Persistence of Bacillus thuringiensis and Bacillus pumilus potential biological control agents of the coffee berry borer under field conditions of Puerto Rico

Abstract

Field trials were conducted in two years to evaluate persistence of B. thuringiensis and Bacillus pumilus under field conditions. Strains of B. thuringiensis (3971) and B. pumilus (4185) were isolated from coffee agro-ecosystem in Puerto Rico. Field trials consisted in plots of nine coffee trees arranged in a randomized complete block design, sprayed with Bt-3971 and Bp-4185 at 108, 109, or 1010 colony forming units CFU ml-1 or non-inoculated. In year 1, B. thuringiensis and B. pumilus survived up to six months after inoculation. Monitoring carried out during year 2, re-confirmed the survival of Bt-3971 and Bp-4185 inoculated in coffee trees under field conditions. Overall, Bt-3971 had significantly more recovery rates than Bp-4185. However, the higher bacterial recoveries were 1.24x1013 CFU ml-1 in coffee trees treated with Bt-3971 and 2.48x1013 CFU ml-1 in coffee trees treated with Bp-4185 in year 1 and year 2, respectively, both sprayed with 1010 spores ml-1. B. thuringiensis (3971) and B. pumilus (4185) isolated from coffee fields of Puerto Rico are well adapted to the environmental conditions of the island, and are valuable biological control agents against coffee berry borer.

Native Bacillus paralicheniformis isolate as a potential agent for phytopathogenic nematodes control

“…Sutto-Ortiz et al ( 2017) and Bacame-Valenzuela et al (2015) reported the isolation of thermotolerant actinomycetes and fungal strains capable of synthesizing enzymes of industrial interest, such as phospholipase A and feruloyl esterases, respectively. Additionally, Camacho-Ruiz et al (2020) reported the isolation from Sonoran Desert soils of Streptomyces, Bacillus, Aspergillus, and Aureobasidium strains able to produce gastrointestinal lipase inhibitors. Moreover, Baqueiro et al (2019) reported the biotechnological potential of Bacillus strains capable of producing stable proteases.…”

“…Subsequently, the endospore suspension was added with 10% (w/v) of maltodextrin as a carrier ( Bhagwat et al, 2020 ; Vignesh et al, 2022 ) and dried using a laboratory spray dryer (Yamato ADL3115) at 110°C and 75°C as inlet and outlet air temperature, respectively, obtaining a fine powder containing around 1 × 10 8 endospores/g. Endospores were quantified, resuspending the powder in water and employing two methods: (a) using a Newbauer chamber (40X); (b) by plate count, according to Bolanos-Carriel and Vazquez Soto (2022) method. Endospores morphological and wall characteristics were verified through the application of the Endospore Stain Protocol, recommended by the American Society for Microbiology ( Hussey and Zayaitz, 2016 ).…”

“…Alsharif et al (2020), Bokhari et al (2020), andFranklin et al (2021) showed that desert microorganisms not only relieve water stress in plants and promote growth but also protect the plant against pathogens, such as PPNs. Moreover, Viljoen and Labuschagne (2019) and Abd-Elgawad and Mahfouz (2020) found that Streptomyces and Bacillus strains isolated from the Egyptian desert are capable of effectively controlling PPNs and surviving in extreme conditions of drought and water stress. In this way, the plant-associated microbiota from deserts is a perfect ecological niche to isolate new microorganisms that are well adapted to extreme conditions and have potential for the biological control of phytopathogens, including PPNs.…”