Current Status of Soybean Anthracnose Associated with Colletotrichum truncatum in Brazil and Argentina

Abstract

Brazil and Argentina have a combined soybean area of 53.6 million hectares, which accounts for over half of the total global production. The soybean crop in South America extends from latitude 8–10° S to 32–36° S. Such a vast, almost contiguous area imposes a serious sanitary risk to the crop. Currently, the prevalence of anthracnose is increasing, with recurring reports of severe epidemics and expressive yield losses. Soybean anthracnose is mainly associated with Colletotrichum truncatum, although other Colletotrichum species have also been reported as causal agents of this disease. Knowledge about the morphological, cultural, and molecular variability of C. truncatum in South America is crucial for disease management. Here, we present data on the molecular, morphological, biological, cultural, and pathogenicity of C. truncatum isolates collected in Brazil and Argentina. Light microscopy and randomly-amplified polymorphic DNA (RAPD) analysis were used for estimating the variability of isolates. Colletotrichum truncatum displayed three types of conidiogenesis, viz. conidial formation from conidiogenous cells on hyphal extremities, in conidiomas in acervuli, and directly from fertile setae (a mechanism yet-unreported for C. truncatum). RAPD profiling was effective in revealing the genetic diversity among C. truncatum isolates. The intra-group similarity was greater among the Argentinian isolates when compared to the Brazilian group. Furthermore, the results indicated a strong correlation between geographical origin and molecular grouping, with the exclusive or semi-exclusive assembling of Brazilian and Argentinian isolates in distinct clades. Finally, a preliminary account of the reaction of soybean accessions to C. truncatum is also included.

Diversity of the Seedborne Fungi and Pathogenicity of Fusarium Species Associated with Intercropped Soybean

“…[ 4 , 10 , 25 , 27 , 37 ]; seedling blight and seed decay caused by Diaporthe/Phomopsis species complex [ 15 , 18 ]; soybean anthracnose caused by Colletotrichum spp. [ 21 , 38 ]; and leaf spot by Alternaria spp. [ 39 ].…”

“…Regarding to the seedborne fungi, the species in the genera of Colletotrichum , Phomopsis , Fusarium and Alternaria are the most frequently isolated fungi from soybean seeds [ 1 , 17 , 18 , 19 , 20 , 21 ]. Among them, Phomopsis longicolla (syn.…”

Soybean anthracnose caused by Colletotrichum species: Current status and future prospects

“…They hypothesized that the genetic resistance of cotyledons and stems might be under the control of genetically independent mechanisms. Sources of resistance of soybean to anthracnose caused by C. truncatum have been reported and studies in Brazil, India, and the USA revealed that 22 commercial cultivars, nine genotypes, and one soybean germplasm are highly resistant to C. truncatum (Costa et al., 2009; Dias et al., 2019; Nagaraj et al., 2014, 2020; Yang & Hartman, 2015). Research on sources of resistance to other Colletotrichum species associated with anthracnose has not yet been performed.…”

“…This study also suggested that Brazilian C. truncatum populations resulted from at least three founder events, which led to three genetic groups that spread throughout the country, conserving syntopy (Rogério et al., 2019). Another study investigated populations of C. truncatum from Brazil and Argentina and identified that intragroup similarity was greater among the Argentinian isolates than the Brazilian group, with a strong correlation between geographical origin and genetic grouping (Dias et al., 2019). Such a large difference in genetic diversity was associated with a greater geographic breadth of the sampling in Brazilian populations, in addition to a greater genetic variability of host cultivars, which could be reflected in the variability of the isolates among Brazilian regions.…”

“…Considering the increase of soybean anthracnose in South America, population studies suggest an association between the inherent variability of the pathogen and the climatic and cultural features, as well the genetic makeup of commercial soybean cultivars used (Dias et al., 2019; Rogério et al., 2019). These population studies highlight intraspecific pathogen variability as a major feature in genetic breeding for anthracnose resistance.…”