The adaptability of Phytophthora sojae to different types of soil determines the distribution of Phytophthora root rot of soybean in Heilongjiang Province of China

Phytophthora root rot, caused by Phytophthora sojae, is one of the most damaging diseases of soybean and the introgression of Rps (Resistance to P. sojae) genes into elite soybean lines is arguably the best way to manage this disease. Current bioassays to phenotype the gene-for-gene relationship are hampered with respect to reproducibility and long-term stability of isolates, and do not accurately predict horizontal resistance individually. The aim of our study was to investigate a new way of phenotyping P. sojae isolates and vertical and horizontal resistance in soybean that relies on zoospores inoculated directly into a hydroponic system. Inoculation of P. sojae isolates against a set of eight differentials accurately and reproducibly identified pathotypes over a period of two years. When applied to test vertical resistance of soybean lines with known and unknown Rps genes, the bioassay relied on plant dry weight to correctly identify all genes. In addition, simultaneous inoculations of three P. sojae isolates, collectively carrying eight major virulence factors against 64 soybean lines with known and unknown levels of horizontal resistance, separated the plants into five distinct groups of root rot, allowing the discrimination of lines with various degrees of partial resistance. Based on those results, this bioassay offers several advantages in facilitating efforts in breeding soybean for P. sojae resistance and in identifying virulence factors in P. sojae.

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Detached-petiole inoculation method to evaluate Phytophthora root rot resistance in soybean plants

Crop and Pasture Science ◽

10.1071/cp17158 ◽

2017 ◽

Vol 68 (6) ◽

pp. 555

Author(s):

Yinping Li ◽

Suli Sun ◽

Chao Zhong ◽

Zhendong Zhu

Keyword(s):

Root Rot ◽

Dominant Gene ◽

Phytophthora Sojae ◽

Single Dominant Gene ◽

Phytophthora Root Rot ◽

Inoculation Methods ◽

Inoculation Technique ◽

Soybean Cultivars ◽

F2 Population ◽

Soybean Resistance

Phytophthora root rot (PRR) caused by Phytophthora sojae, is one of the most destructive soybean diseases. The deployment of resistant cultivars is an important disease management strategy. To this aim, the development of a fast and effective method to evaluate soybean resistance to P. sojae is strategic. In this study, a detached-petiole inoculation technique was developed and its reliability was verified in soybean cultivars and segregant populations for PRR resistance. The detached-petiole and hypocotyl inoculation methods were used to assess the resistance of soybean cultivars, the F2 population of a Zhonghuang47 × Xiu94-11 cross, and the derived F2:3 population. The reactions of 13 analysed cultivars to three P. sojae isolates were consistent between the two inoculation techniques. The reactions of the F2 and F2:3 populations to isolate PsMC1 were 95.20% similar between the two inoculation methods. The segregation of the resistance and susceptibility fit a 3 : 1 ratio. Our results suggest that the detached-petiole technique is a reliable method, and reveal that the PRR resistance in Xiu94-11 is controlled by a single dominant gene. The phenotypic ratios of the tested Jikedou2 × Qichadou1 F2 population using the detached-petiole inoculation technique fit a 3 : 1 ratio (Resistance : Susceptibility). This demonstrated that Qichadou1 contains a single dominant gene conferring resistance to P. sojae. Our new detached-petiole inoculation technique is effective, reliable, non-destructive to the plant, and does not require an excessive amount of seeds. It may be suitable for the largescale screening of soybean resistance to multiple P. sojae isolates.

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Adaptation of Phytophthora sojae to Rps Resistance Genes over the Past Two Decades in North Dakota

Plant Health Progress ◽

10.1094/php-10-18-0062-rs ◽

2019 ◽

Vol 20 (2) ◽

pp. 88-93 ◽

Cited By ~ 3

Author(s):

Hui Yan ◽

Berlin Nelson

Keyword(s):

