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Bacteria from Water Culture of Lettuce Antagonistic to Pythium Ultimu

Md. Babadur Meah
Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh.

Abstract/ Executive Summary:

Bacteria and actinornycetes were isolated by dilution plate count technique from nutrient solution of water culture of lettuce. Out of 300 isolates transferred to slants. twelve bacterial and actinomycete isolates displayed antagonistic activities against Pythinm ultmum, root pathogen of lettuce. On agar plate, the bacterial iso.ates Pseudomonas fluorescens, P. dtmlnuta, Citrobacter freundii and Streptomyces spp , affected the mycelial growth of the test pathogen producing a clear zone of inhibition around the block. The bacterial isolates Erwinla herbicola caused lysis of fungal mycelium. Pseudomonas app. proved most effective against the test pathogen.

Keywords: Bacteria, Lettuce,Water culture

Location:

Start Date:

End Date:

Program Area: Pest Management

Commodity: Amaranth

Objectives:

1.To isolate bacteria and actinomycetes from nutrient solution used in water culture .of lettuce

2To evaluate their antagonistic activities in vitro against Pythium ultimum, root pathogen of lettuce

Methodology:

Six composite samples of nutrient solution, recirculated to 100 lettuce seedlings in water culture system, were collected. The details of the sampling procedure have been given by Meah ( 1983). Three hundred bacterial isolates, 50 from each sample, were transferred to nutrient solution. Two hundred and sixty five isolates that grew 00 transfer were tested for possible antagonistic activities against P'[thium ultimum Trow, root pathogen of lettuce (Watson 1974) by means of usual agar block technique. The isolates were grown on nutrient solution agar medium and the test pathogen on PDA (Potato Dextrose Agar) fer 48hr. Blocks of one em dia of both the bacteria and the test pathogen were cut aseptically. Four blocks, each representing individual isolate were placed on the periphery of the agar plate with simultaneous placing of the fungal block at the middle. Control plates contained only the bacterial isolates or the test pathogen. The plates were incubated at 20 ± I°C and daily observation was made for any kind of microbial interaction. Final measurement for clear zone of inhibition analysis of mycelium was made one week after inoculation.

Source of Information: Bangladesh J. Agril, Sci. 11 (2; ; 157-100 : 1984

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Approximately five percent of the isolates tested showed antagonistic activities against the test lettuce foot pathogen. Out of 14 antagonists, 2 were Streptomyces spp. and the rest 12 Were bacterid isolates . Strepto- myces spp , Pseudomonas spp. and Citro- b icter sp, affected fungal mycelial growth producing a clear zone of inhibition ( Figure IA and IB) around the block. On the other hand, Erwina spp. caused lysis of the fungal mycelium. The diameter of the ZJ:1;:S or in'iibition or lysis as measured in th e final test are given in Table 1. These figures were about the same as found in the primary test. The inhibited zones remained unchanged even one week after first reading. A wide variation in antagonistic activities was noted among tbe isolates tested. Pseudomonas sp, produced the inhibition zone of highest dia while Ci/robacta sp. produced the lowest and Streptomyces displayed medium range of activity.

Knowledge Management: Journal