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Agora exibindo 1 - 20 de 1925

Pestalotiopsis microspora causes leaf spot on Adenium obesum
(2022-06) Jesus, Jéssica Maria Israel de; Rodrigues, Ana Beatriz Lemes; Paula, Kássia Lorrany Marques de; Cunha, Marcos Gomes da
Among the main ornamental plants grown in Brazil, Adenium obesum stands out for its appearance, drought resistance and beautiful flowers. However, diseases can be a limiting factor because they affect crop quality and yield. The aim of this study was to report the first occurrence of Pestalotiopsis microspora as the causal agent of leaf spots on desert rose. A. obesum leaves with necrotic spots on the edges and/or tips were collected for indirect isolation of the pathogen. Three morphologically similar fungal isolates were obtained. In pathogenicity testing, healthy leaves were inoculated with mycelial disks and controls with disks containing potato dextrose agar (PDA) medium. Symptom development was assessed on a daily basis, followed by reisolation. The DNA of pure cultures was extracted and submitted to PCR using the primers ITS1 and ITS4. The PCR product was sequenced. The inoculated leaves initially developed symptoms of chlorosis that progressed to necrosis. The fungal colonies exhibited white mycelia with radial, cottony growth and the formation of dark masses of conidia and hyaline, branched septate hyphae. The euseptate conidia had two hyaline cells (apical and basal) and three dark-coloured fusiform median cells. The morphological characteristics of the isolates were similar to those described for the genus Pestalotiopsis. When compared to sequences deposited in GenBank, the sequences of the ITS gene showed 100% identity with the Pestalotiopsis microspora species. These results extend the range of known hosts of this pathogen, since this is the first report of P. microspora attack in Adenium obesum.
Rapid Identification of Corynespora cassiicola by multiplex PCR
(2022) Jesus, Jéssica Maria Israel de; Cunha, Marcos Gomes da
The target leaf spot, an end-of-cycle disease that can cause soybean losses of 40%, is caused by the fungus Corynespora cassiicola. The aim of this study was to devise and validate a multiplex PCR protocol for the molecular identification of C. cassiicola, in both pure cultures of isolates and plants. For the analysis, a total of 75 samples was evaluated been 57 possible fungal isolates of C. cassiicola and 18 soybean plants displaying symptoms associated with target leaf spot. Total DNA was extracted from the pure cultures of the isolates and of four symptomatic leaf discs taken from each of the plants soybean evaluated and submitted to the conventional multiplex PCR technique using two primer pairs: ITS-1/ITS-4 and GA4-F/GA4-R. The ideal conditions for multiplex PCR were adjusted. The 57 isolates identified as C. cassiicola and among the evaluated plants, 15 samples were infected. Conventional multiplex PCR is efficient at identifying Corynespora cassiicola isolates and for rapid diagnosis of infected plants.
Comparison of loop-mediated isothermal amplification, polymerase chain reaction, and selective isolation assays for detection of Xanthomonas albilineans from sugarcane
(2018) Dias, Vanessa Duarte; Fernandez, Emmanuel; Cunha, Marcos Gomes; Pieretti, Isabelle; Hincapie, Martha; Roumagnac, Philippe; Comstock, Jack C.; Rott, Philippe
A loop-mediated isothermal amplification (LAMP) assay was developed and compared to polymerase chain reaction (PCR), nested PCR, and selective isolation assays for detection of Xanthomonas albilineans, the causal agent of sugarcane leaf scald. The pathogen was isolated on selective medium from 44 out of 45 (98%) samples taken from symptomatic stalks, and from 44 out of 70 (63%) samples from asymptomatic stalks that were collected from plots with symptomatic stalks. Forty-two (93%), 41 (91%), and 42 (93%) symptomatic samples tested positive by LAMP, PCR and nested PCR, respectively. The pathogen was detected in 19 (27%), 8 (11%), and 25 (36%) of the 70 asymptomatic samples by LAMP, PCR and nested PCR, respectively. Symptomatic stalks were mainly, but not always, associated with high populations of the pathogen (107–109 CFU/ml), and asymptomatic stalks with low populations (<103 CFU/ml) or no bacteria. Although our LAMP and nested PCR methods detected 10 CFU/ml of X. albilineans in suspensions prepared with pure culture, they sometimes failed to detect the pathogen in samples with low pathogen populations. Isolation on selective medium along with another method should therefore be used for detection of the pathogen in asymptomatic stalks, especially in quarantine programs.
