Canopy‐microclimate effects on the antagonism between Trichoderma stromaticum and Moniliophthora perniciosa in shaded cacao

Abstract

The collective impact of several environmental factors on the biocontrol activity of Trichoderma stromaticum (Ts) against Moniliophthora perniciosa (Mp), the cause of cacao witches' broom disease, was assessed under field conditions of shaded cacao (Theobroma cacao) in south-eastern Bahia, Brazil. Biocontrol experiments were performed adjacent to an automated weather station, with sensors and Ts-treated brooms placed at different canopy heights. Sporulation occurred at the same dates for all Ts isolates, but in different quantities. Broom moisture >30%, air temperature of approximately 23 ± 3°C, relative humidity >90%, solar radiation intensities <0AE12 KW m )2 and wind speed near zero were the key environmental parameters that preceded Ts sporulation events. A multiple logistic regression indicated that these weather variables combined were capable of distinguishing sporulation from non-sporulation events, with a significant effect of wind speed. Analyses of environmental factors at ground level indicated similar pre-sporulation conditions, with a soil moisture content above a threshold of 0AE34 m 3 m )3 preceding all sporulation events. The sporulation of five selected Ts isolates was compared at four different canopy heights. Isolates responded differently to weather variation in terms of sporulation and antagonism to Mp at different canopy levels, indicating that different microclimates are established along the vertical profile of a shaded cacao plantation. The potential of these findings for development of predictive mathematical models and disease-management approaches is discussed.

Trichoderma stromaticum and its overseas relatives

“…Members of Group 2 sporulated more profusely on rice and pieces of 'dry broom' (dead, proliferated branches of cacao that formed following infection of meristematic tissue by Moniliophthora perniciosa) than members of Group 1. Loguercio et al (2009b) observed that generally members of Group 1 were able to sporulate better in the tree canopy than members of Group 2, and this increased sporulation was correlated with lower incidence of M. perniciosa. When representatives of the two groups were experimentally inoculated into cacao trees in the field, members of both groups were able to develop an endophytic relationship in sapwood of the trees, but Group 2 members were recovered up to 120 days after inoculation whereas Group 1 members were not reisolated (de Souza et al 2008).…”

“…Trichoderma stromaticum is clearly distinguished from all other closely related fungi by its apparent host specialization on Moniliophthora species that parasitize (2006) and Loguercio et al (2009b) distinguished two groups within T. stromaticum based on AFLP patterns; Group 1 corresponds to Clade B (Fig 1) here, and Group 2 corresponds to Clade A. They attributed biological and ecological differences to the respective groups.…”

“…Although in de Souza et al (2006) and Loguercio et al (2009b), AFLP groups 1 (clade B here) and 2 (clade A here) are biologically distinct, and perithecia have not been found for one of those groups (Group 1, Clade A) multilocus phylogenetic data (Fig. 1e) support this clustering only weakly (Clade A is highly supported, but not clade B), and De Respinis et al (2010) did not observe any differences between the groups in MALDI-TOF MS analysis of the proteome.…”

Front line defenders of the ecological niche! Screening the structural diversity of peptaibiotics from saprotrophic and fungicolous Trichoderma/Hypocrea species

“…Examples of successful biocontrol approaches using Trichoderma strains include ‘ Tricovab ’, a Brazilian formulation recently approved (Anonymous 2012) for integrated management of Crinipellis (syn. Moniliophthora ) perniciosa , the causal agent of Witches’ broom of cacao (Pomella et al 2007; Loguercio et al 2009; Medeiros et al 2010). Notably, ‘ Tricovab ’ contains a peptaibiotic-producing strain (Degenkolb et al 2006a) of the hyperparasitic endophyte Trichoderma stromaticum .…”

Editorial - Crop health in agroforestry systems: An introduction to the special issue

“…A better research focus in this regard not only provides insights for their own improvement but also contributes with general theoretical and practical lessons on how to take advantage of vegetation. In particular, more research is needed to better elucidate the role of crop management practices, and in particular shade management, which represents a key agronomic lever affecting crop health in AFSs (Andres et al, 2018;Babin et al, 2010;Loguercio et al, 2009). Pests can threaten crop health in AFSs, either by affecting the crop per se or perturbing associated tree species, thereby altering the delivery of ecosystem services.…”