AQUEOUS EXTRACTS
Aqueous extracts of neem seed kernels, when preincubated with TMV in laboratory and greehouse tests, gave varying results. Strong inhibition in one test was followed by increased numbers of lesions in the next. In general concentrated virus inocula led to less inhibition than more diluted inocula. Using systemise hosts like N.labocum cv.Java, a delay in symptom development was observed, along with much better growth of the neem-treated plants. Using apple mosaic ilavirus and cucumber as a model system, topical applications of aqueous extracts pre and post infection did not lead to a reduction of the symptoms.
METHONOLIC EXTRACTS
Methonolic extracts, as discussed below for Azadirachtin(a2a), bear the problem of methonal itself, either as a denaturating component or as a resistance inducer. Preinoculation applications of methonolic extracts inhibition when the results were compared with the methonal control, but the data differed widely among the various concentrations of neem and there was no correlations with the inhibition values. When the results of the pretreated halves of the leaves were comapred with the untreated ones, there were always fewer Jesions but the difference was not always significant and again there was no correlation with the neem concentration. When no methanol control was used, positive results were always reached, with the above mentioned limitations. When the extract were used only for co-inoculation, a significant reduction - with values above 90% - was obtained again when compared with pure virus control coly. Also the leaf halves inoculated with the virus alone showed nearby the same reduction as the other half with relatede virus. However, in this experiment, no menthol control was used.
BARK AND ROOT EXTRACTS
MURTY described a 87% reduction of TMV infection of N. gluntinoza using an aqueous extract of the bark of the neem tree. In experiments by the author, a methonolic extract from neem bark from Senegal resuspended with the microvolume of methonol and diluted with buffer, gave similar results when preincubated with the virus. Using the half leaf method, the number of lesions also decreased on the control-half of the leaves inoculated without extract, indicating a systemic effect when cv. Xanthi NN used. This effect was less significant using cv. White Burley as test plant. The bark extracts from different sources behaved very similarly. In an additional test, the bark from two different sources in Senegal was compared. With 250 ppm of extract, 57% and 62% inhibition respectively, was obeserved. Inner bank and wood was less effective, with only 43% inhibition. Compared with a methyl tert, buthylether extract of dried leaves from Senegal which gave 74% inhibition, all other bank and wood preparation were weaker. This activity was even weaker when Datura Stramonium was used as the test plant instead of tobacco; the inhibition reached , only 34% and 27% for the outer bank, 36% for the inner bark and wood, and 33% for the left extract. Symptom inhibition was significant only for one of the bark-samples when Nicotiana Benthamiana was used as systematic test plant. When the preincubation period was extended to 5 d, the inner bark and wood extract gave a weak inhibition of <10% and the outer bark, and the leaf extracts showed even an increase in lesions formation on the half-leaf inoculated withn the pretreated inoculum.
In general, there was a great variability in the values obtained for individual leaves when pretreating virus with extracts. Even in control experiments using the half-leaf method, differences of up to 49% could be observed when both parts were inoculated with the same pretreated inoculum, an effect never observed with the virus alone. This indicates that experiments with a low number of replications will occasionally lead to erratic results. Inhibition - with lower than with whole plants - was obtained using leaf discs and pretreated inoculum. When an inhibitor-seaked filter paper was placed on leaf discs. Again the effect could not be enchanced by using more inhibitor-discs. These experiment were performed with N. tabacum. When Nicotiana rustica was used, no inhibition was observed and with D.Stramonium only 30% inhibition was achieved under the same conditions.
Aqueous extracts of neem seed kernels, when preincubated with TMV in laboratory and greehouse tests, gave varying results. Strong inhibition in one test was followed by increased numbers of lesions in the next. In general concentrated virus inocula led to less inhibition than more diluted inocula. Using systemise hosts like N.labocum cv.Java, a delay in symptom development was observed, along with much better growth of the neem-treated plants. Using apple mosaic ilavirus and cucumber as a model system, topical applications of aqueous extracts pre and post infection did not lead to a reduction of the symptoms.
METHONOLIC EXTRACTS
Methonolic extracts, as discussed below for Azadirachtin(a2a), bear the problem of methonal itself, either as a denaturating component or as a resistance inducer. Preinoculation applications of methonolic extracts inhibition when the results were compared with the methonal control, but the data differed widely among the various concentrations of neem and there was no correlations with the inhibition values. When the results of the pretreated halves of the leaves were comapred with the untreated ones, there were always fewer Jesions but the difference was not always significant and again there was no correlation with the neem concentration. When no methanol control was used, positive results were always reached, with the above mentioned limitations. When the extract were used only for co-inoculation, a significant reduction - with values above 90% - was obtained again when compared with pure virus control coly. Also the leaf halves inoculated with the virus alone showed nearby the same reduction as the other half with relatede virus. However, in this experiment, no menthol control was used.
BARK AND ROOT EXTRACTS
MURTY described a 87% reduction of TMV infection of N. gluntinoza using an aqueous extract of the bark of the neem tree. In experiments by the author, a methonolic extract from neem bark from Senegal resuspended with the microvolume of methonol and diluted with buffer, gave similar results when preincubated with the virus. Using the half leaf method, the number of lesions also decreased on the control-half of the leaves inoculated without extract, indicating a systemic effect when cv. Xanthi NN used. This effect was less significant using cv. White Burley as test plant. The bark extracts from different sources behaved very similarly. In an additional test, the bark from two different sources in Senegal was compared. With 250 ppm of extract, 57% and 62% inhibition respectively, was obeserved. Inner bank and wood was less effective, with only 43% inhibition. Compared with a methyl tert, buthylether extract of dried leaves from Senegal which gave 74% inhibition, all other bank and wood preparation were weaker. This activity was even weaker when Datura Stramonium was used as the test plant instead of tobacco; the inhibition reached , only 34% and 27% for the outer bank, 36% for the inner bark and wood, and 33% for the left extract. Symptom inhibition was significant only for one of the bark-samples when Nicotiana Benthamiana was used as systematic test plant. When the preincubation period was extended to 5 d, the inner bark and wood extract gave a weak inhibition of <10% and the outer bark, and the leaf extracts showed even an increase in lesions formation on the half-leaf inoculated withn the pretreated inoculum.
In general, there was a great variability in the values obtained for individual leaves when pretreating virus with extracts. Even in control experiments using the half-leaf method, differences of up to 49% could be observed when both parts were inoculated with the same pretreated inoculum, an effect never observed with the virus alone. This indicates that experiments with a low number of replications will occasionally lead to erratic results. Inhibition - with lower than with whole plants - was obtained using leaf discs and pretreated inoculum. When an inhibitor-seaked filter paper was placed on leaf discs. Again the effect could not be enchanced by using more inhibitor-discs. These experiment were performed with N. tabacum. When Nicotiana rustica was used, no inhibition was observed and with D.Stramonium only 30% inhibition was achieved under the same conditions.
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