Daniel Diego Costa Carvalho

Potencial antagônico de Trichoderma spp. originários de diferentes agroecossistemas contra Sclerotinia sclerotiorum e Fusarium solani

From 40 soil samples collected in the Rio Grande do Sul, Minas Gerais, Sao Paulo, Bahia, Goias and Tocantins states, Brazil, a collection of 230 monosporic isolates of Trichoderma spp. was established using TSM selective media. In order to select efficient isolates for biological control, dual culture tests were carried out on PDA media at 20 oC for Sclerotinia sclerotiorum and at 25 oC for Fusarium solani f.sp. phaseoli. From the whole collection, 50 isolates presented antagonism against F. solani and 111 isolates to S. sclerotiorum. The antagonism against both pathogens was found in only 10% of the isolates. Scanning electron microscopy assessments with seven in vitro selected isolates showed that not all promoted hyperparasitism on the pathogens, suggesting the existence of other mechanisms of antagonism, as antibiosis or competition.

Controle de Fusarium oxysporum f.sp. phaseoli in vitro e em sementes, e promoção do crescimento inicial do feijoeiro comum por Trichoderma harzianum

Este trabalho objetivou avaliar seis isolados de Trichoderma harzianum no controle de Fusarium oxysporum f.sp. phaseoli em sementes, e seu efeito no crescimento inicial do feijoeiro comum. Os isolados foram inicialmente confrontados in vitro com o patogeno em testes de cultura pareada e antibiose a 25oC. Sementes sadias e artificialmente infectadas pelo patogeno foram microbiolizadas com 2 mL de suspensoes dos antagonistas (2,5 x 108 conidios mL-1) para cada 100 g de sementes, em rolo de papel germtest a 20 e 25°C. Os percentuais de incidencia do patogeno e de plântulas normais foram avaliados aos sete e nove dias, respectivamente. Em casa de vegetacao, os isolados foram aplicados a 5 x 109 conidios 500 g-1 de substrato autoclavado, com avaliacao do comprimento das raizes e parte aerea das plantas 11 dias apos o semeio (12 plantas tratamento-1). Todos os isolados apresentaram antagonismo in vitro contra o patogeno. Os isolados CEN202, CEN234, CEN238, CEN240 foram superiores a testemunha no controle de F. oxysporum em sementes, reduzindo entre 35 e 51% da incidencia do patogeno e proporcionando entre 73 e 81% de plântulas normais. O comprimento total das plantas com tratamento CEN239 (37,43 cm) foi superior aos demais, cujo comprimento variou entre 27,84 e 33,95 cm.

Biocontrol of seed pathogens and growth promotion of common bean seedlings by Trichoderma harzianum

The objective of this work was to evaluate isolates of Trichoderma harzianum regarding biocontrol of common bean seed-borne pathogens, plant growth promotion, and rhizosphere competence. Five isolates of T. harzianum were evaluated and compared with commercial isolate (Ecotrich), Carboxin+Thiram, and an absolute control. Bean seeds of the cultivar Jalo Precoce, contaminated with Aspergillus, Cladosporium, and Sclerotinia sclerotiorum, were microbiolized with antagonists, and seed health tests were carried out. Isolates were evaluated on autoclaved substrate and in field conditions. Ten days after sowing (DAS), plant length was measured. To test rhizosphere competence, isolates were applied in boxes containing autoclaved washed sand, and root colonization was evaluated at 10 DAS, using five plants per box. The most effective isolates in the seed health tests were: CEN287 and CEN289 to control Aspergillus; the commercial isolate to control Cladosporium; and CEN287 and CEN316 to control S. sclerotiorum. Isolates CEN289 and CEN290 promoted bean growth in greenhouse and field. Seed treatment with T. harzianum reduces the incidence of Aspergillus, Cladosporium, and S. sclerotiorum in Jalo Precoce common bean seeds.

Biological control of Fusarium oxysporum f. sp. phaseoli by Trichoderma harzianum and its use for common bean seed treatment

Biological control of seed-borne pathogens has shown to enhance germination and physiological quality of seeds. The objectives of this study were to evaluate the in vitro antagonistic effect of five Trichoderma harzianum isolates (CEN287, CEN288, CEN289, CEN290, and CEN316) against Fusarium oxysporum f. sp. phaseoli (Foxy) and test its potential use in seed treatment. Initially, pathogen and antagonists were grown in paired cultures at 25oC, from which samples were assessed using scanning electron microscopy (SEM). Then, clean or Foxy-infected seeds were treated with conidial suspension of the antagonists. Percent of Foxy-infected seeds and normal seedlings were evaluated at seven and nine days of incubation, respectively. All but one Trichoderma isolate (CEN290) inhibited Foxy mycelial growth. SEM analysis revealed that only one Trichoderma isolate (CEN287) showed parasitic interaction with Foxy. Two isolates (CEN287 and CEN316) significantly reduced the Foxy incidence and enhanced seed germination, though less effective than the fungicide mixture (carboxin + thiram). A principal component analysis indicated the importance of volatile metabolites in reducing Foxy incidence on common bean seeds. CEN287 Trichoderma harzianum isolate formed a single group due to its increase in germination rate of Foxyinfected seeds.

