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.
Highlights
As of today, more than 50% of the world’s soybean [Glycine max (L.) Merrill] grain is produced in Brazil and Argentina [1]
Morphometrics of conidia and appressoria of the South American C. truncatum isolates were within the range of 19–26.5 × 3.5–4.5 μm reported by Sutton [17], and in agreement with the epitype description by Damn et al [18] of 21.8 × 3.8 μm
Soybean anthracnose has re-emerged as a yield-limiting factor for soybean production in South
Summary
More than 50% of the world’s soybean [Glycine max (L.) Merrill] grain is produced in Brazil and Argentina [1]. The South American soy crops extend almost uninterruptedly from the southern Amazon (latitudes 8–10◦ S, at the Brazilian states of Maranhão, Piauí, Mato Grosso, and Tocantins), to latitudes 32–36◦ S, at the Argentinian provinces of Buenos Aires, Córdoba, Santa Fe, Plants 2019, 8, 459; doi:10.3390/plants8110459 www.mdpi.com/journal/plants. The area comprises of approximately 53.6 million ha [2,3]2 and is mostly cultivated in monoculture or in wheat/soybean succession, which favors several diseases, including anthracnose. Anthracnose.The. The most typical anthracnose symptoms are depressed, dark, depressed, irregular including most typical anthracnose symptoms are dark, irregular lesions lesions on cotyledons, pods, stems, and petioles, where acervulae and dark setae are observed. On cotyledons, pods, stems, and petioles, where acervulae and dark setae are observed. Another of diagnostic is the characteristic necrotic patterns on theveins
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