Infection of citrus pollen grains by Colletotrichum acutatum     

João Paulo Rodrigues Marques  Lilian Amorim  Marcel Bellato Spósito  Denis Marin  Beatriz Appezzato-da-Glória 《European journal of plant pathology / European Foundation for Plant Pathology》2013,136(1):35-40

Postbloom fruit drop (PFD), an important disease caused by Colletotrichum spp., affects citrus yields in Brazil. PFD is characterised by the presence of necrotic lesions on the petals and stigmas of citrus flowers and by the subsequent abscission of young fruit. PFD epidemics have high disease progress rates, which is unusual for a pathogen that produces acervuli and is dispersed by rain. It is possible that other dispersal agents, such as insects and pollen, are involved in the spread of this disease. The objective of this work was to test whether citrus pollen grains can be colonised by Colletotrichum acutatum. Studies using light and electron microscopy showed that the pollen of Citrus sinensis can be infected by C. acutatum. This pathogen can penetrate and colonise citrus pollen grains 24 h after inoculation with the pathogen. The germ tube of conidia either penetrates the pollen sporodermis directly or passes through pollen germ pores. A single hypha can colonise more than one pollen grain. On the surface of the stigma, conidium formation can be observed. This study shows that Citrus sinensis pollen may, in fact, play a role in the spread of C. acutatum in citrus orchards.  相似文献   

Mineralogical changes caused by grape production in a regosol from subtropical Brazilian climate     

Edson Campanhola Bortoluzzi  Diovane Freire Moterle  Danilo dos Santos Rheinheimer  Carlos Alberto Casali  George W. Melo  Gustavo Brunetto 《Journal of Soils and Sediments》2012,12(6):854-862

Purpose

Inadequate soil use and management practices promote commonly negative impacts on the soil constituents and their properties, with consequences to ecosystems. As the soil mineralogy can be permanently altered due to soil use, this approach can be used as a tool to monitor the anthropogenic pressure. The objective of the present study was to assess the mineralogical alterations of a Brazilian regosol used for grape production for 40?years in comparison with a soil under natural vegetation (forest), aiming to discuss anthropogenic pressure on soils.

Material and methods

Soil samples were collected at depths of 0?C0.20 and 0.20?C0.40?m from vineyard production and natural vegetation sites. Physical and chemical parameters were analysed by classic approaches. Mineralogical analyses were carried out on <2?mm, silt and clay fractions. Clay minerals were estimated by the relative percentage of peak surface area of the X-ray patterns.

Results and discussion

Grape production reduced the organic matter content by 28?% and the clay content by 23?% resulting in a decreasing cation exchange capacity. A similar clay fraction was observed in both soils, containing kaolinite, illite/mica and vermiculite with hydroxy-Al polymers interlayered. Neither gibbsite nor chlorite was found. However, in the soil under native vegetation, the proportion of illite (79?%) was higher than vermiculite (21?%). Whereas, in the soil used for grape production during 40?years, the formation of vermiculite was promoted.

Conclusions

Grape production alters the proportions of soil constituents of the regosol, reducing clay fraction and organic matter contents, as well as promoting changes in the soil clay minerals with the formation of vermiculite to the detriment of illite, which suggests weathering acceleration and susceptibility to anthropogenic pressure.

Recommendations and perspectives

Ecosystems in tropical and subtropical climates can be more easily and permanently altered due to anthropogenic pressure, mainly as a consequence of a great magnitude of phenomena such as temperature amplitude and rainfall that occurs in these regions. This is more worrying when soils are located on steep grades with a high anthropogenic pressure, like regosols in Southern Brazil. Thus, this study suggests that changes in soil mineralogy can be used as an important tool to assess anthropogenic pressure in ecosystems and that soil quality maintenance should be a priority in sensible landscapes to maintain the ecosystem quality.  相似文献   

A study of potassium dynamics and mineralogy in soils from subtropical Brazilian lowlands     