North Dakota ◽

Resistance Genes ◽

Root Rot ◽

Phytophthora Sojae ◽

Red River ◽

Phytophthora Root Rot ◽

Red River Valley ◽

The Past ◽

Primary Management ◽

New Strategies

Phytophthora root rot, caused by Phytophthora sojae, is a major disease of soybean in North Dakota, especially in the Red River Valley (RRV). Planting resistant cultivars is the primary management. The resistance genes Rps 1c, 1k, 3a, and 6 are the most common genes deployed in this region. To determine the efficacy of these genes and document the pathotype changes in the population of P. sojae over several decades, a survey of pathotypes was conducted in 2015 in three counties in the southern RRV and compared with similar surveys conducted in 1991 to 1994 and 2002 to 2004 in the same area. The results showed that from 1991 to 1994 when 6% of the pathotypes could defeat the Rps1c gene, by 2004 it was 57% of the pathotypes, and that percentage remained the same in 2015. However, in 1994 no pathotype could defeat Rps 1k, but by 2004 it was 12% and in 2015 it was 41%. Pathotypes that defeat Rps 3a and 6 have been few over the years. Pathotypes that defeat both 1c and 1k increased from none to 31% between 1994 and 2015. With the increasing complexity of P. sojae pathotypes, new strategies for managing this pathogen in the future will be needed.

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Races of Phytophthora sojae on Soybean in Illinois

Plant Health Progress ◽

10.1094/php-2000-0603-01-hn ◽

2000 ◽

Vol 1 (1) ◽

pp. 32

Author(s):

R. A. Leitz ◽

G. L. Hartman ◽

W. L. Pedersen ◽

C. D. Nickell

Keyword(s):

United States ◽

Glycine Max ◽

Root Rot ◽

The United States ◽

Phytophthora Sojae ◽

Phytophthora Root Rot ◽

Glycine Max L

Phytophthora root rot of soybean (Glycine max (L.) Merr.), caused by Phytophthora sojae M. J. Kauffmann & J. W. Gerdemann, has been isolated throughout the soybean-producing regions of the United States. Posted 3 June 2000.

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Development and Application of qPCR and RPA Genus- and Species-Specific Detection of Phytophthora sojae and P. sansomeana Root Rot Pathogens of Soybean

Plant Disease ◽

10.1094/pdis-09-16-1225-re ◽

2017 ◽

Vol 101 (7) ◽

pp. 1171-1181 ◽

Cited By ~ 20

Author(s):

J. Alejandro Rojas ◽

Timothy D. Miles ◽

Michael D. Coffey ◽

Frank N. Martin ◽

Martin I. Chilvers

Keyword(s):

Mitochondrial Genome ◽

Internal Control ◽

Root Rot ◽

Phytophthora Sojae ◽

Diagnostic Tools ◽

Specific Detection ◽

Phytophthora Root Rot ◽

Phytophthora Spp ◽

Field Season ◽

Species Specific

Phytophthora root rot of soybean, caused by Phytophthora sojae, is one of the most important diseases in the Midwestern United States, and is estimated to cause losses of up to 1.2 million metric tons per year. Disease may also be caused by P. sansomeana; however, the prevalence and damage caused by this species is not well known, partly due to limitations of current diagnostic tools. Efficient, accurate, and sensitive detection of pathogens is crucial for management. Thus, multiplex qPCR and isothermal RPA (recombinase polymerase amplification) assays were developed using a hierarchical approach to detect these Phytophthora spp. The assays consist of a genus-specific probe and two species-specific probes that target the atp9-nad9 region of the mitochondrial genome that is highly specific for the genus Phytophthora. The qPCR approach multiplexes the three probes and a plant internal control. The RPA assays run each probe independently with a plant internal control multiplexed in one amplification, obtaining a result in as little as 20 mins. The multicopy mitochondrial genome provides sensitivity with sufficient variability to discern among different Phytophthora spp. The assays were highly specific when tested against a panel of 100 Phytophthora taxa and range of Pythium spp. The consistent detection level of the assay was 100 fg for the qPCR assay and 10 pg for the RPA assay. The assays were validated on symptomatic plants collected from Michigan (U.S.) and Ontario (Canada) during the 2013 field season, showing correlation with isolation. In 2014, the assays were validated with samples from nine soybean producing states in the U.S. The assays are valuable diagnostic tools for detection of Phytophthora spp. affecting soybean.

