Genetic Variability, Structure Analysis, and Association Mapping of Resistance to Broomrape (Orobanche aegyptiaca Pers.) in Tobacco

Broomrape is a debilitating holoparasiting weed in tobacco (Nicotiana tabacum L.) fields with devastating effects on its production. In this study, the reaction of ۸۹ tobacco genotypes was evaluated against broomrape (Orobanche aegyptiaca) in randomized complete block design with three replications during two years. In each year, genotypes were planted in both non-inoculated and inoculated conditions where the soil of pots was mixed with ۰.۰۶ g of broomrape seed. Considering the average data of two years, studied genotypes did not show infection to broomrape at non-inoculated condition, whereas in inoculated condition, the majority of genotypes showed infection to broomrape. Two genotypes including ‘TB ۲۲’ and ‘Kramograd NHH ۶۵۹’ did not show any infection to broomrape in inoculated condition. In a molecular experiment, the fingerprint of tobacco genotypes was prepared with ۲۶ SSR loci. Using model-based Bayesian approach, the studied association panel was divided into three subgroups. The D¢ was used to test the LD between pairs of SSR loci using the software package TASSEL. ۷.۰۸% of possible SSR locus pairs showed significant level of linkage disequilibrium (P<۰.۰۱). By using mixed linear model, ۵ SSR loci from linkage groups ۲, ۱۰, ۱۱ and ۱۸ of tobacco reference map were identified as DNA markers to be linked to gene(s) controlling broomrape resistance in tobacco.