Cytogenetics of Colletotrichum lindemuthianum (Glomerella cingulata f. sp. phaseoli)

Cytogenetic and morphological studies were conducted with Colletotrichum lindemuthianum (Glomerella cingulata f. sp. phaseoli), the pathogen responsible for anthracnose of common bean (Phaseolus vulgaris). In this species, there is some evidence of genomic variation but it is unknown whether the process occurs in a manner similar to other fungal genetic models. Six isolates from bean plants were used and sexual reproduction was observed in vitro. Meiosis and ascospore formation were investigated by cytogenetical approaches and light microscopy. To study the nucleus and chromosome numbers, a mixture of carmine and orcein propionic dyes was used. Nucleus divisions as well as ascospore maturation were asynchronous. Meiosis was observed in three isolates. In the asexual form, chromosomal polymorphism in conidia was also observed microscopically and the mitosis process was described.

Análise comparativa da variabilidade patogênica de Uromyces appendiculatus em algumas regiões brasileiras

A ferrugem do feijoeiro comum (Phaseolus vulgaris), incitada pelo fungo Uromyces appendiculatus, é uma das mais importantes doenças que afetam essa cultura. Trabalhos anteriores demonstraram a ampla variabilidade patogênica de U. appendiculatus no Brasil. No entanto, o uso de distintos grupos de cultivares diferenciadoras em tais trabalhos dificulta a análise comparativa e a identificação de fontes de resistência de amplo espectro. Assim, os objetivos deste trabalho foram: 1) caracterizar sete isolados de U. appendiculatus, coletados em diferentes regiões do estado de Minas Gerais, frente às 19 cultivares diferenciadoras para ferrugem, adotadas no "The Bean Rust Workshop", realizado em 1983, em Porto Rico, e 2) comparar os padrões de resistência/suscetibilidade obtidos, com aqueles apresentados frente a patótipos isolados nos estados de Santa Catarina, Rio Grande do Sul e Goiás, visando identificar fontes de resistência de amplo espectro. Os sete isolados coletados em Minas Gerais foram classificados com sete patótipos distintos. As cultivares diferenciadoras com os maiores espectros de resistência foram 'Redlands Pioneer', 'California Small White 643', 'Brown Beauty', 'AxS 37' e 'Compuesto Negro Chimaltenango'. Portanto, apesar da exclusão das cultivares California Small White 643, AxS 37 e Brown Beauty da nova série diferenciadora internacional proposta em 2002, na África do Sul, recomenda-se adicionar estas cultivares nas futuras caracterizações de patótipos a serem realizadas no Brasil, como um modo de monitorar a variabilidade patogênica de populações de U. appendiculatus nas regiões produtoras.

Genetic divergence among and within Colletotrichum lindemuthianum races assessed by RAPD

Genetic divergence within and among races of Colletotrichum lindemuthianum was determined using RAPD markers. In addition to the different races of the fungus three isolates of the sexual stage of Colletotrichum lindemuthianum (Glomerella cingulata f.sp. phaseoli) were included in this study. The band patterns generated using 11 primers produced 133 polymorphic bands. The polymorphic bands were used to determine genetic divergence among and within the pathogen races. The isolates analyzed were divided into six groups with 0.75 relative similarity. Group VI, formed by three isolates of the sexual phase of Colletotrichum lindemuthianum, was the most divergent. Races previously determined using differential cultivars did not correlate with the results obtained using RAPD markers.

Identification of Races of Selected Isolates of Uromyces appendiculatus from Minas Gerais (Brazil) Based on the new international classification system

Twelve single-pustule isolates of Uromyces appendiculatus, the etiological agent of common bean rust, were collected in the state of Minas Gerais, Brazil, and classified according to the new international differential series and the binary nomenclature system proposed during the 3rd Bean Rust Workshop. These isolates have been used to select rust-resistant genotypes in a bean breeding program conducted by our group. The twelve isolates were classified into seven different physiological races: 21-3, 29-3, 53-3, 53-19, 61-3, 63-3 and 63-19. Races 61-3 and 63-3 were the most frequent in the area. They were represented by five and two isolates, respectively. The other races were represented by just one isolate. This is the first time the new international classification procedure has been used for U. appendiculatus physiological races in Brazil. The general adoption of this system will facilitate information exchange, allowing the cooperative use of the results obtained by different research groups throughout the world. The differential cultivars Mexico 309, Mexico 235 and PI 181996 showed resistance to all of the isolates that were characterized. It is suggested that these cultivars should be preferentially used as sources for resistance to rust in breeding programs targeting development lines adapted to the state of Minas Gerais.