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Races of Phytophthora sojae on Soybean in Illinois

Plant Disease ◽

10.1094/pdis.2000.84.4.487d ◽

2000 ◽

Vol 84 (4) ◽

pp. 487-487 ◽

Cited By ~ 37

Author(s):

R. A. Leitz ◽

G. L. Hartman ◽

W. L. Pedersen ◽

C. D. Nickell

Keyword(s):

Root Rot ◽

Genetic Resistance ◽

The United States ◽

Phytophthora Sojae ◽

Diseased Plant ◽

American Phytopathological Society ◽

Phytophthora Root Rot ◽

Glycine Max L ◽

New Race ◽

Soybean Diseases

Phytophthora root rot of soybean (Glycine max (L.) Merr.), caused by Phytophthora sojae M. J. Kauffmann & J. W. Gerdemann, has been isolated throughout the soybean-producing regions of the United States. There are more than 39 identified races of P. sojae pathogenic on soybean, and 13 host resistance alleles have been identified at 7 loci (1). None of these alleles confers resistance to all races of P. sojae. The most commonly used resistance allele, Rps1k, confers resistance to the greatest number of races (2). The objective of this study was to identify races of P. sojae in Illinois soybean fields to determine whether the currently used resistance alleles are effective against the P. sojae races found in Illinois. Soybean breeders must be aware of the existence and distribution of races to incorporate appropriate sources of genetic resistance into cultivars. From 192 soil samples collected throughout Illinois in 1997, 33 isolates were obtained and identified to race by inoculating Rps isolines of soybean cv. Williams. A new race with virulence to the Rps1d and Rps7 alleles, designated as race 54, accounted for 48% of the isolates. Another new race with virulence to Rps1d, Rps3a, Rps3c, Rps4, Rps5, Rps6, and Rps7 alleles, designated race 55, was identified in one sample. One isolate, identified as race 41, was obtained from a diseased plant with the Rps1k allele. Another isolate, identified as race 43, was obtained from a diseased plant with the Rps1c allele. Based on virulence patterns of P. sojae, most of the isolates obtained from Illinois soils were races 1, 3, and 4 or variants of these races, such as race 54, with added virulence to the Rps1d allele. References: (1) A. F. Schmitthenner. 1999. Compendium of Soybean Diseases. 4th ed. G. L. Hartman, J. B. Sinclair, and J. C. Rupe, eds. The American Phytopathological Society, St. Paul, MN. pp. 39‐42. (2) A. F. Schmitthenner, M. Hobe, and R. G. Bhat. Plant Dis. 78:269, 1994

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Multi-Year Evaluation of Commercial Soybean Cultivars for Resistance to Phytophthora sojae

Plant Disease ◽

10.1094/pdis-94-3-0368 ◽

2010 ◽

Vol 94 (3) ◽

pp. 368-371 ◽

Cited By ~ 22

Author(s):

T. L. Slaminko ◽

C. R. Bowen ◽

G. L. Hartman

Keyword(s):

Resistance Genes ◽

Root Rot ◽

Rapid Development ◽

Soybean Seed ◽

Phytophthora Sojae ◽

Primary Methods ◽

Phytophthora Root Rot ◽

Soybean Cultivars ◽

Information Program ◽

Poorly Drained Soils

Phytophthora sojae causes damping-off, root rot, and stem rot of soybean, particularly in poorly drained soils. Soybean cultivar resistance is one of the primary methods to control this disease, with Rps1c, Rps1k, and Rps1a being the most commonly used genes. The Varietal Information Program for Soybeans (VIPS) at the University of Illinois evaluates soybean cultivars for resistance to a number of diseases including Phytophthora root rot (PRR). The objectives of this research were to evaluate PRR resistance among commercial cultivars or advanced lines, and to compare these results with the information on PRR resistance provided by the company that entered the cultivar in VIPS. Each year from 2004 to 2008, between 600 and 900 cultivars were evaluated for resistance to either race 17 or 26 of P. sojae using the hypocotyl inoculation method. P. sojae single resistance genes were reported in 1,808 or 51% of the entries based on company information. Of these, the most commonly reported resistance genes were Rps1c (50%), Rps1k (40%), and Rps1a (10%). To a much smaller degree, companies reported using Rps3a (0.3%), Rps1b (0.2%), and Rps7 (0.2%). For the duration of the 5-year testing period, almost half of the cultivars (46%) were entered in VIPS with no reported resistance genes, and only nine out of a total of 3,533 entries (less than 0.3%) reported a stacked combination of resistance genes. Agreement between company-reported genes and any resistance found in the VIPS PRR evaluation was highest for those cultivars claiming to have Rps1c (90%) and Rps1k (83%), followed by Rps1a (70%). On average, 54% of the cultivars submitted to VIPS each year were new, reflecting the rapid development and turnover of soybean cultivars provided by the soybean seed companies.

