James W Buck

University of Georgia | UGA · Department of Plant Pathology

The objectives of this study were to assess the efficacy of various fungicides applied as root dips, soil drenches, or foliar sprays to daylily plants grown in containers and planted in the field to manage rust caused by Puccinia hemerocallidis. Soil drenches and foliar sprays were evaluated in field experiments in Griffin, GA in 2010 and 2011. Dip...

Gladiolus rust, caused by Uromyces transversalis, is a quarantine significant pathogen in the United States. However, the fungus is endemic to commercial gladiolus-producing areas in Mexico and has been intercepted frequently on gladiolus plants entering the United States for the cut-flower market. The present study assessed 15 fungicide active ing...

Phakopsora pachyrhizi is a fungal pathogen and the cause of Asian soybean rust. P. pachyrhizi was first detected in the continental USA in 2004 and has since been a threat to the soybean industry. There are six described loci that harbor resistance to P. pachyrhizi (Rpp) genes. The resistance of PI 423972 was previously shown to be within 5 cM of t...

Soft red winter wheat (SRWW) (Triticum aestivum L.) is a major crop in the southeastern region of the United States and in Georgia. Although wheat acreages have been decreasing in Georgia and the SE region in recent years, more than 100,000 ha were grown to SRWW in 2015. Newly released cultivars must have high yield potential, excellent resistance...

Wheat is the most important source of food, feed, and nutrition for humans and livestock around the world. The expanding population has increasing demands for various wheat products with different quality attributes requiring the development of wheat cultivars that fulfills specific demands of end-users including millers and bakers in the internati...

Frogeye leaf spot, caused by the fungus Cercospora sojina, is a threat to soybeans in the southeastern and midwestern United States that can be controlled by crop genetic resistance. Limited genetic resistance to the disease has been reported, and only three sources of resistance have been used in modern soybean breeding. To discover novel sources...

Southern stem canker (SSC) in soybean, caused by the fungal pathogen Diaporthe aspalathi, is a major disease in the southern United States. It can cause up to 80% yield loss in severely infected fields. PI 398469, a maturity group VI soybean accession from South Korea, is one of six known sources of resistance to SSC. To determine the genetics of t...

Host resistance is an effective and sustainable approach to manage the negative impact of Fusarium head blight (FHB) on wheat (Triticum aestivum L.) grain yield and quality. The objective of this study was to characterize the phenotypic responses and identify quantitative trait loci (QTL) conditioning different FHB resistance types using a panel of...

Soybean rust caused by Phakopsora pachyrhizi is one of the most important foliar diseases of soybean [ Glycine max (L.) Merr.]. Although seven Rpp resistance gene loci have been reported, extensive pathotype variation in and among fungal populations increases the importance of identifying additional genes and loci associated with rust resistance. O...

G11‐7013 (Reg. no. GP‐447, PI 699240) is a conventional maturity group (MG) VII soybean [Glycine max (L.) Merr.] line. It contains a 50% genetic background of an accession from South Africa by pedigree, with resistance to soybean cyst nematode race 3 (Heterodera glycines), southern root‐knot nematode (Meloidogyne incognita), and stem canker (Diapor...

In Georgia and the southeast region of the United States, acreage of soft red winter wheat (SRWW) (Triticum aestivum L.) has decreased in recent years. There is an urgent need to release new cultivars with high yield potential, resistance to yield‐limiting diseases and insects, and good baking quality to maximize value in regional markets. To addre...

Soft red winter wheat (SRWW) (Triticum aestivum L.), historically a major crop in Georgia and the U.S. Southeast (SE) region, has been challenged by numerous biotic and abiotic constraints resulting in decreased hectarage in recent years. Hence, an urgent need exists to release new cultivars with high yield potential, good resistance to predominant...

Frogeye leaf spot (FLS), caused by the fungal pathogen Cercospora sojina K. Hara, is a foliar disease of soybean (Glycine max L. (Merr.)) responsible for yield reductions throughout the major soybean producing regions in the world. In the United States, management of FLS relies heavily on the use of resistant cultivars and in-season fungicide appli...

Soft red winter wheat (SRWW) (Triticum aestivum L.) is a major crop in Georgia and the U.S. Southeast (SE) region. Hence, new cultivars with high yield potential, high resistance levels to predominant pests, and adequate quality parameters are required to capture and maximize regional market values. Therefore, the University of Georgia SRWW breedin...

