Root and Stem Rot of Soybean Caused by Phytophthora Sojae N. Sp PDF Download
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Author: Maurice John Kaufmann
Publisher:
ISBN:
Category :
Languages : en
Pages : 154
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Author: Maurice John Kaufmann
Publisher:
ISBN:
Category :
Languages : en
Pages : 154
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Author: Richard Chemjor Kaitany
Publisher:
ISBN:
Category : Phytophthora sojae
Languages : en
Pages : 266
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Author: Thomas D. Wyllie
Publisher: American Phytopathological Society
ISBN:
Category : Science
Languages : en
Pages : 166
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Provides timely information on the major diseases affecting soybeans in the north central soybean growing area of the United States.
Author: Santiago Xavier Mideros Mora
Publisher:
ISBN:
Category : Phytophthora sojae
Languages : en
Pages : 252
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Abstract: Phytophthora root and stem rot caused by Phytophthora sojae, is a serious limitation to soybean production in the United States. Extensive deployment of Rps genes in soybean cultivars has led to adaptations in the P. sojae populations. Partial resistance to P. sojae in soybeans is effective against all races of the pathogen and is a form of incomplete resistance where the plant reduces the rate of colonization of the pathogen. In addition to partial resistance other types of incomplete resistance have also been described. Rps2 is a single dominant gene that confers incomplete resistance in soybean hypocotyls. Root resistance, thought to be quantitatively inherited, is another form of race specific resistance that appears to function only in the roots. In order to differentiate partial resistance from the other types of incomplete resistance that are race specific, components of resistance were analyzed and the cytology of infection compared. For this study attempts to genetically transform P. sojae to express a marker gene were unsuccessful. Three components were measured (lesion length, oospore production and infection frequency) in 8 soybean genotypes that were inoculated with non-transformed P. sojae isolates on the roots. Light and epifluorescent microscopy were used to study transversal cuts of Trypan blue stained root samples that were also inoculated with P. sojae. Soybean partial resistance was found to be composed of various components that interact to produce the partial resistance phenotype for defense against P. sojae in the roots. It was also found that the Rps2 and root resistant genotypes had significantly reduced levels for all of the components of resistance studied in comparison to the partially resistant genotype Conrad. However, the high levels of partial resistance in Jack were indistinguishable from the Rps2 reaction for all the components studied. In the cytology study it was found that P. sojae penetrates into all the soybean incomplete resistant genotypes: partial resistant, Rps2, and root resistant. Several mechanisms of resistance were observed: i) the resistance phenotype (Rpsla) contained the pathogen biotrophic growth from between 0 to 24 hal in a hypersensitive response; ii) Rps2 and root resistance phenotypes, also stopped growth of the pathogen but this occurred between 24 and 48 hal in a delayed hypersensitive response and iii) the partial resistance and the susceptible phenotypes allowed biotrophic colonization ofF. sojae. Finally a methodology to differentiate among mechanisms of incomplete resistance to P. sojae in soybean was identified based on the number of dead cells and extent of colonization that differed in partial resistance and Rps2 phenotypes.
Author: David Glenn Lohnes
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Diseases are a major factor limiting the yield of soybean (Glycine max (L.) Merr.). Brown stem rot of soybean, caused by Phialophora gregata (Allington and Chamberlain) W. Gams, and phytophthora root rot, caused by Phytophthora sojae Kaufmann & Gerdemann, are major diseases of soybean in Illinois. A gene for resistance to powdery mildew, caused by Microsphaera diffusa Cke. & Pk., has also been found to be linked to a gene for phytophthora resistance. A field study was conducted to determine yield differences between isolines carrying different alleles at the locus for powdery mildew resistance, greenhouse experiments were performed to study the inheritance of brown stem rot resistance, and laboratory experiments were conducted in attempts to find molecular markers linked to brown stem rot, phytophthora, and powdery mildew resistance in soybean. When isolines carrying alleles for powdery mildew resistance are compared, the resistant isolines yielded 7% more than the adult-plant resistant isolines. With this yield advantage, it would be advantageous to use complete resistance to powdery mildew as a marker to select for phytophthora resistance in a soybean breeding program. Classification of reaction to brown stem rot of soybean populations indicates that a Clark isoline contains Rbs3, and that a germplasm line deriving resistance from PI 90.138 contains Rbs1 and another unknown resistance gene. Molecular marker analysis of Harosoy and a Harosoy brown stem rot isoline did not produce any polymorphic markers. Clark, Harosoy, and Williams were screened with several RAPD primers to determine the random amplified polymorphic DNA (RAPD) variability present between these cultivars. The percentage of RAPD products in common was 94% for Clark and Williams, 90% for Clark and Harosoy, and 84% for Harosoy and Williams. The material cost of running a single RAPD reaction ranged from 21 to 76 cents. Linkage analysis of the restriction fragment length polymorphism and disease classification revealed that the loci studied are in classical linkage group 19 and RFLP linkage group J, in the most likely order Rps2 Rmd Rj2 pA233 pA724 pK375. This is the most agronomically important gene-dense region of the soybean molecular map identified to date.
