Efficiency of Marine Bacteria and Yeasts on the Biocontrol Activity of Pythium ultimum in Ancho-Type Pepper Seedlings

Abstract

Ancho-type pepper (Capsicum annuum L.) is a crop susceptible to Pythium ultimum, which has already been controlled with synthetic fungicide applications; however, marine antagonist microorganisms could be an alternative source of control. The efficiency in vitro and in vivo of marine bacteria and yeasts was determined against P. ultimum. The inhibition of the radial growth of P. ultimum was quantified in vitro by the bacteria Stenotrophomonas rhizophila KM01 and KM02; Bacillus subtilis RBM01 and RBM02, B. amyloliquefaciens 2RLBF and 3R4CF; and Pseudomonas spp. 2R6BF and 2RE9CF, as well as the yeasts Debaryomyces hansenii 1R11AB, 1R11CB, and LL01 and Cryptococcus laurentii 2R3BF and 2R1CB. The β-1,3-glucanase activity of the marine microorganisms was quantified in the presence of the phytopathogen. The disease index (DI), growth parameters, and colony forming units (CFU) were determined in ancho-type pepper plants inoculated with marine bacteria, yeasts, and P. ultimum. The radial zone of the phytopathogen was inhibited by 80% and 75% by S. rhizophila KM01 and C. laurentii 2R1CB, respectively. D. hansenii LL01 and S. rhizophila KM02 showed the highest activity of β-1,3-glucanase, with 6060 U/mL and 47 U/mL, respectively. B. subtilis RBM02 protected 100% of the plants from the oomycete, and an increase was quantified in all the growth parameters and CFU. The use of these marine bacteria and yeasts are, therefore, an option for P. ultimum biocontrol in ancho-type pepper plants, thereby minimizing the application of synthetic fungicides.Agronomy 2020, 10, 408 2 of 12 by immediate infection makes management of this phytopathogen very difficult [7]. Several Pythium species, including P. aphanidermatum, P. irregular, and P. ultimum, are known to cause damping-off and root rot diseases in pepper [8][9][10]. Although synthetic fungicides have shown promising results in controlling damping-off disease, phytotoxicity and fungicide residues pose serious problems to human and animal health, as well as the environment. In this context, phytosanitary measures and the management of pepper cultivation should include the application of microorganisms as biocontrol agents to minimize the use of synthetic fungicides [11].Bacteria and yeasts have a high capacity to control phytopathogens without causing damage to human and animal health and the environment [12,13]. Several mechanisms have been proposed for the biocontrol of phytopathogens by bacteria and yeasts, including competition for space and nutrients [14,15], lytic enzyme production such as β-1,3-glucanase [16,17], and induction of host resistance [18,19], among others. Both microorganisms have been isolated in different terrestrial ecosystems, mainly in plants, fruits, and soils; the main bacteria used as biocontrol agents are species of Stenotrophomonas, Bacillus, and Pseudomonas, which have already been reported for the control of Fusarium proliferatum in melon [20]; Sclerotium rolfsii [21] and Rhizoctonia solani in wheat [22]; and F. solani in cassava [23], among others. O...

Pythium Damping-Off and Root Rot of Capsicum annuum L.: Impacts, Diagnosis, and Management

“…Early inoculation of the biocontrol agent before seeding or inoculation close to the seed or seedling can increase the efficacy of an antagonist [ 115 ]. The rapid colonization of an antagonist can also provide an extra advantage for its success [ 109 , 110 ].…”

Metabolomics on the study of marine organisms

“…Using an NMR-based metabolomics approach, it was possible to establish relationships between some NMR signals and the bioactivity, leading to the identification of two phenylethylene amides that were responsible for the activity. To extend their potential use in agriculture, marine microorganisms have been investigated for their biocontrolling capacity against phytopathogens by inoculating the microorganism in the plant or soil (Lara-Capistran et al, 2020;Ortega-Morales et al, 2009;Radovanović et al, 2018). In this kind of marine research, metabolomics allowed not only the identification of the active compounds but provided information allowing a deeper understanding of the relationship between the microorganism of marine origin with the phytopathogen and the plant (Allwood et al, 2008).…”