In vitro production of conidia of Alternaria solani

Abstract

Sporulation of Alternaria solani can be scarce and is often reduced when the fungus is cultivated in vitro. A series of experiments were conducted to assess the effects of moisture, mycelial wounding, light quality and photoperiod, and culture media on conidial production. A procedure to induce sporulation based on mycelial wounding and dehydration was adapted and validated. Best results were obtained when fungal colonies were grown in V8 medium at 25 o C in the dark with agitation for seven days; the mycelium mass was ground, poured into potato dextrose agar (pH 6.5) in plates, and incubated at 25 ± 2 o C under near ultraviolet light and 12 h-photoperiod. The procedure was validated with 30 isolates of A. solani from different hosts, sampling locations, ages, and storage conditions. Conidial production, germination, and infectivity were quantified. Seventy-five percent of the isolates sporulated and the lowest germination rate was 68%. Inoculations of conidial suspension of all isolates resulted in lesions on tomato and potato plants. The effect of subculturing on A. solani sporulation was also assessed. After six subcultures, every seven days, there was no reduction in sporulation of colonies that were induced with the protocol. Key words: early blight, biphasic technique, subculture, infection frequency. RESUMO Produção in vitro de conídios de Alternaria solaniA esporulação de Alternaria solani in vitro pode ser escassa e tende a reduzir após sucessivas repicagens. Conduziram-se vários experimentos para avaliar o efeito da umidade, injúria da colônia, qualidade de luz e fotoperíodo, bem como do meio de cultura na produção de conídios. Adaptou-se a técnica bifásica para induzir esporulação, por meio de injúria de micélio e desidratação do meio de cultura. Obtiveram-se melhores resultados quando colônias cresceram em meio V8 a 25 o C, no escuro, sob agitação durante sete dias; a massa de micélio foi triturada e a suspensão depositada em meio BDA (pH 6,5) em placas de Petri, incubando-se a 25 ± 2 o C, sob luz negra com 12 h de fotoperíodo. Validou-se o protocolo para 30 isolados de A. solani distintos quanto ao hospedeiro, local de origem, idade e forma de armazenamento. Quantificaram-se a produção, germinação e infectividade de conídios. Dos 30 isolados, 75% esporularam e a germinação mínima de conídios foi de 68%. Todos os isolados foram patogênicos em seus respectivos hospedeiros. Avaliou-se, também, o efeito de repicagens sucessivas na esporulação. Todos os isolados produziram conídios após seis repicagens sucessivas. Palavras chave: pinta preta, técnica bifásica, subcultura, frequência de infecção.

Infection cycle ofAlternaria brassicicolaonBrassica oleracealeaves under growth room conditions

“…Conidiogenesis of Alternaria species depends on many environmental and endogenous stimuli, but mainly on available nutrients, photoperiod and temperature (Hubballi et al ., ; Rodrigues et al ., ; Su et al ., ); however, on PDA plates, A. brassicicola sporulates easily in the dark over a wide temperature range. In the present study, conidiogenesis was observed at 48 hpi on all Brassica varieties and, surprisingly, it also occurred at an early stage of the A. brassicicola infection cycle, directly from a mature conidium.…”

Influence of Culture Media and Temperature on Growth and Sporulation of Lasiodiplodia theobromae, Pestalotiopsis microspora and Fusarium oxysporum Isolated from Ricinodendron heudelotii in Cameroon

“…PDA and V 8 juice media were prepared based on Rodrigues et al, (2010) protocol while Pradeep et al, (2013) protocol was used for preparation of MEA medium. A volume of 20 ml sterilized medium was poured in each Petri plate and allowed to solidify.…”

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

“…Leslie and Summerell (2006) have included light as another limiting factor of spore release in Fusarium spp. In addition, culture medium, alternative low-high light, and darkness can facilitate sporulation (Rodrigues et al, 2010). Limited amount of salt (CaCO 3 ) can accelerate spore release in Altarnaria alternate, whereas high concentrations of salt can retard the release (Masangkay et al, 2000), indicating the potential role of chemicals in spore release.…”