Darines Britzke  Leandro Souza da Silva  Diovane Freire Moterle  Danilo dos Santos Rheinheimer  Edson Campanhola Bortoluzzi 《Journal of Soils and Sediments》2012,12(2):185-197

Purpose  

The dynamics and availability of potassium (K) in soils depend on many factors, including the mineralogy of fractions and the soil geochemical conditions. The objective of this work is to quantify K in distinct lowland soil compartments in the south of Brazil, relating them to particle size fractions and mineralogical constitution.  相似文献   

Quantitative detection of <Emphasis Type="Italic">Citrus tristeza virus</Emphasis> in plant tissues and single aphids by real-time RT-PCR     

Edson Bertolini  Aranzazu Moreno  Nieves Capote  Antonio Olmos  Ana de Luis  Eduardo Vidal  Jordi Pérez-Panadés  Mariano Cambra 《European journal of plant pathology / European Foundation for Plant Pathology》2008,120(2):177-188

  相似文献   

Kinetics of Lead Bioaccumulation from a Hydroponic Medium by Aquatic Macrophytes Pistia stratiotes     

Fernando R. Espinoza-Quiñones  Aparecido N. Módenes  Ismael L. Costa Jr.  Soraya M. Palácio  Nayara Szymanski  Daniela E. G. Trigueros  Alexander Dimitrov Kroumov  Edson A. Silva 《Water, air, and soil pollution》2009,203(1-4):29-37

The goal of this work was to study quantitatively lead bioaccumulation from a lead-doped nutrient medium by using a living aquatic macrophytes Pistia stratiotes. Several sets of aquatic plants with approximately 30 g weight were grown in greenhouse conditions and in hydroponic solutions supplied with a non-toxic Pb²⁺ concentration. The synchrotron radiation total X-ray fluorescence spectrometry was used to determine the metal concentrations in dry plants and hydroponic media as a function of time. Four different non-structural bioaccumulation models were applied to describe the process dynamics and to estimate the accumulated lead maximum capacity and rate constants. According to the experimental data, both biosorption and bioaccumulation mechanisms can be considered. Due to the low desorption rate constant, the experimental data were well described by the irreversible kinetic model. The results concerning modeling of living macrophytes’ metal bioaccumulation kinetics can be used to predict the heavy metal removal dynamics from wastewaters in artificial wetlands.  相似文献   

Modelling the progress of Asiatic citrus canker on Tahiti lime in relation to temperature and leaf wetness     

R. S. C. Christiano  M. Dalla Pria  W. C. Jesus Junior  L. Amorim  A. Bergamin Filho 《European journal of plant pathology / European Foundation for Plant Pathology》2009,124(1):1-7

The combined effect of temperature (15°C, 20°C, 25°C, 30°C, 35°C, 40°C and 42°C) and leaf wetness duration (0, 4, 8 12, 16, 20 and 24 h) on infection and development of Asiatic citrus canker (Xanthomonas citri subsp. citri) on Tahiti lime plant was examined in growth chambers. No disease developed at 42°C and zero hours of leaf wetness. Periods of leaf wetness as short as 4 h were sufficient for citrus canker infection. However, a longer leaf duration wetness (24 h) did not result in much increase in the incidence of citrus canker, but led to twice the number of lesions and four times the disease severity. Temperature was the greatest factor influencing disease development. At optimum temperatures (25–35°C), there was 100% disease incidence. Maximum disease development was observed at 30–35°C, with up to a 12-fold increase in lesion density, a 10-fold increase in lesion size and a 60-fold increase in disease severity.  相似文献   

Clinical, cytological and histopathological evaluation of mammary masses in cats from Rio de Janeiro, Brazil     

Amorim FV  Souza HJ  Ferreira AM  Fonseca AB 《Journal of Feline Medicine and Surgery》2006,8(6):379-388

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Multispectral radiometric monitoring of bacterial blight of coffee     