Is it necessary to soak rice grains to prepare Rhizoctonia solani AG-4 inoculum?

A study was conducted to evaluate the effects on the development of root rot on common bean, cv. 'Dufrix' after treatment with four volumes of water (0, 30%, 60%, and 90%, v/w) added to rice grains previously immersed in water for 24 hours before autoclaving and colonization of grains by Rhizoctoniasolani AG-4. Colonized rice grains and non-infested rice grains were mixed in pots with sterilized soil and sand (2:1), where beans were sown. Based on results of area under plant emergence curve, plant height, plant dry weight, and disease severity, we conclude that inoculum is more effective in causing disease when no water is added to the rice grains before autoclaving.

Pseudomonas syringae pv. tabaci in papaya seedlings

The natural occurrence of Pseudomonas syringae pv. tabaci causing leaf spot symptoms in papaya seedlings is reported. The pathogen was identified through biochemical, physiological, serological, and molecular assays and artificial inoculations in papaya plants. It was also shown that the strains were pathogenic to bean and tobacco plants. The restriction patterns obtained with Afa I, Alu I, Dde I, Hae III, Hpa II, Hinf I, Sau 3A I and Taq I of the PCR-RFLP of 16S-23S DNAr were identical to the P. s. pv. tabaci patterns. Primers corresponding to hrpL gene of P. syringae were also tested and the results grouped the papaya strains with P s. pv. tabaci. Bacterial strains were deposited at Coleção de Culturas IBSBF, Instituto Biológico, Campinas, Brazil, under access numbers 1687 and 1822.

Susceptibility of leguminous green manure species to Rhizoctonia solani and Sclerotium rolfsii

We studied the susceptibility of species used as green manure in common bean fields to root rot (Rhizoctonia solani) and southern blight (Sclerotium rolfsii). Seeds of Crotalaria breviflora, Canavalia ensiformis, Cajanus cajan, Dolichos lablab, Stizolobium cinereum, S. aterrimum, and the bean cvs. "Pérola", "Valente" and "Carnaval" were sown in soil infested by either R. solani AG-4 or S. rolfsii in greenhouse. The emergence of D. lablab seedlings in soil infested by R. solani dropped to 62%. C. breviflora, C. ensiformis and cv. "Valente" presented the lowest root rot severity. The pathogen S. rolfsii drastically reduced seedling emergence in all species; no C. cajan and S. cinereum seedling emerged. All plant species presented high southern blight severity. We conclude that leguminous crops are not suitable as green manure for areas of bean cultivation with high R. solani and S. rolfsii populations.

Secondary seed dispersal of Ricinus communis Linnaeus (Euphorbiaceae) by ants in secondary growth vegetation in Minas Gerais

In this study, I tested the efficacy of ants as secondary seed dispersers of Ricinus communis in southeastern Brazil. In a natural population of 143 individuals, I determined the ballistic dispersal distance for 62 seeds and 100 additional seeds were experimentally offered to ants in groups of ten seeds along a transect of 50 m. Fifty-three seeds were removed by ants, mainly by the leafcutter Atta sexdens (90.4%). The dispersal distance by ants was high, compared to the global average (4.38 m ± 0.74 m vs. 0.96 m), but was lower than the ballistic distance (7.27 m ± 0.13 m). Ants increased the total dispersal distance (8.66 m ± 0.60 m), but the main benefit for the plant was the directed dispersal, with seed deposition on the enriched soil of ant nests.

