Australasian Plant Pathology (1995) 24, 137-143

S. Denman, P.S. Knox-Davies, F.J. Calitz and S.C. Lamprecht (1995)
Pathogenicity of Pythium irregulare, P. sylvaticum and P. ultimum var. ultimum to lucerne (Medicago sativa)
Australasian Plant Pathology 24 (2), 137-143
Abstract: The ability of P. irregulare, P. sylvaticum and P. ultimum var. ultimum to induce damping-off of lucerne seedlings cv. SA Standard, grown in South Africa, was tested in artificially infested planting medium. Three levels of sand-bran inoculum were used: 5, 25 and 50 g inoculum/kg planting medium. All the 3 Pythium spp. caused >80% damping-off at each inoculum level and are therefore pathogenic to lucerne. There were differences in virulence among the species and isolates tested. P. sylvaticum was the most virulent, while P. irregulare was the least virulent species. The highest survival rates in inoculated soil were recorded for seedlings growing in soil containing the lowest levels of inoculum for each species tested. At the high inoculum levels (25 and 50 g/kg) (P. sylvaticum and P. ultimum var. ultimum), survival was so low that intra-species differences in virulence could no longer be detected. It is concluded that since there were differences in virulence among the species and isolates tested, it is important to test a number of isolates of a species before drawing conclusions about the pathogenicity of the species as a whole to a particular host, and to select appropriate levels of inoculum to elucidate these differences. This is thought to be the first valid report of P. sylvaticum as a pathogen of lucerne seedlings.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Sandra Denman, Sandra C. Lamprecht

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Globisporangium ultimum	Alfalfa/lucerne (Medicago sativa)	South Africa
	Globisporangium irregulare	Alfalfa/lucerne (Medicago sativa)	South Africa
	Globisporangium sylvaticum	Alfalfa/lucerne (Medicago sativa)	South Africa