Submitted to: Biennial Workshop on Smut Fungi
Publication Type: Abstract Only
Publication Acceptance Date: 6/12/2008
Publication Date: N/A
Technical Abstract: The rate of decline of teliospore viability over a 7-year period was determined for teliospores of Tilletia indica, the causal agent of Karnal bunt of wheat, in field plots in Tucson, AZ. During the study, polyester mesh bags, each containing 3 g teliospore-infested soil, were received from Maryland, Kansas, Arizona, and Georgia were used for the study. They are recovered from two irrigated and two non-irrigated field plots at 6- to 24-month intervals. Each soil sample was extracted by means of a sucrose centrifugation technique, treated with acidic electrolyzed water, and plated onto 2.0 percent water agar containing antibiotics. Eleven days later, germination percentages were determined. One thirty-fifth of the remaining soil residue (containing teliospores not able to be extracted) was treated with acidic electrolyzed water, plated onto water agar containing antibiotics, and quantified as above. For each respective soil sample, the number of viable teliospores calculated to be present in the entire sucrose-centrifugation extract was added to the number of viable teliospores calculated to be present in the soil residue, and the sum was termed “total number of viable teliospores” (TNVT) per 3-g soil sample. Based on nonlinear regressions, the TNVT decreased from 55.7 percent at time zero to 3.9 and 4.6 percent after 7 years in irrigated and non-irrigated field plots, respectively. Using regression analyses, we estimated that the total number of viable teliospores would approach zero in 12.8 years in irrigated field plots, 18.2 years in non-irrigated field plots, and 38.0 years in the same soils maintained in the laboratory. The rates of decline in teliospore viability were greater for soils from Maryland and Kansas than soils from Arizona or Georgia, indicating that longevity of Karnal bunt teliospores varies greatly among soils.