scholarly journals Characterization and Distribution of Two Races of Phialophora gregata in the North-Central United States

2003 ◽  
Vol 93 (7) ◽  
pp. 901-912 ◽  
Author(s):  
T. C. Harrington ◽  
J. Steimel ◽  
F. Workneh ◽  
X. B. Yang
Keyword(s):  
Genetic Variation ◽  
Stem Rot ◽  
North Central ◽  
Brown Stem Rot ◽  
Phialophora Gregata ◽  
The North ◽  
Foliar Symptoms ◽  
Central United States ◽  
Soybean Plants ◽  
Xylem Discoloration

Genetic variation and variation in aggressiveness in Phialophora gregata f. sp. sojae, the cause of brown stem rot of soybean, was characterized in a sample of 209 isolates from the north-central region. The isolates were collected from soybean plants without regard to symptoms from randomly selected soybean fields. Seven genotypes (A1, A2, A4, A5, A6, M1, and M2) were distinguished based on DNA fingerprinting with microsatellite probes (CAT)5 and (CAC)5, with only minor genetic variation within the A or M genotypes. Only the A1, A2, and M1 genotypes were represented by more than one isolate. The A genotypes dominated in the eastern Iowa, Illinois, and Ohio samples, whereas the M genotypes were dominant in samples from western Iowa, Minnesota, and Missouri. In growth chamber experiments, isolates segregated into two pathogenicity groups based on their aggressiveness toward soybean cvs. Kenwood and BSR101, which are relatively susceptible and resistant, respectively, to brown stem rot. In both root dip inoculation and inoculation by injecting spores into the stem near the ground line (stab inoculations), isolates of the A genotypes caused greater foliar symptoms and more vascular discoloration than isolates of the M genotypes on both cultivars of soybean. All isolates caused foliar symptoms in both cultivars and in three additional cultivars of soybean with resistance to brown stem rot. Greater differences between the A and M genotypes were seen in foliar symptoms than in the linear extent of xylem discoloration, and greater differences were seen in Kenwood than in BSR101. Inoculation of these genotypes into five cultivars of soybean with different resistance genes to brown stem rot showed a genotype × cultivar interaction. A similar distinction was found in an earlier study of the adzuki bean pathogen, P. gregata f. sp. adzukicola, and consistent with the nomenclature of that pathogen, the soybean pathogens are named the aggressive race (race A) and the mild race (race M) of P. gregata f. sp. sojae.

scholarly journals Resistance to Phialophora gregata Is Expressed in the Stems of Resistant Soybeans

Plant Disease ◽  
2003 ◽  
Vol 87 (8) ◽  
pp. 970-976 ◽  
Author(s):  
G. M. Tabor ◽  
G. L. Tylka ◽  
S. C. Cianzio ◽  
C. R. Bronson
Keyword(s):  
Stem Length ◽  
Stem Rot ◽  
Growth Chamber ◽  
Inoculation Methods ◽  
Brown Stem Rot ◽  
Phialophora Gregata ◽  
Foliar Symptoms ◽  
Soybean Genotypes ◽  
Soybean Plants ◽  
Resistant Genotypes

Growth chamber experiments were conducted to determine if resistance to Phialophora gregata, the causal agent of brown stem rot (BSR) of soybean, is expressed in the stems of resistant soybean genotypes. Upon introduction of the pathogen into the base of stems of 2-week-old seedlings, the fungus advanced with the growing tips of plants of susceptible genotypes but lagged behind in resistant genotypes. Five weeks after introduction of the pathogen, both mean percent stem length colonized by P. gregata and mean percentage of symptomatic trifoliate leaflets were significantly less for resistant than for susceptible genotypes. These results indicate that resistance can be expressed in the stems of resistant soybean plants and suggest that stem inoculation methods may be useful for assessing resistance to P. gregata. Also, in our experiments, internal stem discoloration was not as useful as colonization and foliar symptoms in discriminating resistant from susceptible genotypes.

scholarly journals Regional Assessment of Soybean Brown Stem Rot, Phytophthora sojae, and Heterodera glycines Using Area-Frame Sampling: Prevalence and Effects of Tillage