Soft red winter wheat (SRWW) cultivar AGS 2038 has a high level of seedling and adult plant leaf rust (LR) resistance. To map and characterize LR resistance in AGS 2038, a recombinant inbred line (RIL) population consisting of 225 lines was developed from a cross between AGS 2038 and moderately resistant line UGA 111729. The parents and RIL populat...

Fusarium head blight (FHB) is one of the most troublesome fungal diseases challenging US wheat (Triticum aestivum L.) production (Savary et al. 2019). Harmful mycotoxin contamination, primarily due to deoxynivalenol (DON) in the Fusarium-damaged kernels (FDK), can negatively impact human and livestock health (McMullen et al. 1997). Although Fusariu...

Among the biotic constraints to wheat (Triticum aestivum L.) production, fusarium head blight (FHB), caused by Fusarium graminearum, leaf rust (LR), caused by Puccinia triticina, and stripe rust (SR) caused by Puccinia striiformis are problematic fungal diseases worldwide. Each can significantly reduce grain yield while FHB causes additional food a...

Fusarium graminearum is a cereal fungal pathogen causing Fusarium head blight (FHB) in wheat (Triticum aestivum L.), a major yield-limiting disease with serious food safety issues associated with mycotoxin Deoxynivalenol (DON) contamination. FHB has become an increasing problem in the southeast United States mainly due to increased corn (Zea mays L...

Uromyces transversalis , the causal agent of Gladiolus rust, is an invasive plant pathogen in the United States and is regulated as a quarantine pathogen in Europe. The aim of this research was to: (i) determine the origin of introductions of U. transversalis to the United States, (ii) track the movement of genotypes, and (iii) understand the world...

Core Ideas The emergence of new virulent Puccinia triticina races requires a continuous search for novel sources of resistance to combat leaf rust (LR) disease Twenty‐two wheat genotypes resistant to four P. triticina races were identified in this study A genome‐wide association study detected 11 quantitative trait loci for LR resistance; five of t...

Leaf rust (LR), caused by Puccinia triticina (Pt), is a major disease of wheat worldwide. Genetic resistance is the most effective, economic, and environmentally safe method to reduce losses caused by LR. Seventy-nine LR resistance genes have been identified so far; however, only a few of them are still effective due to the constant evolution of ne...

Soybean rust, caused by the fungal pathogen Phakopsora pachyrhizi, continues to be a global threat to soybean production, decreasing productivity and increasing the pesticide burden of cropping systems. However, breeders now have access to resistance genes that map to at least seven independent loci which can help protect crops against soybean rust...

Key message: A novel Rpp gene from PI 605823 for resistance to Phakopsora pachyrhizi was mapped on chromosome 19. Soybean rust, caused by the obligate biotrophic fungal pathogen Phakopsora pachyrhizi Syd. & P. Syd, is a disease threat to soybean production in regions of the world with mild winters. Host plant resistance conditioned by resistance t...

Disease resistance is critical in soft red winter wheat (Triticum aestivum L.) cultivars. Leaf rust caused by Puccinia triticina Eriks and stripe rust caused by Puccinia striiformis Westend. f. sp. tritici Eriks. are destructive pathogens of wheat. Phenotypic data were collected at diverse locations for resistance to leaf rust (North Carolina, Texa...

Soft red winter wheat (SRWW) (Triticum aestivum L.) is a major crop in Georgia and the southeastern region of the United States. Despite a decrease of wheat acreages in this region, about 100,000 ha were grown to SRWW in Georgia in 2015. To capture and maximize regional market value of wheat, the new released cultivars must have high yield potentia...

Soybean rust (SBR), caused by an obligate biotrophic basidiomycete fungus, Phakopsora pachyrhizi, arrived in the continental United States in 2004, where it has since proven to be detrimental to southern soybean [Glycine max (L.) Merr.] production due to yield losses, environmental concerns, and expenses caused by reliance on fungicides for control...

Key message: The Rpp6 locus of PI 567102B was mapped from 5,953,237 to 5,998,461 bp (chromosome 18); and a novel allele at the Rpp6 locus or tightly linked gene Rpp[PI567068A] of PI 567068A was mapped from 5,998,461 to 6,160,481 bp. Soybean rust (SBR), caused by the obligate, fungal pathogen Phakopsora pachyrhizi is an economic threat to soybean p...

