Caracterización de aislados y evaluación de curasemillas para el control de Leptosphaeria maculans en colza

The objective of this study was to characterize the aggressiveness of seven Phoma lingam isolates on the canola cultivar Rivette, as well as to evaluate the effect of different seed dressings for preventive disease control in seedlings. Canola is a crop of growing importance in Uruguay, and the disease known as blackleg, caused by the fungus Leptosphaeria maculans (anamorph Phoma lingam), represents a significant threat to its establishment and productivity. The trials were conducted under controlled conditions at the INIA La Estanzuela experimental station in Colonia, Uruguay, using a completely randomized block design with three replicates per treatment. For isolate characterization, seven Phoma strains collected from different locations and years were tested, using a pot with 6 to 10 Rivette plants as the experimental unit. Plants were inoculated at the cotyledon stage with a spore suspension (1×10⁷ spores/mL), and disease severity was measured ten days post-inoculation using a 0-to-9 scale, where 0 indicates the absence of symptoms and 9 represents severe cotyledon lesions. The results showed significant variability in aggressiveness among the isolates. In the first trial, isolate Ph031 exhibited the highest severity, while Ph021 and Ph033 were the least aggressive. In the second trial, the most virulent isolate was Ph026, and the least aggressive was Ph022. These differences reflect the genetic and phenotypic diversity of the pathogen, highlighting the importance of its characterization for effective disease management. For the seed dressing evaluation, various chemicals and biological products were used, including Fluopyram (Fluoram), Zentro, and a biological product (Lalstop), applied at different doses. The isolate used in this phase was Ph042, collected from the same Rivette cultivar. Results showed that treatments with Fluopyram, even at the lowest dose of 150 g a.i/ 100kg seed, achieved complete suppression of symptoms in both trials, while the remaining treatments exhibited varying levels of severity. In conclusion, variability in aggressiveness was identified among Phoma isolates, and the use of Fluopyram as a seed treatment at a low dose proved to be highly effective in preventing early-stage infection. These findings provide valuable tools for the integrated management of blackleg, particularly during crop establishment, and open the possibility of reducing or delaying subsequent foliar fungicide applications. Although the trials were conducted under controlled conditions, field evaluations are recommended to validate these results under real-world production scenarios