Geographic Distribution of Ophiosphaerella Species in the Mid-Atlantic United States

Spring dead spot (SDS) of bermudagrass (Cynodon dactylon) is primarily caused by Ophiosphaerella herpotricha and Ophiosphaerella korrae in North America. These two species respond differently to numerous management practices, grow optimally at different soil pH ranges, and differ in aggressiveness. Understanding the Ophiosphaerella species distribution in regions where SDS occurs will allow turfgrass managers to tailor their management practices toward the predominant species present. A survey was conducted in the Mid-Atlantic United States in which one to 14 samples of bermudagrass expressing SDS symptoms were taken from 51 athletic fields, golf courses, or sod farms across Delaware, Maryland, North Carolina, and Virginia. DNA was isolated from necrotic root and stolon tissue, amplified using species-specific primers, and detected in a real-time PCR assay. At least one isolate of O. herpotricha was recovered from 76% of the locations and O. korrae was recovered from 73% of the locations. Ophiosphaerella herpotricha was amplified from 55% of the samples while O. korrae was amplified from 37% of the samples. There were distinct regions in the Mid-Atlantic in which either O. herpotricha or O. korrae was predominant. Ophiosphaerella herpotricha was predominant in western Virginia, central North Carolina as well as Delaware and eastern Maryland. However, O. korrae was predominant in central Maryland and Virginia as well as eastern Virginia and North Carolina. Ophiosphaerella herpotricha was isolated from certain cultivars more frequently than O. korrae and vice versa. These survey results elucidate the geographic distribution of O. herpotricha and O. korrae throughout the Mid-Atlantic United States.

Graminicolous fungi from Poland. I. Fungi on halophyte Puccinellia distans

The host plant <i>Puccinellia distans</i> was found to be inhabited by the following fungi: <i>Acrospermum graminum, Cladosporium herbarum, Colletotrichum capsici, Dinemasporium slrigosum, Epichloë typhina, Guignardia graminicola, Ophiosphaerella herpotricha, Phaeosphaeria eustoma, Pleospora herbarum, Pyrenophora trichostoma, Puccinia brachypodii var. poae-nemoralis, Acrospermum graminum</i> and <i>Ophiosphaerella herpotricha</i> had not been earlier reported from Poland. On living stromata of <i>Epichloë typhina</i> a mycophilous <i>Alternaria</i> sp. was noted. Mycological data have been used to establish the allocation and relation of the genus <i>Puccinellia</i> with other similar grass genera.

Infection and Colonization of Turf-Type Bermudagrass by Ophiosphaerella herpotricha Expressing Green or Red Fluorescent Proteins

Spring dead spot, caused by Ophiosphaerella herpotricha, is the most important disease of turf-type bermudagrass (Cynodon spp.) in the transition zone of the United States. Despite the importance of the disease, only limited information is available about the host–pathogen interaction at the cellular level. To evaluate the host plant interaction, an isolate of O. herpotricha expressing green fluorescent proteins (GFP) or red fluorescent proteins (tdTomato) was used to study the infection and colonization of roots and stolons of several bermudagrass cultivars. Roots of cultivars Tifway 419 and Midlawn were colonized similarly, resulting in extensive root necrosis, whereas an accession of Cynodon transvaalensis was less necrotic. The stele of C. transvaalensis roots was colonized but not those of Tifway 419 and Midlawn. For intact stolons, colonization was limited to the epidermis and defined macroscopic necrotic lesions were observed on Tifway 419 and Midlawn while C. transvaalensis stolon tissues remained mostly nonnecrotic. Internal colonization of stolons occurred when hyphae grew into wounds, resulting in necrosis in Tifway 419 and Midlawn, but not in C. transvaalensis. These studies suggest that the interaction of O. herpotricha with bermudagrass varies across host genotypes and the host tissues infected. The limited necrosis in C. transvaalensis tissues, though colonized, suggests an inherent tolerance to O. herpotricha.

First Report of Ophiosphaerella herpotricha Causing Spring Dead Spot of Bermudagrass in Mississippi

Spring dead spot (SDS) is the most destructive disease of bermudagrass (Cynodon dactylon (L.) Pers.). Symptoms of SDS appear in the spring when bermudagrass transitions out of winter dormancy. These symptoms include depressed, straw-colored patches that range from several centimeters to a meter in diameter. Infected roots and rhizomes are black, brittle, and necrotic. The disease is caused by three species of fungi: Ophiosphaerella herpotricha (Fr:Fr) J. Walker; O. korrae (J. Walker & A.M. Smith) Shoemaker & C.E. Babcock; or O. narmari (J. Walker & A.M. Smith) Wetzel, Hubert & Tisserat. However, O. korrae is the most prevalent causal organism of SDS in the southeastern United States and was the only species reported in Mississippi (1). In April of 2006, root samples were collected from a bermudagrass putting green in Booneville, MS with a high level of SDS incidence and severity. Symptomatic roots were collected and surface disinfested in 0.6% NaOCl and plated on one-quarter-strength potato dextrose agar (PDA) amended with streptomycin sulfate and chloramphenicol. Hyphae growing from the roots were transferred to full-strength PDA after 5 to 7 days. Mycelium from five pure-culture colonies plus an O. herpotricha control was harvested after 4 weeks of growth and the genomic DNA was extracted. The genomic DNA of the Booneville isolates and the O. herpotricha control were amplified by PCR using species-specific primers OHITS1 and OHITS2 for O. herpotricha (2). Amplification of a 454-bp fragment of DNA confirmed one of the five unknown isolates as O. herpotricha. The other four isolates were not identified. ‘Sahara’ bermudagrass (4 weeks old in 3.8 × 20 cm Cone-tainers containing a sand and soil mixture) was inoculated with the Booneville-O. herpotricha isolate and the O. herpotricha control. One gram of oat seed infested with O. herpotricha isolates was inserted 2 cm below the crowns in the root zone of bermudagrass plugs. The inoculated bermudagrass plants were incubated for 4 weeks in the greenhouse. A control consisting of noninfested sterile oats was included. Following incubation, black, necrotic roots were observed on the plants inoculated with both O. herpotricha isolates. No symptoms were observed on roots of noninfested plants. Symptomatic roots were disinfested and plated on one-quarter-strength PDA. Koch's postulates were completed after O. herpotricha was reisolated from roots of plants inoculated with both O. herpotricha isolates and confirmed by PCR as mentioned above. The identification of O. herpotricha as a causal organism of SDS in Mississippi clarifies the involvement of multiple causal agents in this state and broadens the geographic distribution of this root-rot species. References: (1) F. B. Iriarte et al. Plant Dis. 88:1341, 2004. (2) N. A. Tisserat et al. Phytopathology 84:478, 1994.