Microbial volatiles organic compounds control anthracnose (Colletotrichum lindemuthianum) in common bean (Phaseolus vulgaris L.)
(2019-04) Martins, Samuel Julio; Faria, Amanda Flausino; Pedroso, Marcio Pozzobon; Cunha, Marcos Gomes; Rocha, Mara Rubia; Medeiros, Flávio Henrique Vasconcelos
Some microbial volatile organic compounds (mVOCs) can be toxic to phytopathogens, but information about their in vivo effect and the contribution of individual mVOC to biocontrol is scarce. In this study, we evaluated the in vitro and in vivo effect of Bacillus amylolicefaciens ALB629 and UFLA285 mVOCs on anthracnose (Colletotrichum lindemuthianum) control in common bean (Phaseolus vulgaris L.). ALB629 reduced C. lindemuthianum spore numbers (31%), while UFLA285 and ALB629 inhibited mycelial growth by 16 and 18%, respectively. Both bacterial volatiles controlled anthracnose in vivo (79–85%). The volatiles from UFLA285 and ALB629, identified as 3-methylbutanoic acid and 2-methylbutanoic acid, were toxic to the pathogen when applied individually or in combination, likely being the ones that play a role in common bean protection against anthracnose. Bacterial-VOCs 3-methylbutanoic acid and/or 2-methylbutanoic acid could be used to protect common bean against anthracnose.
Production of microsclerotia by Trichoderma asperellum through submerged liquid fermentation using low-cost nitrogen and carbon sources
(2022-09) Locatelli, Gabriel Olivo; Avelar, Maria Fernanda Pimentel; Bueno, Luciano Avallone; Lobo Junior, Murillo; Mascarin, Gabriel Moura; Finkler, Christine Lamenha Luna
The aim of this work is to optimize the nutritional conditions using low-cost carbon and nitrogen sources for microsclerotia (MS) production of two Brazilian Trichoderma asperellum strains (BRM-29576 and BRM-29104). A fractional factorial design was used to investigate five variables: carbon source, carbon concentration, nitrogen source, C:N ratio and fungal strain. In this study, the optimal nutritional conditions for improving MS yield were achieved using sucrose and autolyzed yeast, carbon concentration at 20 g L−1 and C:N ratio of 10:1 for the BRM-29104 strain, which outperformed the other strain and yielded up to 2.5 (±0.9) × 104 MS mL−1 within 7 days of fermentation. Sucrose and autolyzed yeast are two economically available carbon and nitrogen sources in Brazil that are suitable for MS production by T. asperellum BRM-29104. Vacuum filtration of MS biomass through nylon filter (200 mesh/74 μm) increased MS concentration, resulting in up to 1.8 (±0.2) × 105 MS g−1. Our results support a cost-efficient liquid medium to achieve high MS yields by strain BRM-29104 in combination with an easy method to harvest and concentrate MS from culture broth for further formulation development.
