Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: April 20, 2010
Publication Date: June 20, 2010
Citation: Jaaffar, A.M., Weller, D.M., Paulitz, T.C., Thomashow, L.S. 2010. Effect of pH on the growth of Rhizoctonia spp. from cereal-based cropping systems in eastern Washington State. Phytopathology, Vol. 100, No.6,pg. S85. Technical Abstract: Rhizoctonia root rot caused by Rhizoctonia solani AG 8 and Rhizoctonia oryzae are serious root diseases in dryland cereal production in Washington State. Isolates of Rhizoctonia spp. from fields with different cropping histories in the low- (<12 inches) and moderate- (>12 inches) precipitation zones of eastern Washington State were identified by using six PCR primer sets specific for AG 8, AG 2-1, AG 10, AG I (Ceratobasidium spp.) and 2 groups of R. oryzae. Of 205 isolates, AG 8, AG I, AG 2-1, R. oryzae group 2, R. oryzae group 3, and AG 10 comprised 28%, 19%, 17%, 15%, 13%, and 8% of the isolates, respectively. AG 8 comprised 67% and 33% of the isolates in the low and moderate precipitation zones. The soil pH in fields in eastern Washington varies considerably (<pH 4 to >pH 7.5) because of decades of use of ammonium fertilizer, which lowers soil pH. Rhizoctonia isolates were tested for growth on 1/5-strength PDA adjusted to a range of pH values from 5.6 to 7.6. AG groups differed significantly in growth at the various pH values and in general, growth was significantly reduced above pH 6.8. These results suggest that the composition of Rhizoctonia isolates in a field may be determined in part by the soil pH and precipitation.