The influence of verticillium wilt epidemics on cotton yield in southern Spain

Experiments were conducted in the Guadalquivir Valley of Andalucía, southern Spain, in 1986 and 1987, using field plots naturally infested with different inoculum densities of the defoliating and nondefoliating pathotypes of Verticillium dahliae to determine the influence of verticillium wilt epidemics on yield of cotton cultivar Coker 310. The total number of bolls, the number of open bolls, and seed cotton yield were related to the growth stage of plants at first appearance of foliar symptoms, and to inoculum density and virulence of the V. dahliae pathotype prevailing in the soil. For the three yield components, the greatest reduction was observed in plants showing symptoms before opening of first flowers (about 650 degree-days after sowing). Yield increased with delay in the development of foliar symptoms during the crop season, and the effect of the wilt epidemics on yield was small or nil for plants that developed symptoms after opening of the first bolls (1400–1500 degree-days after sowing). A multiple regression equation was derived that related yield reduction to the physiological time accumulated from the time of sowing until the appearance of foliar symptoms and to the rate of disease intensity increase over physiological time. This multiple point model explained about 70% of the variation in cotton yield loss due to verticillium wilt.     

Comparative effect of root-knot nematode on severity of verticillium and fusarium wilt in cotton

The effect of root-knot nematode (RKN) (Meloidogyne incognita) onVerticillium dahliae andFusarium oxysporum f.sp.vasinfectum in cotton (Gossypium hirsutum) was investigated. Two different inoculation methods were used, one in which inoculum was added to the soil, so that nematode and fungal inoculum were in close proximity; the other, inoculation into the stem, whereby the two inocula were spatially separated. Invasion of the roots by RKN enhanced disease severity, as measured by the height of vascular browning in the stem, following inoculation with either wilt pathogen. The effect of RKN on Fusarium wilt was more pronounced than that on Verticillium wilt. Nematode-enhanced infection byF. oxysporum is a well known effect but there are few reports of enhanced infection byVerticillium due to RKN. Relative resistance of a number of cotton cultivars to both wilt diseases, as measured by height of vascular browning, was similar to the known field performance of the cultivars. The use of vascular browning as an estimate of disease severity was therefore validated. http://www.phytoparasitica.org posting Feb. 3, 2003.     

Mechanism of broccoli-mediated verticillium wilt reduction in cauliflower

ABSTRACT Broccoli is resistant to Verticillium dahliae infection and does not express wilt symptoms. Incorporation of broccoli residues reduces soil populations of V. dahliae. The effects of broccoli residue were tested on the colonization of roots by V. dahliae, plant growth response, and disease incidence of both broccoli and cauliflower in soils with different levels of V. dahliae inoculum and with or without fresh broccoli residue amendments. The three soils included a low-Verticillium soil, a high-Verticillium soil, and a broccoli-rotation soil (soil from a field after two broccoli crops) with an average of 13, 38, and below-detectable levels of microsclerotia per g of soil, respectively. Cauliflower plants in broccoli-amended high-Verticillium soil had significantly (P 相似文献   

Prospects and strategies in controlling verticillium wilt of olive1

Control of verticillium wilt of olive currently depends on preventive measures. Since systemic fungicides are unable to prevent or control the disease, its control should primarily be based on cultural methods, including irrigation systems which restrict dissemination of Verticillium dahliae propagules by irrigation water and avoidance of intercropping with hosts susceptible to V. dahliae. Since leaves from affected olive trees contribute, through formation of microsclerotia, to the inoculum in the soil, pruning should be practised prior to branch defoliation. As for resistant olive rootstocks or cultivars, promising verticillium-wilt resistance has been found in two rootstocks selected in California (US). However, these have to be tested under local conditions before they can be released to Mediterranean growers, while further search for other resistant rootstocks is needed. Soil solarization applied to individual diseased trees in established olive groves could substantially contribute to recovery or long-lasting symptom remission in the treated trees. This effect is mainly attributed to the decrease or eradication of V. dahliae microsclerotia in the treated soil but also to heat-tolerant fungal antagonists of the pathogen. Using herbicides to control weeds, and limiting soil rotovation, can restrict symptom development. Biological control can also be considered as a promising trend in controlling the disease by searching, testing and exploiting potential fungal or bacterial antagonists.     

Evaluation of the susceptibility of olive cultivars to verticillium wilt1

In the present study, we evaluated the susceptibility of different commercial olive cultivars to verticillium wilt. Two Verticillium dahliae isolates, obtained from olive and artichoke, were used in pathogenicity tests. Two-year-old rooted cuttings were inoculated using either the root-dip or the stem-wounding method. The results were similar with both inoculation methods. Cvs Carolea and Cipressino proved to be moderately susceptible whereas Cassanese, Nocellara del Belice, Nocellara Etnea, Tonda Iblea and Uovo di Piccione were very susceptible. The response of cv. Coratina varied from susceptibility to moderate susceptibility.     