Soybean rust (SBR) is caused by the fungal pathogen Phakopsora pachyrhizi and is considered to be the most destructive foliar disease of soybean [Glycine max (L.) Merr.], with soybean yield losses caused by SBR reported to be as high as 80% in severely diseased fields. Studies indicate that most isolates of P. pachyrhizi overcome at least one of th...

Soybean [Glycine max (L.) Merr.] rust is caused by the fungal pathogen Phakopsora pachyrhizi. Six rust resistance loci (Rpp1, 2, 3, 4, 5, and 6) have been reported. Crosses were made between 75 resistant plant introductions (PIs) and a susceptible elite line or cultivar. Bulked segregant analysis (BSA) was used to determine if the PI resistance gen...

Daylily (Hemerocallis spp.) is a popular herbaceous perennial plant and was considered to be relatively disease free until 2000, when daylily rust, caused by Puccinia hemerocallidis, was first detected in the United States. Management of daylily rust in nurseries is dependent on the use of fungicides, which are typically applied to the foliage of l...

Frogeye leaf spot (FLS), caused by the fungus Cercospora sojina K. Hara, may cause a significant yield loss to soybean growers in regions with a warm and humid climate. Two soybean accessions, PI 594891 and PI 594774, were identified to carry a high level of resistance similar to that conditioned by the Rcs3 gene in 'Davis'. Previously, we reported...

Key message Asian soybean rust (ASR) resistance gene Rpp2 has been fine mapped into a 188.1 kb interval on Glyma.Wm82.a2, which contains a series of plant resistance ( R ) genes. Abstract Asian soybean rust (ASR), caused by the fungus Phakopsora pachyrihizi Syd. & P. Syd., is a serious disease in major soybean [Glycine max (L.) Merr.] productio...

Between 2009 and 2012, 118 soybean [Glycine max (L.) Merr.] accessions from the USDA Soybean Germplasm Collection were screened for resistance to soybean rust (Phakopsora pachyrhizi) at up to five locations in the southeastern United States. In 2009, plant introductions (PIs) from maturity groups III through IX were evaluated for relative disease s...

Soybean rust (SBR), caused by Phakopsora pachyrhizi Syd. and P. Syd., is a threat to soybean [Glycine max (L.) Merr.], production in regions of the world where winters are not cold enough to completely eliminate the many hosts of the fungus, so resistant soybean cultivars would be useful in managing this disease. Resistant germplasm accessions have...

The occurrence of geranium rust (caused by Puccinia pelargonii-zonalis) in commercial greenhouses can result in unmarketable plants and significant eco-nomic losses. Currently, detection of geranium rust relies solely on scouting for symptoms and signs of the disease. The purpose of this research was to develop a rapid detection assay for P. pelarg...

Daylily rust, caused by Puccinia hemerocallidis, has been present in the United States since 2000. In 2003, inoculations with a single isolate of P. hemerocallidis identified daylily cultivars with high levels of resistance to the fungus. The present study was carried out to determine if pathotypes of P. hemerocallidis are present in the south east...

R iley' (Reg. No. CV-24, PI 663949), a canola-quality win-ter oilseed rape (Brassica napus L.), was tested under the experimental name KS4158 and developed by the Kansas Agricultural Experiment Station. Riley is named for Riley County, the county in which Kansas State University is located. Riley was publicly released in 2010 because of its disease...

Similar to other rust pathogens, P. hemerocallidis is an obligate parasite and requires a living host for growth and reproduction. P. hemerocallidis is a heteroecious fungus - two unrelated hosts are required to complete its life cycle (Figure 13). It is also considered a macrocylic rust because five different types of spores are produced in the co...

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is an important disease of soft red winter wheat in the eastern region of the USA. Pioneer 26R61 has provided effective resistance to stripe rust for 10 years. To elucidate the genetic basis of the resistance, a mapping population of 178 recombinant inbred lines (RILs) was developed using...

The presence of rusts of daylily and geranium caused respectively by Puccinia hemerocallidis and P. pelargoniizonalis can result in reduced value of these ornamental crops. Experiments were conducted to determine the effects of fluorescent light and sunlight on urediniospore germination, germ tube elongation, lesion development and sporulation of t...

