Black Shank Resistance and Agronomic Performance of Flue‐Cured Tobacco Lines and Hybrids Carrying the Introgressed <i>Nicotiana rustica</i> Region, <i>Wz</i>

Abstract

ABSTRACT Black shank, caused by Phytophthora nicotianae , is one of the most important diseases affecting tobacco ( Nicotiana tabacum L.) production in the United States. Genetic mechanisms are needed that provide resistance to current races and that can be combined into cultivars that provide high yields of cured leaf with acceptable quality. Previous research identified DNA markers associated with an introgressed N. rustica genomic region (designated as Wz ) found to contribute to resistance to race 0 and race 1 isolates. Objectives of the current research were to use DNA markers to transfer Wz into the elite genetic background of flue‐cured tobacco cultivar K 326 and to develop nearly isogenic lines and hybrids with and without the race 0 immunity gene Php . These materials were evaluated in multiple environments for black shank resistance, yield, and quality characteristics. Wz was observed to positively affect resistance in the seven diverse disease environments tested. Genotypes in which Wz was combined with Php exhibited the greatest levels of resistance. No evidence of a negative relationship between Wz and yield and/or quality was observed. Data suggest commercial value for Wz in flue‐cured tobacco‐breeding programs with the goal of developing high‐yielding tobacco cultivars with resistance to race 0 and race 1. Further studies are necessary to determine the durability of Wz ‐mediated resistance, however.