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

Abstract

Elsinoe fawcettii and E. australis are two currently recognized scab pathogens of citrus. E. fawcettii has at least six pathotypes while E. australis has at least two pathotypes. Colonies of E. fawcettii and E. australis do not sporulate in artificial media including potato dextrose agar (PDA). Whiteside's method has been widely used for preparing conidial inoculum in vitro. This study was carried out to develop efficient method for conidia production from artificial media. We developed a shaking method which included the following steps: 1) Colony grown on PDA was mashed with a steel spatula; 2) Mycelia fragments were cultured in 50 ml sterilized rain water in a rotary shaker-incubator (180 rpm) at 25ºC for 24 h: 3) The conidia suspension was filtered through two layers of cheesecloth. Average conidia production of all isolates tested using this shaking method was approximately 13.1 times higher than that from Whiteside's method in this study.

Aetiology and epidemiology of grapevine anthracnose

“…australis (Hyun et al, 2015). This result agrees with the findings for E. ampelina, where isolates rarely produced conidia .…”

“…Elsinoë fawcettii and E. australis, the causal agents of citrus scab, also do not sporulate on artificial media (Hyun et al, 2015). Likewise, conidia production in culture of E. veneta is sparse and variable (Williamson et al, 1989).…”

“…This result agrees with the findings for E. ampelina, where isolates rarely produced conidia . Therefore, Hyun et al (2015) developed an efficient method for sporulation of citrus scab pathogens using rainwater and shaking, resulting in conidia production approximately 13 times higher than that from Whiteside's method.…”

“…Species of the genus Elsinoë are pathogens causing scab and anthracnose on many economically important crops . However, many species including E. ampelina rarely produce conidia in vitro (Williamson et al, 1989;Swart et al, 2001;Hyun et al, 2015;.…”

“…To induce sporulation, a colony fragment (4 × 4 cm) was removed, placed in a sterile Petri dish and mashed using a pestle, resulting in fragments smaller than 2 mm. The small fragments were transferred to a 50 mL conical flask containing 40 mL sterile rainwater and incubated on an orbital shaker (Ratek Instruments) at 200-rpm and room temperature (22 -25 °C) for 7 days (adapted from Hyun et al, 2015). The rainwater was collected and filtered through four layers of gauze to remove the debris prior to sterilization.…”