FIELD EVALUATION OF THE ROLE OF EPICUTICULAR WAX IN RAPESEED AND MUSTARD IN RESISTANCE TO ALTERNARIA BLACKSPOT

Abstract

The role of epicuticular wax in conferring resistance to blackspot, incited by Alternaria brassicae (Berk.) Sacc, has been investigated under field conditions in four cultivars of rapeseed and mustard. In increasing order of resistance to blackspot they were: Torch (Brassica campestris L.), Midas (B. napus L), Lethbridge (LB) 22A (B. juncea (L.) Czern.), and Tower (B. napus). The leaves of Midas and Tower have appreciable amounts of epicuticular wax, and wiping of the leaves with a dry cotton swab significantly increases their susceptibility to the blackspot disease. Torch and LB 22A have minimal amounts of epicuticular wax and their disease susceptibility is generally not significantly altered upon wiping. It is concluded that the epicuticular wax in rapeseed and mustard confers resistance to blackspot and that this character could be used in breeding cultivars resistant to this disease.