Salicylic acid acts on several plant physiological processes. Therefore, the aim of this study was to determine if salicylic acid interferes on the physiological quality of common bean seeds soaked with different concentrations by testing two seed imbibition methodologies. Common bean seeds of the cultivars Fepagro 26 and Predileto were utilized. The seeds were soaked in solutions of salicylic acid with concentrations of zero, 250, 500, 750, 1,000, 3,000 and 5,000 μM. Seed imbibition occurred in two ways: (1) germination paper moistened with salicylic acid solutions, and (2) seed imbibition in salicylic acid solutions in plastic boxes for 24 hours and subsequent sowing on germination paper moistened with distilled water. The experiment was maintained in a germination incubator under 25 °C temperature and with constant light. The number of normal seedlings (first count), length, fresh and dry matter of seedlings were determined on the fifth day after sowing. Germination percentage was assessed nine days after sowing. The study was performed in a completely randomized design with four replicates and 50 seeds were used for each treatment. Regression analysis was performed for salicylic acid concentrations, with no comparison of cultivars and seed imbibition methods. Salicylic acid in concentrations up to 1,000 μM does not negatively affect the common bean seed germination of the cultivars Fepagro 26 and Predileto, using seed soaking for 24 hours and imbibition in the germination paper. Concentrations of salicylic acid up to 1,000 μM and seed imbibition for 24 hours do not affect the vigor (first count) of the two common bean cultivars.
Anthracnose, caused by Elsinoë ampelina, is an economically important grapevine disease in south and southeast Brazil. Control is achieved by lime sulphur application during grapevine dormancy and foliar fungicide sprays until the berries are half‐grown. This study assessed the temporal and spatial progress of grapevine anthracnose under field conditions in order to describe the disease dynamics and its relationship to pathogen survival. The experiment was carried out in a vineyard of table grape Vitis labrusca in Brazil, during the 2014 and 2015 growing seasons. The incidence of vines with diseased leaves, stems and berries and the disease severity on leaves were recorded from bud break to veraison. Monomolecular, logistic and Gompertz models were fitted by non‐linear regression to the incidence and severity data over time to characterize the temporal progress. Ordinary runs, dispersion index, modified Taylor's power law and spatial hierarchy analyses were used to characterize the spatial pattern of diseased plants. The monomolecular model showed the best fit for the incidence progress, with disease progress rates ranging from 0.051 to 0.136 per day. In both seasons, the incidence of diseased plants reached 100% 1 month after bud break. However, the incidence of diseased leaves per plant was around 60% and leaf disease severity was lower than 5% for both years. Ordinary runs and dispersion index analyses revealed that diseased grapevines were distributed randomly on the majority of the assessment dates. Meanwhile, a slight aggregation of diseased vines was observed in the modified Taylor's power law analysis. Our results suggested that the progress of anthracnose incidence and severity over time was governed mainly by the income of the primary inoculum, which survived in the vineyard. Therefore, anthracnose control measures in Brazilian vineyards should be focused on the reduction in inoculum within the vineyard.
