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Effect of antagonistic yeasts from cacao tissues on controlling growth and sporulation of Moniliophthora roreri

Abstract:

Frosty pod rot is the most significant disease of cacao (Theobroma cacao L.) in Tropical America, enormously decreasing cacao production in these regions. The introduction of the disease in Cruzeiro do Sul, Brazil, increased cacao growers' concern. Preventive control measurements are already being studied and established. Therefore, this study aimed to isolate and identify yeasts from cacao tissues with the potential to control Moniliophthora roreri, the causal agent of frosty pod rot disease, and further evaluate some of their possible antagonistic mechanisms of action. The initial screening was conducted through a dual-culture with two M. roreri isolates from Ecuador and forty-four yeast isolates (38 from Ecuador, six from Brazil) from cacao tissues, cultivated separately. Yeast antagonistic activity was verified by co-cultivation, volatile organic compounds, cell-free suspensions, and thermostable compounds. Moreover, the biofilm-forming capacity of yeast isolates was examined. Seven yeast isolates were selected and showed an inhibitory effect of up to 71% in dual-cultures. None of them grew in body temperature. The isolates were identified by primer pairs of the D1/D2 region of the large subunit ribosomal ribonucleic acid (LSU rRNA) of Hannaella pagnoccae (INIAP-YYL 111, INIAP-YYL 112 and INIAP-YML 324), H. luteola (INIAP-YYL 521), Vishniacozyma carnescens (INIAP-YYL 612), Hannaella spp. (INIAP-YYL 123) and Rhodotorula paludigena (LEV 169), the last one already studied against Moniliophthora perniciosa in Brazil. Seven out of the forty-four yeast studied showed high inhibitory potential against M. roreri by different antagonistic mechanisms: co-cultivation in culture medium, volatile organic compounds, cell-free and thermostable compounds, and capacity for biofilm formation, some of these characteristics are promising for further use of yeasts as a biocontrol agent of M. roreri.