Genetic variability of Passiflora spp. from commercial fields in the Federal District, Brazil

This study aimed to characterize the genetic variability in commercial accessions of passion fruit from the Federal District, Brazil, by RAPD markers. Genetic analyses were done with leaf samples of 30 accessions. DNA samples were amplified by RAPD technique, and respective markers converted into a binary matrix, from which the genetic distances between the accessions were estimated. Clustering analyis based on genetic distances allowed to detect a wide range of genetic variabillity among the accessions of sour passion fruit, and to separate them from the two sweet passion fruit. The graphical positioning of BRS Ouro Vermelho confirms its potential to improve the genetic variability of commercial varieties of sour passion fruit. Dispersal of genetic distances among commercial accessions of sour passion fruit supports evidence for different genetic origins of the materials planted in the Federal District. The verified genetic variability indicates the potential success of future breeding programs for this region.

Controle biológico do mofo‑branco por Trichoderma harzianum em feijão em condições de campo

The objective of this work was to evaluate Trichoderma harzianum isolatesfor biological control of white mold in common bean ( Phaseolus vulgaris ). Five isolates were evaluated for biocontrol of white mold in Perola common bean under field conditions, in the 2009 and 2010 crop seasons. Axa0commercial isolate (1306) and a control treatment were included . Foliar applications at 2x10 9 conidiaxa0mL ‑1 were performed at 42 and 52xa0days after sowing (DAS ), in 2009, and at 52 DAS in 2010 . The CEN287, CEN316, and 1306 isolates decreased the number of Sclerotinia sclerotiorum apothecia per square meter in comparison to the control, in both crop seasons. CEN287, CEN316, and 1306 decreased white mold severity during the experimental period, when compared to the control.

Biological control of Fusarium wilt on common beans by in-furrow application of Trichoderma harzianum

Two field trials were conducted during the summer and winter seasons of 2010 to evaluate the effect of biocontrol agents against Fusarium wilt of common bean. Treatments included six Trichoderma harzianum isolates applied in planting furrows at 1.2u2009×u20091012 conidia/ha, and one seed treatment with carboxin + thiram. Non-treated and infested plots served as control. Three T. harzianum isolates, CEN287, CEN290 and CEN316, reduced Fusarium wilt incidence and disease severity in the summer trial; incidence averaged 43.9 and 82.4xa0% in effective treatments and infested control plots, respectively. During the winter season, four isolates, CEN290, 1306, CEN316 and CEN287, reduced wilt incidence by 22.4, 26.7, 41.2 and 51.3xa0%, respectively, compared to the infested control (92.8xa0%) and fungicide-treated seeds (85.8xa0%). In general, ranking of treatments were similar whether incidence or severity was evaluated. However, CEN287 and CEN316 were ranked as the most effective isolates in both seasons. Crop yield-related variables were not affected by the treatments. Fusarium oxysporum population in soil was positively associated with disease incidence and severity, and negatively associated with grain number per pod and 100-grain mass in the summer experiment. In the winter trial, increasing densities of Trichoderma spp. in soil were correlated with increased 100-grain mass and number of grains per pod. The results highlight the value of in furrow applications of biocontrol agents for managing Fusarium wilt of common bean.

Supression of seed borne Cladosporium herbarum on common bean seed by Trichoderma harzianum and promotion of seedling development

Trichoderma harzianum isolates have been broadly used for biocontrol of plant diseases caused by fungi. Cladosporium herbarum is a common saprophyte and seed borne fungus, which is easy to manipulate under controlled conditions. It was chosen as a model to test the effectivity of seed treatments with T. harzianum. Common bean seeds (cv. Perola) contaminated with C. herbarum were treated with conidial suspension (CS) and autoclaved filtrate (AF) of five isolates of T. harzianum and subsequently submitted to health and germination tests. The proportion of normal seedlings formed, the length of roots, hypocotyls and leaves, and total plantlet length, total plantlet biomass, root mass ratio (RMR), stem mass ratio (SMR), leaf mass ratio (LMR), aerial part/root system ratio (AP/RS) and leaf area were also evaluated. Isolates CEN289 and CEN290 (CS and AF) provided 66 to 77% of supression of C. herbarum on seeds and a higher number of normal seedlings as compared with control. It also yielded a higher total biomass of plantlets. Moreover treatment with isolates CEN289 and CEN290 increased root and stem length in the experiments with CS. Such results indicate the potential of T. harzianum for seed treatment and suggest that it should be further tested as control for seed borne fungal diseases and as a plant growth promoter. The better performance found for CEN289 and CEN290 confirms the variability in terms of biocontrol activity among strains of T. harzianum.