Influence of Temperature and Time of Year on Colonization of Bermudagrass Roots by Ophiosphaerella herpotricha

The influence of temperature on the infection of bermudagrass seedlings by Ophiosphaerella herpotricha and colonization of plants in the field was investigated. Bermudagrass seedlings (cv. Jackpot) inoculated with O. herpotricha exhibited dark lesions after 8 days. Root lesion length was greatest at 17°C and was similar for all temperatures examined below 21°C. Seedlings grown at 25 or 30°C had small lesions that remained similar in size when evaluated at 8 and 10 days post inoculation. Colonization of bermudagrass roots from field plots were examined in July, October, and November of 2003 and 2004. In 2003, no differences between sampling dates were observed for plants sampled from the edge of the spring patch in 5.4-cm increments to a total distance of 21.6 cm. In 2004, July and October samples were similar; however, an increase in root colonization was found between the October and November samplings. These studies suggest that infection and colonization of bermudagrass roots by O. herpotricha occurs over a wide range of cool soil temperatures, occurs in the spring, and can be variable in the autumn.

Spring Dead Spot of Buffalograss Caused by Ophiosphaerella herpotricha in Kansas and Oklahoma

Buffalograss (Buchloe dactyloides) is widely planted in the Great Plains region of the United States as an amenity turfgrass. In May 1993, we observed circular dead spots in buffalograss lawns that were resuming growth following winter dormancy. The dead spots, 12 to 40 cm in diameter, were slowly filled in by buffalograss during the summer but reappeared in the same locations the following spring. Roots and stolons at the patch margins were colonized by darkly pigmented, ectotrophic fungal hyphae. Ophiosphaerella herpotricha, a cause of spring dead spot disease of bermudagrass (Cynodon spp.), was consistently isolated from diseased buffalograss roots collected in Kansas and Oklahoma. Identification of O. herpotricha was confirmed by the use of species-specific polymerase chain reaction (PCR) primers. To complete Koch's postulates, a 3-year-old stand of buffalograss cv. Sharp's Improved located in Manhattan, KS, was inoculated in September 1994 with O. herpotricha. Eleven soil cores, 10 cm in diameter × 8 cm deep, were removed at 1.2-m intervals across the turf. Five grams of oat seed infested with O. herpotricha (isolate KS221) wasadded to each hole and the soil plug was reinserted. For controls, 5 g of sterile oat seed was inserted in the bottom of each of 11 additional holes. No symptoms developed the following spring, but circular dead spots, ranging in size from 18 to 43 cm in diameter, were observed at 10 of 11 and 6 of 11 inoculation sites in May 1996 and 1997, respectively. No spots were noted in areas amended with sterile oats. O. herpotricha was consistently isolated from the roots at the margins of the patches. This is the first report of O. herpotricha causing spring dead spot in buffalograss.

Bermudagrass Resistance to Spring Dead Spot Caused by Ophiosphaerella herpotricha

Field and greenhouse studies were conducted to evaluate the resistance of seed- and vegetatively propagated bermudagrass entries (Cynodon spp.) to spring dead spot caused by Ophiosphaerella herpotricha. In Kansas greenhouse studies, O. herpotricha caused root discoloration and root weight reductions in all entries tested. However, in Kansas field plots, root weight reductions were not different among entries and were not correlated with disease severity ratings. In an inoculated field study in Oklahoma, diseased areas ranged from 47 cm2 for the entry Jackpot to 262 cm2 for Poco Verde in 1995, and from 121 to 1,810 cm2 for the entries Guymon and Common in 1996. African bermudagrass (Cynodon transvaalensis) exhibited the greatest number of live shoots per diseased area in both years, due in part to its greater shoot density, but also indicating greater potential to recover from the disease. African bermudagrass, Guymon, Sundevil, Midlawn, Midfield, Ft. Reno, Mirage, and several experimental seed-propagated entries were most resistant to spring dead spot, having the lowest diseased area and greatest number of live shoots within diseased areas. In Oklahoma, severity of spring dead spot among bermudagrass entries was correlated with feeeze injury that occurred during the first winter after planting.