Comparison of methodologies for conidia production by Alternaria alternata from citrus

Abstract

Conidia production is a problem in the study of Alternaria alternata from citrus. Thus, this study aimed to compare existing methodologies for conidial production of A. alternata isolated from Ponkan tangerine (2 isolates), Cravo lemon (1 isolate), Pêra orange (2 isolates) and Murcott tangor (1 isolate). The methodologies used were conidia production with 12 and 24 hours under white fluorescent light, evaluation with 24 and 48 hours after applying fungal mycelium stress technique, cold stress followed by injury of mycelium and evaluation with 24 hours, using healthy vegetable tissue and the use of black fluorescent near ultraviolet (NUV) lamp. Satisfactory result was obtained with A. alternata isolate from Murcott tangor, with the production of 2.8 x 10 5 conidia mL -1, when fungal mycelium was stressed (Petri dish with 66.66% of fungi growth) and subsequently 24 h of growth. The use of white light (24 h) and black fluorescent NUV lamp also induced expressive conidia production by one isolate of Ponkan tangerine, which produced 17.2 x 10 5 and 10.1 x 10 5 conidia mL -1 and another of Murcott tangor, which produced 13.9 x 10 5 and 10.1 x 10 5 conidia mL -1, respectively. The remaining methodologies analyzed in this study were not able to induce conidia production in satisfactory quantity. The use of both mycelium stress technique and white light (24 h) and black fluorescent NUV lamp allowed the production of enough quantities of conidia to be used in vitro (detection of fungitoxic substances) and in vivo (pathogenicity test) assays, respectively.

Improved Method to Increase Conidia Production from Isolates of Different Pathotypes of Citrus Scab Pathogen Elsinoe spp.

“…It has been reported that light and physical force can influence spore release in Altarnaria (Carvalho et al, 2008) and Mycospaerella figiensis (Peraza-Echeverrıa et al, 2008). Leslie and Summerell (2006) have included light as another limiting factor of spore release in Fusarium spp.…”

Morphological Characteristics and Genetic Variability of Trichoderma spp. From Conventional Cotton Crop Soils in Federal District, Brazil

“…Under light and on PDA, T. crassum exhibited characteristics described by Samuels et al (2009), such as intensive conidiation bundled up in tiny pustules near the point of inoculation. A possible explanation for these results could be attributed to the light of fluorescent lamps inducing conidial production in some hyphomycetes (Carvalho et al, 2008). Moreover, typical yellow pigments verified in colonies of T. aureoviride when on PDA (b) and OA are not seen in dark-grown cultures (Samuels et al, 2009), confirming the importance of fluorescent light in the study of cultural characteristics of some Trichoderma species.…”

Chalcones to control Alternaria alternata in murcott tangor fruits

“…The fungus A. alternata pathotype tangerine used in this study was obtained as described by Carvalho et al (2008). Briefly, fungal plugs (90 mm Ø) were transferred to PDA plates, which were maintained for seven days at 25ºC, under constant illumination provided by Philips daylight fluorescent lamps (20W, TLT, 75RS).…”

“…However, mandarin growers face a number of phytosanitary problems, among which we can highlight the Alternaria brown spot (ABS), which is caused by the fungus Alternaria alternata pathotype tangerine.This disease has been a serious threat for the production of mandarin in Brazil since 2006, when it was detected in Citrus reticulata var. Ponkan and hybrid tangor Murcott (Citrus reticulata x Citrus sinensis) (CARVALHO et al, 2008;STUART et al, 2009).…”