Control of root rot (Phytophthora cinnamomi) in avocado (Persea Americana) with bioagents

Abstract

Despite the favorable edaphoclimatic conditions for avocado production in Brazil, diseases such as root rot caused by the pathogen Phytophthora cinnamomi compromise the crop. With the aim of managing root rot in avocado, the present study aimed to evaluate chemical and biological control with isolates of Trichoderma spp. and Pseudomonas fluorescens. Thus, three assays were conducted to assess: (i) mycelial inhibition of P. cinnamomi by isolates of Trichoderma spp. and P. fluorescens from different crop systems; (ii) effect of autoclaved and non-autoclaved metabolites of P. fluorescens, and (iii) chemical or biological treatment of avocado seedlings on the control of root rot under field conditions. The isolates of Trichoderma spp. from maize cultivation soil and the commercial products formulated with Trichoderma presented greater antagonism (p <0.05) to the pathogen P. cinnamomi in the in vitro tests. Similarly, non-autoclaved metabolites of P. fluorescens presented antagonistic potential to control P. cinnamomi. Under field conditions, the fungicide metalaxyl and the bioagents showed effectiveness in controlling P. cinnamomi, as well as greater root length and mass. Results demonstrated potential for the biological control of avocado root rot with Trichoderma spp. and P. fluorescens.

Effect of Co-Inoculation with Growth-Promoting Bacteria and Arbuscular Mycorrhizae on Growth of Persea americana Seedlings Infected with Phytophthora cinnamomi

“…Even a systematic review has pointed out that Bacillus is very promising for controlling and inhibiting several species of Phytophthora [35]. Another study has demonstrated the potential for biological control of avocado root rot with P. fluorescens [7]. This bacterium also induces root and apical growth of avocado, even under P. cinnamomi infection conditions [17].…”

“…Available control methods can reduce this disease's severity [6]. However, the current trend is to incorporate new technologies that reduce agrochemical use to obtain healthier products and, at the same time, open more demanding markets [7]. In this sense, rhizobacteria and mycorrhizae constitute important sources of potentially beneficial microorganisms with plant growth-promoting activity and antagonistic effects against phytopathogens [8,9].…”

A systematic review about biological control of phytopathogenic Phytophthora cinnamomi

“…P. cinnamomi Rands infection is a destructive disease in avocado (Persea americana Mill.) crop, and to assess the potential of biological agents against P. cinnamomi, Sumida and colleagues (2020) [49] evaluated the effects of Trichoderma spp. and Pseudomonas fluorescens and their metabolites.…”

“…The non-autoclaved metabolites from P. fluorescens C1, C2, and a mixture of C1 + C2 inhibited the mycelial growth of P. cinnamomi by more than 90%, meanwhile, the autoclaved metabolites of C1 presented only 39% of inhibition, and C2 and C1 + C2 inhibited by 60%. The experiments in avocado seedlings investigating the application of treatments after P. cinnamomi inoculation showed that the chemical compounds presented the most efficient control of the pathogen and the plants were symptomless in both root and aerial parts, but promising results were observed in the plants treated with P. fluorescens C1 isolate since plants remained symptomless and presented enhanced length and weight of dry matter in the aerial portion [49].…”

“…Economically important plants are among the host of P. cinnamomi, such as ornamental crops, avocado, and chestnut trees. The avocado cultivars are highly susceptible to pathogen infection and, historically, cause economic losses linked to a decline in quality and production (reviewed in Belisle et al 2019;Sumida et al 2020). Similarly, the European chestnut tree crop is hugely affected by the chestnut ink disease, caused by P. cinnamomi infection, besides affecting negatively non-target organisms, such as beneficial microorganisms [12].…”