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

Abstract

Broomrape is a debilitating holoparasiting weed in tobacco ( Nicotiana tabacum L.) fields with devastating effects on its production. In this study, the reaction of 89 tobacco genotypes was evaluated against broomrape ( Orobanche aegyptiaca ) in randomized complete block design with three replications durin g two years. In each year, genotypes were planted in both non-inoculated and inoculated conditions where the soil of pots was mixed with 0.06 g of broomrape seed. Considering th e average data of two years, studied genotypes did not show infection to broomrape at no n-inoculated condition, whereas in inoculated condition, the majority of genotypes sho wed infection to broomrape. Two genotypes including ‘TB 22’ and ‘Kramograd NHH 659’ did not show any infection to broomrape in inoculated condition. In a molecular e xperiment, the fingerprint of tobacco genotypes was prepared with 26 SSR loci. Using mode l-based Bayesian approach, the studied association panel was divided into three su bgroups. The D ′ ′′ ′ was used to test the LD between pairs of SSR loci using the software pac kage TASSEL. 7.08% of possible SSR locus pairs showed significant level of linkage dis equilibrium (P<0.01). By using mixed linear model, 5 SSR loci from linkage groups 2, 10, 11 and 18 of tobacco reference map were identified as DNA markers to be linked to gene (s) controlling broomrape resistance in tobacco. Keywords: Association analysis, Broomrape, Linkage disequilibrium, Tobacco.