Stem and root resistance to tobacco black shank

Stem lesion development in the absence of root decay in tobacco black shank caused by Phytophthora parasitica var. nicotianae has become common in the Coastal Plain tobacco growing area in Georgia. All aboveground symptoms of wilting, blackening of lower stem, and destruction of the pith can occur o n tobacco without or with minor root decay. This type of black shank diseas e development occurred in 14 of 15 locations evaluated and accounted for ab out 30% of diseased plants. Cultivars with Florida 301-derived resistance h ad very low stem resistance to race 0 of the pathogen. However, root inocul ations of these cultivars resulted in disease reactions typical of those ex pected in vivo in Georgia. Cultivars Coker 371-Gold and NC 71 and the breed ing line 1071 demonstrated high resistance to inoculation with race 0 of P. parasitica var. nicotianae in both the stem and the roots, but they were s usceptible when stem-inoculated with race 1 of the pathogen. Severity of ro ot decay was isolate dependent.