The Effects of Host Diversity in Anthracnose Management and Race Composition of Colletotrichum sublineolum in Sorghum Lineage Mixtures

Alternative strategies of management of sorghum diseases were implemented using field experiments conducted in Embrapa Maize and Sorghum Research Center, Brazil in 2001 until 2003 to evaluate the efficacy of lineage mixtures of Sorghum bicolor for the control of anthracnose (caused by Colletotrichum sublineolum). The calculated values for disease severity considered the area under the disease progress curve (AUDPC) observed for the nine susceptible and resistant elite strains of sorghum planted in 30 stands randomly. Each stand was drawn in mixtures of three genotypes each, in the same proportions per plant. This design was compared with the severity of the disease measured in AUDPC calculated for each of the same nine strains of sorghum in pure stands. In most of the cases, the disease severity on the susceptible cultivars was decreased; and in some cases, reached 85% of disease reduction compared with disease progress in pure stand of correspondent plant. The implication and effect of these sorghum mixtures on the populations of C. sublineolum on each treatment were evaluated and revealed that there was an increase of frequency of complex races in most of these mixtures and a highest phenotypic diversity for virulence to pathogen populations from pure stands, than the characterized on populations collected from the mixtures, despite of the effectiveness on decrease of the anthracnose severity.