Abstract
ABSTRACT: Ecuador is responsible for up to 70 % of the world’s production of fine flavor cocoa. Although fungal diseases have reduced cocoa production, eco–friendly alternatives have been implemented to control the spread of phytopathogens. This study aimed to explore the potential of endophytic strains isolated from fine flavor Nacional cocoa trees to synthetize compounds with antimicrobial and surface active properties. It was determined that under in vitro conditions, seven strains (DS03, DS07, DS18, DS23, DS31, DS34 and DS50) exhibited antifungal activity that inhibited the mycelial growth of Moniliophthora roreri and Moniliophthora perniciosa. The strains were identified based on their morphological (pattern forming Bacilli) and genetic characteristics using the 16S SSU rRNA gene sequences. Furthermore, we determined that the endophytic strains contained genes that encoded the lipopeptides Fengycin (fenA, fenB, fenC, fenE), Iturin (ituB, ituC, ituD), and Bacyllomicin D (bamC, bamD). The production of biosurfactant compounds was determined by a reduction in surface tension in the mineral medium. Additionally, the biosurfactant crude extract (BCE) was tested for its inhibitory activity against M. perniciosa and M. roreri. The minimal inhibitory concentration (MIC) was determined to be 0.07 and 0.035 mg mL−1, respectively, in both cases in a fungistatic action mode. The swelling granulation and fragmentation of both phytopathogens’ hyphae were observed using the BCE treatment. These results suggested the biocontrol capacity of the endophytic strains, which under in vitro conditions, have the ability to synthesize antifungal and surface active compounds that might be used as an ecological alternative in cocoa plants to prevent infection by phytopathogens.
Highlights
Cocoa is an agricultural, economic commodity considered essential to millions of people worldwide
Endophytic strains were isolated from Naranjal and Balao cocoa plantations located on the Ecuadorian coast, where fine flavour National and CCN51 cocoa varieties are commonly cultivated
51 bacterial isolates exhibited promising antifungal activity by being able to inhibit the mycelial growth of M. roreri and M. perniciosa
Summary
Economic commodity considered essential to millions of people worldwide. Cocoa bean production is severely limited by diseases that have caused a reduction in annual yield of approximately 20 %, the percentage loss may vary across different production regions (Ploetz, 2016). (Evans, 1981; McElroy et al, 2018) They have a narrow geographic distribution and are usually non–lethal diseases, they impact yields by rendering beans in affected pods commercially useless (Ploetz, 2016). Ecuador and Perú are among the top 10 cocoa–producing countries where devastating losses could occur if these phytopathogens were to spread (Evans, 2016; Ploetz, 2016)
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