Stacy A. Bonos

Transgenic creeping bentgrass with delayed dollar spot symptoms

Creeping bentgrass (Agrostis palustris Huds) is animportant turfgrass used on golf course greens and fairways. It is susceptibleto a number of fungal pathogens and requires considerable fungicide use fordisease control. Transgenic approaches may be useful in improving the level ofdisease resistance. We have generated transgenic creeping bentgrass plantsexpressing PR5K from Arabidopsis thaliana (L.) Henyh. PR5Kis a receptor protein kinase whose extracellular domain is homologous to thePR5family of pathogenesis-related proteins. In a field test of plants inoculatedwith the fungal pathogen dollar spot (Sclerotiniahomoeocarpa F.T. Bennett) four of the eight transgenic lines showeddelays in disease expression of 29 to 45 days, relative to the control plants.

Expression of pokeweed antiviral proteins in creeping bentgrass

Abstract. Fungal diseases of creeping bentgrass, an important amenity grass used extensively on golf courses, are a serious problem in golf course management. Transgenic approaches to improving disease resistance to fungal diseases are being explored in many species, and in some cases ribosome-inactivating proteins have been found to be effective. We have generated transgenic creeping bentgrass plants expressing three forms of ribosome-inactivating proteins from pokeweed, which are termed pokeweed antiviral proteins (PAP). PAP-Y and PAP-C are nontoxic mutants of PAP; PAPII is the native form of another ribosome-inactivating protein from pokeweed. In creeping bentgrass, PAP-C transformants did not accumulate the protein, suggesting that it is unstable, and in a field test these plants were not protected from infection by the fungal pathogen Sclerotinia homoeocarpa, the causal agent of dollar spot disease. PAPII transformants could accumulate stable levels of the protein but had symptoms of toxicity; one low-expressing line exhibited good disease resistance. PAP-Y transformants accumulated stable levels of protein, and under greenhouse conditions they appeared to be phenotypically normal.

Heritability of dollar spot resistance in creeping bentgrass.

ABSTRACT The dollar spot disease incited by Sclerotinia homoeocarpa is an important disease of creeping bentgrass (Agrostis stolonifera). Genetic resistance is an important control strategy and could reduce fungicide use. Despite recent research, the genetic mechanism of dollar spot resistance in turfgrasses is still not fully understood. The objectives of this study were to (i) determine narrow-sense heritability and predicted gain from selection for dollar spot resistance in creeping bentgrass and (ii) evaluate inheritance characteristics of dollar spot disease resistance. Inheritance characteristics such as the detection of major genes, heterosis, maternal effects, and combining ability were determined by evaluating the disease severity of progeny from crosses between resistant and susceptible bent-grass clones. Parental clones and progenies from crosses were established in a field trial in a randomized complete block design and inoculated with one isolate of S. homoeocarpa applied at a rate of 0.25 g m(-2) of prepared inoculum. Differences in progeny means between crosses were observed over both years. Progeny from resistant x resistant crosses had significantly less disease severity than resistant x susceptible and susceptible x susceptible crosses. High narrow-sense heritability estimates (0.79 [2002], 0.79 [2003]) and large mean squares for general combining ability support the idea that additive gene action plays a significant role in disease resistance and support previous research that dollar spot resistance is most likely quantitatively inherited.

Identification of a Gene in the Process of Being Lost from the Genus Agrostis

Lineage-specific gene loss is considered one of the processes contributing to speciation and genome diversity. Such gene loss has been inferred from interspecies comparisons of orthologous DNA segments. Examples of intraspecific gene loss are rare. Here we report identification of a gene, designated Crs-1 (creeping specific-1), that appears to be in the process of being lost from heterozygous populations of the species creeping bentgrass (Agrostis stolonifera). The Crs-1 gene encodes a protein with an N-terminal dirigent protein domain and a C-terminal lectin domain and is similar to the maize (Zea mays) β-glucosidase aggregating factor. Most individual creeping bentgrass plants examined are lacking Crs-1. Some individuals are hemizygous for the Crs-1 locus, indicating major haplotype noncolinearity at that locus. Crs-1 was not detected in several other Agrostis species, indicating it is being lost from the genus. The Crs-1 locus in creeping bentgrass provides a rare example of the evolutionary process of gene loss occurring within a plant species.

Colonial Bentgrass Genetic Linkage Mapping

Colonial bentgrass (Agrostis capillaris) is an important turfgrass species used on golf courses in temperate regions, although the related species, creeping bentgrass (A. stolonifera), is often preferred. One of the major management problems for creeping bentgrass is the fungal disease called dollar spot. Colonial bentgrass as a species has good resistance to dollar spot and may be a source of novel genes or alleles that could be used in the improvement of creeping bentgrass. As one approach to ultimately identifying the genes in colonial bentgrass that confer dollar spot resistance, we are developing a genetic linkage map of colonial bentgrass. To provide tools for mapping genes, we have generated expressed sequenced tag (EST) resources for both colonial and creeping bentgrass, and have developed a new approach to gene-based marker development.