Manuscrito recibido el 27 de julio de 2015 y aceptado para su publicación el 2 de febrero de 2016.
RESUMENEl cancro del tallo (CTS) ha sido la enfermedad más destructiva de la soja en el sudeste de la provincia de Buenos Aires en los últimos ciclos agrícolas. Considerando la inserción actual del cultivo en los sistemas productivos de esta zona, que el CTS es una enfermedad prevalente y que Diaporthe caulivora (Dc) es el agente causal predominante en Argentina, es importante conocer la identidad del agente prevalente en el área. Los objetivos fueron reconocer por características morfológicas las especies del complejo Diaporthe/Phomopsis presentes en cultivos de soja, en los ciclos agrícolas 2010/11-2011/12-2012/13, y confirmar molecularmente mediante PCR-RFLP, que la especie predominante causante
ABSTRACTDiaporthe caulivora: predominant causal agent of stem canker in soybean crops in the southeast of Buenos Aires province.Stem canker (SC) has been the most destructive disease of soybean in the southeast of Buenos Aires in the last agricultural cycles. Considering the current inclusion of the soybean in the production systems in this area, that the SC is a prevalent disease, and that Diaporthe caulivora (Dc) is the predominant causal agent in Argentina, it is important to know the identity of the agent prevalent in the area. The objectives of the study were to recognize by morphology the species of the Diaporthe/Phomopsis complex present in soybean crops during the agricultural cycles 2010/11-2011/12-2012/13, and confirmed using PCR-RFLP that the predominant species causing symptoms of SC was Dc. Out of 39 isolates, 61% corresponded to Dc, 26% to P. longicolla,
A survey of 67 commercial fields in 19 locations was conducted in the southern Pampean region of Argentina for Phomopsis stem canker of sunflower (Helianthus annuus L.) between 2014 and 2019. A total of 210 plants having typical symptoms of Phomopsis stem canker were randomly sampled, and fungal isolation was performed. Of the 187 isolates of Diaporthe that were recovered, 94% of the isolates showed morphological characteristics similar to D. helianthi, 3% to D. gulyae, 1% to D. caulivora, 1% to D. sojae, 0.5% to D. kongii, and 0.5% to D. longicolla. Following morphological characterization, the identity of the six morpho-species was confirmed by phylogenetic analyses of β-tubulin, translation elongation factor 1-α, and internal transcribed spacer gene regions. Koch’s postulates were completed for the six fungi by inoculating one susceptible sunflower hybrid with one isolate each of the six species of Diaporthe using the stem-wound inoculation method. Seven days postinoculation, significant differences in disease severity were observed between the six isolates (P < 0.0001), with D. helianthi and D. gulyae isolates causing significantly greater disease severity. To our knowledge, this is the first report of D. kongii, D. longicolla, D. caulivora, and D. sojae associated with Phomopsis stem canker of sunflower in Argentina.
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