Soil solarization for the control of verticillium wilt of greenhouse tomato

Verticillium dahliae, the causal agent of Verticillium wilt of tomato, causes serious damage to crops grown in unheated greenhouses. To control this disease, growers are obliged to employ strong soil disinfestants. The possibility of controllingV. dahliae by using soil solarization during the months of June — August was examined. The soil was covered with transparent polyethylene sheets for 10 weeks. The pathogen could not be isolated from the solarized soil, whereas the inoculum level in the nonsolarized soil remained high (1379–1806 propagules/g soil). The yield from the solarized soil was increased by 112.4% in comparison with the control, and no infected plants were observed. The percentage of infected roots was very low (0.3–0.4%) in relation to the nonsolarized soil (66.7–67.1%). From these results it was concluded that solarization can effectively control Verticillium wilt of greenhouse-grown tomato under the summer conditions in Crete.     

Effect of light duration and growth season on verticillium wilt in potato

The tolerance response to Verticillium in potato is affected by external abiotic and biotic factors. Short-day photoperiod enhanced disease level in the susceptible cvs. ‘Nicola’ and ‘Maris Bard’, as well as in the tolerant cvs. ‘Cara’ and ‘Désirée‘. This was observed under field conditions, where plant reaction in the spring was compared with that in autumn. In some cases the disease was more pronounced in autumn, with its shorter days, than in spring, when the days are longer. The effect was measured by disease symptom severity, fungus colonization in the plants, plant height and final yield. This disease enhancement was more pronounced under controlled growth room conditions, where the only different parameter was illumination. A short photoperiod of 8 h increased the disease level relative to 16 h of light.     

黄芪黄萎病病原菌鉴定

甘肃素有"千年药乡""天然药库"等美称,全省有中药材资源2 540种,大宗药材30多种,黄荏(Astragalus menbranaceus Bge.)作为"十大陇药"之一,黄(红)芪种植面积达2.8万hm2,占全国的40％.黄芪补脾益气,具有生血摄血,增强免疫功能、保肝、利尿、抗衰老、抗应激、降压的功能.随着我省黄芪...     

Sources of verticillium wilt resistance in wild olive germplasm from the Mediterranean region

Fifty-seven wild olive accessions collected from the Mediterranean basin were screened under greenhouse conditions for their resistance to verticillium wilt. Plants were root-dip inoculated. One defoliating and one non-defoliating isolate of Verticillium dahliae , both obtained from diseased plants in southern Italy, were used. Plants of the highly susceptible cv. Cima di Mola, frequently used as a rootstock in Apulia, were also included in this test. Disease reactions were evaluated on the basis of external symptoms, vascular browning and by calculating areas under disease progress curves ( audpc ). On the basis of audpc values and external symptom severity, accessions were grouped into four phenotypic groups: highly resistant, moderately resistant, susceptible and highly susceptible. Three accessions showed high resistance to both V. dahliae pathotypes. Forty resistant plants were selected from accessions that had shown the highest levels of resistance. Clones were obtained from each of these plants by in vitro micropropagation for further testing. Ten clones showed the resistance characteristics of their original mother plants, while others suffered greater levels of disease severity than their mother plants. Several new olive rootstocks were identified that were highly resistant to verticillium wilt and could be included in breeding programmes for resistance of olive to V. dahliae .     

Long-term effect of soil solarization in controlling verticillium wilt of globe artichokes in Greece

Soil solarization, either singly or in combination with a reduced dosage (34 g/m²) of methyl bromide, was effective in controlling verticillium wilt of globe artichokes for three successive cropping seasons. Both treatments resulted in greatly reduced natural populations of Verticillium dahliae microsclerotia, which were positively correlated with significant reductions in diseased plants as well as with the early formation of primary artichoke heads and increased yield. Propagules of Talaromyces flavus increased and survived better in solarized than in solarized and fumigated soils and could be partially involved in the effectiveness of solarization. Propagules of Aspergillus terreus invariably increased in treated plots but their involvement in the longevity of the treatment is questionable.     

桃树黄萎病在我国首次发生报道

在甘肃省农业科学院林果所2010年建植的桃园内,自2011年以来,每年6-8月都陆续出现枯死的桃树;严重年份桃树病株率达20%。经病原菌分离培养、形态观察和致病性测定,确认桃树枯死是由大丽轮枝菌(Verticillium dahliae)侵染所致。这是桃树黄萎病在我国的首次发生报道。     

The solar chamber: an innovative technique for controlling verticillium wilt of olive1

Control of olive tree wilt, caused by Verticillium dahliae, is not easy. A simple solar-chamber technique has been developed to achieve effective control. The treated tree is irrigated, the soil is covered by a plastic sheet, and a chamber made of a metal framework covered with plastic sheets is placed over the tree. Trees were exposed for 10, 15 and 20 days. Using this approach the temperature in the chamber reached 55°, and soil temperatures at 5 and 15 cm depth reached 55 and 45°, respectively. It was no longer possible to isolate V. dahliae from infected trees after 15–20 days. Growth of treated trees was improved as compared with the untreated ones. Laboratory studies on the efficacy of dry heat on the survival of V. dahliae in diseased branches showed that 50–55°C was lethal after 1 h. On PDA medium, the fungus was killed in 1 h at 50°C and in 45 min at 55°C.     

