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Light and Scanning Electron Microscopy on Colletotrichum Capsici – a Fruit Rot Pathogen and Interaction with a Susceptible Chilli Variety

M. M. E. Rahman
Senior Scientific Officer
Plant Pathology Division, Bangladesh Agricultural Research Institute, Gazipur-1701

M. L. Rahman
Chief Scientific Officer
Training and Communication Wing, Bangladesh Agricultural Research Institute, Gazipur-1701

M. S. Ali
Scientific Officer
Plant Pathology Division, Bangladesh Agricultural Research Institute, Gazipur-1701

Abstract/ Executive Summary:

The experiment was conducted at laboratory Plant Pathology Division, Bangladesh Agricultural Research Institute, Gazipur. Light and scanning electron microscopy was done on fruit rot pathogen Colletotrichum capsici for a susceptible chilli (Capsicum annuum) variety in relation to rapid pathogenesis and host pathogen interaction. It was observed that the pathogen produced spherical, hemispherical and irregular acervuli 100-180 μm in diameter which was associated with many conspicuous setae of 93-110 μm length. Each acervulus was filled up with numerous curve conidia with 18-25 μm length. After inoculation conidia of the pathogen adhered intimately on the curved fruit surface and germinated within 24 hours to produce germ tube and formed sub-globose appressoria for initiating infection. Infected host cells became discoloured or dead in addition to extensive degradation of cell wall. Protruding fruiting bodies of the pathogen caused easy disruption of epidermal layers of host tissues.

Keywords: Chilli, Fruit rot, Colletotrichum, Scanning electron microscopy

Location: Laboratory Plant Pathology Division, Bangladesh Agricultural Research Institute, Gazipur.

Start Date: 00-00-2012

End Date: 00-00-2013

Program Area: Pest Management

Commodity: Chilli

Objectives:

To generate information on interaction regarding pathogenesis and rapid infection process of C. capsici especially on the fruit of a susceptible chilli variety through light and scanning electron microscopic study.

Methodology:

The experiment was conducted at laboratory Plant Pathology Division, Bangladesh Agricultural Research Institute, Gazipur. Light microscope and scanning electron microscope (SEM) of Plant Pathology Division, Bangladesh Agricultural Research Institute were used in the investigation. The study included sample collection and preservation, detection of inoculum source, inoculum preparation, and inoculation on chilli fruit and finally observation with light microscope and scanning electron microscope. Inoculum source: Infected and healthy fruits of a susceptible chilli variety (BARI lanka^-1) were collected from experimental fields of BARI. Samples were cleaned, processed and finally preserved in a refrigerator at 50^C for further study. Sign and symptoms of infected chilli fruits were studied with the help of a light microscope. Acervuli produced by the pathogen including host tissue were observed through stereo-microscope and compound microscope. Images were taken by scanning electron microscope for clear and detail study relate to the infection process of the pathogen. Inoculum preparation: The pathogen C. capsici was isolated from infected fruit on sterilized potato dextrose agar (PDA) medium. The isolated pathogen was transferred to new PDA plate and allowed to grow for 7 days. The conidia and mycelia were harvested from 7 days old culture by rinsing with sterilized water and rubbing gently with a clean brush that helped the conidia and mycelial fragments easy release for better harvest. The suspension was sieved to remove agar lumps and blended for 1.5 minutes with the help of a mechanical rotary blender which culminated the fungal suspension. Fruit inoculation: Fruits of chilli were surface sterilized with 10% Clorox and washed repeatedly with distilled water. The fruits were inoculated with the pathogen C. capsici by placing single drop of fungal suspension that smeared over the fruit surface (1 cm²). Inoculated fruits were incubated at 20±2°C in an incubator for initiating infection. SEM observation: Samples for SEM observation were prepared . Both healthy and diseased surface of chilli fruits with acervuli were observed under SEM. In addition, after 24 hrs of artificial inoculation of the pathogen, specimens were taken for microscopic study. The specimens were dehydrated under ambient condition and adhered onto aluminum specimen mounts with sticky carbon tape. Then the specimens were coated with platinum for 30 sec through a vacuum evaporator and photographs were taken with the help of JEOL SEM (JSM6490 LA). Data on morphomatrix of acervuli, setae and conidia of the pathogen grown on PDA were also recorded under the SEM.

Source of Information: Int. J. Expt. Agric. 4(1):22-25, (2014)

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The light microscopy and scanning electron microscopy in the present study has helped in achieving a clear picture of rapid pathogenesis of Colletotrichum capsici causing fruit rot of a susceptible chilli variety and also beveled the mechanism of obstructing pathogenic advancement.

Knowledge Management: Journal