STUDIES ON SOME ASPECTS OF SOYBEAN RUST CAUSED BY Phakopsora pachyrhizi Syd.
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Date
1999
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University of Agricultural Science, Dharwad
Abstract
"Studies on soybean rust revealed that disease was wide spread in
severe form (64.99%) on soybean in Northern Karnataka and parts of
Maharashtra during kharif 1996, 1997 and 1998. Onset and more severity
were recorded in villages situated on Krishna River Bank and are
considered as hot spots of disease.
Deposition of uredospores on slide kept in aeroscope commenced 6 to
9 days before onset of disease. Fluctuations in uredospore deposition were
observed. More uredospores were trapped between 75 to 90 DAS and rust
severity was maximum at this stage. Autoregression model of seventh
order was found to be accurate for prediction of uredospores load in
atmosphere. Logistic model and linear environmental model were
appropriate for predicting rust epidemics.
Uredospores survived for 12 to 15 days in infected host debris.
Disease prevailed on soybean throughout the year with difference in
severity. Cowpea, pea, greengram, horsegram, redgram and frenchbean
were found to be collateral hosts.
Onset of rust was delayed on early sown crop and severity increased
with delayed sowing in kharif. Drastic reduction in yield and seed weight
was recorded with delayed sowing. Among the varieties PK-1029 recorded
the least severity with all the sowing periods.
Among germplasms S-22, WC-12 and 92-10 performed better in yield
with resistant reaction. Among varieties PK-1162, PK-1029, JS-80-21 and
PK-1024 showed moderately resistant reaction with good yield.
Three and two sprays of hexaconazole (0.1%) were required to
manage rust on a susceptible {JS-335) and a moderately resistant (PK-
1029) varieties respectively. Yield loss of 81.94 and 65.73 per cent due to
rust was observed with JS-335 and PK-1029 respectively. Yield loss model
could be developed by using AUDPC as input variable. Severity at 75 and
85 DAS was highly significant and positively correlated with yield loss in
JS-335 and PK-1029 respectively."
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No. of references 144