Section 6
Chapter 5,240

Effect of flooding on the soil gas composition and the production of micro sclerotia by verticillium dahliae in the field

Ioannou, N.; Schneider, R.W.; Grogan, R.G.

Phytopathology 67(5): 651-656


ISSN/ISBN: 0031-949X
Accession: 005239424

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The production of microsclerotia (MS) in tomato tissues infected with V. dahliae was examined in soil subjected to different water treatments (no irrigation, 1 irrigation, and 10, 20 and 40 days of continuous flooding) under field conditions. About equal numbers of MS were produced in the dry and 1-irrigation treatments. No, or very few, MS were produced during the flooding and this inhibition was due in large part to decreased O2 and increased CO2 concentrations in the flooded soil. Upon drainage, the concentrations of O2 and CO2 returned rapidly to normal atmospheric levels and MS production resumed. The numbers of MS eventually produced in the 10-, 20- and 40-day flooding treatments were 90, 44 and 46%, respectively, of the average numbers in the nonflooded treatments. The reduction was significant (P = 0.05) only in the 20- and 40-day flooding treatments. Ethylene, at levels ranging from traces to about 6.5 .mu.l/l was detected in all treatments. Highest concentrations occurred in flooded or nearly saturated soils with added plant debris, but there was no indication that ethylene affected the production of MS.

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