Losses due to soybean anthracnose, caused by Colletotrichum truncatum, have not been systematically quantified in the field, and the efficacy of chemical control of this disease is not known. This study shows an estimate of losses associated with the disease in soybean crops in the north of the country. Two trials with cv. M9144 RR were carried out in commercial fields in Tocantins State in the 2010/2011 and 2011/2012 growing seasons, in randomized blocks, with four replicates. Foliar applications were performed on plants at R1/R2 and R5.2 stages, employing CO2-pressurized equipment and application volume of 200 L ha-1. Nine fungicides and one untreated control were compared, and the disease gradients in the two seasons were obtained. The percentage of infected pods was calculated at the R6 stage. Grain yield ranged from 3,288 to 3,708 kg/ha in the untreated plots in 2010/2011 and 2011/2012, respectively, and from 3,282 to 4,110 kg/ha in the treated plots. In the 2010/2011 season, only azoxystrobin + cyproconazole significantly reduced the disease incidence, compared to untreated control plots, not differing from the remaining treatments. In the 2011/2012 season, there were no significant differences between treated and untreated plots. Highly significant correlations (p < 0.01) were found between yield and soybean anthracnose incidence on pods in both years (r = -0.85). For each 1% increment in the disease incidence, c. 90 kg/ha of soybean grain were lost. The current study determined that significant losses due to anthracnose occur in commercial crops in the north of the country and highlighted the limitation of chemical control as anthracnose management method.

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.

Soybean anthracnose is a complex disease, comprising isolates of Colletotrichum truncatum and at least six other species. In Brazil, C. cliviae was recently reported as a novel causal agent of soybean anthracnose but very little information is available about the C. cliviae-soybean pathosystem. Here we report the occurrence of C. cliviae in commercial soybean fields in the Tocantins State, TO (Northern Brazil). We also describe its most distinctive morphological, biological, cultural, and pathogenic aspects, particularly in contrast with C. truncatum (the prevalent anthracnose-causing species in Brazil), including symptoms, production of sexual structures, host range, seed infection and aggressiveness to soybean cultivars. The results indicated that the involvement of C. cliviae as an anthracnose-inducing species might impact current control strategies, including crop rotation systems and the replacement of susceptible cultivars. Studies were also carried out to clarify if the Brazilian soybean-infecting C. cliviae isolates were introduced into the country via contaminated seeds or if populations are endemic. The haplotype diversity of Brazilian as well as of a worldwide collection of C. cliviae isolates (available at the GenBank) was investigated based upon polymorphisms in three genomic regions (β-tubulin 2, glyceraldehyde-3-phosphate dehydrogenase, and actin). Nine haplotypes were identified among worldwide C. cliviae isolates from six different hosts. The Brazilian soybean isolates were placed into the closely related haplotypes 5 (composed by isolates from Mato Grosso State) and 6 (which included the isolate from TO), which were discriminated from each other by one single nucleotide polymorphism. Haplotype 6 group was also composed by a Chinese isolate from Camelia sinensis. The results suggest that this cosmopolitan fungal species is more likely endemic to Brazil where it has been reported in association with plant species across distinct botanical families. Therefore, the recent outbreaks of C. cliviae isolates on soybeans can be explained by either previous misdiagnosis or they may represent a recent shift/adaptation of this fungus to this legume crop. Thus far, the geographic occurrence of C. cliviae on soybeans is restricted to northern (warm) tropical regions of Brazil. The present report adds novel and relevant information with potential for the control of anthracnose caused by C. cliviae isolates in Brazil, and possibly in warm regions elsewhere.

RESUMOEspécies do gênero Colletotrichum são agentes etiológicos de importantes doenças do cafeeiro, porém, ainda pouco estudadas no Brasil. Diante desse fato, objetivou-se com este trabalho foi estudar o efeito da temperatura no crescimento, produção e germinação de conídios de diferentes isolados de Colletotrichum spp. Foram avaliados 8 isolados, obtidos de folhas com sintoma de mancha manteigosa, seca de ponteiros e assintomático. Os isolados apresentaram comportamento diferenciado na velocidade de crescimento micelial, capacidade de esporulação e na formação de estruturas reprodutivas, com alta capacidade adaptativa em diferentes temperaturas.Termos para indexação: mancha manteigosa, café, temperatura. ABSTRACTThe objective of this study was to assess the effect of temperature on micelial growth, production and conidial germination of Colletotrichum spp. isolates from branches, leaves and fruits of coffee with symptoms of blister spot and tip blight. The isolates presented differentiated behavior regarding the speed of mycelial growth, sporulation capacity and the formation of reproductive structures, showing high capacity of adaptation to different temperatures.