Entoleuca sp. infected by mycoviruses as potential biocontrol agents of avocado white root rot
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Entoleuca sp. infected by mycoviruses as potential biocontrol agents of avocado white root rot Juan M. Arjona-López López-Herrera
&
Carlos J.
Accepted: 17 November 2020 # Koninklijke Nederlandse Planteziektenkundige Vereniging 2020
Abstract Rosellinia necatrix Prill. the causal agent of white root rot diseases causes major losses in avocado crops in Spain. To study the biocontrol of this disease, 31 antagonistic isolates were collected from the avocado rhizosphere and identified as Entoleuca sp. Studies were carried out in mycovirus detection, in vitro optimal growth temperature, mycelial compatibility groups of these isolates, and their inhibition of R. necatrix growth. The pathogenicity of these antagonistic isolates and their biocontrol of white root rot on avocado plants were also studied. The presence of mycoviruses was detected in all 31 Entoleuca sp. isolates studied and the optimal growth temperature for almost all the isolates (> 80%) was 25 °C. Dual culture showed different responses, with some isolates compatible and others incompatible with each other, showing inhibition halos and black lines. Twenty-five of the 31 isolates showed significant growth inhibition to a virulent R. necatrix isolate in in vitro conditions. In addition, none of the Entoleuca sp. isolates produced any symptoms on inoculated avocado plants and in 24 of them, symptoms of avocado white root rot were reduced, with significant differences among the Entoleuca sp. isolates when they were used as biocontrol agents. New virus-carrying Entoleuca sp. isolates were obtained, which are capable of controlling avocado white root rot. J. M. Arjona-López : C. J. López-Herrera (*) Institute for Sustainable Agriculture, Spanish Research Council, Alameda del Obispo s/n, 14004 Córdoba, Spain e-mail: [email protected]
Keywords Antibiosis . dsRNA . Dual culture . Mycelial compatibility groups . Persea americana . Rosellinia necatrix
Introduction Avocado (Persea americana Mill.) has been an important crop along the coastal area of southern Andalusia in the provinces of Malaga and Granada, Spain, since it was established in the late 1970s (López-Herrera and Zea-Bonilla 2007). Spain is the highest avocadoproducing country in the European Union, with a total of 91,724 tons in 2018, and within Spain, Andalusia is the highest producing region of this crop, with a total production of 78,023 tons (MAPA 2019). Avocado white root rot (AWRR) caused by Rosellinia necatrix Prill. is a major disease in the avocado production areas in Spain (López-Herrera 1989). Since the first detection of R. necatrix in Spain in 1987 (López-Herrera 1989), AWRR incidence has been increasing progressively (López-Herrera et al. 1998). This pathogen also causes large-scale destruction and economic losses in many crops and ornamental plants (Arakawa et al. 2002; Sztejnberg and Madar 1980; ten Hoopen and Krauss 2006). Furthermore, R. necatrix has been detected in other avocado-producing countries such as Mexico, Dominican Republic, Colombia, Brazil, USA (California), China, De
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