Use of a Seed Scarifier for Detection and Enumeration of Galls of Anguina and Rathayibacter Species in Orchard Grass Seed

Abstract

Seed galls, caused by Anguina spp., are normally detected visually in cereals such as wheat and barley. However, in grasses such as orchard grass, the presence of galls induced by Anguina or Rathayibacter spp. are difficult to detect visually due to their infrequent occurrence and masking by lemmas and paleas. To develop improved seed assays for the presence of the nematode and bacterial galls, a small scarifier was used to remove lemmas and paleas without causing major damage to seeds or galls. Following scarification, the galls were visually identified and manually counted under a dissecting microscope. Using the scarifier, several orchard grass seed lots were screened for Anguina and Rathayibacter spp. The percentage of samples of orchard grass seed harvested in the Willamette Valley of Oregon during 1996, 1997, and 2000 containing galls of Anguina sp. were 37, 46, and 48, respectively. The percentage of samples containing bacterial galls with Rathayibacter sp. was 27, 31, and 40, respectively. Total galls with Anguina sp. per 25 g of orchard grass sample ranged from 1 to 24. The mean of Anguina sp. galls per sample in 1996, 1997, and 2000 were 4, 5, and 5, respectively. Total galls with bacteria per 25 g of sample ranged from 27 to 40; mean number of galls per sample in 1996, 1997, and 2000 were, 6, 5, and 11, respectively. This is the first report confirming the presence of Rathayibacter sp. galls in orchard grass in Oregon.