In August 2012, symptoms of black foot disease were observed on 21-year-old grapevines (Vitis labrusca cv. Bordô; own-rooted cultivar) at Nova Pádua city, Rio Grande do Sul state, Brazil. Symptomatic plants showed reduced vigor, vascular lesions, decline and death of vines, and necrotic lesions on roots. Isolation of fungi associated with necrotic root tissue was made on potato dextrose agar (PDA) medium containing 0.5 g L−1 streptomycin sulfate. Cultures were incubated at 25°C for 7 days in darkness, and single-spore cultures were obtained from the colonies emerging from the diseased tissue. For morphological characterization, cultures were transferred to PDA and spezieller nährstoffarmer agar (SNA) medium with addition of two pieces of 1 cm2 filter paper. One representative isolate (Cy9UFSM) was used for morphological and molecular characterization and pathogenicity confirmation. After 10 days growth on PDA at 20°C in the dark, colonies were umber to chestnut in color (3), appeared cottony to felty in texture, and sporulated profusely. After 5 weeks on SNA and under dark conditions at 20°C, cultures formed macroconidia predominantly on simple conidiophores, 1 to 3 septate, with both ends slightly rounded. Macroconidia varied in size depending on the number of cells as follows: one-septate (23-) 27.7 (-31) × (4.5-) 5.8 (-7) μm; two-septate (26-) 30.1 (-34) × (5-) 5.6 (-6) μm; and three-septate (24-) 31.2 (-35) × (5-) 5.8 (-6.5) μm. Microconidia were observed and did not have a visible hilum (6-) 11.2 (-17) × (3.5-) 4.2 (-5) μm (n = 30 observations per structure). Brown, thick-walled globose to subglobose chlamydospores were produced abundantly on PDA, (8.5-) 13.8 (-17) μm. To confirm the species, primer pairs H3-1a and H3-1b (2) were used to amplify a portion the histone H3 gene. Sequence of this region showed 98% similarity with a reference sequence for Ilyonectria robusta (A.A. Hildebr.) A. Cabral & Crous (GenBank Accession No. JF735530). Thus, both morphological and molecular criteria supported identification of the strain as I. robusta. This isolate was deposited in GenBank as accession KF633172. To confirm pathogenicity, 4-month-old rooted cuttings of Vitis labrusca cv. Bordô were inoculated by immersing roots in a conidial suspension (106 ml−1) for 60 min. After inoculation, the cuttings were planted in 1-L bags containing commercial substrate (MecPlant). Thirty days later, each plant was re-inoculated by applying 40 ml of a conidial suspension (106 ml−1) to the commercial substrate. Ten single-vine replicates were used for each isolate, and 10 water-inoculated vines were included as controls. After 4 months, the inoculated plants showed a 22.5% reduction of root mass, with root and crown necrosis, browning of vessels, and 20% mortality. Control plants treated with water remained symptomless. The fungus was re-isolated from blackened tissue of wood from the basal end of rooted cuttings, thereby satisfying Koch's postulates. I. robusta was first associated with black foot disease of grapevine in Portugal in 2012 (1). To our knowledge, this is the first report in southern Brazil of I. robusta associated with black foot disease of grapevine. References: (1) A. Cabral et al. Mycol. Prog. 11:655, 2012. (2) N. L. Glass et al. Appl. Environ. Microbiol. 61:1323, 1995. (3) R. W. Rayner. A mycological colour chart. Commonwealth Mycological Institute and British Mycological Society, 1970.
The objectives of this work were to evaluate and adequate the method of thermotherapy via humid heat for the treatment of safflower seeds (Carthamus tinctorius L.) and, to verify its effect on the physiological and sanitary quality of seeds. The experiment was performed in the period from September to November, 2016 and from May to July, 2017, in entirely randomized design, arranged in 5 × 6 + 1 factorial scheme, with five temperatures: 25, 35, 45, 55 and 65 ºC and with six time periods: 5, 10, 15, 30, 45 and 60 min, plus the additional treatment (control), with eight repetitions. The seeds were packaged in glass of 500 mL and disposed in thermodigital water bath device with heated water according to the abovementioned factorial. We evaluated the degree of humidity of the seeds after thermotherapic treatments, the germination of normal seedlings, the emergence at field, the speed indexes of germination and emergence, the length and dry mass of seedlings and the sanity test. We observed that the treatment of seeds via humid heat thermotherapy was efficient in the control of phytopathogens, without damage to the physiological quality until 45 ºC. The treatment of 45 ºC for 15 min provided the greater reduction of the pathogens on the safflower seeds, incrementing its germinative potential and emergence at field.
Buckwheat is a species with great economic and production potential, which has gained increasing importance. This study aimed to determine the physical, physiological, and sanitary quality of samples from seed lots, and to evaluate the pathogenicity of Fusarium spp. in buckwheat plants. Physical and physiological quality was evaluated by the thousand-seed weight, moisture content, germination test (5th and 7th days), seedling length, and seedling dry mass, while sanitary quality was determined by the health test on filter paper, with the seeds subjected to asepsis and without asepsis. Isolates of Fusarium spp. were obtained from symptomatic seedlings in the paper roll germination test. To identify and characterize fungal isolates, morphological and molecular approaches were used. Pathogenicity was determined on healthy plants in a controlled environment. The lots showed high physiological quality in the germination evaluation (5th and 7th days). There was a high incidence of Fusarium spp. in all lots, which can be reduced with seed asepsis. The isolates were identified as Fusarium incarnatum-equiseti species complex, and were pathogenic to buckwheat plants.
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