dc.contributor.author | Wahome, JKi | |
dc.date.accessioned | 2013-05-10T15:26:23Z | |
dc.date.available | 2013-05-10T15:26:23Z | |
dc.date.issued | 1998-11 | |
dc.identifier.citation | Wahome J K(1998). Characterization and determination of lethal dose (LDSO)of metabolites from two soil Bacilli and evaluation of their If efficacy in the control of bean anthracnose in the greenhouse. | en |
dc.identifier.uri | http://erepository.uonbi.ac.ke:8080/xmlui/handle/123456789/21582 | |
dc.description | Msc- Thesis | en |
dc.description.abstract | Two Bacillus isolates coded as CA5 and CAIO were retrieved from sterile
loam soils where they had been preserved. They were tested against four
fungal pathogens of agricultural importance namely Fusarium sp
Colletotrichum lindemuthianum, Helminthosporium nodulosum and
Alternaria sesami in vitro. Bothisolates CA5 and CA10 were shown to be
antagonistic to each of the above pathogens, however CA5 was more
active than CA10. Growth of Colletotrichum lindemuthinum was reduced
by 45% and 47% by CA10 and CA5 respectively.
The two Bacillus isolates produced appreciable amounts of antibiotics in
liquid medium containing soybean meal and glucose. Culture filtrate from
isolate CA5 showed stronger antibiotic activity against all the four fungal
pathogens when compared to isolate CA10. This was demonstrated using
Colletotrichum lindemuthianum where CA5 produced a mean inhibition
zone of 27mm compared to 20mm by CA10.
Paper chromatography combined with bioautography for both isolates CA5
and CA10 produced one continuos zone of inhibition against Fusarium spp
indicating that each isolate contained one active compound against
Fusarium spp.
The culture filtrate from isolate CA10 was found to be stable on a wide
range of pH levels between 4 and 10 as opposed to CA5 that was stable
between pH 4 and pH 8. Tests on temperature stability showed that CA5
was more heat stable than CA10. Activity was demonstrated by CA5 after
autoc1aving at 1210C but CA10 was inactivated at temperatures above
1000C.
The antibiotics from the two isolates retained activity when stored for 120
days at room temperature (220C) and in the refrigerator at 40C. Using
storage temperature of 40C the inhibition zones produced at 120th day by
CA5 and CAI0 on Colletotrichum lindemuthianum were 27.3 mm and
20.1mm respectively while those at room temperature were 27.lmm and
20.6 mm respectively. The zones were not significantly different at (p S
0.05).
Partial purification of the two antibiotics were done by adsorbing them onto
activated charcoal and later eluting with a solution of 80% acetone in
water. The partial purification enhanced the activity of the filtrates. This
was reflected by the increase in the size of the clear zones produced. For
partially purified antibiotic from CA5 the inhibition zone against
Colletotrichum lindemuthianum was 11% more than that of crude filtrate
and 20% more with CA10 antibiotics.
In vivo tests in the greenhouse using the two antibiotics showed that they
significantly delayed and suppressed (pS5%) the development of bean
anthracnose caused by C lindemuthianum on bean leaves sprayed with
culture filtrates. Isolate CA5 compared favorably with benlate 50% W.P, a
systemic fungicide used in the control of bean anthracnose. Both benlate
and isolate CA5 gave a mean disease score of 2.3 and 2.5 respectively
compared to 7.3 recorded in the control. The culture filtrates however,
were found to be a little phytotoxic.
Determination of the lethal dose (LD50) to the mice of the two culture
filtrates after freeze drying was done using three weeks old male albino
mice that weighed between 20g and 40g body weight. Injecting the
reconstituted culture filtrates intraperitoneally the LD50 of CA5 and CAI0
antibiotics were determined and found to be 2.35 and 2.93g/Kg body
weight respectively. According to the World Health Organisation (WHO)
classification of toxicity and according to Loomis (1974) any substance
with LD50 of lrng/Kg or less is graded as extremely toxic and products
giving LD50 of 5g/Kg are graded as relatively harmless. The two culture
filtrates from CA5 and CAI0 can be classified therefore, as slightly toxic
and thus safe for agricultural use. | en |
dc.description.sponsorship | University of Nairobi | en |
dc.language.iso | en | en |
dc.subject | Lethal dose (LDSO | en |
dc.subject | Metabolites | en |
dc.subject | Soil Bacilli | en |
dc.subject | Bean anthracnose | en |
dc.subject | Greenhouse. | en |
dc.title | Characterization and determination of lethal dose (LDSO)of metabolites from two soil Bacilli and evaluation of their If efficacy in the control of bean anthracnose in the greenhouse. | en |
dc.type | Thesis | en |
local.publisher | Department of Plant Science and Crop Protection, University of Nairobi | en |