Marin  Diego Bedin  de Carvalho Alves  Marcelo  Pozza  Edson Ampélio  Belan  Leônidas Leoni  de Oliveira Freitas  Marcelo Loran 《Precision Agriculture》2019,20(5):959-982

Precision Agriculture - Bacterial blight of coffee caused by Pseudomonas syringae pv. garcae shows great destructive potential in the main coffee producing regions in Brazil and worldwide. Remote...  相似文献   

Performance,endocrine, metabolic,and reproductive responses of Nellore heifers submitted to different supplementation levels pre- and post-weaning     

Aline Gomes da Silva  Mário Fonseca Paulino  Lincoln da Silva Amorim  Luciana Navajas Rennó  Edenio Detmann  Felipe Henrique de Moura  Marcos Rocha Manso  Paulo Henrique Silva e Paiva  Román Enrique Maza Ortega  Luciano Prímola de Melo 《Tropical animal health and production》2017,49(4):707-715

The present study was conducted to evaluate the effects of high and low supplementation levels pre- and post-weaning on performance, endocrine, metabolic, and reproductive responses of Nellore heifers. Fifty Nellore heifers with 132?±?9.9 kg average body weight (BW) and 138?±?19 days of age were supplemented from 4 to 14 months. The heifers were distributed into five supplementation plans: HH—6 g/kg of BW of supplement pre- and post-weaning, HL—6 g/kg of BW of supplement pre-weaning and 3 g/kg post-weaning, LH—3 g/kg of BW pre-weaning and 6 g/kg of BW post-weaning, LL—3 g/kg of BW pre- and post-weaning, and CC—control, no supplementation. Interactions were not significant (P?>?0.10). The level of supplement fed pre-weaning did not affect any of the performance variables evaluated at the end of the experiment (P?>?0.10). There was a significant effect of supplementation and level of supplementation fed post-weaning on average daily gain (ADG) and final BW (P?<?0.05). Overall ADG was also affected only by supplementation and level of supplement fed post-weaning (P?<?0.05) with animals receiving 6 g/kg of BW post-weaning gaining more weight. Follicular diameter was greater in animals that received 6 g/kg of BW post-weaning (P?<?0.05). In summary, performance, endocrine, metabolic, and reproductive variables evaluated in the current study were improved by the level of supplement fed post-weaning. Heifers receiving supplementation of 6 g/kg of BW post-weaning had greater responses, independent of the level received during the pre-weaning phase.  相似文献   

Honeybees can spread Colletotrichum acutatum and C. gloeosporioides among citrus plants          下载免费PDF全文

M. C. G. Gasparoto  S. A. Lourenço  F. A. O. Tanaka  M. B. Spósito  L. C. Marchini  G. J. Silva Junior  L. Amorim 《Plant pathology》2017,66(5):777-782

Postbloom fruit drop (PFD) is an important citrus disease that causes up to 100% yield losses during years in which conditions are favourable for the occurrence of epidemics. The conidia of Colletotrichum acutatum and C. gloeosporioides, causal agents of PFD, are predominantly dispersed by rain splash. At the beginning of epidemics, the distribution of diseased plants is random and the disease progress rate is very high, which is unusual for pathogens spread by rain splash. As the pathogen produces abundant conidia on diseased petals, pollinating insects may contribute to disease dispersal. This study investigated honeybees (Apis mellifera) as dispersal agents of C. acutatum and C. gloeosporioides among citrus plants. Two experiments were carried out in a screenhouse in which citrus plants were protected (or not) in insect‐proof cages. The source of inoculum was placed on one side of the screenhouse, and a honeybee hive was placed on the opposite side. All uncaged plants showed symptoms of the disease, and none of the caged plants exhibited PFD symptoms. The monomolecular model showed a good fit to disease progress in both experiments. Conidium‐like structures of Colletotrichum spp. were identified attached to the bodies of the honeybees by scanning electron microscopy. These results have revealed that honeybees disperse Colletotrichum among citrus plants.  相似文献