Management of Congo grass cover crop affects timing of Sclerotinia sclerotiorum carpogenic germination and decay of soybean stem rot
(2019-02) Civardi, Ederson Antonio; Görgen, Cláudia Adriana; Ragagnin, Vilmar Antonio; Silveira Neto, Américo Nunes da; Carneiro, Luciana Celeste; Lobo Junior, Murillo
The effects of cover crop management on the carpogenic germination of Sclerotinia sclerotiorum sclerotia and stem rot disease of soybean were investigated during three seasons (2008/2009 to 2010/2011) in a commercial farm of Goiás State, Brazil. Congo grass (Urochloa ruziziensis) annually grown during the fall at different densities (150, 300, 450 and 600 units of pure live seeds) was evaluated as cover crop and compared with a spontaneous weeds treatment. The germination of sclerotia was evaluated during cover crop growth in the spring season and in the summer, during soybean flowering. In general, apothecia density, disease incidence and disease severity index assessed at the 5.2 and 5.5 stages decreased with the increase of cover crop density. Trichoderma harzianum doses did not affect disease variables Soybean yield was not affected by any treatment. Principal component analysis clustered grass-soybean treatments apart from the spontaneous weeds-soybean sequence in all seasons. Carpogenic germination under the Congo grass canopy was negatively associated with apothecia density and disease during soybean growth. Mulching with Congo grass stimulates early carpogenic germination of S. sclerotiorum, enhancing soil disinfestation rather quickly. Adjustments in soybean crop stand are suggested to match improved disease management with higher soybean yields.
Comparison of inoculation methods for selecting common bean genotypes with physiological resistance to white mold
(2018-09) Ferreira, Lenio Urzeda; Ribeiro, Victor Alves; Melo, Patrícia Guimarães Santos; Lobo Junior, Murillo; Costa, Joaquim Geraldo Caprio da; Pereira, Helton Santos; Melo, Leonardo Cunha; Souza, Thiago Lívio Pessoa Oliveira de
Although different methods of inoculation have been proposed to assess the reaction of common bean to white mold (WM) caused by Sclerotinia sclerotiorum, a thorough comparison among them is lacking. In this study, six approaches were tested to identify the most reproducible and efficient method for discriminating six common bean genotypes of carioca market class based on their resistance to white mold. These included: modified straw test (ST), cotton pad (CP), infected flower on intact plant (IFIP) or on detached leaf (IFDL), and mycelium disc on intact plant (MDIP) or on detached leaf (MDDL). All experiments were conducted in a greenhouse or laboratory in a completely randomized design with four replicates. Several statistics including coefficient of variation (CV), standard deviation, intraclass correlation coefficient (ICC), p value for Bartlett’s test for homoscedasticity and sensitivity ratio (SR) were used as criteria for discrimination. The Spearman’s correlation coefficient was used to test the association between the methods. Results showed ST as the most suitable for selecting WM-resistant genotypes, followed by the IFIP method.
Reliability and discrepancies of rainfall and temperatures from remote sensing and Brazilian ground weather stations
(2020-04) Aguiar, Jordene Teixeira de; Lobo Junior, Murillo
Insufficient ground meteorological stations limit agricultural research in wide geographic areas, but high-quality data from remote sensing may decrease information gaps, when surface stations are scarce. This study compared meteorological datasets, estimated from satellite and ground meteorological stations in latitudes from 0 to 33 °S, to support agricultural research in Brazil. The dataset comprised 3600 records of monthly temperatures and rainfall from 01 Jan 2004 to 31 Dec 2014 in 30 Brazilian municipalities distributed in six regions, labeled according to their precipitation homogeneity. Climatic records from NASA's Prediction of Worldwide Energy Resource (POWER) online database were compared with data from Brazilian surface stations managed by National Institute of Meteorology (INMET). Monthly rainfall data showed satisfactory correlation coefficients for almost all locations, between 0.75 and 0.95 (p < 0.01), and simple linear models were fit for estimated (satellite) and observed (ground) rainfall relationship (p < 0.001). Complimentary accuracy and precision tests endorsed rainfall satellite-estimated data according to the root mean square error (RMSE) and the modified index of agreement. Maximum and minimum temperatures estimated by remote sensing in the Brazilian South Region were also statistically supported, but unsuitable results were found especially in lower latitudes, based on higher RMSE. The Pearson's correlation coefficient for temperatures increased proportionally with latitude, while rainfall did not show this correlation. These results showed satellite-data quality varies regionally and is affected by seasonal variation. Remote sensors may not detect extreme climatic events such as heavy rainfall or draught and, therefore, need to be appraised carefully.
