Abstract:
A series of experiments were undertaken to study the activity of
thidiazuron(TDZ) as Striga germination stimulant on filters paper and soil, its
persistence on filter paper and soil, stability in soil and toxicity to
sorghum..Striga seeds were surface sterilized, conditioned and exposed to
different concentrations of TDZ and GR24 in Petri-dishes and soil for 24 or 48 h
and examined for germination. Persistence of TDZ at 2 and 8 ppm on filter paper
was examined 0, 6, 9, 12 and 24 h after application. Persistence in soil of 8 ppm
TDZ was examined 0, 7, 14, 21 and 28 days after treatment. Sorghum seedling
emergence, plant height and dry weight were determined.
The compoundTDZ effectively, induced germination of Strigahermonthicaseeds
in soil and in Petri dishes in a concentration dependent manner. The highest
concentration,10 ppm, induced 63% germination in Petri dishes,the lowest
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concentration, 0.1 ppm, elicited the lowest germination (21%). The compound
displayed less activity in soil. At 10 ppm TDZ induced 42% germination.
Decreasing the concentration of TDZ to 1 ppm resulted in 11%
germination.Persistence of GR24 and TDZ on filter paper declined with time.
GR24 1ppm applied0,6, 9, 12, 24 h priorto seed placement induced 53.2, 39.5,
31.3, 16.2, and 13.2% germination, respectively. The corresponding figures for
TDZ at 2 ppm were 55.6, 51.6, 41.1, 37.1, and 18 %. In soil TDZ placed 0, 7, 14,
21, 28 days prior to seed insertion induced 40.9, 34.7, 23.2, 18.5 and 5.5 %
germination, respectively. TDZ persistence in soil decreased with time.In soil
TDZ reduced sorghum emergence, height and dry weight. TDZ delayed,
inconsistently, but significantly sorghum emergence at 4 days after sowing.
However, at 5 days both reduction and stimulationof sorghum emergence,
pending TDZ concentration, were observed. TDZ at the 0.25 ppm had no adverse
effect on sorghum dry weighbutat 0.5 ppm itincreased sorghum dry weight over
the control significantly. It isconcluded that TDZ induced germination of S.
hermonthicasuicidal germination, but it showed considerable toxicity to
sorghum. However, further research is needed to synchronize sorghum planting
and application time. Pre- planting applications of TDZ as a measure to reduce
toxicity to sorghum have to be investigated.
