Establishment of a semi-selective method for the detection of Sclerotinia sclerotiorum in dry bean and soybean seeds

Abstract

The objective in this work was to improve the existing methodology for the detection of Sclerotinia sclerotiorum in dry bean and soybean seeds through the use of water restrictors in place of 2,4-dichlorophenoxyacetic acid, in PDA substrate containing bromophenol blue and antibiotics (Neon-S). Firstly, the effects of the water restrictors mannitol, sodium chloride, and polyethyleneglycol (PEG6000) at different osmotic potentials were evaluated on the mycelial growth of S. sclerotiorum isolates and on the radicle protrusion of seeds of the species studied. The use of water restrictors with osmotic potentials of up to -0.5 MPa for PEG and -1.0 MPa for mannitol and sodium chloride did not affect the mycelial growth of the isolates tested, and proved to be satisfactory to inhibit the radicle protrusion of the seeds tested. In the second stage of this work, alternating light and continuous darkness were tested in the detection of fungus in the seeds of both species by the modified Neon method. The methodology composed by solid medium PDA, bromophenol blue (100 ppm), chloramphenicol (50 ppm) and water restrictor mannitol (-1.0 MPa) at a temperature of 20 °C with incubation in darkness, proved to be effective and reliable in the detection of that pathogen in routine analysis laboratory.

Inoculação de Sclerotinia sclerotiorum em sementes de oleaginosas: transmissão e seus efeitos sobre a emergência de plantas

“…Este patógeno pode ser transmitido, associado às sementes na forma de micélio dormente ou acompanhando o lote por meio de estruturas de resistência, chamadas escleródios (KAWASAKI & MACHADO, 2013). Infecção de sementes tem sido relatada em alguns hospedeiros, os quais incluem girassol, soja e feijão (GOMES et al, 2006;HENNEBERG et al, 2012;BOTELHO et al, 2013).…”

Quantification and conceptual validation of the inoculum potential of Sclerotinia sclerotiorum in soybean and bean seeds

“…Seed Health test: This assay was conducted following the methodology used by Kawasaki and Machado (2013): 25 seeds were randomly placed in each of eight Petri dishes (15 cm in diameter) containing neon medium (39 g of PDA, 150 mg/L of Bromophenol Blue, 50 g of chloramphenicol, 70.1 g of mannitol, pH at 4.7), in a total of 200 seeds for each treatment. The plates were incubated at 20 °C in the dark, and readings were taken at five to eight days after the start of incubation.…”

“…Then, 75 mL of deionized water was added to each cup, and kept for 24 hours in a BOD chamber in the dark at 25 °C. After this period, the electrical conductivity of the solution was measured through readings with the aid of a MS Tecnopon conductivity meter, and the results were expressed in µS.cm -1 .g -1 of seeds (Krzyzanowski et al, 1999).…”

Potential of phosphite products in the control of Sclerotinia sclerotiorum in vitro

“…The transmission of the pathogen may be through mycelium dormant or the presence of sclerotia in seed lots (KAWASAKI & MACHADO, 2013), which is a method that infects areas over long distances. Another method of infection is through the release of ascospores through apothecia, which are structures formed from the germination of sclerotia, this is a method that infects areas at short distances, since it has been verified that ascospores remain in a range of 100 meters from the source of inoculum (BEN-YEPHET & BITTON 1985).…”