Kegunaan pseudomonas species sebagai agen kawalan biolo gi bipolaris maydis penyebab penyakit hawar daun jagung selatan
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Date
1993-12
Authors
Mohamed Masthan Ghani, Seeni
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Abstract
Of the two hundred and fourty eight bacterial isolates from
soi 1 and the maize phyllopl ane tested in in vitro, 67.2% of
fluorescent pseudomonad and 66.2% nonfluorescent pseudomonad
were inhibitory to radial growth of Bipolaris maydis on at
least one of the media types used. Isolates from the
phylloplane inhibited growth of B. maydis by 72.6% compared
to soil isolates which inhibited in the region of 64.6%.
Twenty-eight isolates (20 fluorescent and 8 nonfluorescent
isolates) from 106 isolates tested in planta were found to
effectively control this disease giving a disease rating of
below 2 as compared to a rating of 5 for control plants.
The seven best isolates were selected for further studied in
vitro and in planta are strain P0402, P0904, PJ0205, PJ0210
and PJ0304 which were identified as Pseudomonas fluorescens
and K0801 and NJ0104 which were identified as P. putida.
A number of tests in agar media, cavity slides, acetone
extraction, the addition of nutrients in vitro or in planta
and the use of siderophore negative mutant have shown that
competition for nutrients and not antibiosis was involved
in the inhibition of B. maydis growth.
i i i
1 ~ general, control of SCLB by the 7 isolates decreased when
t~e concentration of B. maydis spores increased whereas, the •
reverse occurred when the concentration of bacterial
antagonists increased with a fixed concentration of 8/' :·~-
maydis. The antagonists that were tested were able to
colonize and survive on the maize leaves and also able' to
reduce disease up to 15 days after initial application in
the plant house.
Histopathological studies demonstrated that 8. maydis spores
were able to germinate, g,row and penetrate leaf tissue
either through appresorial formation or directly through
stomata to initiate infection. The additional of antagonists
together with 8. maydis spores on the maize leaf also
reduced the rate of B. maydis growth and subsequent
infection.
Strain PJ0210 gave a better control of SCLB compared to
P0904 at a mini-field study. A. rifampicin resistant mutant
of PJ0210 and P0904 were reisolated from maize leaves up to
25 and 15 days respectively, after the initial application.
The number of mutant PJ0210 cells which be reisolated from
rnaize 1 eaves increased when 1 eaves were wet but adversed
effect was found when the leaf surface was dry.
In planta, strain PJ0210 reduced new spores production by
50% up to 30 days. A mutant strain of PJ0210 resistant to
rifampicin was reisolated from infected and rotted leaf
debris up to 30 days.
Description
Keywords
Pseudomonas species , Bipolaris maydis