Mathematical models to describe the volumetric shrinkage rate of red beans during drying

The present study aimed to determine the volumetric shrinkage rate of bean (Phaseolus vulgaris L.) seeds during air-drying under different conditions of air, temperature and relative humidity, and to adjust several mathematical models to the empiric values observed, and select the one that best represents the phenomenon. Six mathematical models were adjusted to the experimental values to represent the phenomenon. It was determined the degree of adjustment of each model from the value of the coefficient of determination, the behavior of the distribution of the residuals, and the magnitude of the average relative and estimated errors. The rate of volumetric shrinkage that occurred in bean seeds during drying is between 25 and 37%. It basically depends on the final moisture content, regardless of the air conditions during drying. The Modified Bala & Woods' model best represented the process.

Quality of beans stored under hermetic conditions

This study aimed to evaluate the quality of beans (Phaseolus vulgaris L.) stored with different moisture contents under hermetic conditions. Beans with 12.3%, 15.7%, and 17.8% moisture content were used in the experiment. They were packed in bag type silos (3 kg), PET bottles (1.5 L), and glass containers (3 L), covered with organza fabric (control), and stored at 25 ºC and 70±5% relative humidity, for 120 days. The evaluated characteristics included moisture content, apparent density, electrical conductivity, germination percentage, cooking time, and bean classification, every 30 days. Except for the electrical conductivity and cooking time, the other characteristics were kept for 120 days in the stored product with moisture contents of 12.3% and 15.7% in hermetic conditions. Beans with 17.8% of the moisture content, electrical conductivity and cooking time increased, and apparent density and germination were reduced. Beans stored in the control, with any of the moisture contents, showed high quality loss during the long storage. It was concluded that it is possible to storage beans with moisture contents of 12.3% and 15.7%, with quality, for until 120 days, in hermetic conditions.

Carbon footprint of the colombian cocoa production

ABSTRACT Cocoa is an important commercial crop in the tropics; and estimating the carbon emissions in the producing-areas is a worthwhile effort. The main goal of the current paper was to evaluate the carbon footprint (CF) per kilogram of Colombian cocoa bean produced under conventional and agroforestry managements, following the methods proposed by PAS 2050. In this research, we compared our results to other worldwide researches, showing an overview of the current limitations and challenges involving the CF researches. Our results showed that all calculated environmental burdens were lower for the conventional management. In the agroforestry practice, composting of cocoa pod husks contributed with approximately 34.00E+00 g methane and 2.55E+00 g nitrous oxide emissions per kilogram of cocoa grain produced. Therefore, such practice could reduce CF by 6.00E+00 kg CO2 Eq kg-1, which is certainly a significant amount. These cocoa residues left on the ground have a strong impact on CF of both studied managements due to the anaerobic decomposition of organic matter, which represents more than 85% of emissions. We concluded that both evaluated production processes can emit environmental burdens at the same magnitude. Definitely, there is a widespread need to improve cocoa production system by changing old and less productive plants to the so called clones to ensure cocoa yield and quality worldwide.

Spontaneous poisoning by Ricinus communis (Euphorbiaceae) in cattle

The aim of this study is to report cases of spontaneous poisoning of cattle by Ricinus communis (castor beans) in Paraíba, a semiarid region of northeastern Brazil. The cases were observed in 2 herds on neighboring properties in 2013. Clinical signs developed within 6-24 h and consisted of weakness, tachycardia, dyspnea, profuse watery diarrhea, dehydration, depression, instability, cramps, permanent lateral recumbency and death within 48-72 h. Of the 60 cattle at risk, 19 were affected and 14 died. Five fully recovered after the course of 12 days. Three animals were necropsied. The main gross lesions were hemopericardium, hemothorax, pulmonary edema, petechial hemorrhages in the epicardium and endocardium, ecchymoses at the papillary muscles and suffusions on the intercostal muscles. Hemorrhages were also observed in the abdominal cavity, spleen and mucosa of the abomasum and small intestine. The rumen content was liquid with a large amount of castor bean seeds. There were circular, whitish and focally diffuse areas in the liver parenchyma. The main microscopic lesions consisted of multifocal coagulative myocardial necrosis with the presence of mononuclear cell infiltration and varying degrees of bleeding between cardiac muscle fibers. The abomasum and small intestine mucosae and submucosa had mild edema and mononuclear and polymorphonuclear inflammatory cell infiltration. The diagnosis of R. communis was based on the history of plant consumption, clinical signs, pathology of the disease and the presence of large amounts of castor bean seeds in the forestomachs.