1999 ◽  
Vol 89 (3) ◽  
pp. 204-211 ◽  
Author(s):  
F. Workneh ◽  
G. L. Tylka ◽  
X. B. Yang ◽  
J. Faghihi ◽  
J. M. Ferris
Keyword(s):  
Heterodera Glycines ◽  
Phytophthora Sojae ◽  
Soil Samples ◽  
Stem Rot ◽  
Population Densities ◽  
Brown Stem Rot ◽  
Phialophora Gregata ◽  
The North ◽  
No Till ◽  
Central United States

The prevalence of brown stem rot (caused by Phialophora gregata), Heterodera glycines, and Phytophthora sojae in the north central United States was investigated during the fall of 1995 and 1996. Soybean fields were randomly selected using an area-frame sampling design in collaboration with the National Agricultural Statistics Service. Soil and soybean stem samples, along with tillage information, were collected from 1,462 fields in Illinois, Iowa, Minnesota, Missouri, and Ohio. An additional 275 soil samples collected from Indiana were assessed for H. glycines. For each field, the incidence and prevalence of brown stem rot was assessed in 20 soybean stem pieces. The prevalence and recovery (expressed as the percentage of leaf disks colonized) of P. sojae and the prevalence and population densities of H. glycines were determined from the soil samples. The prevalence of brown stem rot ranged from 28% in Missouri to 73% in Illinois; 68 and 72% of the fields in Minnesota and Iowa, respectively, showed symptomatic samples. The incidence of brown stem rot was greater in conservation-till than in conventional-till fields in all states except Minnesota, which had few no-till fields. P. sojae was detected in two-thirds of the soybean fields in Ohio and Minnesota, whereas 63, 55, and 41% of the fields in Iowa, Missouri, and Illinois, respectively, were infested with the pathogen. The recovery rates of P. sojae were significantly greater (P ≤ 0.05) in conservation-till than in conventional-till fields in all states except Iowa. H. glycines was detected in 83% of the soybean fields in Illinois, 74% in Iowa, 71% in Missouri, 60% in Ohio, 54% in Minnesota, and 47% in Indiana. Both the prevalence and population densities of H. glycines were consistently greater in tilled than in no-till fields in all states for which tillage information was available.

scholarly journals Molecular Identification of Fungi Associated with Vascular Discoloration of Soybean in the North Central United States

Plant Disease ◽  
2000 ◽  
Vol 84 (1) ◽  
pp. 83-89 ◽  
Author(s):  
T. C. Harrington ◽  
J. Steimel ◽  
F. Workneh ◽  
X. B. Yang
Keyword(s):  
Dna Sequences ◽  
Selective Medium ◽  
Colony Morphology ◽  
Stem Rot ◽  
Internal Transcribed Spacer Region ◽  
Brown Stem Rot ◽  
Phialophora Gregata ◽  
The North ◽  
Vascular Discoloration ◽  
Central United States

Brown stem rot is a common but poorly understood vascular wilt disease of soybean. In order to more clearly delimit the causal agent (Phialophora gregata) and distinguish it from other morphologically similar fungi from discolored soybean stems, fungi were isolated on a semi-selective medium from discolored and non-discolored soybean stems collected at random across Iowa, Illinois, Minnesota, Missouri, and Ohio. A total of 11 fungi were commonly isolated and characterized based on colony morphology and DNA sequences of the internal transcribed spacer region of the rDNA operon. Phomopsis longicolla was the most frequently isolated fungus, but it was isolated more commonly from lightly discolored or non-discolored stems than from discolored stems. Phialophora gregata was the next most frequently isolated fungus and was isolated more commonly from discolored stems and more commonly in 1996 than in 1995, which had a warm growing season and relatively little brown stem rot. In inoculation experiments, only P. gregata was capable of causing the vascular discoloration and leaf symptoms typical of brown stem rot; none of the seven isolates could be considered non-defoliating. Two other fungi, Plectosphaerella cucumerina and Gliocladium roseum, were similar in colony morphology to Phialophora gregata but were not pathogenic to soybean, and these may be the same species as those referred to by earlier workers as Acremonium spp. or the non-defoliating form of P. gregata.

scholarly journals Genetic Variation of Sclerotinia sclerotiorum from Multiple Crops in the North Central United States

