Biological control of southern blight disease of tomato caused by Sclerotium rolfsii with simplified mycelial formulations of Trichoderma koningii

Two simple formulations of an antagonistic strain of Trichoderma koningii were employed against southern blight disease caused by Sclerotium rolfsii in seedling, potted outdoor and field-grown tomatoes (cvs. Ife No. 1 and Ibadan Local). Corn cob germling inoculum and mycelium powder of T. koningii significantly controlled ( P ≤0·05) symptoms of damping off, blight and wilting in both tomato cultivars. The populations of the antagonist increased from an initial 1 × 10⁴ to about 1 × 10⁶ colony-forming units per g of soil in the protected plants. Moreover, sclerotial counts decreased significantly ( P ≤0·05) in these soils and those sclerotia found had been parasitized by T. koningii. Trichoderma -protected plants were more vigorous than those in the other treatment categories. The significance of these results is discussed in relation to the use of Trichoderma in appropriately simplified formulations.     

Application of Trichoderma and Gliocladium in alginate pellets for control of Rhizoctonia damping-off

Alginate pellets were prepared from wet fermentor biomass of 11 isolates of Trichoderma spp. and Gliocladium virens , with wheat bran as a food base carrier. Pellets with eight of the isolates reduced survival (34-78%) of Rhizoctonia solani in infested beet seed in soil. Pellets containing a T. harzianum isolate (Th-58) and a T. hamatum isolate (TRI-4) were the most effective. All isolates significantly reduced growth of the pathogen from infested beet seed into natural soil. Populations of isolates proliferated in soil to 10⁶−10¹¹ colony-forming units/g (cfu) from propagules within the pellets. Pellets with TRI-4 reduced pathogen survival and growth (>70%) in six different soils and were effective against six R. solani isolates in a natural loamy sand. Survival of R. solani in infested beet seed was not reduced when TRI-4 pellets were added to soil 1-6 weeks before the pathogen; however, saprophytic growth was prevented. Small amounts of biomass (3.0–7.5 g wet weight) in pellets were as effective as a large amount (300 g) in suppressing the pathogen. The storage of pellets for more than 6 weeks at 5 or 25C reduced their effectiveness against R. solani. Pellets prepared with four and three of the 11 isolates prevented damping-off of cotton and sugar beet in the greenhouse, respectively.     

苹果白绢病防治药剂的筛选及使用方法

白绢病是苹果苗期和幼树期的重要病害,可导致死树和死苗。为了筛选有效的杀菌剂,提供有效的病害防控技术,通过花盆土壤施药、撒施药土等方法测试了9种杀菌剂和生石灰对白绢病菌的抑制效果。结果表明,95%甲基立枯磷TC和99%噁霉灵TC两种药剂能有效抑制白绢病菌的生长和菌核的形成,抑制率在80%以上;25 g/L咯菌腈FSC和45%抑菌脲SC对白绢病菌的生长和菌核形成也有抑制效果,但其抑制率不足50%。9种杀菌剂都不能杀死菌核中的病菌。生石灰能有效抑制白绢病菌生长扩展,其抑菌范围超过5 cm,但不能抑制病菌形成菌核。将生石灰撒于根围或土表,或混入育苗基质、锯末或土壤中,可预防苹果苗期和幼树期的白绢病。甲基立枯磷和噁霉灵可用于苗木消毒、浇施、地面喷雾或随滴灌使用。     