Diversity and pathogenicity of rhizoctonia species from the Brazilian Cerrado
(2018-04) Blanco, Angel José Vieira; Costa, Marília Oliveira; Silva, Roberto do Nascimento; Albuquerque, Fábio Suzart de; Melo, Arthur Tavares de Oliveira; Lopes, Fabyano Alvares Cardoso; Steindorff, Andrei Stecca; Barbosa, Elder Tadeu; Ulhoa, Cirano José; Lobo Junior, Murillo
Eighty-one Rhizoctonia-like isolates were identified based on morphology and nuclei-staining methods from natural and agricultural soils of the Cerrado (Brazilian savanna). The nucleotide similarity analysis of ITS1-5.8S-ITS2 regions identified 14 different taxa, with 39.5% of isolates assigned to Waitea circinata (zeae, oryzae, and circinata varieties), while 37.0% belonged to Thanatephorus cucumeris anastomosis groups (AGs) AG1-IB, AG1-ID, AG1-IE, AG4-HGI, and AG4-HGIII. Ceratobasidium spp. AG-A, AG-F, AG-Fa, AG-P, and AG-R comprised 23.5%. Rhizoctonia zeae (19.8%), R. solani AG1-IE (18.6%), and binucleate Rhizoctonia AG-A (8.6%) were the most frequent anamorphic states found. Root rot severity caused by the different taxa varied from low to high on common beans, and tended to be low to average in maize. Twenty-two isolates were pathogenic to both hosts, suggesting difficulties in managing Rhizoctonia root rots with crop rotation. These results suggest that cropping history affects the geographical arrangement of AGs, with a prevalence of AG1 in the tropical zone from central to north Brazil while the AG4 group was most prevalent from central to subtropical south. W. circinata var. zeae was predominant in soils under maize production. To our knowledge, this is the first report on the occurrence of W. circinata var. circinata in Brazil.
Characterization of extracellular secondary metabolites in Oudemansiella canarii BRM-044600 displaying antifungal activity against the phytopathogen Sclerotinia sclerotiorum
(2021) Vieira, Vandinelma de Oliveira; Conceição, Aparecido Almeida; Silva, Caio de Oliveira Gorgulho; Romero Peláez, Ruben Darío; Lobo Junior, Murillo; Abdelnur, Patrícia Verardi; Almeida, João Ricardo Moreira de; Almeida, Euziclei Gonzaga de; Siqueira, Félix Gonçalves de
White mold disease, caused by the phytopathogen Sclerotinia sclerotiorum, provokes severe productivity losses in several economically important crops. Biocontrol agents, especially antagonist filamentous fungi, are environmentally friendly alternatives to the chemical fungicides used in white mold management. The objective of this study was to screen for basidiomycete fungi capable of inhibiting S. sclerotiorum and investigate their bioactive metabolites responsible for antifungal activities. Two out of 17 tested basidiomycete isolates inhibited the mycelial growth of S. sclerotiorum in pair culture experiments on agar plates, namely Oudemansiella canarii BRM-044600 and Laetisaria arvalis ATCC52088. O. canarii BRM-044600 liquid culture filtrate exhibited the greatest antifungal activity and was selected for further investigation. UHPLC-MS analysis suggests that six putative strobilurins, including strobilurin A and/or stereoisomers of this compound (m/z 259.1299, [M + H]+) and three putative strobilurins with m/z 257.1184 ([M + H]+) are likely responsible for the antifungal activity observed in the culture filtrate. For the first time, this work demonstrated the potential of O. canarii for white mold biocontrol and strobilurin production.
