Multiple Introductions of Moniliophthora roreri from the Amazon to the Pacific Region in Ecuador and Shared High Azoxystrobin Sensitivity

Abstract

One of the main problems in the production of cacao in Ecuador is the disease caused by the fungus Moniliophthora roreri (frosty pod rot) which affects the pods. Here, we evaluate the genetic diversity of this fungus in Ecuador, and its sensitivity to the fungicide azoxystrobin. We evaluated 76 monosporic cultures from the Amazon and the Pacific coast regions. In vitro sensitivity assays tested several doses of the fungicide azoxystrobin to determine the percent of growth inhibition and the IC50. Concentrations of 1 to 0.1 µg mL−1 inhibited the growth of at least 91% of the isolates. Three isolates were the less sensitive (IC50 = 0.0220–0.0364 µg mL−1), two from Guayas (Pacific coast) and one from Sucumbíos (Amazon) provinces. However, M. roreri is highly sensitive, and it could be used in integrated management of the disease. Genetic analyses were carried out by amplifying microsatellite markers (SSR). All the genetic diversity statistics show a higher diversity in the Amazon compared to samples of the coast region; however, the molecular variance was low (FST = 0.11). Discriminant analysis clearly distinguishes three clusters concurrent with the provinces (Sucumbíos, Orellana and El Oro) and a group with the rest of the provinces. Minimum spanning networks shows, unexpectedly, that M. roreri from the coast were derived from at least three independent introductions from the Amazon. Findings are discussed in light of previous Pan-American genetic studies and available historical reports.

Geographic distribution, conservation, and genomic resources of cacao Theobroma cacao L

“…Ecuador and Colombia are ideal countries for breeding resistance to FPR, considering the introduction of different strains of M. roreri in areas of intense cacao cultivation (Díaz‐Valderrama et al., 2022; Espinoza‐Lozano et al., 2022; Jaimes et al., 2016). For example, artificial inoculation of five cultivated clones with seven isolates of M. roreri in Colombia identified the hybrid ICS 95 (Amelonado × Criollo) as a resistant clone (Phillips‐Mora et al., 2005).…”

“…However, recent population analysis of M. roreri based on SSR and SNP markers identified six genetic clusters in areas of intense cultivation in tropical America: Four clusters represented Coastal Ecuador and three—Magdalena Valley in Colombia, and one cluster included both countries (Díaz‐Valderrama et al., 2022). Another study based on SSR markers identified high genetic variation in M. roreri from the Ecuadorian Amazon where three clusters were identified (Espinoza‐Lozano et al., 2022). A comparison of M. roreri collected from plantations in coastal Ecuador and a cluster representing Amazonia suggests the introduction of M. roreri from the Ecuadorian Amazon to Coastal Ecuador (Espinoza‐Lozano et al., 2022).…”

“…Another study based on SSR markers identified high genetic variation in M. roreri from the Ecuadorian Amazon where three clusters were identified (Espinoza‐Lozano et al., 2022). A comparison of M. roreri collected from plantations in coastal Ecuador and a cluster representing Amazonia suggests the introduction of M. roreri from the Ecuadorian Amazon to Coastal Ecuador (Espinoza‐Lozano et al., 2022).…”

“…A comparison of M. roreri collected from plantations in coastal Ecuador and a cluster representing Amazonia suggests the introduction of M. roreri from the Ecuadorian Amazon to Coastal Ecuador(Espinoza-Lozano et al, 2022).…”

Chemical Characterization of Trichoderma spp. Extracts with Antifungal Activity against Cocoa Pathogens

“…The typical symptoms include abnormal shoots that display stem swellings, bud proliferation, and vegetative brooms, which inspired the name witches’ broom disease in cocoa [ 5 ]. The results of recent studies from the major cocoa-producing provinces of Ecuador showed that Moniliophthora species possess high morphological and genetic diversity [ 6 , 7 , 8 , 9 ]. For this reason, some alternatives such as cacao agroforestry systems [ 1 ] and biological controls using products based on endophytic organisms, including the combined application of natural or chemical products [ 10 ], have been used to reduce the impact of diseases, minimize the utilization of fungicides, and improve the yield of cocoa production.…”