PLoS ONE ◽  
2015 ◽  
Vol 10 (9) ◽  
pp. e0139188 ◽  
Author(s):  
Laura Aldrich-Wolfe ◽  
Steven Travers ◽  
Berlin D. Nelson
Keyword(s):  
United States ◽  
Genetic Variation ◽  
Sclerotinia Sclerotiorum ◽  
North Central ◽  
The North ◽  
Central United States

scholarly journals Brown Stem Rot Resistance in Soybean Germ Plasm from Central China

Plant Disease ◽  
1997 ◽  
Vol 81 (8) ◽  
pp. 953-956 ◽  
Author(s):  
M. S. Bachman ◽  
C. D. Nickell ◽  
P. A. Stephens ◽  
A. D. Nickell
Keyword(s):  
Germplasm Collection ◽  
Central China ◽  
Stem Rot ◽  
Disease Assessment ◽  
Sources Of Resistance ◽  
University Of Illinois ◽  
Brown Stem Rot ◽  
Phialophora Gregata ◽  
Foliar Symptoms ◽  
Resistant Lines

Soybean accessions from China were screened in an attempt to identify unique sources of resistance to Phialophora gregata, the cause of brown stem rot. In 1994, over 500 accessions from the USDA Soybean Germplasm Collection, University of Illinois, Urbana-Champaign, were evaluated in the field at Urbana, IL, for reaction to brown stem rot. The accessions originated from nine provinces in central China and ranged in maturity from groups II to IV. Disease assessment was based on incidence of foliar symptoms and severity of stem symptoms produced by infection with natural inoculum. Based on field results, 64 putatively resistant lines were selected and evaluated in the greenhouse by a root-dip inoculation method. Thirteen accessions with levels of resistance equal to those of resistant standards were identified from five provinces. These lines may have value as donors of unique sources of resistance to brown stem rot.

scholarly journals Field Response of Glyphosate-Tolerant Soybean to Herbicides and Sudden Death Syndrome

Plant Disease ◽  
2001 ◽  
Vol 85 (7) ◽  
pp. 773-779 ◽  
Author(s):  
S. Sanogo ◽  
X. B. Yang ◽  
P. Lundeen
Keyword(s):  
Sudden Death ◽  
Field Experiments ◽  
Foliar Application ◽  
The United States ◽  
Sudden Death Syndrome ◽  
North Central ◽  
The North ◽  
Foliar Symptoms ◽  
Field Response ◽  
Soybean Plants

Three-year field experiments were conducted to assess the development of sudden death syndrome (caused by Fusarium solani f. sp. glycines) in three soybean cultivars, tolerant (P9344 and A3071) and nontolerant (BSR101), to glyphosate following foliar application of four herbicides (acifluorfen, glyphosate, imazethapyr, and lactofen) commonly applied to soybeans in the north-central region of the United States. Cultivar A3071 is resistant to sudden death syndrome, whereas cultivars P9344 and BSR101 are susceptible to this disease. There was no statistically significant cultivar-herbicide interaction with respect to the severity of foliar symptoms of the disease and the frequency of isolation of F. solani f. sp. glycines from roots of soybean plants. Across all herbicide treatments, the level of sudden death syndrome was lower in the disease-resistant cultivar than in the susceptible ones. There was an increase in the disease levels under application of acifluorfen, glyphosate, and imazethapyr compared with nontreated or lactofen-treated plants. The results obtained indicate that the response of glyphosate-tolerant soybeans to sudden death syndrome is not different from the response of conventional soybeans to this disease following application of the selected herbicides, and the resistance of soybean to sudden death syndrome was not changed with application of glyphosate.

scholarly journals Genotypes A and B of Cadophora gregata Differ in Ability to Colonize Susceptible Soybean

Plant Disease ◽  
2007 ◽  
Vol 91 (5) ◽  
pp. 574-580 ◽  
Author(s):  
G. M. Tabor ◽  
G. L. Tylka ◽  
C. R. Bronson
Keyword(s):  
Screening Method ◽  
Stem Length ◽  
Brown Stem Rot ◽  
Phialophora Gregata ◽  
Foliar Symptoms ◽  
Soybean Genotypes ◽  
Soybean Resistance ◽  
Soybean Plants ◽  
Resistant Genotypes ◽  
Genotype A

