Cultural practices and infectious crop diseases , Cultural practices and infectious crop diseases , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Cultural practices and infectious crop diseases.

A plant growth-promoting bacterial strain, GRC2, was isolated from potato rhizosphere and characterized as fluorescent Pseudomonas. It produced a hydroxamate-type siderophore in iron-deficient tryptic soy medium. The production of hydrocyanic acid and indole acetic acid was also recorded under normal growth conditions. The strain showed a strong antagonistic effect against Macrophomina phaseolina, a charcoal rot pathogen of peanut, when co-cultured on tryptic soy agar medium. The growth inhibition of M. phaseolina was 74% after 5 days of incubation. Bacterization of peanut seeds with fluorescent Pseudomonas GRC2 resulted in increased seed germination, early seedling growth, fresh nodule weight, grain yield and reduced charcoal rot disease of peanut in M. phaseolina-infested soil as compared with control. A streptomycin-resistant marker of the bacterium GRC2
strep+ was used to monitor root colonization, which positively confirmed the efficient colonization of peanut root. Seed bacterization reduced charcoal rot disease in M. phaseolina-infested soil as compared with the control by 99%, making the organism a potential biocontrol agent against charcoal rot of peanut.

Plant growth enhancement and suppression of macrophomina phaseolina causing charcoal rot of peanut by fluorescent pseudomonas

The fungus Macrophomina phaseolina is a causative agent of diseases in more than 500 plant species. The fungus is primarily soil-inhabiting but is also seed-borne in many crops including soybean. It survives in the soil mainly as microsclerotia that germinate repeatedly during the crop-growing season. Low C : N ratio in the soil and high bulk density as well as high soil moisture content adversely affect the survival of sclerotia. The disease can be managed to some extent by cultural practices, organic amendments, seed treatment and genetic host resistance. The scattered literature on these aspects is reviewed in this paper.

Biology, Epidemiology and Management of the Pathogenic Fungus Macrophomina phaseolina (Tassi) Goid with Special Reference to Charcoal Rot of Soybean (Glycine max (L.) Merrill)

Soil solarization, summer irrigation and amendments for the control of Fusarium oxysporum f. sp. cumini and Macrophomina phaseolina in arid soils

Survival of a heat-tolerant pathogen Macrophomina phaseolina, causing dry root rot of clusterbean, was studied by incorporation and retrieval of infected residue samples at various stages of the composting process of pearl millet (Pennisetum glaucum) and clusterbean (Cyamopsis tetragonoloba) residues. During the heating phase, temperatures varied from 48–51°C at 30cm and 60–62°C at 60cm depth in compost pits. Reduction in survival of M. phaseolina propagules (13–23%) was significantly higher in the residues enriched with 4% urea-N and kept at 60cm compared to 2% urea-N and at 30cm. However, a heat phase (48–62°C) was not enough to completely eradicate M. phaseolina propagules from infected residues. Further reductions (54–61%) in survived propagules were achieved by sub-lethal temperatures (48–53°C) when moistened compost materials were exposed to heat during summer days. Beneficial effects of composts were ascertained on dry root rot intensity, seed yield of clusterbean and densities of M. phaseolina,Nitrosomonas and antagonists in soil. In a two-year field study, all the composts significantly reduced plant mortality due to dry root rot and increased the yield of clusterbean. The highest disease suppression and yield promotion were recorded in soil amended with pearl millet compost and cauliflower leaf residue compost, respectively. Soil amendment with compost also lead to a significant reduced density of M. phaseolina and an increased density of antagonistic actinomycetes, lytic bacteria and Nitrosomonas. Among composts, greater potential of cauliflower compost in enhancing population of antagonists in soil was discernible.

Inactivation of Macrophomina phaseolina Propagules during Composting and Effect of Composts on Dry Root Rot Severity and on Seed Yield of Clusterbean

The effect of five herbicides, EPTC, dinoseb, alachlor, fluorodifen and fluometuron, on the inoculum density of Macrophomina phaseolina (Tassi) Goid. was tested in two field soils. The herbicides were applied at commercially recommended rates. All herbicides tested incited a significant drop in the population of M. phaseolina. In soils treated with dinoseb, the population of M. phaseolina declined by 96 % in sandy-clay-loam and by 61 % in sandy-loam soil 10 days after treatment. In fluorodifen treated sandy-loam soil, the population dropped gradually by 85 %, whereas in sandy-clay-loam soil, it declined by 50 %, over a fifty day test period. The population of M. phaseolina dropped by 46 % to 63 % in both soils treated either with EPTC, fluometuron or alachlor, over the entire test period. There was a significant interaction between herbicide and soil, as affecting population decline of M. phaseolina in soil.

Effect of herbicides on survival of Macrophomina phaseolina in soil

Population changes of Macrophomina phaseolina (Tassi) Goid were followed in two soils amended with either wheat, corn, bean or alfalfa straw, or with nitrogen-enriched wheat straw or glucose and sodium nitrate at different C:N ratios The population declined significantly initially in both soils with any amendment but later increased in soils amended with wheat or corn straw and in one soil amended with bean or alfalfa straw Population declined with no subsequent increase when soil was amended with nitrogen-enriched wheat straw or glucose and sodium nitrate at C:N ratios equal to that of the natural plant residues In general the population declined more rapidly when soil was amended with nitrogen-enriched wheat straw or glucose and nitrogen than if amended with either corn, bean or alfalfa straw and when soil was amended with low C:N ratios

Edgar S. Filho

Papers

Effect of herbicides on survival of Macrophomina phaseolina in soil

Population changes of Macrophomina phaseolina in amended soils

Survival of Macrophomina phaseolina sclerotia in nitrogen amended soils.