Studies on Oat-Attacking and Wheat-Attacking Isolates of Ophiobolus Graminis in Australia

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Differences in pathogenicity of various Ophiobolus graminis isolates have been observed frequently (Davis 1925; Padwick 1936; Hynes 1937; White and McIntyre 1943; Henry and Gilpatrick 1947; Henry and McKenzie 1959). However, most workers give little or no information about the interval between isolation and testing of pathogenicity, although it is evident some isolates have been in culture for long periods. As virulence may vary considerably with repeated subculturing (Russell 1934, 1939), it is possible that some studies have been made with cultural variants which do not exist in nature. This communication, therefore, describes tests using the initial growth from fresh monosporous field isolates of O. graminis.

Section: Methodsmentioning

confidence: 99%

Pathogenic Variation in Ophiobolus Graminis

Sc¹

1970

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“…However, in a pathogenicity test (Chambers and Flentje 1967a) the growth of runner hyphae along the roots of V. myuros was less extensive than those on H. leporinum roots. Nevertheless, V. myuros can be regarded as being moderately susceptible and survival of O. graminis on a host would therefore appear to depend on more than susceptibility alone.…”

Section: (B) Survival On Artificially Infected Materials In the Fieldmentioning

confidence: 99%

“…Two South Australian isolates, WI and W2, from Alford and Glen Osmond respectively, were used for studies with artificially infected material (Chambers and Flentje 1967a).…”

Section: (A) Isolates Of O Graminismentioning

confidence: 99%

Saprophytic Survival of Ophiobolus Graminis on Various Hosts

Chambers¹,

Flentje²

1968

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SummarySurvival of Ophiobolus graminis on artificially infected straw of several hosts was studied under field and laboratory conditions over a period of 24 weeks. Survival, estimated by percentage of straws containing viable hyphae of O. graminis, was greater on barley than on wheat, Hordeum leporinum, Lolium rigidum, and Vulpia myuros. Survival was higher under laboratory than summer field conditions, and in the field was greater at 1 than at 6 in. below the surface; survival was increased under laboratory conditions by nitrate enrichment of soil.In a field experiment, O. graminis was carried over at a high level on naturally infected Bromus gussonii, Hordeum hystrix, and H. leporinum, but not on Ehrharta calycina, L. rigidum, and V. myuros. Estimated yields of wheat sown after these grasses ranged from 18·8 to 4·0 bushels per acre for E. calycina and H. leporinum respectively.

“…The mean lengths of asci and ascospores from these perithecia in culture were greater than those of the asci and ascospores from field material from which the parent WI was originally isolated (cf. Chambers and Flentje 1967).…”

Section: (A) Colony Characteristics and Pathogenicity Of Monosporous mentioning

confidence: 99%

“…Wheat isolate WI (Chambers and Flentje 1967) and its progeny were used exclusively in these studies. Ascospores were cultured singly to give a range of monosporous isolates.…”

Section: (A) Isolatesmentioning

confidence: 99%

Studies on Variation with Ophiobolus Graminis

Chambers¹,

Flentje²

1967

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SummaryVariations were studied in the monosporous Fl progeny ot an isolate of Ophiobolus graminis from wheat. All Fl ascospores from perithecia on living host tissue were strongly pathogenic, but half from a perithecium in culture were weakly pathogenic. Perithecia were formed in culture and on host tissue only by strongly pathogenic progeny. Strongly pathogenic progeny survived well on artificially infected wheat straw buried in unsterilized soil, but weakly pathogenic progeny did not. Survival of all isolates was increased by nitrate enrichment of soil.