Severidade de diferentes isolados de Fusarium spp. e Diaporthe spp./Phomopsis spp. na necrose interna da haste da soja cultivar BMX Desafio RR

Abstract

Internal necrosis of the soybean stem can be caused by different fungal species of the Diaporthe spp./Phomopsis spp Complex. and Complex Fusarium spp., presenting different levels of severity according to the fungus species. This work aimed to evaluate the severity of isolates from the Diaporthe spp./Phomopsis spp. and the Fusarium spp. Complex, through the “Straw test” inoculation method, a procedure similar to that proposed by Petzoldt & Dickson (1996) and the systemic transmission of the pathogen from the plant to the seed. The cultivar used was BMX Desafio RR. Fifty fungal isolates were used, the seeds were sown in vases and fungal inoculation occurred at the V3 stage. A completely randomized design with 3 replications was used, with each replication consisting of one plant. The length of necrosis was evaluated. The evaluation of the transmission of the pathogen from the inoculated plants to the seeds was carried out through the Blotter Test. The experiment allowed the identification of the most aggressive and least aggressive isolates, confirming the existence of genetic variability of the isolates. The Blotter Test allowed the identification of the transmission rate of the plant-to-seed pathogen. Isolates 50 and 37 (Fusarium spp.) stood out as the most aggressive, causing greater length of necrosis. Isolates 47, 10, 14 and 27 (Diaporthe spp./Phomopsis spp., Diaporthe miriciae, Fusarium solani complex and Fusarium oxysporum, respectively) were less aggressive, with reduced necrosis or absence of internal stem necrosis. The Fusarium solani Complex, Fusarium spp., Fusarium oxysporum, Fusarium spp., Fusarium solani Complex and Fusarium spp. (Access Lamip 44, 34b, 43b, 62b, 41 and 62) showed a higher incidence of the pathogen in seeds.