Effect of propiconazole on growth and sterol biosynthesis by Sclerotium rolfsii

Germination of sclerotia ofSclerotium rolfsii on agar nutrient medium was delayed or slightly inhibited by concentrations of propiconazole between 0.4 and 4.0 μg ml^?1, but was strongly inhibited by 8 μg ml^?1 and completely inhibited by 16 μg ml^?1. On the other hand, growth of hyphae from the germinated sclerotia was strongly inhibited by propiconazole at 1 μg ml^?1 or greater. Hyphal growth from agar discs on agar medium was about 8 times less sensitive than hyphal growth from the sclerotia or from hyphal inoculum in liquid media. Propiconazole at 0.25 and 1.0 μg ml^?1 strongly inhibited ergosterol biosynthesis, but this was not associated with large accumulations of C-14 methyl sterols. The ratio of eburicol to ergosterol in hyphae grown in the presence of 0.25 μg ml^?1 propiconazole for 16, 30 or 45 h was 0.11, 0.13 and 0.04, respectively, for the three intervals while for hyphae grown in the presence of 1 μg ml^?1, the ratios were 0.29, 0.36 and 0.30, respectively, for the same intervals. In view of a ratio of 23.5 for¹⁴C-acetate incorporation into the two sterols during the initial 6 h growth period in the presence of propiconazole, it is believed that the lack of large accumulation of C-14 methyl sterols is due to the feedback inhibition by eburicol or to cell lysis when the content of ergosterol becomes too low in the actively growing cells.     

Effect of aBacillus subtilis isolate on southern blight (Sclerotium rolfsii) and lipid composition of peanut seeds

Sclerotium rolfsii Sacc. was the cause of both the spoilage and the reduction in quality of peanut seeds as well as the decrease in quality and quantity of the oil during pathogenesis. The application of a biocontrol agent,Bacillus subtilis, counteracted the negative effect of the seedborne pathogen (S. rolfsii) on the chemical and physical properties of the oil content. Moreover, the changes in fatty acids composition of peanut seed oil have been related to a tolerance mechanism againstS. rolfsii and to the induction of systemic physiological changes which result in greater improvement of oil quality and quantity.     

Induction of resistance to Sclerotium rolfsii in different varieties of onion by inoculation with Trichoderma asperellum

We evaluated the ability of Trichoderma asperellum Samuels, Lieckfeldt & Nirenberg to induce resistance to the fungal plant pathogen, Sclerotium rolfsii Saccardo, in three onion (Allium cepa L.) varieties. Both the severity of disease and the activities of glucanase, chitinase and peroxidase (enzymes involved in plant resistance) were evaluated in onions inoculated with T. asperellum alone, S. rolfsii alone, or both T. asperellum and S. rolfsii (dual-inoculation) and compared to uninoculated (control) plants. In dual inoculations, the presence of T. asperellum reduced the severity of disease symptoms caused by S. rolfsii. Inoculation with T. asperellum alone increased glucanase, chitinase and peroxidase activity in bulbs, roots and leaves of all three onion varieties compared to uninoculated controls; bulbs of the variety Red Satan (RS) had the highest enzyme activity. In plants inoculated with S. rolfsii alone, enzyme activity was only increased in bulbs and roots compared to uninoculated controls. The highest levels of enzyme activity also occurred only in bulbs and roots of plants that had been dual-inoculated with T. asperellum and S. rolfsii. Plants of the RS variety showed the highest enzyme activities (both constitutive and induced) and showed the lowest severity of disease. Therefore, application of T. asperellum has potential as a biological control alternative to synthetic fungicides for protection of onion crops against infection by S. rolfsii. This protection depends on both constitutive and induced defence responses and varies amongst onion varieties.     

Efficacy of Different Fungicides against Foot and Root Rots caused by Sclerotium rolfsii of Wheat

Abstract

Twelve fungicides used for seed treatment were evaluated against Sclerotium rolfsii under unsterilised soil conditions. Tritisan. Brassicol and thiram were found to promote best seedling vigour and root development and also to reduce pre- and post-emergence rot. Captan and Ceresan wet reduced total mortality of the seeds and seedlings. Harvesan and Tillex were effective only at the pre-emergence mortality phase and allowed increased seed emergence.     

Molecular diversity and fingerprints of Trichoderma associated with antagonistic potentials against Sclerotium rolfsii Sacc.

Journal of Plant Diseases and Protection - Antagonistic potentials of Trichoderma isolates were evaluated against the phytopathogen Sclerotium rolfsii causing stem rot in groundnut. The in vitro...     

