A Rapid Seedling Based Screening Technique to Assay Tobacco for Resistance to Phytophthora nicotianae

Black shank caused by Phytophthora nicotianae is a serious root and stem disease of cultivated tobacco worldwide. In this study, a rapid seedling-based screening technique was developed to evaluate tobacco cultivars for resistance to P. nicotianae. This technique was compared with a stem inoculation technique commonly used on adult plants. The overall aim was to develop an improved and rapid technique that could also be used to characterize races of P. nicotianae. A strong positive correlation was found between results of the seedling assay and adult plant trials for all isolates and cultivars tested. Furthermore, P. nicotianae isolates could be characterized as race 0 or 1 using both stem inoculation and the rapid seedling assay. This assay will facilitate rapid and large-scale screening for black shank resistance and therefore has the potential to reduce yield losses because of this disease in the field.