels in field soils.  相似文献   

8.
Rhizoctonia solani Kühn is an important pathogen of sugar beet (Beta vulgaris L.) that can cause damping-off and crown and root rot. Commercial cultivars which are highly resistant to the pathogen are not as high yielding as susceptible cultivars under low or absent disease pressure. These resistant cultivars often do not have resistance to other common pathogens such as Aphanomyces cochlioides, Cercospora beticola, and Fusarium oxysporum. Fungicides, such as azoxystrobin which belongs to the quinone outside inhibitors (QoI) class, are necessary for controlling Rhizoctonia solani, but there are concerns about the buildup of fungicide-resistant strains in the targeted pathogen population. There is a need to find effective fungicides from different chemical groups so they can be rotated with the current widely-used azoxystrobin to manage R. solani. The objective of this greenhouse study was to evaluate the efficacy of penthiopyrad, a succinate dehydrogenase inhibitor (SDHI), in managing R. solani on sugar beet using three different application methodologies. Penthiopyrad effectively controlled R. solani on sugar beet when applied at 210, 280, 420, or 550 g a.i./ha in-furrow at planting and as a soil drench at the 4-leaf stage. However, foliar application of penthiopyrad failed to provide disease control. These trials indicated that penthiopyrad needs to be in close proximity or direct contact with R. solani in the soil to provide effective control. Penthiopyrad has the potential to be used as an effective alternate partner with azoxystrobin for controlling R. solani and to help in mitigating the development of fungicide resistant isolates of R. solani.  相似文献   

9.
根据Thanatephorus cucumeris G蛋白β亚基序列（AY884129）设计引物,对水稻立枯丝核菌AG 1IA的 G蛋白β亚基基因进行了克隆。PCR结果得到1条约为1.9 kb的扩增片段,包含1个约1.7 kb的完整开放阅读框,编码366个氨基酸。同源性检索发现该序列与大量Ｇ蛋白β亚基基因明显同源,一致性介于57.34%~88.14%。根据其推导cDNA序列设计引物进行RT PCR分析,发现该基因在对数生长期表达量最高,提示水稻立枯丝核菌AG 1IA G蛋白β亚基基因可能具有时空表达特性。  相似文献   

10.
Application of Trichoderma harzianum, to soil or by coating tomato fruits, reduced Rhizoctonia solani fruit rot by up to 43% and 85%, respectively, under laboratory conditions. When mixed with naturally infested soil, Trichoderma reduced R. solani inoculum potential by 86% in field trials. It also significantly reduced fruit rot by 27–51%.  相似文献   

11.
Environmentally friendly control measures are needed for soilborne diseases of crops grown in organic and conventional production systems. We tested ethanol extracts from cultures of Serratia marcescens N4-5 and N2-4, Burkholderia cepacia BC-1 and BC-2, and Burkholderia ambifaria BC-F for control of damping-off of cucumber caused by the soilborne pathogens Pythium ultimum and Rhizoctonia solani; ethanol being an Organic Materials Review Institute (OMRI) -approved solvent for use in certain applications in organic crop production. Ethanol extracts from strains N4-5 and N2-4 inhibited mycelial growth and germination of sporangia of P. ultimum in vitro but those from strains BC-1, BC-2, BC-F, and the ethanol control did not. Ethanol extracts from strains BC-2 and BC-F inhibited mycelial growth of R. solani in vitro while ethanol extracts from strains BC-1, N2-4, N4-5, and the ethanol control did not. Thin-layer chromatography demonstrated that ethanol extracts from strain N4-5 contained prodigiosin while ethanol extracts from strains BC-2 and BC-F contained pyrrolnitrin; extracts from strains N2-4 and BC-1 did not contain either of these compounds. DNA sequencing confirmed the presence of a biosynthetic gene for prodigiosin in strain N4-5 and its absence in strain N2-4, while a biosynthetic gene for pyrrolnitrin was found in strains BC-2 and BC-F but not in strains N2-4, N4-5, and BC-1. Prodigiosin was previously implicated in inhibition of P. ultimum while pyrrolnitrin has been shown to inhibit R. solani. Certified-organic cucumber seed treated with an ethanol extract of strain N4-5 was the only extract treatment from any of these five microbial strains to effectively suppress damping-off caused by P. ultimum in growth chamber pot experiments. This ethanol extract provided suppression of P. ultimum on cucumber that was similar to that provided by a commercially available seed treatment pesticide and greater than that provided by a commercially available biocontrol agent for this pathogen. The inhibitory factor(s) in ethanol extracts of strain N4-5 was stable as a seed treatment for at least 14 weeks when incubated at 4 °C in the dark. No ethanol extracts applied as treatments of organic cucumber seed consistently suppressed damping-off caused by R. solani in growth chamber pot experiments. Experiments reported here suggest that certain natural products from microbial strains as seed treatments are promising alternatives for control of soilborne diseases in conventional or organic cucumber production systems.  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.
Helminthosporium solani is a slow-growing fungal pathogen belonging to the family Massarinaceae. It causes blemishes on potato tubers, affecting processing and fresh market trade. Despite its worldwide distribution, little is known about the biology of H. solani. Here we report the generation of a draft genome sequence of H. solani with an estimated genome size of ~35 megabases, for use in phylogenetic and pathogenicity studies of this fungal pathogen. This sequence is also the first reference genome within the family Massarinaceae. We identified a large suite of genes in the H. solani genome that encode putative cell wall degrading enzymes. Based on comparison with other genomes, we speculate that H. solani is a hemibiotroph or necrotroph. The presence of a large number of genes in the glycoside hydrolase (GH) 10 and 43 families, which aid in the hydrolysis of glucoronoarabinoxylan, also suggests that H. solani may be able to survive on grass hosts and indicates the need to re-examine the life cycle and host range of this pathogen.  相似文献   

