Molecular mapping of bunchy top disease resistance in Gossypium hirsutum L.

Cotton bunchy top (CBT) is an aphid transmitted Polerovirus disease and a significant threat to the Australian cotton industry. Symptoms include stunted plant growth, and leaves often display pale green angular patterns at the leaf margins and dark green centers with a leathery texture. Resistance to CBT was evaluated in 206 F-2 plants and 76 F-2:3 families derived from the resistant cultivar 'Delta Opal' crossed to the susceptible cultivar 'Sicot 70', and in 25 other cultivars the majority susceptible to CBT. CBT resistance in 'Delta Opal' was shown to be controlled by a single dominant locus designated Cbt. A combination of AFLP and single nucleotide polymorphism markers located Cbt on chromosome A10, close to the mapped resistance locus in 'Delta Opal' to another Polerovirus disease of cotton; cotton blue disease. The markers identified flanking CBT resistance will provide useful tools for breeders for marker-assisted selection to alleviate the impact of this disease on cotton production.