Aricléia de Moraes Catarino

Guaraná is indigenous to the Brazilian Amazon where it has cultural and agroeconomic significance. However, its cultivation is constrained by a disease termed oversprouting of guaraná caused by Fusarium decemcellulare, with yield losses reaching as high as 100%. The disease can affect different parts of the plant, causing floral hypertrophy and hyperplasia, stem galls, and oversprouting of vegetative buds. To date, no study has been conducted characterizing the genetic diversity and population structure of this pathogen. Here, we report genetic diversity and genetic structure among 224 isolates from eight guaraná production areas of Amazonas State, Brazil, that were genotyped using a set of 10 inter-simple-sequence repeat (ISSR) markers. Despite moderate gene diversity (Hexp = 0.21 to 0.32), genotypic diversity was at or near maximum (223 multilocus genotypes among 224 isolates). Population genetic analysis of the 10 ISSR marker fragments with STRUCTURE software identified two populations designated C1 and C2 within the F. decemcellulare collection from the eight sites. Likewise, UPGMA hierarchical clustering and discriminant analysis of principal components of the strains from guaraná resolved these same two groups. Analysis of molecular variance demonstrated that 71% of genetic diversity occurred within the C1 and C2 populations. A pairwise comparison of sampling sites for both genetic populations revealed that 59 of 66 were differentiated from one another (P < 0.05), and high and significant gene flow was detected only between sampling sites assigned to the same genetic population. The presence of MAT1-1 and MAT1-2 strains, in conjunction with the high genotypic diversity and no significant linkage disequilibrium, suggests that each population of F. decemcellulare might be undergoing sexual reproduction. Isolation by distance was not observed (R² = 0.02885, P > 0.05), which suggests that human-mediated movement of seedlings may have played a role in shaping the F. decemcellulare genetic structure in Amazonas State, Brazil.

The use of bacteria in growth promotion and biological control of plant diseases can minimize environmental contamination caused by the indiscriminate use of pesticides and chemical fertilizers. We aimed to evaluate growth promotion and biological control of Corynespora cassiicola in tomato seedlings mediated by beneficial bacteria isolated from a non-rhizospheric Amazon soil containing different amounts of biochar, and to identify to which groups of bacteria the strains belong. We obtained 200 strains of bacteria from experimental plots containing biochar doses of 0, 40, 80 and 120 t ha-1. Of these, 53 strains were selected by root colonization tests. Based on growth promotion parameters, 25 strains were screened, identified by molecular characterization and evaluated for indoleacetic acid (IAA) production, phosphate solubilization and biological control. The best dose of biochar for colony formation was 40 t ha-1, and a regression model indicated 34 t ha-1 as the optimal dose. The production of IAA was observed in 18 (75%) strains, and two (8%) strains were able to solubilize phosphate. The efficiency in root growth promotion was up to 125%, and the percentage of plant protection ranged from 50 to 59%. Molecular characterization showed that the bacteria used in this study belong to the genera Bacillus and Lysinibacillus.

Arcopilus is a genus recently proposed after the taxonomic restructuring of Chaetomium with only seven described species so far. During the characterization of the microbiome of the Amazonian guarana plant (Paullinia cupana var. sorbilis), nine red pigment-producing strains of fungi were isolated. These strains were identified through morphological characterization and phylogenetic analysis based on the internal transcribed spacer (ITS), 28S large subunit (LSU), partial second largest subunit of RNA polymerase II (RPB2) and β-tubulin (TUB2) regions. Moreover, chemical profiles were obtained via high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS), in which the isolated strains were able to produce significant amounts of the polyketide oosporein. The obtained results indicate the occurrence of a new fungal species, A. amazonicus. Chemical analyses showed that oosporein is overproduced by these strains under laboratory culture conditions.

Caryota mitis Lour. is a species of palm tree of Asian origin, adapted to the tropical climate, that is economically important in culinary, landscaping, in addition to anti-allergenic properties an...

Rice is one of the world’s most consumed cereals, however, its production is affected by fungal diseases. Thus, the objective of this work was to evaluate the severity of diseases and grain yield potential of upland rice with silicon fertilization combined with seed microbiolization with Bacillus methylotrophicus isolates. Two experiments were conducted, one in Igarapé do Meio, Maranhão (MA), Brazil, with rice seeds of the variety Palha-Murcha and one in São Bento MA with rice seeds of the variety BRS-Primavera. A randomized block experimental design in a split-plot arrangement with five replications were used in both experiments, with agro-silicon rates (0.0, 1.0, 2.0, 4.0 and 6.0 Mg ha-1) in the plots and microbiolized and non-microbiolized rice seeds with B. Methylotrophicus at concentration of 108 CFU ml-1 in the subplots. The seedling emergence, grain yield, number of panicles, plant height, plant dry weight and severity of brown leafspot, leaf scald and grain spot were evaluated. Soil fertilization with agro-silicon affected positively the plant height of the variety Palha-Murcha and the number of panicles, plant dry weight and grain yield of the variety BRS-Primavera, and negatively the germination of the variety BRS-Primavera. Leaf scald severity in the variety BRS-Primavera reduced with microbiolized seeds with B. methylotropicus. Microbiolization with B. methylotropicus had no effect on severity of brown leafspot and grain spot in the varieties evaluated.

The objective of this study was to evaluate the morphological and physiological characteristics of F. oxysporum f. sp. passiflorae. Isolates were obtained from yellow passion fruit plants with fusariosis symptoms grown in four production poles. The pathogenicity test was carried out on seedlings of this crop, under greenhouse conditions. The morphological characters evaluated were the size of macroconidia and microconidia in single conidiophores or in false heads; number of septa, presence of basal cell in the macroconidia and chlamydospores, and the aspects of the colonies of the isolates cultivated in PDA culture medium for aerial mycelium formation and colony coloration. The carbon sources: starch, lactose, maltose and sucrose were tested for the three most virulent isolates obtained in the pathogenicity test. The mycelial growth was obtained through readings every 24 hours of the diameter of the colony in two diametrically opposite directions. Sporulation determination was performed by counting spores in a Neubauer chamber. The isolate Fusarium oxysporum f. sp. passiflorae 4 (FOP 4) was the most virulent. There was variation in the morphological characteristics of all the isolates. The starch provided the highest mycelial growth and the isolates showed preferences for a particular carbon source in the sporulation test.

The cercospora leaf spot, caused by Cercospora abelmoschi Ellis and Everhart, is quite common in okra culture. Therefore, this study aimed to evaluate the efficiency of aqueous extracts of neem (Azadirachta indica A. Juss), citronella (Cymbopogon nardus (L.) Rendle), eucalyptus (Eucalyptus grandis L.), ecolife®, A. indica oil and fungicide cercobin 700 PM® in control of cercospora leaf spot on okra in greenhouse. The extracts and neem oil were tested in concentration 10%, the fungicide cercobin 700PM® in dose 2.5 g.l-1, applied 10 days after pathogen inoculation by leaf spray and the citric biomass extract ecolife® in concentration 5.0 ml.l-1, applied 10 days before pathogen inoculation. All treatments, except ecolife®, were effective in controlling cercospora leaf spot and may be recommended as alternatives in agroecological systems. © JASEM Keywords: Abelmoschus esculentus, aqueous extracts, Cercospora abelmoschi, fungicide cercobin and greenhouse.