Plant-parasitic Nematodes Associated with Commercial Orchards of Passion Fruit and Adjacent Cerrado Vegetation in the Brazilian Federal District

Empresa Brasileira de Pesquisa Agropecuaria, Embrapa Cerrados, BR 020, Km 18, 73310-970, Planaltina, DF, Brazil(Received on January 18, 2012; Revised on July 6, 2012; Accepted on July 7, 2012)Populations of plant-parasitic nematodes were evaluat-ed in soil and root samples from areas planted withpassion fruit, or covered with adjacent native cerradovegetation, in five different cropping regions of theBrazilian Federal District. From July 2007 to January2008, twenty samples had been collected in five RuralCenters (Nucleo Rural–NR) planted with passion fruit.In five sites, samples were also collected in native cerradovegetation. Specimens of nine genera of plant-parasiticnematodes ( Meloidogyne , Helicotylenchus , Rotylenchulus ,Scutellonema, Pratylenchus, Paratylenchus, Hemicyclio-phora, Xiphinema and Criconemoides ) were found in thepresent survey. Important nematode pathogens, such asRotylenchulus reniformis and Meloidogyne spp. wereobserved in the passion fruit plantations throughoutfive major producing regions of the Brazilian FederalDistrict. Keywords : field survey, Meloyogyne, Passiflora spp, root-knot nematodes, Rotylenchulus reniformisPassiflora edulis Simmonds f. flavicarpa Degener is aplant species of a high economic importance in America,whereas Brazil and Ecuador are important world producersand consumers of passion fruit (Souza et al., 2008). Theeconomic importance of P. edulis and other Passifloraspecies relies on the quality of the fruits for consumptionand on its medicinal properties (Crochemore et al., 2003).Due to favorable climatic and soil conditions, extensiveproduction of sour passion fruit occurs in commercialorchards in the Brazilian Cerrado. Despite the advantages mentioned above, sour passionfruit is susceptible to pests and diseases. Soil pathogens areof main concern among passion fruit growers, especiallyplant-parasitic nematodes. Nematodes belonging to severalgenera have been reported in association with Passifloraroot systems in Brazil (Sharma et al., 1999; Soares et al.,2003; Dias-Arieira et al., 2008), however, for the majorityof them their role as pathogens remains unknown forthis crop. On the other side, the root-knot nematodes(Meloidogyne javanica, M. incognita, and M. arenaria),and the reniform nematode (Rotylenchulus reniformis) areamong the most destructive soil pathogens for passion fruit.These sedentary nematodes lead to root damage, poor plantdevelopment, and consequently to decreased yield andplant longevity.In addition to preventive measures, such as planting insoil free of harmful nematodes, crop rotation is the mostappropriate control measure available to lower populationlevels of nematodes in passion fruit plantations underBrazilian conditions. At the present time there is no nemati-cide registered for this crop. Despite richness of geneticvariability among Passiflora germplasm, and efforts tobreed nematode resistant varieties (Castro et al., 2011; El-Moor et al., 2009; Sharma et al., 2002), commercial vari-eties are not yet available to growers. Thus, knowledge ofthe distribution and population levels of nematodes isrequired for implementation of management practices.Direct field seeding, instead of planting seedlings fromnurseries is a common practice among passion fruit growersin the Brazilian Federal District (DF). This practice contri-butes to avoid dissemination of nematodes and otherpathogens from the nurseries through planting materials.Under these conditions, the sources of soil contamination ofplant-parasitic nematodes in the commercial orchards arepossibly from previous crops, weeds, or accidental intro-duction of infested soil from other locations. Susceptibleplants from the native vegetation may also be the source ofplant-parasitic nematodes when the area is claimed foragricultural purposes. For instance, Souza et al. (1994)reported the association of Meloidogyne spp. with severalnative plants of cerrado vegetation in Brazilian FederalDistrict (DF). The fact that the same plant-parasitic nema-todes appear associated with crops and plants in theassociated native vegetation is an indication that these

Reaction of Cauliflower Genotypes to Black Rot of Crucifers

This study aimed to evaluate six cauliflower genotypes regarding their resistance to black rot and their production performance. To do so, it was conducted two field experiments in Ipameri, Goiás, Brazil, in 2012 and 2013. It was used a randomized block design, with four replications (total of 24 plots). Each plot consisted of three planting lines 2.5 m long (six plants/line), spaced 1.0 m apart, for a total area of 7.5 m2. Evaluations of black rot severity were performed at 45 days after transplanting, this is, 75 days after sowing (DAS), and yield evaluations at 90 to 105 DAS. The Verona 184 genotype was the most resistant to black rot, showing 1.87 and 2.25% of leaf area covered by black rot symptom (LACBRS) in 2012 and 2013. However, it was not among the most productive materials. The yield of the genotypes varied between 15.14 and 25.83 t/ha in both years, Lisvera F1 (21.78 and 24.60 t/ha) and Cindy (19.95 and 23.56 t/ha) being the most productive. However, Lisvera F1 showed 6.37 and 9.37% of LACBRS and Cindy showed 14.25 and 14.87% of LACBRS in 2012 and 2013, being both considered as tolerant to black rot.