Viabilidade do uso de herbicidas em mistura com vinhaça para o controle de plantas daninhas em soqueiras de cana-de-açucar

No presente estudo comparou-se a aplicação de herbicidas em mistura com vinhaça, com aplicação pelo sistema convencional, em soqueira de cana-de-açúcar. Os herbicidas usados foram oryzalin, diuron, 2,4 -D, ametryne e tebuthiuron. A aplicação em mistura com vinhaça foi feita com caminhão-tanque com capacidade para 7000 litros, provido com uma barra de distribuição de vazão controlada. A dose de aplicação foi de 25.000 1/ha. A distribuição dos herbicidas com equipamento convencional foi feita com pulverizador John Bean», provido com 16 bicos «Teeject» 110.04, trabalhando com pressão de 1,4 kg/cm². Usou-se delineamento experimental de blocos casualizados com parcelas subdivididas, com quatro repetições. Pelos resultados obtidos constatou-se que, à exceção do diuron, os demais herbicidas não foram prejudicados quando aplicados com vinhaça. O 2,4-D e a ametryne melhoraram a sua ação no controle de plantas daninhas e seu efeito residual aumentou, quando aplicados em mistura com vinhaça. O tebuthiuron e o oryzalin apresentaram comportamento semelhante no controle das plantas daninhas, nos dois sistemas de aplicação. O diuron aplicado em mistura com vinhaça apresentou resultados altamente negativos no controle das planta daninhas.

Weed control in young coffee plantations through post emergence herbicide application onto total area

This study was carried out to investigate the efficiency of several herbicides under field conditions, by post-emergence application onto the entire area, their effect on the control of weeds in young coffee plantations and commercial coffee and bean intercropping system, as well as on both crops. Seedlings of Coffea arabica cv. Red Catuaí with four to six leaf pairs were transplanted to the field and treated according to conventional agronomic practices. A bean and coffee intercropping system was established by sowing three lines of beans in the coffee inter-rows. At the time the herbicides were sprayed, the coffee plants had six to ten leaf pairs; the bean plants, three leaflets; and the weeds were at an early development stage. Fluazifop-p-butyl and clethodim were selective for coffee plants and controlled only Brachiaria plantaginea and Digitaria horizontalis efficiently. Broad-leaved weeds (Amaranthus retroflexus, Bidens pilosa, Coronopus didymus, Emilia sonchifolia, Galinsoga parviflora, Ipomoea grandifolia, Lepidium virginicum, and Raphanus raphanistrum) were controlled with high efficiency by sole applications of fomesafen, flazasulfuron, and oxyfluorfen, except B. pilosa, C. didymus, and R. raphanistrum for oxyfluorfen. Sequential applications in seven-day intervals of fomesafen + fluazifop-p-butyl, or clethodim, and two commercial mixtures of fomesafen + fluazifop-p-butyl simultaneously controlled both types of weed. Cyperus rotundus was only controlled by flazasulfuron. Except for fluazifop-p-butyl and clethodim, all herbicide treatments caused only slight injuries on younger coffee leaves. However, further plant growth was not impaired and coffee plant height and stem diameter were therefore similar in the treatments, as evaluated four months later. Fomesafen, fluazifop-p-butyl, and clethodim, at sole or sequential application, and the commercial mixtures of fomesafen + fluazifop-p-butyl were also highly selective for bean crop; thus at doses recommended for bean crop, these herbicides may be applied to control weeds in coffee and bean intercropping systems by spraying the entire area.

Weed mapping using a machine vision system

Weed mapping is a useful tool for site-specific herbicide applications. The objectives of this study were (1) to determine the percentage of land area covered by weeds in no-till and conventionally tilled fields of common bean using digital image processing and geostatistics, and (2) to compare two types of cameras. Two digital cameras (color and infrared) and a differential GPS were affixed to a center pivot structure for image acquisition. Sample field images were acquired in a regular grid pattern, and the images were processed to estimate the percentage of weed cover. After calculating the georeferenced weed percentage values, maps were constructed using geostatistical techniques. Based on the results, color images are recommended for mapping the percentage of weed cover in no-till systems, while infrared images are recommended for weed mapping in conventional tillage systems.