Greenhouse experiments were conducted to evaluate the effect of post-symptomatic fungicide applications on urediniospore production of leaf rust of wheat, Puccinia triticina, and daylily rust, P hemerocallidis. Fungicides from five chemical classes were evaluated for their effect on urediniospore production at 24-h intervals post application for 96...

The effects of light on urediniospore germination and germ tube elongation was studied with eight species of rust fungi that infect ornamental plants or row crops. Exposure of six species of fungi to cool white fluorescent light at 400 or 600 micromol s(-1) m(-2) for 24 h significantly reduced germination with largest decreases typically observed a...

A growth-chamber experiment was conducted to determine how foliar disease or wounding affects the ability of 2 phylloplane yeasts (Rhodotorula glutinis and Cryptococcus laurentii) to colonize leaves of tall fescue (Festuca arundinacea). Yeasts were applied separately and together onto healthy leaves, leaves infected with Rhizoctonia solani (disease...

Previously known only from the southern United States, hosta petiole rot recently appeared in the northern United States. Sclerotium rolfsii var. delphinii is believed to be the predominant petiole rot pathogen in the northern United States, whereas S. rolfsii is most prevalent in the southern United States. In order to test the hypothesis that dif...

Six replicate trials were conducted to determine the short-term temporal dynamics and the effects of foliar applications of nutrients on the phylloplane yeast community of tall fescue (Festuca arundinacea Schreb.). In each trial, 2% sucrose + 0.5% yeast extract solution or sterile deionized water (control) was applied to the experiment plots. Twelv...

Four experiments were conducted to assess the effect of foliar applications of various nutrient solutions on the phylloplane yeast community of tall fescue (Festuca arundinacea Schreb.). In the first three experiments, increasing concentrations of sucrose (2-16%), yeast extract (0.5-2.5%), and sucrose plus yeast extract (2.5-18.5% total) were appli...

Outbreaks of rust caused by the fungus Puccinia pelargonii-zonalis on geraniums can result in large losses due to the plants' reduced aesthetic value and eradication efforts. To assess the potential risk of a rust outbreak in geranium production facilities, 77 commercial varieties of geranium were inoculated with a mixture of two isolates of P. pel...

Irrigation and an in vitro agitation assay were used to determine the percentage of the epiphytic yeast community (Cryptococcus, Pseudozyma, Rhodotorula, and Sporobolomyces) adhering to the phylloplane of creeping bentgrass (Agrostis palustris (Huds.) Pers.). Colony-forming units (cfu) of total epiphytic yeast populations (adherent and nonadherent...

The recent introduction and rapid spread of rust on daylilies, caused by Puccinia hemerocallidis, suggested a need for fungicide treatments that reduce urediniospore viability on plant surfaces. Twelve fungicides in seven chemical classes were evaluated in vitro for toxicity to urediniospores of rust fungi that occur on daylily (P. hemerocallidis),...

The ability of yeasts to attach to hyphae or conidia of phytopathogenic fungi has been speculated to contribute to biocontrol activity on plant surfaces. Attachment of phylloplane yeasts to Botrytis cinerea, Rhizoctonia solani, and Sclerotinia homoeocarpa was determined using in vitro attachment assays. Yeasts were incubated for 2 d on potato dextr...

Efficacy of the yeast Rhodotorula glutinis isolate PM4 as a biological control agent against 29 isolates of Botrytis cinerea obtained from greenhouse-grown ornamentals was assessed in vitro on geranium leaf disks. Isolates of B. cinerea varied in aggressiveness in the absence of either biological or chemical controls; diameters of lesions produced...

The effect of mechanical wounding or foliar diseases caused by Sclerotinia homoeocarpa or Rhizoctonia solani on the epiphytic yeast communities on creeping bentgrass and tall fescue were determined by leaf washing and dilution plating. Total yeast communities on healthy bentgrass and tall fescue leaves ranged from 7.9 x 103 to 1.4 x 105 CFU.cm-2 an...

Application of yeasts as biocontrol agents to prevent mold decay of fruits and vegetables has been described. We examined 10 yeasts for potential antagonistic activity against survival and growth of Salmonella Poona in cantaloupe juice and decay by Cladosporium cladosporioides and Geotrichum candidum in wounds on cantaloupe rind. Cantaloupe juice w...

