Location of Genomic Regions Contributing to Phytophthora nicotianae Resistance in Tobacco Cultivar Florida 301

Black shank, caused by Phytophthora nicotianae, is typically the most important disease affecting tobacco (Nicotiana tabacum L.) production in the United States. Pedigree information suggests that most black shank resistance was derived from the cigar tobacco cultivar Florida 301. This resistance is thought to be polygenic in nature. The objectives of the current experiment were to (i) evaluate lines from a recombinant inbred line population derived from a cross between Florida 301 and the black shank-susceptible cultivar Hicks for partial resistance using replicated field and greenhouse testing, (ii) genotype the population and use quantitative trait loci (QTL) analyses to identify Florida 301 genomic regions associated with resistance, and (iii) compare results with those obtained from a previous QTL analysis of a population derived from a cross involving 'Beinhart 1000'. A total of 11 QTL affecting area under the disease progress curve were identified in both the field and greenhouse experiments. The QTL with the largest effect explained 16.9 and 18.6% of the phenotypic variation in the field and greenhouse experiments, respectively. This QTL was also found to have the largest effect on resistance in a Beinhart 1000 x Hicks doubled haploid mapping population. A major QTL found to affect resistance on linkage group 15 in the latter population, however, was not found to be important in the current population. Quantitative trait loci identification using greenhouse data was comparable to, if not superior to, use of field data.