Trichoderma harzianum and Trichoderma asperellum are potential biocontrol agents of Meloidogyne javanica in banana cv. Grande Naine
(2022-01) Almeida, Nayane Oliveira; Oliveira, Camilla Martins de; Côrtes, Márcio Vinícius de Carvalho Barros; Ulhoa, Cirano José; Lobo Junior, Murillo; Rocha, Mara Rúbia da
Biological control of plant-parasitic nematodes by Trichoderma has been widely studied, especially in annual crops such as soybean and cotton, but scarcely explored in the banana crop. Phytonematodes often attack banana plantations, and the species of Meloidogyne typically are the most frequent. Depending on the nematode population, they lead to yield losses or even plant death. Despite several Trichoderma commercial products registered in Brazil as biofungicides or bionematicides, there is a single one recommended to manage Meloidogyne incognita, with no approvals for M. javanica. The objective of this study was to evaluate two Trichoderma harzianum isolates (ALL42 and IBLF006) and the T. asperellum T00 strain as antagonists of M. javanica and as inducers of systemic resistance on bananas. Greenhouse experiments were conducted by treating seedlings of the Grande Naine susceptible cultivar with conidia suspension of the isolates. The enzymatic activity of CHId and GLUeon banana leaves was evaluated at 7, 14, and 21 days after inoculation (DAI). Plant growth and nematode population were evaluated at 60 DAI. T. harzianum ALL42 and T. harzianum IBFL006 reduced the M. javanica population on banana roots by up to 55.2 % and 67.9 %, respectively, in contrast to T. asperellum T00 that was inefficient. Enzymatic activity of CHI in plants non-inoculated with the nematode was higher at 14 DAI and decreased afterward. CHI and GLU activity were higher at 21 DAI in plants treated with isolate IBFL006 and grown in infested soil. The treatments did not promote plant growth. The effect of T. harzianum isolates was tested “in vitro” as filtrate or conidia suspension on mortality of J2 individuals. ALL42 and IFBL006 non-autoclaved filtrates promoted the highest M. javanica mortality rates of 59.6 %, and 68.8 % respectively.
Preparation, characterisation and cell viability of encapsulated Trichoderma asperellum in alginate beads
(2020) Lopes, Allyson Rodrigo de Oliveira; Locatelli, Gabriel Olivo; Barbosa, Raquel de Melo; Lobo Junior, Murillo; Mascarin, Gabriel Moura; Finkler, Christine Lamenha Luna
Aim: The encapsulation of Trichoderma asperellum BRM-29104 using Ca-alginate matrix was evaluated. Methods: Intact and freeze-dried beads containing submerged conidia and microsclerotia (MS) of T. asperellum grown in liquid culture were prepared and characterised. Beads were stored at 8, 25, and 35 °C over 120 days. Results: The mean sizes of beads before and after freeze-drying were 2.5 ± 0.2 mm and 1.5 × 1.1 mm (± 0.1 mm), respectively. Freeze-dried beads stored at 8 °C were more effective in maintaining conidia concentration, while MS concentrations yielded 102 MS/g for both beads at 8 and 25 °C. The concentration of viable cells in freeze-dried beads stored at 8 °C attained 3.0 × 108 CFU/g after 120 days. FIRT analysis showed an interaction between the alginate and the cell wall of the fungus. Conclusion: These findings support the use of alginate beads followed by freeze drying and cold storage for maintenance of viability of T. asperellum.
Dynamics of common bean web blight epidemics and grain yields in different tillage systems
(2016) Costa-Coelho, Gesimária Ribeiro; Toledo-Souza, Eliane Divina de; Café Filho, Adalberto Corrêa; Lobo Junior, Murillo
The effects of tillage systems on the dynamics of web blight caused by Thanatephorus cucumeris and yield of common bean (Phaseolus vulgaris) cv. Pérola were studied in three field experiments during the planting seasons of 2004/2005, 2005/2006 and 2006/2007. Congo grass (Urochloa ruziziensis) was managed in a naturally infested field to establish the following cropping systems: no-till (NT), minimum-tillage (MT) (disking with partially incorporated straw); and conventional tillage (CT) (residues burial by soil plowing). The area under disease progress curves (AUDPCs) and the disease progress rates were generally low in the NT system during the three cropping seasons, most likely due to the benefits of grass mulching. In general, AUDPC values were higher in the 2005/2006 compared to the other seasons due to more uniform rainfall distribution during the crop cycle. Bean yield was highest in CT despite a higher the high AUDPC, probably due to immobilization of nutrients in the soil after herbicide-burning of U. ruziziensis. An additional study conducted in 2006/2007 showed that distribution of 2 to 10 t. ha−1 of U. ruziziensis straw over bare soil increased average yield by 29.9 %, while disease severity was reduced by 31.1 %, in comparison to control plots with no mulch.
