Induced systemic resistance in Stylosanthes spp. to Colletotrichum gloeosporioides

Abstract

Systemic resistance to anthracnose caused by Colletotrichum gloeosporioides was induced in Stylosanthes humilis cv. Paterson and S.guianensis cv. Endeavour plants by protection inoculation (PI) with sub-lethal amounts of C. gloeosporioides inoculum. The protection was demonstrated on leaves produced after the plants had first become infected. When challenged with inoculum, these leaves produced significantly less severe lesions than on corresponding leaves on non-protected plants. The induced resistance effect diminished with time on the youngest leaves of plants which were challenged up to 39 days from the PI. The experiments also showed that young Stylosanthes spp. leaves (up to seven days after first appearance) were more susceptible to anthracnose infections than older leaves. When leaves of S. humilis and S. guianensis were inoculated at 24 and 30 days after first appearance respectively, very few infections occurred. These two factors may help explain observed anthracnose occurrence patterns in Stylosanthes spp. pastures.