大丽轮枝菌在茄田土壤中的分布及抽样方法

对茄子黄萎病在田间的空间分布及取样方法进行了研究,并探讨了田间土壤带菌量的准确测定方法。研究结果表明:用分布型指数法测定茄田土壤中微菌核的空间分布型,当菌核数量在8-63 ～39-93 个/g 干土范围内,为聚集分布。当茄田发病率小于75 % 时,病株在田间均属聚集分布;发病率大于75 % 时呈均匀分布。土壤中微菌核的调查方法以棋盘式为最适宜。     

大丽轮枝菌在茄田土壤中的分布及抽样方法

对茄子黄萎病在田间的空间分布及取样方法进行了研究,并探讨了田间土壤带菌量的准确测定方法。研究结果表明:用分布型指数法测定茄田土壤中微菌核的空间分布型,当菌核数量在8-63 ～39-93 个/g 干土范围内,为聚集分布。当茄田发病率小于75 % 时,病株在田间均属聚集分布;发病率大于75 % 时呈均匀分布。土壤中微菌核的调查方法以棋盘式为最适宜。     

Modes of action of the protective strain Fo47 in controlling verticillium wilt of pepper

The protective fungus Fusarium oxysporum Fo47 reduces the severity of wilt caused by the soilborne pathogen Verticillium dahliae in pepper. Modes of action responsible for the biocontrol activity were studied. Microscopic observations of fluorescent protein‐transformed strains colonizing the root surface show that the colonization patterns of Fo47 and V. dahliae were similar. Pixel counting of the images obtained by confocal microscopy showed that Fo47 reduces colonization of the root surface by V. dahliae, suggesting a possible role of competition for nutrients at the root surface. Besides these effects on surface colonization, the hormonal pathways activated during priming of plant defence responses were identified by measuring the amount of some phytohormones and their derivatives in roots and stems of pepper. Results showed an early, slight increase of jasmonyl isoleucine, followed by a transient increase of salicylic acid during the pre‐challenged phase of priming and an increase of 12‐oxo‐phytodienoic acid during the challenge phase of priming. The caffeic, ferulic and chlorogenic acids, known to play a role in plant defence reactions, showed a strong antimicrobial activity against V. dahliae in vitro. In pepper roots, Fo47 stimulated the biosynthesis of caffeic acid and primed that of chlorogenic acid. These results demonstrated that the effective control of V. dahliae provided by Fo47 is based on different but complementary mechanisms.     

新疆主要棉区棉花黄萎病发生概况

为了解目前新疆棉花黄萎病的发生现状,对新疆主要植棉地区棉花黄萎病发生程度、落叶型菌系分布以及代表棉区主栽品种黄萎病抗性类型、棉花黄萎病发生规律进行了调查研究。结果表明:在调查的新疆棉田中棉花黄萎病发病田占58.2%,其中病情指数达5.0以上的棉田占28.1%;新疆棉花黄萎病菌系中37.3%为落叶型菌系;阿克苏棉区主栽的棉花品种(系)‘中棉49号’、‘中棉414号’、‘2905’棉花黄萎病抗性表现为耐病,生产上缺乏抗病品种。阿克苏棉区棉花黄萎病发生始期较往年趋早,发病程度趋于严重,6月下旬至7月下旬为棉黄萎病快速发展期,后期由于高温抑制作用,发病趋缓。     

Morphophysiological response of young olive trees to verticillium wilt under different surface drip irrigation regimes

The effects of irrigation on verticillium wilt in olive, in terms of morphological, biomass and physiological parameters were evaluated on pot‐grown trees maintained in the field for 3 years. Plants inoculated and noninoculated with Verticillium dahliae were irrigated to high and low range of soil water content (HR and LR) at daily (DF; about 2 days/event), weekly (WF) and daily‐weekly (DWF) drip‐irrigation frequency. Morphological parameters, relative biomass and biomass water‐use efficiency were higher at LR than at HR (with few exceptions) and at DF than at other frequencies in noninoculated and inoculated plants, but the fungus reduced those parameters by 17.0–38.5%. Lower root weight ratio, relative biomass and shoot length as area originated at HR in noninoculated plants, could be favourable to the accumulation of root infections and the amount of fungus per tissue length in inoculated plants because higher infection was known at HR. Moreover, higher aerial biomass and length promoted by irrigation at DF could prevent the more severe expression of symptoms, which occurred at WF and DWF in the presence of Verticillium. Negative correlations were found between indicated parameters and disease. Lower water stress (S_Ψ), and higher stomatal conductance (g_s) and net photosynthesis at DF in noninoculated plants could limit the disease by improving water status, as S_Ψ was increased by the fungus only at WF and DWF, and g_s and disease were negatively correlated. LR‐DF treatment minimized the disease and kept the growth, water‐use efficiency and physiological parameters in inoculated plants to levels close to noninoculated plants.