Biological control of Pratylenchus brachyurus with isolates of Trichoderma spp. on soybean
(2021-01) Oliveira, Camilla Martins de; Almeida, Nayane Oliveira; Côrtes, Márcio Vinícius de Carvalho Barros; Lobo Junior, Murillo; Rocha, Mara Rúbia da; Ulhoa, Cirano José
Pratylenchus brachyurus is an important species of nematode as it causes significant yield losses in soybean crops in Brazil. The efficacy of Trichoderma asperellum T00 and Trichoderma harzianum ALL 42 were evaluated as biocontrol agents against P. brachyurus. The experiments were conducted under greenhouse conditions using the BRSGO Caiapônia and BRS 8560RR cultivars of soybeans. The application of these two fungal species significantly reduced the population density (PD) and reproductive factor (RF) of P. brachyurus in the cultivar BRSGO Caiapônia. In contrast, the PD and RF values for P. brachyurus in the cultivar BRS 8560RR remained stable after treatment with both species. The treatment of P. brachyurus (J2) with non-volatile metabolites from T. asperellum T00 and T. harzianum ALL42 resulted in mortality rates of 41% and 65%, respectively. The exposure to T. asperellum T00 and T. harzianum ALL42 did not alter the height, the size of the roots (RL), or the fresh mass of the aerial part (FSM) of BRSGO Caiapônia. On the other hand, the treatment of BRS 8560RR resulted in an increase in plant height, with no differences in RL and FSM. The activity of defense-related enzymes was determined in leaves of the two cultivars. In general, it was observed that the enzymes β-1,3-glucanase, chitinase and peroxidase showed higher activities in cultivar BRS 8560RR, while phenylalanine ammonia-lyase activity was higher in BRSGO Caiapônia. This study demonstrated that these two isolates of Trichoderma have potential for use in biological control of P. brachyurus in soybeans.
Influence of the biocontrol agents Trichoderma spp. on the structure and functionality of the edaphic microbial community in common bean cultivars (Phaseolus vulgaris L.) inoculated with Sclerotinia sclerotiorum (Lib.) de Bary
(2021-12) Silva, Fábio de Azevedo; Vieira, Vandinelma de Oliveira; Carrenho, Rosilaine; Rodrigues, Vinícius Barros; Lobo Junior, Murillo; Silva, Gilvan Ferreira da; Soares, Marcos Antônio
Control of agricultural pathogens can be achieved by biological control agents, but information about their impacts on the native microbiota is scarce. In this work, the commercial biocontrol agent Trichoderma harzianum ESALQ-1306 and the experimental strain Trichoderma asperellum BRM-29104 were selected to determine the effects of their application on the edaphic microbial community and on their functional traits in common bean cultivation (Phaseolus vulgaris L.) infected with Sclerotinia sclerotiorum (Lib.) de Bary in the Brazilian savannah. Soil samples were collected before planting and after 90 days of cultivation. The bean yield and disease severity were estimated. Spores of arbuscular mycorrhizal fungi (AMF) were quantified and identified, and the rate of root colonisation was measured. The total colony-forming units (CFU), species richness and alpha diversity, production of hydrolytic enzymes, microbial carbon biomass, microbial soil respiration, metabolic diversity and glomalin mass were quantified. After 90 days of cultivation, the microbial richness, diversity and abundance increased significantly, stimulated by bean plant development. The biocontrol strains did not significantly change the abundance of CFU with enzymatic activity, as well as microbial soil respiration, the microbial carbon biomass, metabolic diversity, the glomalin mass and the root colonisation rates; however, they changed the composition of cultivable microbial communities. S. sclerotiorum was controlled, and bean productivity was maintained. Therefore, the cultivation time is the variable with the major influence over the structure and functionality of cultivable microbial communities and AMF. We identified microbial species not previously reported in this biome and determined that T. asperellum BRM-29104 has the potential to be used as a new eco-friendly commercial product against white mold.
