Common root rot is a major disease of commercially grown snap bean
(Phaseolus vulgaris L.) on the irrigated sandy soils of central Wisconsin. The
objective of this study was to determine the relationships between soil properties
and suppressiveness to common root rot of snap bean (causal agent Aphanomyces
euteiches) in soils. The soils had been annually amended for three years in a field
trial on a Plainfield sandy loam in Hancock, WI. Soils were amended each year
from 1998 to 2001 with three rates of fresh paper-mill residuals (0, 22 or 33 dry Mg
ha�����) or composted paper-mill residuals (0, 38 or 76 dry Mg ha�����). Soil was
removed from each treatment in April (one year after last amendment) and brought
to the laboratory. This was repeated with a field soil sample taken in September,
2001. The soils from the two samplings were incubated at room temperature and
periodically assayed (days 9, 44, 84, 106, 137, 225 and 270 for April sampling)
(days 13, 88 and 174 for September sampling) for suppressiveness of snap bean
root rot (0 to 4 where 0=healthy and 4=dead plant). The same days, incubated
soils were characterized for ��-glucosidase, arylsulfatase and fluorescein diacetate
activities; microbial biomass C (by chloroform fumigation); water stable
aggregation (WSA) and total C. In the first incubation, there were large differences
between field amendment treatments in terms of snap bean root rot incidence. The
disease was suppressed by both fresh and composted amendments, but compost
was most suppressive at high compost rates with disease incidence <40% which are
considered healthy plants that can reach full yield potential. In the second
incubation, disease severity difference among treatments were similar to the first
incubation. This would indicate the suppression was induced prior to initiation of
this experiment.
Disease severity of bean plants grown in unamended field soil was high but
in amended soils tended to decrease in intensity over time. Root rot severity was
negatively related to ��-glucosidase, and microbial biomass at the beginning and the
end of the first incubation period, respectively. FDA hydrolysis was not correlated
with disease severity and WSA moderately correlated with disease. The best
indicator of disease severity was arylsulfatase which was significantly and
negatively correlated with disease severity in 4 of 5 sampling periods. / Graduation date: 2003
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/32042 |
| Date | 31 May 2002 |
| Creators | Cespedes Leon, Maria Cecilia |
| Contributors | Dick, Richard P. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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