ABSTRACT The use of cover crop in agricultural fields has been well elucidated, especially regarding nitrogen fixation from legume crops and their function as weed protection. Furthermore, to cover crops can benefit the soil microbial community. This study aimed to evaluate and compare the benefits of mulching and cover cropping systems on soil microbial growth and activity, and their effects on plant mineral nutrition in pomelo (Citrus maxima ) and macadamia ( Macadamia integrifolia ) orchards. The treatments included: 1) control [Glyphosate herbicide (Roundup at 4 l per ha)], 2) manual weed control, 3) mulching with dead leaves from their respective trees (macadamia and pomelo), 4) millet, 5) faba bean, 6) millet + faba bean. All the treatments were applied for 120 days before soil and plant leaves were sampled for analyses. Plant mineral nutrition, soil microbial biomass C (MBC) and soil microbial biomass N (MBN); basal respiration (BRA), arbuscular mycorrhizal fungi (AMF) colonization (COL); number of AMF spores (SPO) in soil; total organic carbon (TOC) and total nitrogen (TN) were evaluated. Plant nutrition was not altered by the treatments; however, the MBC, COL and SPO markedly increased in response to mulching and faba bean + millet treatments. Especially in macadamia soils, these treatments had a great response to soil microbiology. Significant negative correlations were also detected for the COL, SPO, BRA and TOC with the Nutrient Balance Index (NBI). These results indicate that in short-term the cover cropping system is useful to improve the soil microbial growth and AMF formation in soils of pomelo and macadam orchards.

Resumo Este trabalho visou a desenvolver um método alternativo para o armazenamento pós-colheita de mamão (Carica papaya L.), var. “Tainung 1”, e controlar as principais doenças nesta fase. Foram avaliadas duas condições de armazenamento (temperatura ambiente e câmara fria); seis tratamentos (Controle, Samurai 40 mL/20l de água, Serenade® 40mL/20l de água, Fungicida EUPROOFF® 10mL/20l de água, EUPROOFF® + Serenade® + Samurai, Serenade® + Samurai); cinco períodos de armazenamento (0;3; 6; 9 e 12 dias) e três meses (dezembro, janeiro e fevereiro). A perda de massa dos frutos (PMF), a cor, o número e o tamanho das lesões foram avaliados e utilizados para calcular a incidência da doença bem como a média desta incidência. A PMF e a cor dos frutos foram mais afetadas pela variação mensal do que os tratamentos, principalmente o Samurai. O crescimento da incidência da doença foi mais lento em câmara fria. Entre os tratamentos, o Samurai foi o mais eficaz de todos; mas, se misturado a outros produtos, sua eficiência não foi observada. Esses resultados sugerem que o uso do Samurai somente em condições de câmara fria pode ser mais eficaz no controle de doenças pós-colheita do mamão.

Abstract This study aimed to establish an alternative treatment for post-harvest storage of Papaya (Carica papaya L.), var “Tainung 1” and to control major diseases at this stage. Two storage place were evaluated (room temperature and cold room); Six treatments (Control, Samurai 40ml/20l water, Serenade® 40ml/20l water, Sanatizer EUPROOFF® 10ml/20l water, EUPROOFF® + Serenade® + Samurai, Serenade® + Samurai), five storage periods (0, 3, 6, 9 and 12 days) and three seasons (December, January and February). Fruit weight loss (FWL), color index, number and size of lesions were evaluated and used to calculate the disease incidence and average of disease incidence. The FWL and index color of fruits were more affected by monthly variation than the treatments, especially the Samurai one. The growth of disease incidence were slower under cold room. Among the treatments, the Samurai was the most efficient,but if mixed to others products their efficiency was not observed. These results suggest that the using of Samurai only in cold room conditions can be more effective in control of post-harvest diseases of papaya.

As estruturas de armazenamento em esporos de Gigaspora margarita Becker & Hall, um fungo micorrízico arbuscular, foram analisadas por microscópio eletrônico de transmissão (MET) e espectroscopia com perda de energia em elétrons (EEES). Os esporos foram hidratados, criofixados por pressão em baixa temperatura e submetidos a substituição em congelamento, embebidos e preparados para observações no MET. As técnicas de criofixação revelaram que as estruturas de armazenamento nos esporos são compostas de lipídios, grânulos elétron densos (GED), corpos protéicos e partículas de glicogênio. Por EEES foi detectada a presença de nitrogênio (N) e carbono (C) nestas estruturas de armazenamento e em organismos similares a bactérias (OSB). Uma pequena quantia de P foi detectada nos vacúolos e nos OSB. O exame por MET e EEES indicaram a presença de estruturas de armazenamento nos esporos e alguns elementos essenciais (N, P e C) nessas.

The storage structures of spores of Gigaspora margarita Becker & Hall, an arbuscular mycorrhizal fungus, were analyzed by a transmission electronic microscope (TEM) and electron energy loss spectroscopy (EELS). The spores were hydrated, cryofixed using high pressure freezing, submitted to freeze substitution, embedded and prepared for TEM observations. The cryotechniques revealed that the storage structures in the spores are composed of lipids, electron dense granules (EDG), protein bodies and glycogen particles. The EELS detected the presence of nitrogen (N) and carbon (C) in these storage structures and in Bacteria-like organisms (BLO). Some amount of P was detected in the vacuoles and in BLO. The TEM and EELS techniques indicate the presence of storage structures in the fungal spore, and some essential elements (N, P and C) in these structures.