Occurrence and correlations of nematodes, Fusarium oxysporum and edaphic factors on banana plantations
(2018-04) Almeida, Nayane Oliveira; Teixeira, Renato Andrade; Carneiro, Franciele Alves; Oliveira, Camilla Martins de; Ribeiro, Victor Alves; Júnior, Murillo Lobo; Rocha, Mara Rúbia da
Problems caused by nematodes and Fusarium wilt (Panama disease) on banana plantations are responsible for yield losses and are limiting to its cultivation. In the state of Goias, there is little information about the nematode occurence on this crop, and its relation with the incidence of Fusarium oxysporum f.sp. cubense (Foc). This research had the purpose to identify the occurrence of plant-parasitic nematodes on banana plantations and to verify its correlation with the Fusarium wilt and with the soil attributes (pH, texture, nutrients). Twelve banana orchards in the state of Goias were sampled in the municipalities of Anapolis, Caiaponia, Goiatuba, Itaguaru, Itumbiara (two areas), Jatai, Morrinhos, Ouro Verde, Palestina, Taquaral and Uruana. All sampled areas, except Morrinhos, revealed contamination with Foc, and all areas had different genera of nematodes either in the soil or in the roots samples. Meloidogyne sp., Helicotylenchus sp. and Rotylenchus sp. were the main genera of plant-parasitic nematodes found in the samples, with Meloidogyne sp. and Rotylenchus sp. being the most dominant and abundant genera. The presence of Pratylenchus sp. increases the population levels of F. oxysporum. Helicotylenchus sp. is highly correlated with high concentrations of Mn. High population density of Meloidogyne sp. was found in irrigated areas with low concentrations of P, Ca, Mg and soil pH.
Annotated plant pathology databases for image-based detection and recognition of diseases
(2018-06) Barbedo, Jayme Garcia Arnal; Koenigkan, Luciano Vieira; Halfeld-Vieira, Bernardo Almeida; Costa, Rodrigo Veras; Nechet, Katia de Lima; Godoy, Claudia Vieira; Lobo Junior, Murillo; Patricio, Flavia Rodrigues Alves; Talamini, Viviane; Chitarra, Luiz Gonzaga
Over the last few years, considerable effort has been spent by Embrapa in the construction of a plant disease database representative enough for the development of effective methods for automatic plant disease detection and recognition. In October of 2016, this database, called PDDB, had 2326 images of 171 diseases and other disorders affecting 21 plant species. PDDB size, although considerable, is not enough to allow the use of powerful techniques such as deep learning. In order to increase its size, each image was subdivided according to certain criteria, increasing the number of images to 46,513. Both the original (PDDB) and subdivided (XDB) databases are now being made freely available for academic research purposes, thus supporting new studies and contributing to speed up the advances in the area. Both collections are expected to grow continuously in order to expand their reach. PDDB and XDB can be accessed in the link https://www.digipathos-rep.cnptia.embrapa.br/.
