Growth Chamber Evaluation of a Tobacco ‘Beinhart 1000’ × ‘Hicks’ Mapping Population for Quantitative Trait Loci Affecting Resistance to Multiple Races of Phytophthora nicotianae

Abstract

ABSTRACTMultiple races of Phytophthora nicotianae (van Breda de Haan) cause the black shank disease of tobacco (Nicotiana tabacum L.). Identification of novel alleles affecting resistance and associated DNA markers might help increase the range and level of cultivar resistance. A doubled haploid mapping population generated from a highly resistant × susceptible cross (‘Beinhart 1000’ × ‘Hicks’) was evaluated for resistance after inoculation with either race 0 or race 1 in a growth chamber and also genotyped at 206 microsatellite marker loci. Multiple interval mapping identified two major genomic regions affecting resistance to both races. A quantitative trait locus (QTL) on linkage group 8 explained 54.7 and 45.5% of the observed variation for end percent survival after race 0 and race 1 inoculation, respectively. A QTL on linkage group 4 explained a larger proportion (16.8%) of phenotypic variation for race 1 resistance as compared to race 0 resistance (1.8%). In combination with previously reported field data, the study authenticates the role of these two regions on black shank resistance. Correlations of line performance under field and growth chamber environments were good, and agreement was excellent at extreme levels of resistance or susceptibility. With appropriate isolate selection, growth chamber inoculations may provide a superior alternative to field evaluations for mapping QTL affecting black shank resistance. Identified QTL and associated markers may be useful for increasing levels of resistance to P. nicotianae in tobacco cultivars.