14.
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   

15.
Crop rotation can be an effective mechanism for reducing disease incidence and contributing nitrogen (N) to succeeding crops. Interactions of plant pathogen suppression and soil nutrient availability may also exist, adding to the cropping system complexity. This study examined the impact of crop rotation, N fertilization, and their interaction on growth, yield, andRhizoctonia solani incidence in potato (Solanum tuberosum L. Norwis). Potato was grown continuously and in two-year rotations with annual alfalfa (Medicago sativa L. Nitro), hairy vetch (Vicia villosa Roth), white lupin (Lupinus albus L. Ultra), and oat (Avena sativa Astro). Fertilizer was banded at potato planting with 0, 45, 90, 135, 180, or 225 kg N ha?1 as (NH4)2SO4. Approximately 58% of continuous potato possessed stem lesions caused byR. solani, but only 12 to 22% of potato stems from other rotations possessed lesions. Tuber dry weight was affected by crop rotation in 1989, a dry year, but not in 1990. Apparent N fertilizer replacement values for hairy vetch, Nitro alfalfa, white lupin, and oat were 65, 43, 26, and 11 kg N ha?1, respectively. All crop rotations studied appeared to enhance potato production by reducing stem infection byR. solani. Vetch and alfalfa provide additional benefits through their N contributions.  相似文献   

16.
A long-term study was conducted between 2000 and 2009 to characterize the incidence, progress and causal agents of cucumber vine decline in Oman. A survey in 175 different greenhouses showed that disease incidence levels range from 0 to 50%, with the highest levels of mortality being in the hotter seasons. Detailed temporal disease increase data from 24 different greenhouses showed mortality progress consists of two phases. The first phase is characterized by attack of young seedlings (<3 weeks old), resulting in damping-off disease. The second phase was characterized by re-appearance of symptoms and plant death (vine decline) during the fruit setting period, 35-50 days after transplanting. Isolations from 148 declining adult cucumber plants yielded Pythium aphanidermatum (80%), Pythium spinosum (13%), Fusarium equiseti (12%), Fusarium solani (8%), Rhizoctonia solani (5%) and one isolate each of Trichoderma hamatum and Bionectria sp. P. aphanidermatum, P. spinosum, R. solani and F. solani were found to be pathogenic on cucumber, with P. aphanidermatum being the most aggressive. This appears to be the first report of association of P. spinosum with vine decline in greenhouse cucumbers and the first report of the high susceptibility of adult cucumber plants to vine decline during the initial period of fruit setting. In addition, this is the first report of association of R. solani and F. solani with declining adult cucumber plants in Oman and the first report of the occurrence of T. hamatum and Bionectria species in the country.  相似文献   

17.
Field burning of residue is a traditional management tool for irrigated wheat (Triticum aestivum L.) production in the Inland Pacific Northwest of the United States (PNW) that can result in reduced air quality. A 6-year no-till field experiment to evaluate two complete cycles of a 3-year irrigated crop rotation of winter wheat–spring barley (Hordeum vulgare L.)–winter canola (Brassica napus L.) was sown (i) directly into standing residue of the previous crop, (ii) after mechanical removal of residue and, (iii) after burning of residue. The traditional practice of continuous annual winter wheat sown after burning residue and inverting the topsoil with a moldboard plow was included as a check treatment. Over-winter precipitation storage efficiency (PSE) was markedly improved when residue was not burned or burned and plowed after grain harvest. Grain yield of winter wheat trended higher in all no-till residue management treatments compared to the check treatment. Average grain yields of spring barley and canola were not significantly different among the no-till residue management treatments. Winter canola failed in 5 of 6 years due to a combination of a newly identified Rhizoctonia damping-off disease caused by Rhizoctonia solani AG-2-1 and cold temperatures that necessitated replanting to spring canola. Six-year average net returns over total costs were statistically equal over all four systems. All systems lost from $358 to $396 ha?1. Soil organic carbon (SOC) increased linearly each year with no-till at the 0–5 cm depth and accumulated at a slower rate at the 5–10 cm depth. Take-all of wheat caused by Gaeumannomyces graminis var. tritici was most severe in continuous annual winter wheat. The incidence and severity of Rhizoctonia on roots of wheat and inoculum of R. solani AG-8, was highest in the no-till treatments, but there was no grain yield loss due to this disease in any treatment. Residue management method had no consistent effect on Rhizoctonia root rot on barley. The annual winter grass downy brome (Bromus tectorum L.) was problematic for winter wheat in the standing and mechanically removed residue treatments, but was controlled in the no-till residue burned and the burn and plow check. Another winter annual grass weed, rattail fescue (Vulpia myuros L.), infested all no-till treatments. This was the first comprehensive and multidisciplinary no-till irrigated crop rotation study conducted in the Pacific Northwest.  相似文献   

