Publication Date

1997

Description

Isolates of Colletotrichum gloeosporioides which cause anthracnose disease in the tropical pasture legume Stylosanthes were collected from its centre of diversity in South America. These and other isolates from Asia, Africa and Australia were studied using Random Amplified Polymorphic DNA (RAPD) markers and virulence on host differentials to assess the threat to Australian Stylosanthes cultivars from exotic races of this pathogen. A phenetic analysis of 90 isolates using RAPD markers showed a wide genetic diversity in the overall pathogen population. Compared to this, genetic diversity in the Australian population was very limited. A similar situation was noted for pathogenic variation where 43 of the 69 South American isolates could not be classified using linear discriminant functions developed using isolates of the current Australian races. Some isolates from Brazil caused serious anthracnose on Australian cultivars and accessions which are moderate to highly resistant to the Australian races. If accidentally introduced, these isolates may pose a potential threat to the Australian Stylosanthes cultivars.

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Variation in the Stylosanthes Anthracnose Pathogen: Implications for Australian Cultivars

Isolates of Colletotrichum gloeosporioides which cause anthracnose disease in the tropical pasture legume Stylosanthes were collected from its centre of diversity in South America. These and other isolates from Asia, Africa and Australia were studied using Random Amplified Polymorphic DNA (RAPD) markers and virulence on host differentials to assess the threat to Australian Stylosanthes cultivars from exotic races of this pathogen. A phenetic analysis of 90 isolates using RAPD markers showed a wide genetic diversity in the overall pathogen population. Compared to this, genetic diversity in the Australian population was very limited. A similar situation was noted for pathogenic variation where 43 of the 69 South American isolates could not be classified using linear discriminant functions developed using isolates of the current Australian races. Some isolates from Brazil caused serious anthracnose on Australian cultivars and accessions which are moderate to highly resistant to the Australian races. If accidentally introduced, these isolates may pose a potential threat to the Australian Stylosanthes cultivars.