Growth chamber experiments were conducted to determine if extent of colonization of soybean stems by genotypes A and B of Cadophora gregata (Phialophora gregata), the causal agent of brown stem rot (BSR) of soybean, is similar in soybean plants resistant or susceptible to genotype A. Upon introduction of the two genotypes separately into the base of stems of 2-week-old seedlings, genotype A advanced with the growing tips of susceptible but not resistant genotypes. In contrast, genotype B did not advance with the growing tips of either resistant or susceptible soybean. In similar experiments, 5 weeks after introduction of genotype A, both mean percent stem length colonized by C. gregata and mean percentage of symptomatic trifoliate leaflets were significantly less for resistant than for susceptible genotypes. For genotype B, there was no or a slight difference between resistant and susceptible soybean genotypes in mean percent stem length colonized and no difference in mean percentage of symptomatic trifoliate leaflets 5 weeks after introduction of the pathogen. These results indicate that genotype A and genotype B differ not only in the severity of foliar symptoms they cause on genotype A-susceptible soybean plants, but also in how severely they colonize the stems of these soybean plants. In our experiments, genotype A and genotype B did not differ consistently in their ability to cause internal stem discoloration. The two genotypes of C. gregata can be distinguished based on how severely they colonize stems of genotype A-susceptible soybean. Thus, a BSR resistance screening method, which relies on assessment of stem colonization by C. gregata, works only for screening soybean lines resistance to genotype A. In light of these results, it is important to distinguish soybean resistance to genotype A versus genotype B of C. gregata. Whether genotype B causes yield loss and whether soybean plants can be distinguished as resistant or susceptible to genotype B needs to be investigated.

scholarly journals Prevalence of Sclerotinia Stem Rot of Soybeans in the North-Central United States in Relation to Tillage, Climate, and Latitudinal Positions

2000 ◽  
Vol 90 (12) ◽  
pp. 1375-1382 ◽  
Author(s):  
F. Workneh ◽  
X. B. Yang
Keyword(s):  
United States ◽  
Stem Rot ◽  
Sclerotinia Stem Rot ◽  
North Central ◽  
The North ◽  
No Till ◽  
Central United States ◽  
Zigzag Pattern ◽  
Tillage System ◽  
Investigation Period

Since the early 1990s, Sclerotinia stem rot, caused by Sclerotinia sclerotiorum, has caused considerable damage to soybean production in the north-central United States. To determine the extent of its distribution and associated factors, investigations were conducted in 1995 and 1996 in Illinois, Iowa, Minnesota, Missouri, and Ohio. Investigations also were conducted in 1997 and 1998 in Iowa, Minnesota, and Missouri. In each state, soybean fields were randomly selected in collaboration with the National Agricultural Statistics Service. From each field, 20 soybean stems 20 cm long (from the base) in 1995 and 1996 and full-length stems in 1997 and 1998 were sampled in a zigzag pattern. During the 4-year period, stem samples were collected from 1,983 fields and assessed for the presence or absence of the disease. Of the five states, Sclerotinia stem rot was most prevalent in north-central Iowa and southern Minnesota. Sclerotinia stem rot was not detected in Missouri during the 4-year investigation period. The disease was most prevalent in 1996 and least prevalent in 1995. The prevalence of the disease was strongly related to cumulative departures from normal maximum and minimum temperatures in July and August. The disease was more prevalent when yearly temperatures were below normal than when they were above normal. In 1996, a year with a cooler-than-normal summer, the disease was detected farther south than in 1995. In both years, the prevalence of the disease was exponentially related to latitudinal positions of the fields (R2 = 0.93 and 0.83 for 1995 and 1996, respectively) reflecting the effect of the north-south variations in temperature. During the 4-year period, there was no relationship between precipitation and the prevalence of the disease. The lack of relationship may suggest that there was no shortage of moisture since it is one of the primary factors for disease development. The prevalence of Sclerotinia stem rot was less in no-till than in minimum-till or conventional-till fields (P = 0.001 and 0.007, respectively) and greater in minimum-till than in conventional-till fields (P = 0.07). Fields that had Sclerotinia stem rot, however, did not differ in incidence of the disease regardless of the tillage system.

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