Author: Martin Alan Draper
Publisher:
ISBN:
Category : Phytophthora diseases
Languages : en
Pages : 4
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Author: Robert F. Nyvall
Publisher:
ISBN:
Category : Phytophthora sojae
Languages : en
Pages : 4
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Author: Vinicius Castelli Garnica
Publisher:
ISBN:
Category : Herbicides
Languages : en
Pages : 142
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Soybean seedling diseases and Phytophthora stem and root rot (PSRR; caused by Phytophthora sojae) are two of the most economically important diseases in North Central U.S. Remarkable differences in disease incidence occur each year, which demonstrate that abiotic and biotic factors must interact for disease onset and development. During 2017 and 2018, field studies were conducted to (i) address the efficacy of seed treatment and genetic resistance for PSRR management on soybean population, canopy coverage (CC), and yield, and (ii) investigate potential interactions between pre-emergence (PRE) herbicides and the incidence of seedling diseases in alluvial soils in Nebraska. Despite field history, PSRR developed in only four of six environments studied. Commercial seed treatment had a positive effect on plant population density, CC, and yield in at least three environments. Compared to non-treated control, seed treatment increased emergence between 11,600 to 53,700 plants ha-1 and early-season CC between 0.7 to 1.2%. Under high disease pressure, management programs using moderately resistant cultivars improved yields when compared to moderately susceptible cultivars. By contrast, minimum yield differences were detected between Rps1k andRps1c genotypes, except in one environment. While a weak to moderate correlation was observed between CC and incidence of P. sojae symptomatic plants, a moderate to strong association was found between CC and yield. Across multiple environments, PRE herbicides chlorimuron-ethyl, metribuzin, saflufenacil, sulfentrazone, and flumioxazin had no impact on seedling root rot (disease severity index; DSI) when compared to the non-treated control. Similarly, no significant differences between PRE herbicides were detected on plant population, plant height, and yield. Community composition depicting primary pathogenic genera Fusarium, Phytophthora, Pythium, and Rhizoctonia did not occur at random but rather varied across environments and DSI classes. In two of the three environments, Phytophthorastructured approximately 22% of primary pathogenic genera, whereas, Rhizoctoniarecovery was low (
Author: Sirjana Devi Shrestha
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The oomycete Phytophthora sojae causes stem and root rot of soybean plants. The interaction of pathogen avirulence (Avr) and host resistance (R)-genes determine the disease outcome. The Avr3a mRNA transcript level is variable among P. sojae strains and determines virulence towards the R-gene Rps3a. To study the inheritance of virulence, genetic crosses and self-fertilizations were performed. A cross between P. sojae strains ACR10 and P7076 causes transgenerational gene silencing of Avr3a allele, and this effect is meiotically stable up to the F5 generation. However, test-crosses of F1 (Avr3aACR10/Avr3aP7076) with strain P6497 result in expression of Avr3a in all progeny and release of silencing of the Avr3aP7076 allele. Progeny from P6497 X ACR10 crosses showed unusual inheritance for Avr3a expression. Overall, we conclude that Avr3a gene silencing is strain specific and could rely on epistatic factors. This study will lead to a better understanding of infection and virulence mechanisms that will help to better manage and safeguard soybean production.
Author: Robert F. Nyvall
Publisher:
ISBN:
Category : Phytophthora sojae
Languages : en
Pages : 2
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