André Costa da Silva

Macrophomina phaseolina is a soil-dwelling fungus that causes charcoal rot in maize. Its wide host range, microsclerotia formation, and the lack of effective chemical control and resistant maize genotypes make it a major agricultural challenge. This study aimed to identify potential biological control agents (BCAs) against M. phaseolina and elucidate their mechanisms of action. An initial in vitro bioprospecting was performed using 59 bacterial and fungal isolates. Selected isolates were characterized for direct antagonism, antibiosis mediated by volatile (VOCs) and non-volatile compounds (NVOCs), hyperparasitism, growth promotion in maize seedlings, and induction of antioxidant and defense responses through modulation of catalase (CAT), superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL). Trichoderma harzianum (CCT 7589), T. asperellum (ASN 60), Bacillus velezensis (OQ268070.1), and B. subtilis amyloliquefaciens (ASN 09) significantly inhibited M. phaseolina mycelial growth. Trichoderma isolates exhibited strong hyperparasitism, competition for space and nutrients, and antibiosis via VOCs and NVOCs, whereas Bacillus isolates showed greater antibiosis mediated by both compounds. All BCAs increased root biomass in healthy maize seedlings, while only T. harzianum and B. velezensis also enhanced shoot biomass. The BCAs also modulated antioxidant and defense responses: CAT activity increased following treatment with T. harzianum and B. velezensis , SOD activity was enhanced by T. asperellum , T. harzianum , and B. velezensis , and PAL activity by B. subtilis amyloliquefaciens and B. velezensis . These findings indicate that the efficacy of Trichoderma and Bacillus isolates against M. phaseolina results from the integration of direct antagonism, plant growth promotion, and modulation of biochemical defense responses in maize seedlings.

Soil‐borne pathogens of the Fusarium oxysporum species complex (FOSC) reduce soybean production, yet their mechanisms of dispersal in the field conditions remain insufficiently understood. Diabrotica speciosa is a widespread pest in South America, but its potential role in disseminating soil‐borne fungi needs further research. This study evaluated the carriage and contribution of D. speciosa to disperse FOSC members in soybean fields. Larvae and adults of D. speciosa were collected from two commercial areas and dissected and fungi associated with their cuticle, mouthparts, digestive tract and prothorax were isolated. Seven fungal genera were recovered and a FOSC member was consistently detected in all larval body parts and in multiple regions of adults of D. speciosa . Morphological and phylogenetic analyses confirmed its placement within FOSC and it induced characteristic root rot symptoms in soybean in pathogenicity assays. This is the first characterisation of the fungal microbiota associated with distinct body regions of D. speciosa and also the evidence of an interaction between this insect and a FOSC member. These findings revealed an unrecognised pathway for FOSC dissemination in soybean systems with new insights into the epidemiology of soybean root rot, with implications to develop more effective management strategies.

Soybean is one of the most important commodities in the world and is affected by several phytopathogens, such as the fungus Macrophomina phaseolina , which can occur at all stages of development, causing significant production losses. The use of different cultural, chemical and genetic control strategies has shown low efficiency against this phytopathogen. Thus, the objective of this study was to evaluate the use of Trichoderma asperellum , T. endophyticum, and T. harzianum in seed treatment to control M. phaseolina and promote plant growth. Healthy seeds inoculated with M. phaseolina were treated with the three Trichoderma species, the plant growth regulator Stimulate®, the insecticide Thiamethoxam, and combinations of Trichoderma species with Stimulate® or Thiamethoxam. The antagonistic capacity of Trichoderma species against M. phaseolina , their compatibility with Stimulate® and Thiamethoxam, seed germination, seedling vigor, plant growth, and their dry biomass were evaluated. Trichoderma species showed antagonism against M. phaseolina , especially T. endophyticum . In vitro , Stimulate® reduced the growth of T. endophyticum and T. harzianum , while Thiamethoxam reduced the growth of T. harzianum . M. phaseolina reduced soybean seed germination by approximately 80%. The three Trichoderma species increased the germination and vigor of infected seeds. In healthy seeds, T. harzianum reduced germination, while T. endophyticum combined with Stimulate® increased seedling vigor. These results show that T. endophyticum , T. harzianum, and T. asperellum are effective in treating seeds infected with M. phaseolina , and that the use of T. harzianum isolate CCT 7589 is not recommended for the treatment of healthy soybean seeds.

Soybean is one of the most important commodities in the world, and is affected by several phytopathogens, such as the fungus Macrophomina phaseolina , which can occur at all stages of development, causing significant losses in production. The use of different cultural, chemical and genetic control strategies has shown low efficiency against this phytopathogen. Thus, the objective of this study was to evaluate the use of Trichoderma asperellum , T. endophyticum and T. harzianum in seed treatment to control M. phaseolina and promote plant growth. Healthy seeds inoculated with M. phaseolina were treated with the three Trichoderma species, the plant growth regulator Stimulate®, an insecticide based on Thiamethoxam and combinations of Trichoderma species with Stimulate® or Thiamethoxam. The antagonistic capacity of Trichoderma species against M. phaseolina and their compatibility with Stimulate® and Thiamethoxam, germination and seedling vigor, growth and dry biomass of plants were evaluated. Trichoderma species showed antagonism against M. phaseolina , especially T. endophyticum . In vitro , Stimulate® reduced the growth of T. endophyticum and T. harzianum , while Thiamethoxam reduced the growth of T. harzianum . M. phaseolina reduced approximately 80% of soybean seed germination. The three Trichoderma species increased germination and vigor of infected seeds. In healthy seeds, T. harzianum reduced germination, while T. endophyticum combined with Stimulate® increased seedling vigor. These results show that T. endophyticum , T. harzianum and T. asperellum are effective in treating seeds infected with M. phaseolina , and the use of T. harzianum isolate CCT 7589 is not recommended for the treatment of healthy soybean seeds.

