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Pathogenicity of Seed Borne Fusarium Spp. and Alternaria Spp. to Onion Plants

R. Hossain
Associate Co-ordinator, Ecological Agricultural Program, PROSHIKA, Dhaka

H. A. Naznin
Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh, Bangladesh

I. Hossain
Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh, Bangladesh

Abstract/ Executive Summary:

Seed samples were collected from the market as well as from the researchers to study the seed borne pathogenic fungi, Fusarium (F. oxysporum, F. culmorum and F. poae) and Alternaria (A. porri and A. tenuis). The isolated fungi were stored at 4°C and their pathogenicity tests were conducted by inoculating the plants grown in pots. Among the five fungi tested, Fusarium oxysporum, F. culmorum and F. poae were found pathogenic to the onion plants causing damping-off and wilting. F. oxysporum and F. poae were found slightly more pathogenic than F. culmorum. Alternaria porri and A. tenuis were found pathogenic to onion plants and they produced leaf spots and purple blotch. Alternaria porri was found more pathogenic than A. tenuis.

Keywords: Pathogenicity, Seed borne, Fusarium, Aliernnria, Onion plant

Location: Faridpuri, Taherpuri, Goldenball and Kalosnagori were collected from different shops of local seed market and Department of Horticulture, Bangladesh Agricultural University, Mymensingh.

Start Date:

End Date:

Program Area: Pest Management

Commodity: Onion

Objectives:

To identify the pathogenic effect of seed borne Fusarium spp. and Alternaria spp. to onion plants.

Methodology:

All together 15 seed samples of four cultivars of onion viz. Faridpuri, Taherpuri, Goldenball and Kalosnagori were collected from different shops of local seed market of Mymensingh town and Department of Horticulture, Bangladesh Agricultural University, Mymensingh. For detection of seed borne Fusarium and Alternaria spp., 200 seeds from each sample were taken randomly and tested by Blotter method following the International Rules for Seed Testing. These seed borne fungal pathogens were identified by observing their growth characters on the infected seed under stereomicroscope and their structures on the prepared slide under compound microscope. The fungi associated with onion seeds in blotter were isolated and grown on PDA. Hyphal tip and/or conidia of fungi were transferred to PDA and incubated at 25 ºC for luxuriant growth. Then pure cultures of the identified fungi were maintained and stored in a refrigerator at 5 ºC for further use. The collected soil and cowdung (4:1) were mixed thoroughly and earthen pots (10 inches dia.) were filled two third portion with the mixture. After preparation of the pot five onion bulbs per pot were sown for raising of onion plants. For each treatment three replicated pots were used. Tested fungi were transferred from pure culture and grown on PDA in petridishes for 10 days at room temperature (23-25 ºC). Then the petridishes of Fusarium spp.and Alternaria spp. were kept under near UV light for maximum conidia formation for 7 days. The spores along with mycelium were scraped off from the agar surface of PDA with the help of a sterile scalpel and transferred to a beaker with distilled water. Then suspensions were filtered through cheese cloth to remove mycelial fragments and lumps of agar and one drop of tween-20 was added in the suspension for even distribution of spores and the concentration of the spore suspension was adjusted at 10⁴ conidia/ml. Alternaria porri and A. tenuis were selected for leaves inoculation. Inoculation was done by spraying spore suspension on the leaves of onion plants using a self compressed hand sprayer. The pots with inoculated and uninoculated (only water was sprayed /control) plants were covered with previously moistened polythene bags for 36 hrs. for maintaining moisture. For inoculation at the base of the plants Fusarium oxysporum, F. culmorum and F. poae were used. Mycelium blocks were cut from pure culture of the respective pathogens with the help of sterile block cutter. For side inoculation, 3-4 mycelial blocks were placed at the base of the onion seedlings (one month old) and covered with cotton around the base of the plant and for middle inoculation, mycelial blocks were placed at the middle/ centre of the leaf base and also covered with cotton around the inoculated portion. Then pots were covered with previously moistened polythene bags for 36 hrs. The experiment was conducted following CRD. Data recorded on number of spot/leaf and number of wilted plant/pot.

Source of Information: Progress. Agric. 15(1) : 283-286, 2004, ISSN 1017-8139

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Fusarium culmorum and F. poae were new detection from the onion seeds which were pathogenic to cause wilting and damping off. Among the two methods of pathogenicity test of Fusarium species, middle inoculation ( at the middle of the leaf base) was more effective for pathogenicity test of three species of Fusarium. This study clearly elucidate the importance of seed borne Alternaria spp. and Fusarium spp. for their pathogenicity. Moreover, Alternaria tenuis, Fusarium culmorum and F.poae are new records of their pathogenicity on onion plants. This findings is of great importance to the researchers as well as onion growers.

Knowledge Management: Journal