Marsha Browning

Pathogenicity of the entomopathogenic fungus Metarhizium anisopliae (Deuteromycetes) to Ixodes scapularis (Acari: Ixodidae).

The entomopathogenic fungus Metarhizium anisopliae is highly pathogenic to the black-legged tick, Ixodes scapularis. Spore concentrations of 10(8)/ml for engorged larvae and 10(7)/ml for engorged females resulted in 100% tick mortality, 2 wk postinfection. The LC50 value for engorged larvae (concentration to kill 50% of ticks) was 10(7) spores/ml. Metarhizium anisopliae shows considerable potential as a microbial control agent for the management of Ixodes scapularis.

Co-transfer and expression of chitinase, glucanase, and bar genes in creeping bentgrass for conferring fungal disease resistance

Abstract 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.

Morphological, pathogenic, and genetic comparisons of Colletotrichum graminicola isolates from poaceae

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.

Glufosinate reduces fungal diseases in transgenic glufosinate-resistant bentgrasses (Agrostis spp.)

Abstract 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. Nomenclature: Glufosinate; phosphinothricin; creeping bentgrass, Agrostis palustris Huds. AGSPL; velvet bentgrass, Agrostis canina L. AGSCN.