SELECTION OF STRAINS OF Beauveria bassiana AND Metarhizium anisopliae (ASCOMYCOTA: HYPOCREALES) FOR ENDOPHYTIC COLONIZATION IN COCONUT SEEDLINGS

Abstract

Beauveria bassiana and Metarhizium anisopliae are considered virulent pathogens of the coconut weevil Rhynchophorus palmarum (Linnaeus). The objective of this study was to determine the ability of B. bassiana (Beauveriplant SBb36) and M. anisopliae (JGVM1) to establish an endophytic relationship with coconut Cocos nucifera (Linnaeus) seedlings. Strains were selected based on the mortality of adults of R. palmarum exposed to these fungi. Three methods of inoculation were used to inoculate the seedlings obtained through seed germination: foliar spray, stem injection and drench to the roots. Immersion of seedlings in a conidial suspension was used to inoculate seedlings obtained from tissue culture. Colonization was determined through the re-isolation of the fungi four weeks after inoculation. Beauveriplant SBb36 and JGVM1 colonized endophytically 100% of the seedlings obtained through tissue culture and 91.6% of seedlings obtained from germinated seeds. For plants inoculated by immersion with B. bassiana, the colonization rate in petioles (43%) was higher than in leaves and roots, 14 and 17%, respectively. Metarhizium anisopliae did not show significant differences in the colonization rate in leaves, petioles and roots. Plants inoculated by foliar spraying showed that colonization was higher in leaves > petioles > stems > roots. Colonization in stem injection was higher in stems than in the roots. Soil drench inoculation was higher in roots > stems. To our knowledge, this is the first report describing the endophytic relationship that B. bassiana and M. anisopliae establish with coconut seedlings obtained through seed germination and tissue culture when targeted inoculations are performed. SBb36 de B. bassiana y la cepa JGVM1 de M. anisopliae, para establecer una relación endofítica con plantas de coco Cocos nucifera (Linnaeus) obtenidas a partir de semilla sexual y de cultivo de tejidos. Se evaluaron diferentes métodos de inoculación: aspersión foliar, inyección en tallo y aplicación de suspensión conidial en las raíces, fueron usados para inocular plantas obtenidas a partir de semilla sexual, mientras que el método de inmersión fue usado para inocular plantas obtenidas a partir de cultivo de tejidos. El porcentaje de colonización en diferentes tejidos de las plantas se determinó a través del re-aislamiento de los hongos cuatro semanas después de la inoculación. Las cepas Beauveria bassiana (Beauveriplant SBb36) y Metarhizium anisopliae (JGVM1) colonizaron endofíticamente el 100% de las plantas de coco obtenidas a partir de cultivo Chilean J. Agric. Anim. Sci., ex Agro-Ciencia (2020) 36(1): 4 3-13. de tejidos y el 91.6% de las plantas de coco obtenidas por semilla sexual. En el presente estudio, se reporta por primera vez que B. bassiana and M. anisopliae establecen una relación de endofitismo con plántulas de coco obtenidas a partir de la germinación de semilla sexual y cultivo de tejidos a través de inoculaciones dirigidas. RESUMEN Beauveria bassiana y Metarhizium anisopliae son considerados patógenos virulentos...

Field Evaluation of Promising Indigenous Entomopathogenic Fungal Isolates against Red Palm Weevil, Rhynchophorus ferrugineus (Coleoptera: Dryophthoridae)

“…Our results are supported by other research studies where the application of B. bassiana through trunk injection suppressed RPW by up to 90% in the field [ 35 , 36 ]. Conidial suspensions of B. bassiana and M. anisopliae showed high survival rates when injected into coconut seedlings against Rynchophorus palmarum (Linnaeus, 1758) (Coleoptera: Dryophthoridae) [ 37 ]. The efficacy of applying microbial agents to palm trees to control insect borers can be easily assessed using acoustic sensors to detect the presence of insect borers in the trees [ 38 ].…”

Effects of Myco-Entomopathogens on Bio-Control of Trialeurodes Vaporariorum, Endophytic Colonization of Tomato, and Compatibility with selected pesticides

“…These entomopathogenic fungal strains recovered from different parts of tomato plant tissues (roots, stems, and leaves) that con rmed their potential to move and establish throughout the plant parts. The entophytic colonization of tomato (Mwamburi, 2021;Silva et al, 2020), soybean (Russo et al, 2019), pecan (Ramakuwela et al, 2020), and coconut (Gaviria et al, 2020) have been achieved by both B. bassiana and M. anisopliae strains. This suggests that these entomopathogenic fungal isolates have the potential to colonize different plant species besides to tomatoes.…”

Ecology, invasion history and biodiversity-driven management of the coconut black-headed caterpillar Opisina arenosella in Asia

“…Endophyte-mediated biological control manages several limiting pests and diseases of perennial crops such as bananas or cacao ( Akello et al., 2007 ). Exploratory work has shown how entomo-pathogenic fungi such as Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metsch) endophytically colonize 100% of tissue-culture coconut plantlets ( Gaviria et al., 2020 ). Laboratory assays have also documented the antagonistic effects of various mycorrhizal fungi and bacteria on coconut pests and diseases such as leaf spot disease, basal stem rot disease, or burrowing nematode ( Eris et al., 2019 ).…”