Soybean is one of the main agricultural commodities, and its productivity is limited by several diseases, such as anthracnose, which is caused by a complex of fungal species, with Colletotrichum truncatum being the most prevalent. Management is mainly carried out through chemical seed treatment. However, a reduction in the sensitivity of C. truncatum to fungicides was observed. Therefore, it is extremely important to search for products that are effective in controlling the disease. The objectives of this study were to evaluate the efficacy of commercial formulations of copper, potassium, manganese, and zinc phosphites in the treatment of soybean seeds infected by C. truncatum, as well as their direct fungitoxicity and ability to induce soybean defense mechanisms. For this purpose, seeds inoculated with C. truncatum were subjected to phosphites and a fungicide (carbendazim + thiram). The seeds were exposed to germination, health, and vigor tests. Fungal toxicity and the ability of phosphites to induce defense through the activities of catalase, peroxidase, and superoxide dismutase enzymes, as well as the levels of lignin and total soluble phenols, were also evaluated. Mn and Zn phosphites showed direct toxicity to C. truncatum and were as effective as the fungicide (carbendazim + thiram) in treating soybean seeds infected by the fungus. Mn phosphite induced the production of catalase (CAT), peroxidase (POX) and lignin, while Zn phosphite increased the production of CAT and POX. These results demonstrate the efficacy of Mn and Zn phosphites in controlling C. truncatum in infected soybean seeds, their direct toxic action, and their ability to induce resistance.

Soybean is one of the main agricultural commodities, and its productivity is limited by several diseases, such as anthracnose, which is caused by a complex of fungal species, with Colletotrichum truncatum being the most prevalent. Management is mainly carried out through chemical seed treatment. However, a reduction in the sensitivity of C. truncatum to fungicides was observed. Therefore, it is extremely important to search for products that are effective in controlling the disease. The objectives of this study were to evaluate the efficacy of commercial formulations of Cu, K, Mn and Zn phosphites in the treatment of soybean seeds infected by C. truncatum and their ability to induce defense mechanisms against the fungus. For this purpose, seeds inoculated with C. truncatum were treated with phosphites and a fungicide (carbendazim + thiram). The seeds were subjected to germination, health and vigor tests. Fungal toxicity and the ability of phosphites to induce defense through the activities of catalase, peroxidase and superoxide dismutase enzymes, as well as the levels of lignin and total soluble phenols, were also evaluated. Mn and Zn phosphites were toxic to C. truncatum and effective in controlling anthracnose in infected soybean seeds, showing no difference in relation to the fungicide. Mn phosphite induced the production of CAT, POX and lignin, while Zn phosphite increased the production of CAT and POX. These results demonstrate the effectiveness of Mn and Zn phosphites in controlling anthracnose in infected soybean seeds, their direct toxic action and their ability to induce defense mechanisms.

The cajuzinho do cerrado (Anacardium humile—Anacardiaceae), a shrub species native to Brazil, is harvested for multiple uses in food and medicine. Members of a harvesting community, near the municipality of Bonito de Minas, Minas Gerais state, Brazil reported characteristic symptoms of shoot blight and dieback reducing pseudofruit and seed production by this plant. This study aimed to identify the etiological agent of this disease. Two fungal isolates were obtained from symptomatic leaf samples and morphologically and molecularly characterized. The fungus was identified, based on morphological analyses, as a probable new species of Pseudoplagiostoma. Phylogenetic analyses based on a combination of DNA sequence data (nuc rDNA ITS1-5.8S-ITS2 region, tef1-α and tub2), confirmed this hypothesis. The isolates obtained were allocated to a distinct, well-supported clade (IB = 0.99, ML = 100%), placed as a unique lineage here proposed as a new species named Pseudoplagiostoma humilis. The pathogenicity test confirmed that this new species was the causal agent of shoot blight and dieback on A. humile. This is the fourteenth Pseudoplagiostoma species reported in the world and the third in Brazil.

The fungus Austropuccinia psidii infects young tissues of Eucalyptus plants until they are two years old in the nursery and field, causing Myrtaceae rust. The characteristics making older eucalypt leaves resistant to A. psidii and the reason for the low levels of this pathogen in older plants need evaluations. The aim of this study was to evaluate the morphological differences between Eucalyptus grandis leaves of different growth stages and two plant ages to propose a visual phenological scale to classify E. grandis leaves according to their maturation stages and to evaluate the time of leaf maturation for young and adult plants. A scale, based on a morphological differentiation for E. grandis leaves, was made. The color, shape and size distinguished the leaves of the first five leaf pairs. Anatomical analysis showed a higher percentage of reinforced tissue, such as sclerenchyma-like tissue and collenchyma, greater leaf blade thickness, absence of lower palisade parenchyma in the mature leaves and a higher number of cavities with essential oils than in younger ones. Changes in anatomical characteristics that could reduce the susceptibility of older E. grandis leaves to A. psidii coincide with the time of developing leaf resistance. Reduced infection of this pathogen in older plants appears to be associated with a more rapid maturation of their leaf tissues.