Glufosinate-resistant transgenic creeping and velvet bentgrass plants expressing a bar gene under the control of the maize ubiquitin promoter were inoculated separately with the fungal pathogens, Rhizoctonia solani and Sclerotinia homoeocarpa, before or after treatment with 560 ing L-1 of glufosinate at a rate of 0.56 kg ha(-1). Application of the herbicide 3 h before or 1 d after fungal inoculation significantly reduced infection of these transgenic grasses by R. solani and S. homoeocarpa. Assessment of the in vitro antifungal activity of the herbicide showed that 336 and 448 mg L-1 glufosinate completely inhibited the mycelial, growth of S. homoeocarpa and R. solani, respectively. The results suggest that the nonselective herbicide glufosinate may also be used to suppress the activity of some fungal pathogens in turf composed of these transgenic glufosinate-resistant creeping and velvet bentgrasses.

Bacterial wilt of Poa annua has been seen increasingly in the Northeast and mid-Atlantic United States in the past few years. The disease causes severe injury to putting greens and can kill large stands of turfgrass. For some time, however, both the bacterial origin of the disease and the causal agent were in doubt. In order to investigate the identity of the causal agent, isolation of the pathogen was undertaken and pathogenicity was confirmed using Koch's postulates on P. annua. Additional pathogenicity trials then were undertaken to determine the host range of the causal bacterium. Ability of the bacterium to cause disease was restricted to P. annua var. annua and P. attenuata. However, the bacterium was able to survive asymptomatically in vascular systems of P. annua var. reptans and P. trivialis. Experiments to determine the optimal growth temperature of the organism demonstrated that the bacterial growth peaked between 30 and 35°C. Fatty acid analysis suggested that the bacterium might be a species of Xanthomonas but was inconclusive. Ribosomal RNA analysis demonstrated significant similarity to the American Type Culture Collection isolate of Xanthomonas translucens pv. poae at 99.8%. Comparison of the host range to previously reported data agrees with our molecular findings and indicates that the likely casual organism of bacterial wilt of annual bluegrass is X. translucens pv. poae.

Glufosinate-resistant transgenic creeping and velvet bentgrass plants expressing a bar gene under the control of the maize ubiquitin promoter were inoculated separately with the fungal pathogens, Rhizoctonia solani and Sclerotinia homoeocarpa, before or after treatment with 560 mg L−1 of glufosinate at a rate of 0.56 kg ha−1. Application of the herbicide 3 h before or 1 d after fungal inoculation significantly reduced infection of these transgenic grasses by R. solani and S. homoeocarpa. Assessment of the in vitro antifungal activity of the herbicide showed that 336 and 448 mg L−1 glufosinate completely inhibited the mycelial growth of S. homoeocarpa and R. solani, respectively. The results suggest that the nonselective herbicide glufosinate may also be used to suppress the activity of some fungal pathogens in turf composed of these transgenic glufosinate-resistant creeping and velvet bentgrasses.

A construct containing a rice chitinase gene and an alfalfa glucanase gene was co-transferred with a construct containing a bar gene as a selectable marker into creeping bentgrass using microprojectile bombardment. PCR analysis confirmed the presence of bar in the genomic DNA of transformed plants. Most of the transgenic plants were consistently resistant to 0.5–4.0% Finale® (a commercial brand of herbicide glufosinate, ammonium salt of phosphinothricin). The integration of the chitinase and glucanase genes into genomes of eight lines and the bar gene into all tested lines was confirmed by Southern hybridization analyses. Northern hybridization analyses indicated that the bar gene was transcribed in 15 transgenic lines at the mRNA level and that the chitinase gene was transcribed in 5 transgenic lines, but no glucanase mRNA was detectable. The frequency of the linked co-transfer of chitinase and glucanase genes was 100%, and the frequency of the unlinked co-transfer of the bar and chitinase/glucanase genes was 50–79%. The glufosinate-resistant transgenic lines exhibited resistance to fungal pathogens, Sclerotinia homoeocarpa and Rhizoctonia solani, when 0.5% Finale® was sprayed 3 h before the pathogen inoculation. When no Finale® was applied, the five transgenic lines expressing the chitinase gene were not resistant to the pathogens.

Plant pathogenic bacteria are singlecelled, usually rod-shaped organisms that re p roduce at an extraordinarily high rate by b i n a ry fission. (In binary fission, the pare n t cell divides to form two similar daughter cells, which also divide to form two more cells each, and so on.) Most bacteria have rigid cell walls, and some are motile by means of flagella. Because bacteria have no means of penetrating cells, they must enter plants through natural openings such as stomata and hyd a t h o d e s ( a p e rt u res in plant surfaces, usually leave s , t h rough which liquid is secreted) or thro u g h wounds. Once inside plants, bacteria cause damage by enzyme activity, toxin pro d u c t i o n and vascular plugging. By occluding xylem vessels, they interrupt water transport, causing plants to wilt and eventually die. Ba c t e r i a l diseases are uncommon in turfgrasses. In fact, bacterial wilt of creeping bentgrass (Ag ro s t i s

Isolates of Colletotrichum graminicola from annual blue grass and creeping bent grass were investigated for their morphological characteristics, host specificity, and genetic relatedness. One isolate from maize and one from sorghum (C. sublineolum) were included for comparison. Recently isolated cultures of C. graminicola from annual blue grass were readily distinguished from those isolated from creeping bent grass on the basis of pigmentation. Differences in appressoria size and shape were found only between the turf grass isolates and those from maize and sorghum. Spore length varied significantly between host groups. Differences in host range and virulence were also apparent. In general, isolates from creeping bent grass incited disease on both creeping bent grass and annual blue grass, while those from annual blue grass essentially were limited to host. Random amplified polymorphic DNA (RAPD) marker analysis of C. graminicola isolates from turf grass revealed that a high degree of genetic similarity exists among isolates recovered from the same host, but exceptions were found. Therefore, an absolute distinction between isolates recovered from two turf grass hosts could not be made based on RAPD markers.

JACKSON, N., and P. H. DERNOEDEN. 1980. Sclerophthora macrospora: The incitant of yellow tuft disease of turf grasses. Plant Disease 64:915-916. were used. Two soil pH levels were included because of a report that pH may affect zoospore germination (5). Cylinders containing five seeds of each species were placed on both soils in sufficient number to allow three replications of each of four inoculum treatments designated 0, X, 2X, and 3X using zoospores from Agropyron repens. Inoculum comprising 0.5 ml of zoospore suspension (about 10,000 spores) was withheld (0), applied once (X), twice (2X), or three times (3X) over a 3-day period to the appropriate cylinders. The water level in the soil containers (and hence in the cylinders) was held just above the level of the seeds during this period, and the temperature was maintained at 15 C. After 3 days, excess water was drawn off, and the seedlings were placed under diffuse light on a window bench at prevailing laboratory temperatures. Infection of the plants was determined after 2-3 wk by inspecting leaf and/or crown tissue with a microscope for the presence of the distinctive S. macrospora mycelium (4). Tissues were cleared in boiling 5% potassium hydroxide solution,