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Pestalotiopsis Guepinii (desm.) Stay. – a New Pathogen of Black Spot Disease of Rose in Bangladesh

Shamim Shamsi
Department of Botany, University of Dhaka, Dhaka-1000, Bangladesh

Anita Ghosh
Department of Botany, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

An investigation was conducted during November 2009 to October 2010 to determine causal fungi of black spot disease of rose (Rosa centifolia L.). Black spot infected leaf samples were collected from different locations of Dhaka city. The fungi associated with the samples were isolated and identified. The principal fungal pathogen associated with the diseased specimens was Diplocarpon rosae Wolf (imperfect stage Marssonina rosae). Other fungal pathogens associated with the disease were Pestalotiopsis guepinii and its two culture types (Pestalotiopsis guepinii-1, P. guepinii-2). The fungi belong to the class Coelomyecetes under the Division Deuteromycota. The fungi were frequently isolated from black spot infected leaf samples of the rose. After inoculation of detached leaves and seedlings of rose, P. guepinii and its two culture types developed characteristics symptoms of black spot. The pathogen was reisolated from black spot infected inoculated leaves to fulfill Koch’s postulate. The findings of the investigation indicate that P. guepinii is another fungal pathogen of black spot of rose in addition to D. rosae. This is a new record about causal agents of black spot disease of the cut flower.

Keywords: Black spot, Rose, Pestalotiopsis guepinii

Location: Herbarium of the Department of Mycology and Plant Pathology, University of Dhaka

Start Date: 00-11-2009

End Date: 00-10-2010

Program Area: Pest Management

Commodity: Rose

Objectives:

The present investigation was undertaken to identify the fungal pathogens associated with black spot disease of rose plant other than D. rosae.

Methodology:

Healthy and diseased leaves of rose were collected from different locations of Dhaka city during November 2009 to October 2010. Fungi were isolated from black spot infected leaf samples following “Tissue Planting method” on PDA medium and pure culture of the isolated fungi were prepared following single spore method. Morphological characteristics of the fungi were recorded under a compound microscope and identified using standard key books. All diseased specimens and associated fungi were preserved in the Herbarium of the Department of Mycology and Plant Pathology, University of Dhaka. Pathogenicity test of the isolated fungi was performed following modified detached leaf assay technique. Fresh, healthy and mature leaves of rose were collected, washed with distilled water, surface sterilized with 1.0% Clorox for five minutes and rinsed in sterilized water. Ventral and dorsal sides of the leaflets with and without pricking with needles were inoculated with 2 mm diameter mycelial block of the isolated fungi previously grown on PDA medium for seven days. Another set of leaves with and without pricking and without inoculation were maintained, which served as controls. Three replicated leaflets were used for each treatment. The inoculated leaflets were placed in Petri dishes containing water soaked filter paper and cotton ball to maintain sufficient humidity to initiate infection. The plates were incubated at 25-28⁰C. The inoculated and non inoculated leaflets were checked for symptom development starting from 3 days of inoculation and continued up to 7-10 days. Seedling inoculation method was also followed to confirm pathogenicity of the isolated fungi. Healthy seedling of rose plant was transplanted in pots (30 cm Diam.) containing sterilized soil at three seedlings per pot and allow to grow for three month in a nethouse providing necessary water and nutrients. Healthy leaves of seedlings were washed with sterilized water and surface sterilized with 1.0% Chlorox and rinsed with sterilized distilled water. Surface sterilized leaves were pricked with sterilized needle. Pricked and unpricked leaves were inoculated with the test fungi by rubbing sporulating PDA culture of the test fungus. Leaves under control received only fresh PDA medium without fungal inoculum. Plants were covered with polythene bags to maintain proper humidity level and to avoid contamination. Three seedlings were inoculated for each treatment. The inoculated plants were placed in a clean bench. The plants were examined daily and continued up to 10 days to record the development of symptoms. Symptoms developed on artificial inoculated leaves were recorded and compared with the symptoms of those observed on naturally inoculated leaves. The fungus was resonated from the inoculated leaves of rose to fulfill Koch’s postulates.

Source of Information: Bangladesh J. Plant Pathol. 29 (1&2): 11-14, 20013; ISSN 2012-9279

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Results of the present study revealed that P. guepinii and its two culture types can develop symptoms of black spot only when test leaves are pricked with dorsally before inoculation. It indicates that injury is essential for penetration of the fungus. Black spot caused by D. rosae and its imperfect stage has been reported earlier from Bangladesh as well as abroad.

Knowledge Management: Journal