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Cellulase Activity as a Mechanism for Suppression of Phytophthora Root Rot in Mulches

Phytopathology ◽

10.1094/phyto-04-10-0125 ◽

2011 ◽

Vol 101 (2) ◽

pp. 223-230 ◽

Cited By ~ 16

Author(s):

Brantlee Spakes Richter ◽

Kelly Ivors ◽

Wei Shi ◽

D. M. Benson

Keyword(s):

Root Rot ◽

Phytophthora Cinnamomi ◽

Cellulase Activity ◽

Enzyme Concentration ◽

Disease Suppression ◽

In Vitro Assays ◽

Infested Soil ◽

Phytophthora Root Rot ◽

Standard Curve

Wood-based mulches are used in avocado production and are being tested on Fraser fir for reduction of Phytophthora root rot, caused by Phytophthora cinnamomi. Research with avocado has suggested a role of microbial cellulase enzymes in pathogen suppression through effects on the cellulosic cell walls of Phytophthora. This work was conducted to determine whether cellulase activity could account for disease suppression in mulch systems. A standard curve was developed to correlate cellulase activity in mulches with concentrations of a cellulase product. Based on this curve, cellulase activity in mulch samples was equivalent to a cellulase enzyme concentration of 25 U ml–1 or greater of product. Sustained exposure of P. cinnamomi to cellulase at 10 to 50 U ml–1 significantly reduced sporangia production, but biomass was only reduced with concentrations over 100 U ml–1. In a lupine bioassay, cellulase was applied to infested soil at 100 or 1,000 U ml–1 with three timings. Cellulase activity diminished by 47% between 1 and 15 days after application. Cellulase applied at 100 U ml–1 2 weeks before planting yielded activity of 20.08 μmol glucose equivalents per gram of soil water (GE g–1 aq) at planting, a level equivalent to mulch samples. Cellulase activity at planting ranged from 3.35 to 48.67 μmol GE g–1 aq, but no treatment significantly affected disease progress. Based on in vitro assays, cellulase activity in mulch was sufficient to impair sporangia production of P. cinnamomi, but not always sufficient to impact vegetative biomass.

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Phytophthora Root Rot Resistance in Soybean E00003

Crop Science ◽

10.2135/cropsci2012.11.0631 ◽

2014 ◽

Vol 54 (2) ◽

pp. 492-499 ◽

Cited By ~ 9

Author(s):

Zhongnan Zhang ◽

Jianjun Hao ◽

Jiazheng Yuan ◽

Qijian Song ◽

David L. Hyten ◽

...

Keyword(s):

Root Rot ◽

Phytophthora Root Rot

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Genetic Mapping and Molecular Characterization of a Broad-spectrum Phytophthora sojae Resistance Gene in Chinese Soybean

International Journal of Molecular Sciences ◽

10.3390/ijms20081809 ◽

2019 ◽

Vol 20 (8) ◽

pp. 1809 ◽

Cited By ~ 7

Author(s):

Chao Zhong ◽

Yinping Li ◽

Suli Sun ◽

Canxing Duan ◽

Zhendong Zhu

Keyword(s):

Genetic Mapping ◽

Candidate Gene ◽

Broad Spectrum ◽

Genomic Region ◽

Phytophthora Sojae ◽

Genetic Population ◽

Phytophthora Root Rot ◽

Different Origins ◽

Lrr Domain

Phytophthora root rot (PRR) causes serious annual soybean yield losses worldwide. The most effective method to prevent PRR involves growing cultivars that possess genes conferring resistance to Phytophthora sojae (Rps). In this study, QTL-sequencing combined with genetic mapping was used to identify RpsX in soybean cultivar Xiu94-11 resistance to all P. sojae isolates tested, exhibiting broad-spectrum PRR resistance. Subsequent analysis revealed RpsX was located in the 242-kb genomic region spanning the RpsQ locus. However, a phylogenetic investigation indicated Xiu94-11 carrying RpsX is distantly related to the cultivars containing RpsQ, implying RpsX and RpsQ have different origins. An examination of candidate genes revealed RpsX and RpsQ share common nonsynonymous SNP and a 144-bp insertion in the Glyma.03g027200 sequence encoding a leucine-rich repeat (LRR) region. Glyma.03g027200 was considered to be the likely candidate gene of RpsQ and RpsX. Sequence analyses confirmed that the 144-bp insertion caused by an unequal exchange resulted in two additional LRR-encoding fragments in the candidate gene. A marker developed based on the 144-bp insertion was used to analyze the genetic population and germplasm, and proved to be useful for identifying the RpsX and RpsQ alleles. This study implies that the number of LRR units in the LRR domain may be important for PRR resistance in soybean.

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