Reação de cultivares de soja e agressividade de isolados de Colletotrichum spp., agente causal da antracnose da soja

Abstract

Anthracnose is presented as one of the most relevant phytosanitary problems to the soybean in the Cerrado. The genetic improvement contributes to the increase of productivity in the state through its capacity to resist to adverse factors, such as the diseases. The most used commercial soy cultivars is resistant to diseases, although, with regard to anthracnose, there is difficulty in obtaining resistant cultivars, due to the great variability of the pathogenic agent. Based on that, the aim was to evaluate the trees damping off in pre and pos emergency, the occurrence and the severity in 6 soy cultivars (Agroeste 3820 IPRO, TMG 1188 RR, TMG 132 RR, M-SOY 8866 conventional, TMG 1179 RR and M-SOY 9144 RR), inoculated with Colletotrichum isolates, collected by soy tress which present the symptoms. The assessments happened between the Vc and V3 phenological stages. The damping off was evaluated on the seventh day after the sowing. The first incidence and severity evaluation happened seven days after the sowing and the following assessments were carried out every four day, totaling five evaluations, Severity was evaluated according to Anthracnose diagrammatic scale. The incidence and severity data were undergone to the Area Under Progress Curve Disease (AUDPC) calculation, in order to observe the advance of the disease through time. It was observed significant interaction between isolated and cultivars. The inoculated plants presented anthracnose symptoms; however, the witnesses did not present the disease symptoms, thus demonstrating the pathogenicity of the twenty-seven tested isolates. The M-SOY 8866 conventional, TMG 1179 RR and M-SOY 9144 RR cultivars statistically differ from the Agroeste 3820 IPRO, TMG 1188 RR and TMG 132 RR cultivars presenting high percentage of AUDPC damping off. The IT-4, IT-6, LU-3, NU-5, PN-1, QU-2, SO-11, VE-5 and VR-1 isolates presented higher aggressiveness.