Seed Transmission of Cephalosporium gramineum in Winter Wheat

Timothy D Murray

doi:10.1094/PD-90-0803

Although isolation of Cephalosporium gramineum from wheat (Triticum aestivum) seed has been reported, development of Cephalosporium stripe in plants from infected seed has not been demonstrated experimentally. Winter wheat seed was collected from three experimental field plots where Cephalosporium stripe was present, and C. gramineum was isolated from the seed following surface-disinfection and incubation on a semi-selective medium. C. gramineum was isolated from 0.10 to 0.88% of seed from 11 of 12 cultivars in a field experiment at Pullman, WA, and from 0.10 to 0.30% of seed from 3 of 4 genotypes in a field experiment at Fort Hall, ID; differences among cultivars were not significant in either experiment. C. gramineum was isolated from 0.35 and 0.55% of cv. Stephens plants with no symptoms and severe symptoms, respectively, from a uniform seeding in Pullman. Seed of the four genotypes from Fort Hall and Stephens from Pullman were grown under controlled environment in a soilless potting mix with no added inoculum and in which C. gramineum was not detected. Symptoms of Cephalosporium stripe developed in 0.08 and 0.17% of Stephens and breeding line 87-00314A plants, respectively, from Fort Hall, and from 0.18 and 0.55% of Stephens plants with no symptoms and severe symptoms, respectively. Although development of Cephalosporium stripe in plants grown from seed lots harvested from diseased plants was low, infected seed can provide an important source of inoculum for introducing the pathogen and initiating epidemics in areas where the pathogen did not occur previously. Cephalosporium stripe is a vascular wilt disease of winter wheat and other cereal crops as well as several grasses. In fields where the disease is established, the pathogen survives a few years between susceptible crops in colonized plant residue in soil and produces spores that are washed into soil and infect plant roots. Because this pathogen was isolated from seed when the disease was first described, it was assumed that the pathogen was also seed transmitted (i.e., able to survive in seed and infect the plant that developed), but conclusive experimental evidence for this was never published. Seed transmission could provide a source of inoculum for the establishment of the pathogen in areas where it doesn't occur and possibly for the initiation of epidemics. Consequently, this research tried to answer the question “Can this pathogen be transmitted from infected seed to plants grown from that seed, and if so, what might be the potential impact?” Seed was collected from plants with Cephalosporium stripe from three different field plots, two in Washington State and one in Idaho, and evaluated for the amount of seed infection and whether the pathogen was transmitted to plants grown from the seed. Seed lots known to have infected seed were planted in pots with a potting mix in which the pathogen did not occur, and a small percentage of the plants that grew developed disease, thereby demonstrating conclusively that the pathogen can be seed transmitted. Although the rate of transmission was too low to initiate an epidemic in the first year of introduction, it was high enough to establish the pathogen in fields where it was not present and produce enough infected plants to initiate an epidemic in subsequent crops.

Seed Transmission of Cephalosporium gramineum in Winter Wheat

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