ABSTRACT This study analyzes the in vitro antagonistic activity of Trichoderma sp. isolates against Fusarium subglutinans and evaluates the effect of the pine seeds treatment with Trichoderma sp. on the incidence of root rot. Twelve Trichoderma sp. isolates and two F. subglutinans isolates were included in the study. Trichoderma sp. inhibited F. subglutinans mycelial growth through direct contact with hyphae and the production of volatile antifungal compounds. Pine seeds treatment with the antagonist Trichoderma sp. reduced the incidence of root rot, increased the emergence and initial growth in the height of seedlings, and improved seedling health.

RESUMO A podridão-de-raiz (PR), causada por Fusarium spp., ocasiona perdas de plântulas no viveiro que apresentam, inicialmente, descoloração das acículas para tom verde-amarelado seguida de curvatura apical, murcha e consequente morte da muda. Os objetivos deste trabalho foram: a) determinar o método adequado e eficiente para detecção de Fusarium spp. nas sementes de Pinus taeda; b) verificar se há transmissão de Fusarium spp. das sementes para as plântulas de Pinus taeda; c) desenvolver uma escala descritiva para avaliar a severidade da PR em mudas de Pinus taeda; d) avaliar a patogenicidade, agressividade e área abaixo da curva de progresso da doença (AACPD) de isolados de Fusarium spp. Para detecção foram aplicados três tratamentos em seis lotes de sementes de Pinus taeda, sendo quatro repetições de 25 sementes: blotter test, papel-cartão e meio seletivo. A transmissão foi avaliada em sementes de seis lotes de Pinus taeda durante 60 dias contabilizando-se a percentagem de plântulas emergidas (PE), sementes não germinadas (SNG) e de SNG com Fusarium spp. Uma escala descritiva de notas foi desenvolvida para avaliar a severidade de PR em mudas de Pinus taeda. A severidade e a incidência da doença foram avaliadas aos 7, 14, 21 e 28 dias após a inoculação das mudas de Pinus taeda de seis meses de idade. Foi avaliada a patogenicidade, a severidade e a incidência de doze isolados de Fusarium spp. obtidos no teste de detecção Para o teste de patogenicidade e agressividade foram 13 tratamentos com 15 repetições. O método de detecção mais sensível ao detectar Fusarium spp. em sementes de Pinus taeda foi o meio seletivo. Não foi observada transmissão de Fusarium spp. das sementes para as plântulas, no entanto, Fusarium spp. causou apodrecimento de sementes na fase de germinação; a escala descritiva permitiu a avaliação da progressão dos sintomas da doença PR; nove isolados de Fusarium spp. mostraram-se patogênicos a mudas de Pinus taeda, reproduzindo sintomas típicos da PR, sendo o isolado L3R2 o mais agressivo e o que exibiu maior AACPD.

ABSTRACT The root rots (RR), caused by the Fusarium spp., causes loss of seedling in the nursery that show, initially, discoloration of the needles to a yellowish-green tone followed by apical curvature, wilt and the consequent death of the seedling. The objectives of this work were to: a) define the most appropriate and efficient method to detect Fusarium spp. in Pinus taeda seeds; b) verify if there is transmission of Fusarium spp. from seeds to Pinus taeda seedlings; c) develop a descriptive scale to evaluate the severity of the RR in Pinus taeda seedlings; d) evaluate the pathogenicity, aggressiveness and area under the disease progress curve (AUDPC) of isolated Fusarium subglutinans. For detection three treatments were applied to six lots of Pinus taeda seeds, bein four repetitions of 25 seeds: blotter test, paper card and selective medium. The transmission was evaluated in seeds from six lots of Pinus taeda during 60 days counting the percentage of emerged plantlet (EP), non-germinated seeds (NGS) and from NGS seeds with Fusarium spp. A descriptive scale of grades was developed to evaluate the severity of RR in Pinus taeda seedlings. The severity and the incidence of the illness were evaluated at 7, 14, 21 and 28 days after the inoculation from Pinus taeda seedlings of six months of age. The pathogenicity, severity and incidence of twelve isolated Fusarium subglutinans obtained in the detection test. To test for pathogenicity and aggressiveness 13 treatments with 15 replications were applied. The most sensitive detection method to detect Fusarium spp. on Pinus taeda seeds was the selective medium; transmission was not observed of Fusarium spp. from seeds to the seedlings; the descriptive scale allowed evaluating the progression of RR symptoms; nine isolated of Fusarium spp. were found to be pathogenic to Pinus taeda seedlings, reproducing typical symptoms of RR, being isolated L3R2, the most aggressive and that exhibited higher AUDPC.