6.17
DISTRIBUTION OF STAGONOSPORA MELILOTI AND ACROCALYMMA MEDICAGINIS, PATHOGENS CAUSING RED-CROWN ROT IN LUCERNE, MEDICAGO SATIVA, IN AUATRALIA AND CALIFORNIA

M COLE

Charles Sturt University, Wagga Wagga, Australia

Background and objectives
Stagonspora meliloti and Acrocalymma medicaginis cause stand decline of lucerne in Australia [1]. S. meliloti is responsible for leaf-spotting, which causes a loss of productivity in lucerne as a fodder legume in Australia and the USA, but is found also in the crown and root area. A. medicaginis is a newly described pathogen found in the crown and root of lucerne only along with S. meliloti . Both of these pathogens are implicated in red-crown rot. This project set out to determine how widely distributed both these organisms are throughout Australia and if A. medicaginis is present in lucerne in the USA.

Results
S. meliloti is distributed widely throughout Australian lucerne-growing regions from sub-tropical (southern Queensland) to cool temperate (northern and central Tasmania). It causes losses to fodder legume as the leaf-spotting pathogen and stand decline when it enters the crown and root [2]. In the USA, the leaf-spotting phase is more important because lucerne is replanted on a shorter cycle than in Australia. A. medicaginis has been found not to be a leaf-spotting pathogen and is present only in the crown-root area, causing stand decline. A collecting trip through the lucerne-producing regions of California, from Bakersfield in the south to Davis in the north, found S. meliloti in the red streaking in roots but not A. medicaginis.

References
1. Alcorn JL, Irwin JAG, 1987. Transactions of the British Mycological Society 88, 163-167.
2. Irwin JAG, 1989. In Marlin GC, ed., Persistence of Forage Legumes. Madison, Wisconsin, USA, pp. 399-418.