Evaluation of actinomycetes associated to Coffea canephora as biocontrol agents of Hemileia vastatrix

Abstract

The objective of this study was to isolate, select, and evaluate in the field crude chitinolytic cultures (CCC) derived from actinomycete strains associated with the rhizosphere of Robusta coffee plants (Coffea canephora) to determine their potential as biocontrol agents against coffee rust (Hemileia vastatrix). Rhizosphere soil samples were collected from a Robusta coffee plantation located in the municipality of Tapachula, Chiapas, Mexico, at an elevation of 300 meters above sea level. Twenty-five microbial isolates were obtained; of these, 11 were actinomycete strains, six of which exhibited chitinolytic activity in M9 medium supplemented with colloidal chitin as the sole carbon source. Strains IBC-CcR1 and IBC-CcR6 were selected due to their high chitinase activity, and their CCCs (applied individually or in combination) were evaluated in the field as biocontrol agents against rust on Robusta coffee plants. Statistical analysis showed similarities among the treatments, but differences compared to the control regarding the area under the disease progress curve (AUDPC). The CCC from strains IBC-CcR1 and IBC-CcR6 delayed disease progression by 34 and 32 days, respectively, whereas copper oxychloride caused a delay of 20 days compared to the control.