Variation in morphology and pathogenicity of Pleiochaeta setosa isolates from Lupinus spp. and other legumes

Two morphological types of Pleiochaeta setosa are described from Australia, the lupin-type (isolates collected from Lupinus spp.), and the serradella-type (isolates collected from Ornithopus spp.). The lupin-type produces smaller conidia (64–70 × 17–19 μm) with 3–5 septa and 2–4 appendages. The terminal appendages are predominantly unbranched (91–100%). The serradella-type produces larger conidia (80–85 × 20–23 μm) with 4–6 septa and 3–5 appendages. A much higher proportion of the conidia of the serradella-type have branched terminal appendages (47–79%). The difference in conidial morphology between the two types is stable after cross-infection to opposite host plants and re-isolation. The delineation of the two Australian types is supported by random amplified polymorphic DNA (RAPD) analysis. The lupin-type is highly virulent to lupin, causing severe leaf infection and root rot, but is only weakly virulent to leaves and roots of serradella and biserrula (Biserrula pelecinus). The serradella-type is more virulent than the lupin-type to serradella and biserrula, causing severe disease on leaf, root and hypocotyl tissues. However, the serradella-type can also cause significant leaf, but not root, infection on lupin. Conidial morphology and RAPD analysis of isolates from other parts of the world reveal that additional types exist within the species P. setosa. The pathogenicity of imported cultures could not be determined due to quarantine restrictions.