Integrated disease management should provide the most effective means of controlling rusts on ornamental crops over time, and fungicides are an important component of an integrated rust management program. Proper timing of fungicide applications is critical for effective disease management; however, information about application timing is lacking f...

ABSTRACT Control of Botrytis cinerea on geranium seedlings was evaluated in treatments with phylloplane yeasts in combination with 10 fungicides used to manage Botrytis blight of ornamental plants. Rhodotorula glutinis PM4 significantly reduced the development of lesions caused by B. cinerea on geranium cotyledons; however, yeast biocontrol efficac...

Chrysanthemum white rust was introduced into England from Japan in 1963 (36). For more than twenty years an eradication campaign and quarantine measures were in place to prevent movement of the pathogen. These measures were ultimately unsuccessful and in 1989 the quarantine was lifted. Chrysanthemum white rust is now endemic in England (36). The ru...

Daylilies (Hemerocallis sp.) have traditionally been considered to be pest-free. However, a rust disease caused by Puccinia hemerocallidis Thüm. has become an in-creasing problem in the United States since 2000. The objective of this study was to evaluate daylily cultivars for resistance to daylily rust. From a greenhouse evaluation of 84 inoculate...

Powdery mildew has been a major concern for greenhouse growers. Acidic electrolyzed oxidizing (EO) water was evaluated for the management of powdery mildew on gerbera daisy. EO water significantly reduced percent powdery mildew when sprayed twice a week and when sprayed every other week, alternating with fungicides. Studies were completed to determ...

Experiments in controlled environments were completed to determine the influence of light intensity, temperature, and leaf wetness duration on daylily rust caused by Puccinia hemerocallidis. As light intensity increased, there was a significant decrease in urediniospore germination (R2 = 0.88 and Y = 96 - 0.6x). Urediniospores germinated in vitro b...

In response to the recent introduction and rapid spread throughout the United States of daylily rust caused by Puccinia hemerocallidis, research was conducted on the relative efficacy of seven fungicides (myclobutanil, propiconazole, flutolanil, triadimefon, chlorothalonil, mancozeb, and azoxystrobin) for control of this disease. Fungicides were ap...

Acidic electrolyzed oxidizing (EO) water quickly kills a variety of fungi and shows promise as a broad-spectrum contact fungicide for control of foliar diseases of greenhouse-grown ornamentals. One requirement for use in the greenhouse is that EO water will not cause excessive phytotoxic symptoms on a wide variety of species. In one experiment, two...

No single strategy will be successful in eliminating contamination of fresh produce and seed by human pathogenic bacteria, but a multi-pronged approach may reduce the risks of outbreaks. An integrated pest management model is likely to work for minimizing the risk of human pathogenic bacteria on seed and fresh produce. Accepted for publication 20 D...

The influence of inoculum and nutrient concentrations on the in vitro antagonism of Botrytis cinerea by phylloplane yeasts was investigated with detached leaf disk and conidial germination assays. Rhodosporidium toruloides Y-1091 significantly reduced lesion development after 96 h on geranium leaf disks when co-inoculated at 1 × 106 or 1 × 107 yeas...

The effects of fungicides on population size and the development of fungicide resistance in the phylloplane yeast flora of bentgrass was investigated. In the spring of 2001, azoxystrobin, chlorothalonil, flutolanil, and propiconazole were applied separately over a 6-week period to creeping bentgrass (Agrostis palustris Huds.). Total and fungicide-r...

Acidic electrolyzed oxidizing (EO) water, generated by electrolysis of a dilute salt solution, recently gained attention in the food industry as a nonthermal method for microbial inactivation. Our objective was to determine if EO water has potential to control foliar diseases in greenhouses. Test fungi suspended in distilled water were combined wit...

The physicochemical forces that mediate attachment of yeasts to the phylloplane are unknown. Cell surface charge and hydrophobicity and adhesion to polystyrene, glass, and barley were assessed for wild-type Rhodosporidium toruloides and attachment-minus (Att-) mutants. Cells were grown under conditions promoting (excess carbon) or not promoting (ex...

To investigate whether leaf-surface yeasts adhere to the phylloplane in a two-phase manner, with weak, nonspecific attachment followed by stronger, time-dependent adhesion, we observed adhesion kinetics of the basidiomycete yeast Rhodosporidium toruloides to barley. While 50-60% of the cells adhered in short-term assays (up to 3 h), fewer than 10%...