18.
Streptomyces philanthi RM-1-138, isolated from the rhizosphere soil of chili pepper in southern Thailand, was investigated for its antagonistic activity against phytopathogenic fungi. In dual culture on glucose yeast-malt extract (GYM) agar plates, this strain suppressed the mycelial growth of all seven plant pathogenic fungi tested (Rhizoctonia solani PTRRC-9, Pyricularia grisea PTRRC-18, Colletotrichum gloeosporioides NBCRSR-3, Colletotrichum capcisi NBCRSR-15, Ganoderma boninense NBCRSR-26, Fusarium fujikuroi PTRRC-16 and Bipolaris oryzae PTRRC-36) with an 82.2–89.2% inhibition and that was most pronounced on R. solani PTRRC-9. Heat treatment of the culture filtrate from growing R. solani PTRRC-9 at 40 °C, 60 °C, 80 °C, and 100 °C for 30 min and 121 °C for 15 min had no negative effect on the inhibitory activity against R. solani PTRRC-9 tested on both solid and liquid culture. The effective dose (>80% inhibition) of culture filtrate in liquid culture was at 5.0% (v/v) while it was at 10% (v/v) on the solid medium. This effectiveness was similar to those of the four chemical fungicides tested. The effect of S. philanthi RM-1-138 against R. solani PTRRC-9 was investigated using SEM and TEM. The compounds produced by S. philanthi RM-1-138 induced alterations to the cell-wall structure of R. solani PTRRC-9, that resulted in the loss of cytoplasm materials by partial lysis. The greenhouse experiment revealed that using either the culture filtrate or the autoclaved culture filtrate from S. philanthi RM-1-138 effectively suppressed rice sheath blight disease by up to 65.6 and 60.8%, respectively.  相似文献   

19.
Silver scurf, caused byHelminthosporium solani, and black dot, caused byColletotrichum atramentarium, are pathogens of tuber periderm whose presence in Colorado was only recently reported. A field survey conducted in September 1977 revealed thatC. atramentarium was more prevalent (21.8% tuber infection) and had a wider distribution thanH. solani (5.4% tuber infection). A greater incidence of both pathogens was observed on thin skinned tubers of chipping cultivars (49.0% infection) than on thicker skinned tubers of table stock cultivars (9.1% infection). Conidial development ofH. solani is tretic, pleurogenous, and requires 17–21 hours per conidium. Conidial septations appear while conidial elongate, and require 3–5 hours per septum. Light microscopy revealed that at least 11 conidia per conidiophore are produced in culture in 54 hours at 20–25 C (68–77 F) and humidity >90%. Scanning electron microscopy showed that fructifications ofH. solani (conidiophores-conidia) arise from beneath infected tuber periderm. Histological studies indicate some peridermal loosening and sloughing. Heavy deposition of unidentified compounds was observed in infected periderm, and hyphae were restricted to periderm cells. Fresh weight loss of tubers naturally infected withC. atramentarium was significantly greater than fresh weight loss of nearly noninfected (< 1% surface area infected) control tubers. Periderm infected with eitherH. solani orC. atramentarium appeared similar, i.e. shriveled, suggesting infections from either pathogen may result in increased fresh weight loss through alteration of the periderm.  相似文献   

20.
【目的】为明确南繁区水稻纹枯病菌(RhizoctoniasolaniAG-1IA)的遗传分化及遗传多样性与致病力的关系,【方法】采用AFLP分子标记技术和离体叶片接种法对南繁核心区(三亚、乐东、陵水)和非核心区(琼中、屯昌和定安)共60株水稻纹枯病菌的遗传多样性、遗传结构和致病力分化进行了测定,并分析了遗传多样性与致病力之间的关系。【结果】聚类分析结果表明,核心区菌株的遗传多样性相对更高;群体遗传结构分析表明,核心区群体的多态性位点百分率(PPL)、Nei基因多样性指数(H)、Shannon信息指数(I)和基因流(N_m)分别为82.24%、0.1932、0.3062和2.5627,高于非核心区群体的67.49%、0.1535、0.2447和0.9365;而核心区群体的基因分化系数(Gst)为0.1633,低于非核心区群体的0.3481。【结论】核心区菌株的遗传变异程度比非核心区菌株高;核心区不同群体间存在较多的基因交流,而非核心区菌体间的基因交流较少,但遗传变异均主要来自于群体内;总体而言,核心区菌株的遗传分化程度更高。菌株的致病力及其与菌株遗传多样性的相关性分析表明,核心区菌株以中等致病型为主,而非核心区菌株则以中、强致病型为主,但与菌株的AFLP谱系之间的相关均未达显著水平。  相似文献   

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