Combining ability as a strategy for selecting common bean parents and populations resistant to white mold
(2018) Ferreira, Lenio Urzeda; Melo, Patrícia Guimarães Santos; Vieira, Rogério Faria; Lobo Junior, Murillo; Pereira, Helton Santos; Melo, Leonardo Cunha; Souza, Thiago Lívio Pessoa Oliveira de
Common bean parents and populations resistant to white mold (WM, caused by Sclerotinia sclerotiorum) were selected based on estimates of general combining ability (GCA) and specific combining ability (SCA) for WM severity in three field nurseries in Brazil. Twenty-seven populations were obtained by partial diallel crosses between parents from two groups: GI) three sources of partial resistance identified abroad and GII) nine Brazilian cultivars and elite lines. Populations were advanced in bulk up to the F6 generation. The overall mean of WM severity from combined analysis ranged from 2.83 to 5.03 (scale of 1 to 9 scores) in the F6 population. The score of the susceptible control BRS Requinte was 7.21. The GI parents K-59, in Oratórios, MG, and Viçosa, MG, and K-407 and PI204717, in Goianira, GO, contributed to increase resistance to WM. The most promising populations for obtaining elite lines resistant to WM were K-59/BRS Executivo, PI204717/BRS Campeiro, PI204717/Jalo Precoce, K-59/BRS Radiante, and K-407/BRS Cometa.
Relações entre testes com metabólitos e seleção de isolados de Trichoderma spp. antagônicos a Sclerotinia sclerotiorum
(2016-03) Louzada, Gisele Angélica de Souza; Barbosa, Hellen Nogueira; Carvalho, Daniel Diego Costa; Martins, Irene; Lobo Junior, Murillo; Mello, Sueli Corrêa Marques de
Fungi of the Trichoderma genus have a versatility of action, as they can act by direct and/or indirect mechanisms. In view of this, multivariate analysis has been used in order to summarize and identify correlations among different mechanisms of biological control. We aimed to evaluate the antagonism of 16 Trichoderma spp. isolates against Sclerotinia sclerotiorum and identify the variables that best explain the antagonistic activity of Trichoderma spp. isolates against the pathogen in vitro. For that, isolates were confronted with the pathogen in paired culture (PC) and had the effect of their metabolites on the pathogen growth evaluated in volatile (VM), thermolabile (TLM), and non-thermolabile metabolite (NTLM) assays. Isolate CEN654 allowed only 17.1, 9.5, and 0.3% of pathogen growth in relation to the control in the VM, TLM, and NTLM assays respectively, standing out from the other isolates in the principal component analysis (PCA). The PCA also suggested that the PC and TLM assays are more suitable for the in vitro selection of isolates with antagonistic activity against S. sclerotiorum than the VM and NTLM ones.
Potential worldwide distribution of Fusarium dry root rot in common beans based on the optimal environment for disease occurrence
(2017-11) Macedo, Renan; Macedo, Lilian Patrícia Sales; Yoshida, Fernanda; Abud, Lidianne Lemes Silva; Lobo Junior, Murillo
Root rots are a constraint for staple food crops and a long-lasting food security problem worldwide. In common beans, yield losses originating from root damage are frequently attributed to dry root rot, a disease caused by the Fusarium solani species complex. The aim of this study was to model the current potential distribution of common bean dry root rot on a global scale and to project changes based on future expectations of climate change. Our approach used a spatial proxy of the field disease occurrence, instead of solely the pathogen distribution. We modeled the pathogen environmental requirements in locations where in-situ inoculum density seems ideal for disease manifestation. A dataset of 2,311 soil samples from commercial farms assessed from 2002 to 2015 allowed us to evaluate the environmental conditions associated with the pathogen's optimum inoculum density for disease occurrence, using a lower threshold as a spatial proxy. We encompassed not only the optimal conditions for disease occurrence but also the optimal pathogen's density required for host infection. An intermediate inoculum density of the pathogen was the best disease proxy, suggesting density-dependent mechanisms on host infection. We found a strong convergence on the environmental requirements of both the host and the disease development in tropical areas, mostly in Brazil, Central America, and African countries. Precipitation and temperature variables were important for explaining the disease occurrence (from 17.63% to 43.84%). Climate change will probably move the disease toward cooler regions, which in Brazil are more representative of small-scale farming, although an overall shrink in total area (from 48% to 49% in 2050 and 26% to 41% in 2070) was also predicted. Understanding pathogen distribution and disease risks in an evolutionary context will therefore support breeding for resistance programs and strategies for dry root rot management in common beans.

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