Biological control by Trichoderma harzianum of damping-off of lettuce caused by Rhizoctonia solani1

Ten isolates of Trichoderma harzianum were tested for their ability to control lettuce seedling damping-off caused by introduced Rhizoctonia solani. T. harzianum isolates TRC 9 and 28 both reduced damping-off. Dual culture experiments were used to select isolates for the study of antibiotic production and mycoparasitism. T. harzianum isolate TRC 12 produced volatile and non-volatile antibiotics, whilst TRC 33 produced only non-volatile antibiotics. T. harzianum isolates 018-2/Y and TRC 9,15 and 28 mycoparasitized R. solani by coiling around and lysing the host hyphae. It appeared that mycoparasitism was more important than antibiosis in the biological control of damping-off.     

Sclerotium rolfsii on Alstroemeria in Alberta, Canada

Sclerotium rolfsii was isolated from diseased rhizomes of greenhouse–grown Alstroemeria ( Alstroemeria sp.) in Edmonton in 1992. The underground portions of the plants were attacked resulting in leaf chlorosis which started on the lower leaves and gradually moved upwards. The characteristics of the isolates from diseased Alstroemeria were compared with those from other crops. This is the first report of S. rolfsii on Alstroemeria in Canada.     

Properties and inhibition of Sclerotium rolfsii chitin synthetase

A chitin synthetase (CS) preparation was obtained from mycelium of the plant pathogen Sclerotium rolfsii and partially characterised. The CS activity was stimulated by N-acetyl-D-glucosamine and magnesium cations with an optimum temperature of 30°C and an optimum pH of 6.4. The enzyme required proteolytic activation and so apparently existed in a zymogenic form. The fungal CS was strongly inhibited by the nucleoside-peptide antibiotics polyoxin-D and nikkomycin, and weakly inhibited by the terpenoyl benzimidazole, 1-geranyl-2-methylbenzimidazole. It was insensitive to captan and to insecticidal benzoylphenyl ureas. Disrupted chitin formation caused by polyoxin-D showed as swollen hyphae containing numerous depressions. The antibiotic also reduced formation of sclerotia and the few that did form were large, irregular in shape and light coloured.     

Antifungal potentials of some botanicals on Sclerotium rolfsii schum., the causal pathogen of damping-off of Gmelina arborea Roxb. in Ibadan,Southwestern Nigeria

Journal of Plant Diseases and Protection - Gmelina arborea (Gmelina) is a drought-tolerant tree species with rapid growth. It has excellent wood properties, and these have made this tree an...     

向日葵菌核病研究简报

向日葵菌核病在黑龙江省发生分布及为害情况过去没有记载。我院于1960—1961年进行了调查研究,初步了解此病分布在尚志、讷河、嫩江等县部分地区,而且常年发病严重。其他如海伦、阿城、召东、召州等县,在个别年分也发生为害。根据嫩江九三农場1958年的调查,发病率一般在50％左右,1959年高达80％,个别地块颗粒无收。成为向日葵上的毁灭性病害。该病在向日葵整个生育期都能侵染为害,表现立枯和烂盘两个类型。立枯型自苗期开始到花盘形成前均能发病;幼苗期发病部位主要在茎基     

Biological Control of Sclerotium rolfsii and Verticillium dahliae by Talaromyces flavus Is Mediated by Different Mechanisms

ABSTRACT Ten wild-type strains and two benomyl-resistant mutants of Talaromyces flavus were examined for their ability to secrete the cell wall-degrading enzymes chitinase, beta-1,3-glucanase, and cellulase, to parasitize sclerotia of Sclerotium rolfsii, to reduce bean stem rot caused by S. rolfsii, and to secrete antifungal substance(s) active against Verticillium dahliae. The benomyl-resistant mutant Ben(R)TF1-R6 overproduced extracellular enzymes and exhibited enhanced antagonistic activity against S. rolfsii and V. dahliae compared to the wild-type strains and other mu tants. Correlation analyses between the extracellular enzymatic activities of different isolates of T. flavus and their ability to antagonize S. rolfsii indicated that mycoparasitism by T. flavus and biological control of S rolfsii were related to the chitinase activity of T. flavus. On the other hand, production of antifungal compounds and glucose-oxidase activity may play a role in antagonism of V. dahliae by retardation of germination and hyphal growth and melanization of newly formed microsclerotia.