Use of spectrophotometry as a tool to quantify the sporulation of Penicillium allii in garlic lesions

Abstract

A technique to measure the concentration of conidia in damp chamber experiments by spectrophotometry was developed. A negative linear correlation (R 2 =0.56) was observed between transmittance at 340 nm and the concentration of conidia in water agar 0.05%. The equation that relates transmittance (T) with concentration (conidia mL -1 ) (y) is: y = 9.3 10 6 -86497 T. The method was assayed by inoculating 43 strains in two garlic cultivars. The method proved to be more rapid than the traditional use of a hemocytometer with an improved accuracy. The CV of the number of conidia per hemocytometer reticule was of 35.04%, while the transmittance CV was of 2.73%. The extreme values chosen for T were 40 and 80 because the sensitivity of the method decreased when concentrations of conidia were out of this range.Additional keywords: L., blue mold, hemocytometer. RESUMOPenicillium allii em lesões no alho em experimentos de alho em câmara úmida. Foi observada uma correlação linear negativa (R 2 =0.56) entre a transmitância a 340 nm e a suspensão conidial de em agar-água 0.05%. O método foi calibrado com um hemocitômetro e a equação que relaciona a transmitância (T) com a concentração (conídio mL -1 ) (y) é: y = 9.3 10 6 -86497 T. A técnica foi testada inoculando 43 isolados de enquanto que o CV da transmitância foi de 2.73%. Os valores extremos escolhidos para T foram 40 e 80 devido ao fato que a sensibilidade do método diminuiu em altas ou baixas concentrações de conídios.Palavras-chave adicionais: L., mofo azul, hemocitômetro.

Identification, pathogenicity and distribution of Penicillium spp. isolated from garlic in two regions in Argentina

“…Mycelia were removed by sterile forceps and 100 µ L were diluted in 5 mL of water. Transmittance of the suspension at 340 nm was measured on a Spectronic 20D spectrophotometer (Milton Roy) and suspension concentration was estimated as y = –86 497 T + 9·3 × 10 6 (Valdez & Piccolo, 2006) where y was the concentration (conidia mL −1 ) and T the transmittance. Tubes were stored at –20°C prior to morphological re‐identification to confirm Koch's postulates.…”

Methods for Fungicide Efficacy Screenings: Multiwell Testing Procedures for the Oomycetes Phytophthora infestans and Pythium ultimum

“…Since the use of mycelial fragments in OD measurements is subject to higher standard deviations compared to the use of spores [ 67 ], the initial status of a mycelial suspension must be accounted to ensure reproducibility. Moreover, to avoid any problems of fragment decantation in the early phases, which can lead to absorbance reduction, a small amount of agarose was added to the medium [ 68 , 69 ]. Homogenized hyphal biomass has been proven to correlate linearly with dry cell weight [ 70 ].…”

Influence of Spore Morphology on Spectrophotometric Quantification of Trichoderma Inocula

“…When using this approach, absorbance should be plotted against particle count to generate a calibration curve for estimation of the particle concentration for each species. Valdez and Piccolo [11] used optical density at 340 nm to quantify spores of Penicillium allii on necrotic garlic tissue, having to deal with interfering soluble garlic compounds. Inocula of Geotrichum candidum and Trichoderma viride were measured at 550 nm; however, only for spore concentrations lower than 9 × 10 6 cells/ml [12,13].…”