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Report on Alternaria Blight of Tagetes Erecta and Tagetes Patula Caused by Alternaria Alternata (fr.) Keissler

MAHFUZA AKTAR
Department of Botany, University of Dhaka, Dhaka-1000, Bangladesh

SHAMIM SHAMSI
Department of Botany, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

Severe blight symptom was recorded on Tagetes erecta L. and Tagetes patula L. during the tenure of January to April 2009, 2010, 2011, 2012 and 2013. Samples were collected from Chittagong, Comilla, Dhaka, Gazipur, Khulna, Pabna, Rajshahi and Sylhet. Fungi associated with infected samples were isolated following “Tissue Planting” and “Blotter” methods at temperature 25-28⁰C and pH 6.0. Alternaria alternata (Fr.) Keissler was isolated from diseased leaves, buds, calyx and petals of both selected plant species. The pathogenicity of the isolated fungus was tested following modified “detached leaf technique” and spraying of spore suspension methods. Alternaria alternata was found to be pathogenic to Tagetes spp. This is the first report on Alternaria blight of T. erecta and T. patula from Bangladesh.

Keywords: Report, Alternaria blight, Alternaria alternata, T. erecta, T. patula, Bangladeshs

Location: Department of Botany, University of Dhaka, Dhaka

Start Date: 00-00-2009

End Date: 00-00-2013

Program Area: Pest Management

Commodity: Marigold

Objectives:

1. Present study was undertaken to find out the presence of pathogenic fungi with marigold in Bangladesh.

Methodology:

In the present study fungi were isolated from infected leaves, buds and flowers of Tagetes erecta and Tagetes patula. Samples were collected from BARI, Chittagong, Comilla, Dhaka, Gazipur, Joydebpur, Khulna, Pabna, Rajshahi and Sylhet during the period of January to April 2009, 2010, 2011, 2012 and 2013. All these samples showed severe blight symptom on leaves, bud and flowers. Sixty samples were examined from infected plant parts of both species. Fungi associated with healthy and infected samples were isolated following “Tissue Planting” and “Blotter” method. Experiment was conducted in the Laboratory of Mycology and Plant Pathology, Department of Botany, University of Dhaka. In case of Tissue Planting” method, 30 inocula each measuring 2 square mm. were cut with a sterilized scalpel from a particular specimen and kept in a sterile Petri plate. The inocula were washed in sterile water and then surface sterilized by dipping in 10% Clorox for 3-5 minutes. Then the inocula were transferred in to a sterile Petri plate containing sterile blotting paper to remove the surface water. Three inocula were placed in each plate containing sterilized Potato Dextrose Agar (PDA) medium in pH 6 and incubated for 5-7 days at temperature 25 to 28⁰ C. In “Blotter” method, moist chambers were made by placing two layers of filter paper on the bottom of the Petri plates, moistened with sterilized water, covered with upper lids and were sterilized (autoclaved at 15 lbs pressure and 120°C temperature). Four square mm. sized inocula were prepared from the samples, surface sterilized with 10% chlorox for 3-5 minutes. A total number of 30 inocula was transferred in 10 Petri plates and incubated for 5-7 days at temperature 25 to 28⁰ C. The fungi growing out of the inocula were transferred to separate plates and slants for further studies and storage. Percentage association of the fungi was also recorded. Identification of the isolates was determined by following the standard literatures ( Ellis 1971). All the specimens were preserved in the Herbarium, Mycology and Plant pathology section, Department of Botany, University of Dhaka, Bangladesh. The pathogenicity of all the isolated fungi was tested following modified “detached leaf technique”. Moist chamber was prepared by placing small cotton bar at the corner of Petri plate and autoclaved. Six treatments with three replications for each fungi were used as follows: T₁ = (control) dorsally uninoculated leaflets, T₂ = (control) ventrally uninoculated leaflets, T₃= dorsally unpricked inoculated leaflets, T₄ = ventrally unpricked inoculated leaflets, T₅ = dorsally pricked inoculated leaflets and T₆ = ventrally pricked inoculated leaflets. Healthy seedlings of Tagetes erecta and T. patula were separately transplanted in earthen pots (10 inch diameter.) containing sterilized soil at three seedlings per pot and allow to grow for one month in net house providing necessary water and nutrients. Identified fungus were purified and its pathogenicity was examined by inoculating fresh healthy plants following spraying of spore suspension method. Conidia from seven days old culture of test fungus were taken in 250 ml conical flask with sterilized water. Ten ml water suspension of test fungus at 104 ml conc. were taken in a hand sprayer and sprayed on healthy potted plant. Control received only sterilized water without fungal inoculum. Five pots were inoculated for each treatment. The inoculated and control plants were placed in a clean bench in net house following completely randomized design. The plants were examined daily and continued for 10 days for recording the development of symptoms. Symptom produced on artificial inoculated plants was recorded and compared with those observed on naturally infected plants. The fungus was reisolated from the inoculated plants of Tagetes spp. on PDA medium to fulfill Koch’s postulates.

Source of Information: J. Asiat. Soc. Bangladesh, Sci. 40(1): 133-140, June 2014

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Alternaria alternata showed symptom on all the inoculated leaflets and plants of Tagetes spp. in vitro and in vivo except control leaflets and plants. The fungus was successfully reisolated from inoculated leaflets and plants. This is the first report of Alternaria blight of Tagates spp. from Bangladesh. Present investigation will be helpful for designing successful control measures of the disease.

Knowledge Management: Journal