Farrer Centre Research Report 1998

The production, germinability and infectivity of survival structures of Rhynchosporium alismatis, a candidate mycoherbicide for the control of Alisma lanceolatum and Damasonium minus in rice

Research Supervisors

Dr Gavin Ash and Dr Eric Cother

Research Staff:

Mr Vincent Lanioslet

Funding:

$6,000

Duration:
1998

Project Summary:
Damasonium minus (Starfruit) and Alisma lanceolatum are two important weeds of irrigated rice found in New South Wales, Australia. Control of D. minus is becoming increasingly difficult due to its resistance to Londaxâ (Bensulfuron). As a result, the pathogenic Rhynchosporium alismatis is being studied as a potential biological control agent. R. alismatis produces both conidia and chlamydospores: this study investigated the potential use of the chlamydospores as a biocontrol agent for these two weeds.

The production, germinability and infectivity of chlamydospores were investigated. Bioassay leaf discs were used to study the lesion development caused by chlamydospores. Scanning Electron Microscopy pictures showed that R. alismatis can

infect D. minus, by direct penetration, by intercellular penetration or through stomata. At 20⁰C, the fungus completed its lifecycle within 4 days.

Potato Dextrose Agar permitted to produce 3.6 million chlamydospores per square centimetre within 15 days. The optimum temperature for chlamydospore production was 25⁰C; for chlamydospores germination 30⁰C and for lesion development 25⁰C. Light cycle had no significant effect on the production. Three months of storage did not affect the germination rate of chlamydospores.