Influence of Soil Inoculum Concentrations on Host Range and Disease Reactions Caused by Isolates ofThielaviopsis basicolaand Comparison of Soil Assay Methods

Publisher Website
Google Scholar
Abstract
Nine isolates of T. basicola were tested for host specificity at 102, 103 and 104 endoconidia/g soil and for disease reactions caused on cotton, bean, pea, peanut and soybean. Sunflower, a nonhost, served as control. The isolates of various geographic origin were from cotton, bean, soybean, orange, sesame and field soils cropped to soybean, tobacco, peanut or guar. Cotton was the most susceptible at each of the inoculum concentrations, and sunflower apparently was not affected by any of the inoculum concentrations. For all isolates, host specificity was most apparent at an inoculum concentration of 104 endoconidia/g soil, except for cotton and bean; isolate 415 was nonpathogenic on bean but caused severe black root rot on cotton at 104 endoconidia/g soil. Although isolates of T. basicola were from various hosts, they were not specic for these hosts. In assays for T. basicola in soils from 9 cotton fields in the San Joaquin Valley in California [USA], each with a history of seedling disease problems, 8 fields had 10 or fewer propagules/g soil and 1 field had 70 propagules/g soil. Of various selective media compared for sensitivity in detecting low concentrations of propagules of T. basicola from naturally infested soils, the carrot disk technique was the most sensitive.

This publication has 1 reference indexed in Scilit: