RESUMO Os nematoides das galhas (Meloidogyne spp.) causam danos severos na cultura do tomateiro. Dessa forma, o presente estudo objetivou avaliar o biocontrole de M. javanica mediado pelo fungo micorrízico arbuscular Rhizophagus clarus comparado aos fungos Trichoderma harzianum e Pochonia chlamydosporia em tomateiro e atividade de enzimas relacionadas à defesa vegetal em raízes micorrizadas. Três experimentos foram realizados a fim de avaliar: a colonização micorrízica, a penetração, desenvolvimento e reprodução de M. javanica, o desenvolvimento do tomateiro e a atividade de enzimas relacionadas a defesa em raízes micorrizadas. Observou-se que a colonização por R. clarus em tomateiro foi crescente com as épocas de avaliação e, apesar de não impedir a penetração e desenvolvimento de M. javanica nas raízes, foi eficiente em reduzir o número total do nematoide. Os tratamentos R. clarus, T. harzianum e P. chlamydosporia reduziram a reprodução do nematoide em 56,5, 54,4 e 56,9%, respectivamente, se comparados à testemunha. Além disso, R. clarus aumentou as massas de parte aérea do tomateiro e a atividade das enzimas fenilalanina amônia-liase e peroxidase.

ABSTRACT Root-knot nematodes (Meloidogyne spp.) cause severe damage to tomato crop. This study aimed to investigate the biocontrol potential of the arbuscular mycorrhizal fungus Rhizophagus clarus compared with that of the fungi Trichoderma harzianum and Pochonia chlamydosporia against Meloidogyne javanica in tomato and assess the activity of defense-related enzymes in mycorrhizal roots. Three experiments were carried out to evaluate mycorrhizal colonization, nematode penetration, development, and reproduction, plant growth, and enzyme activity in mycorrhizal roots. We observed that R. clarus colonization of tomato roots increased with time. Although R. clarus did not prevent nematode penetration or development in roots, it was efficient in reducing total nematode numbers. R. clarus, T. harzianum and P. chlamydosporia treatments reduced nematode reproduction by 56.5, 54.4, and 56.9%, respectively, compared with the control. Moreover, R. clarus increased tomato shoot weight and phenylalanine ammonia-lyase and peroxidase activities.

Abstract Sugarcane crop conventional tillage has been replaced by deep soil preparation with few studies about its effect on soil quality and sustainability. The aim of this study was to assess structural volumes ina dystrophic Red-Yellow Latosol subjected to conventional tillage (CT) and deep localized soil tillage (DLST) to verify how the microbiological parameters were affected. The study was conducted in a soil derived from the Caiuá Sandstone formation in Brazil. Four trenches were dug for each soil tillage system to describe the cultural profile and evaluate carbon microbial biomass (CMB) and nitrogen (NMB), basal respiration (BR), and metabolic quotient (qCO2). CT profiles exhibited a predominance of cracked soil volumes, medium-sized and large compact clods with some porosity, and continuous volumes with no cracks and of intermediate porosity. DLST profiles were predominantly free-soil volume with no cohesion and porous in appearance, and compact, cohesive volumes with no porosity visible. The highest levels of CMB and NMB were in the cracked soil under CT. Higher microbial activity indicated by BR and qCO2 were in the free powdery soil under DLST. Soil pulverization caused by DLST could cause serious consequences on soil functionality, boosting erosion, and metabolic stress in the microbiota.

ABSTRACT Maize (Zea mays L.) is one crop of major relevance in Brazil; however, nematodes are limiting factors in maize growth and productivity due to the difficulty to control them. Studies point out that arbuscular mycorrhizal fungi (AMF) increase plant tolerance to nematodes. Thus, the aim of this study was to assess the association between AMFs and Pratylenchus brachyurus in maize growth. Six AMF species (Rhizophagus clarus, Claroideoglomus etunicatum, Gigaspora rosea, G. margarita, Scutellospora calospora, S. heterogama), as well as a control treatment free of mycorrhizae, were assessed under two different nematode inoculum conditions (presence and absence). Plants were collected and analyzed 60 d after inoculation. The nematode population was higher in the treatments inoculated with AMFs. On the other hand, just the plants inoculated with R. clarus did not present improved development in comparison to the control. Nematodes increased AMF spore density, but despite the fact that AMFs have presented different root colonization capacity (ranging from 2.3% to 95.0%), such capacity was not affected by the nematodes

Abstract Soybean is one of the most important crops in the world and presents great versatility. This study aims to investigate the effect of the Bradyrhizobium japonicum inoculant at 0, 600 and 1200 mL ha1 on soybean crop, with and without 1 L ha-1 calcium (Ca 41%) + 0.4 L ha-1 boron (B 14%). Plants were grown for 90 days in plastic pots with 3 kg of sand and vermiculite (v/v) autoclaved at 121oC for 1 h. The experiment was conducted in a completely randomized design with five replications in a greenhouse. Soybean yield parameters were evaluated, such as, dry weight of shoot, root and total; plant height, nitrogen in the shoot; number and dry weight of nodules; chlorophyll index in the leaves; number of pods per plant (NPPL); number of grains per pod (NGP); and number of grains per plant (NGPL). The addition of Ca + B increased significantly NPPL, NGPL and NGP. The NPPL, NGPL were significantly increased with 600 mL ha-1 of the inoculant. The dose of 600 mL ha-1 of the inoculant combined with Ca+B significantly stimulated NPPL, NGPL and NGP. It is concluded that the productivity of soybean was increased with addition of 600 mL ha-1 inoculant, in combination with Ca and B.

Resumo A soja é uma das oleaginosas mais importantes no mundo e possui grande versatilidade. O objetivo deste estudo foi estudar o efeito da inoculação de 600 e 1200 mL ha-1 de um inoculante líquido com Bradyrhizobium japonicum e com ou sem adição de 1 L de cálcio ha-1 (Ca 41%) e de 0,4 L de boro ha-1 (B 14%) na cultura da soja. As plantas foram crescidas por 90 dias em potes plásticos com 3 kg de areia: vermiculita (v:v) autoclavados (121°C, 1 h). O experimento foi conduzido em delineamento inteiramente casualizado, com 5 repetições em casa de vegetação. Foram determinados parâmetros relacionados com o desenvolvimento e produtividade da soja, como: a massa seca da parte aérea, de raízes e total, nitrogênio da parte aérea, número e massa seca de nódulos, índice de clorofila das folhas, número de vagens por planta (NVPL), número de grãos por vagens (NGV) e número de grãos por planta (NGPL). A adição de Ca+B aumentou significantemente NVPL, NGPL e NGV. O NVPL, NGPL foram aumentados significantemente com a adição de 600 mL ha-1 inoculante. A adição de 600 mL ha-1 inoculante juntamente com a adição de Ca+B estimulou significativamente o NVPL, NGPL e NGV. Conclui- se que a produtividade da cultura da soja foi aumentada com a adição de 600 mL ha-1 inoculante juntamente com a adição de Ca e B.

A produtividade e sustentabilidade das culturas têm sido frequentemente relacionadas com a matéria orgânica e a biomassa microbiana do solo, especialmente devido ao seu papel na ciclagem de nutrientes do solo. Este trabalho teve como objetivo avaliar a biomassa de fungos e bactérias do solo por microscopia de epifluorescência e a densidade de esporos de fungos micorrízicos arbusculares (FMAs) em lavouras de cana de açúcar (Saccharum officinarum L.) sob diferentes manejos. Foram coletadas amostras de solo de lavouras manejadas com ou sem queima, com ou sem colheita mecanizada, com ou sem aplicação de vinhaça e de matas ciliares adjacentes. As amostras de solo foram coletadas a 10 cm de profundidade e mantidas a 4°C até o momento das análises. A biomassa fúngica variou de 25 a 37µg C g-1 de solo seco e a bacteriana, de 178 to 263µg C g-1 de solo seco. A razão média entre a biomassa fúngica e bacteriana do solo nos diferentes manejos de canaviais foi de 0,14. A densidade de esporos de FMAs variou de 9 a 13 esporos g-1 de solo seco. Os diferentes manejos da cana de açúcar não afetaram significativamente a densidade de esporos de FMAs. Em geral, não foram encontradas mudanças significativas na biomassa microbiana nos diferentes manejos de solo com cana de açúcar em comparação com a mata ciliar. Todavia, a soma das biomassas fúngicas e bacterianas (208 a 301µg C g-1 de solo seco) determinadas por microscopia de epifluorescência foram similares a resultados da biomassa total do solo encontrados em outros estudos com métodos tradicionais (e.g. fumigação-extração). Os resultados evidenciam que a determinação da razão fungo/bactéria por microscopia de epifluorescência, associada a outros parâmetros, é uma metodologia promissora para compreender a funcionalidade microbiana e ciclagem de nutrientes sob diferentes manejos do solo.

Crop productivity and sustainability have often been related to soil organic matter and soil microbial biomass, especially because of their role in soil nutrient cycling. This study aimed at measuring fungal and bacterial biomass by epifluorescence microscopy and arbuscular mycorrhizal fungal (AMF) spore density in sugarcane (Saccharum officinarum L.) fields under different managements. We collected soil samples of sugarcane fields managed with or without burning, with or without mechanized harvest, with or without application of vinasse and from nearby riparian native forest. The soil samples were collected at 10cm depth and storage at 4°C until analysis. Fungal biomass varied from 25 to 37µg C g-1 dry soil and bacterial from 178 to 263µg C g-1 dry soil. The average fungal/bacterial ratio of fields was 0.14. The AMF spore density varied from 9 to 13 spores g-1 dry soil. The different sugarcane managements did not affect AMF spore density. In general, there were no significant changes of microbial biomass with crop management and riparian forest. However, the sum of fungal and bacterial biomass measured by epifluorescence microscopy (i.e. 208-301µg C g-1 dry soil) was very close to values of total soil microbial biomass observed in other studies with traditional techniques (e.g. fumigation-extraction). Therefore, determination of fungal/bacterial ratios by epifluorescence microscopy, associated with other parameters, appears to be a promising methodology to understand microbial functionality and nutrient cycling under different soil and crop managements.