Charcoal rot of soybean (Glycine max (L.) Merr.), caused by Macrophomina phaseolina (Tassi) Goid., is an economically important disease worldwide. In recent years, charcoal rot has become a concern for farmers in north-western Argentina. The present work aimed to (1) evaluate disease incidence of charcoal rot; (2) assess morphological and genetic characteristics of M. phaseolina isolates from soybean and other hosts collected in north-western Argentina; and (3) compare genetic diversity between soybean isolates of M. phaseolina from Argentina and the USA. Incidence of charcoal rot evaluated in 11 locations during five growing seasons (2008-2012) was 1%, 1%, 1%, 5-10% and 90%, respectively, indicating a gradual increase over the cropping seasons. Cluster analysis by AFLP of Argentinean isolates exhibited one main group, with isolate Mp56 separated at a genetic distance of 0.70. Four main groups were identified using SSR markers at the same genetic distance, with Mp56 and Mp53 separated from them. There was no clear association between AFLP, SSR profiles, morphological characteristics or host of origin within isolates from Argentina. However, using principal coordinate analysis of SSRs, 22 isolates of M. phaseolina from soybean from north-western Argentina were clearly distinguished from 11 isolates previously collected from two states in the USA. Our results confirmed the increasing importance of charcoal rot in north-western Argentina and identified characteristics of isolates that may be useful for breeding for disease resistance and developing integrated management programmes for charcoal rot in Argentina in the future.Keywords: charcoal rot, disease development, Macrophomina phaseolina, pathogen genetic diversity, SSR markers Résumé: La pourriture noire du soya (Glycine max (L.) Merr.), causée par Macrophomina phaseolina (Tassi) Goid., est une maladie économiquement importante dans le monde entier. Depuis les dernières années, elle préoccupe les producteurs du nord-ouest de l'Argentine. Ces travaux visaient à: (1) estimer l'incidence de la maladie; (2) évaluer les caractéristiques morphologiques et génétiques des isolats de M. phaseolina collectés sur le soya et d'autres hôtes du Nord-Ouest argentin; et (3) comparer la diversité génétique entre les isolats de M. phaseolina collectés sur le soya en Argentine et aux États-Unis. L'incidence de la pourriture noire évaluée à 11 endroits durant 5 saisons de croissance (de 2008 à 2012) était de 1%, 1%, 1%, 5-10% et 90%, respectivement, ce qui indique une progression graduelle d'une saison à l'autre. L'analyse typologique des données AFLP des isolats argentins a fait ressortir un groupe principal incluant l'isolat Mp56 séparé par une distance génétique de 0.70. Quatre groupes principaux ont été identifiés à l'aide de marqueurs SSR à la même distance génétique, Mp56 et Mp53 en étant séparés. Il n'y avait pas de corrélation nette entre les données AFLP, les profiles SSR, les caractéristiques morphologiques ou l'hôte d'origine parmi les isolats argentins. Tout...

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Currently, fungicide application in soybean production accounts for an important amount of global pesticide use, and it is therefore most desirable to find new healthier and more environmental friendly alternatives for the phytosanitary management in this crop. In this study, we present convincing evidence for effective induction of disease protection by the agricultural biostimulant PSP1, a formulation based on the plant-defense eliciting activity of the fungal protease AsES (Acremonium strictum elicitor subtilisin), in multiple field trials in Argentina.PSP1 was shown to combine well with commercial spray adjuvants, an insecticide, a herbicide and fungicides used in Argentinian soybean production without losing any defense-inducing activity, indicating an easy and efficient adaptability to conventional soybean production and disease management in the region. Results from multiple soybean field trials conducted with different elite genotypes at several locations during two consecutive growing seasons, showed that PSP1 is able to induce an enhanced pathogen defense which effectively reduced late season disease (LSD) development in field-grown soybean. This defense response seems to be broad-range as disease development was clearly reduced for at least three different fungi causing LSDs in soybean (Septoria glycines, Cercospora kikuchii and Cercospora sojina). It was noteworthy that application of PSP1 in soybean alone gave a similar protection against fungal diseases as compared to the commercial fungicides included in the field trials and that PSP1 applied together with a fungicide at reproductive stages enhanced disease protection and significantly increased grain yields.PSP1 is the first example of an elicitor-based strategy in order to efficiently control multiple fungal diseases under field conditions in the soybean crop. These results show the feasibility of using induced resistance products as complements or even full-good replacements to currently used chemical pesticides, fulfilling a role as important components of a more sustainable crop disease management system.