Adaptation of Phytophthora nicotianae to multiple sources of partial-resistance in tobacco.

Plant Disease ◽  
2021 ◽  
Author(s):  
Jing Jin ◽  
Kestrel Lannon McCorkle ◽  
Vicki Cornish ◽  
Ignazio Carbone ◽  
Ramsey Lewis ◽  
...  
Keyword(s):  
Partial Resistance ◽  
Single Gene ◽  
Field Studies ◽  
Phytophthora Nicotianae ◽  
Multiple Sources ◽  
Rapid Loss ◽  
Sources Of Resistance ◽  
Black Shank ◽  
Race 1

Host resistance is an important tool in the management of black shank disease of tobacco. While race development leads to rapid loss of single-gene resistance, the adaptation by Phytophthora nicotianae to sources of partial resistance from Beinhart 1000, Florida 301, and the Wz gene region introgressed from Nicotiana rustica is poorly characterized. In greenhouse environments, host genotypes with QTLs conferring resistance from multiple sources were initially inoculated with an aggressive isolate of race 0 or race 1 of P. nicotianae. The most aggressive isolate was selected after each of six host generations to inoculate the next generation of plants. The race 0 isolate demonstrated a continuous gradual increase in disease severity and percent root rot on all sources of resistance except the genotype K 326 Wz/--, where a large increase in both was observed between generations two and three. Adaptation by the race 0 isolate on Beinhart 1000 represents the first report of adaptation to this genotype by P. nicotianae. The race 1 isolate did not exhibit significant increases in aggressiveness over generations, but also exhibited a large increase in aggressiveness on K 326 Wz/-- between generations 3 and 4. Molecular characterization of isolates recovered during selection was completed using ddRADseq, but no polymorphisms were associated with the observed changes in aggressiveness. The rapid adaptation to Wz resistance and the gradual adaptation to other QTLs highlights the need to study the nature of Wz resistance and for conducting field studies on efficacy of resistance-gene rotation for disease management.

Components of aggressiveness in Phytophthora nicotianae during adaptation to multiple sources of partial resistance in tobacco

Plant Disease ◽  
2020 ◽  
Author(s):  
Jing Jin ◽  
H. David Shew
Keyword(s):  
Partial Resistance ◽  
Single Gene ◽  
Phytophthora Nicotianae ◽  
Root Tip ◽  
Multiple Sources ◽  
Root Tips ◽  
Black Shank ◽  
Resistance Sources ◽  
Infected Root ◽  
Race 1

Black shank is a devastating disease of tobacco caused by Phytophthora nicotianae. Host resistance has been an integral part of black shank management, but after the loss of Php single-gene resistance following its widespread deployment in the 1990s, growers have relied on varieties with varying levels of partial resistance. Partial resistance is effective in suppressing disease, but continued exposure can result in an increase in pathogen aggressiveness that threatens durability of the resistance to P. nicotianae. Aggressiveness components in P. nicotianae were characterized following adaptation on two sources of partial resistance, Fla 301 and the Wz gene from Nicotiana rustica. An aggressive isolate of the two major races of P. nicotianae, race 0 and race 1, were adapted for either ‘one/two’ or ‘five/six’ generations on the two resistance sources, giving four sets of isolates based on race, number of generations of adaptation, and source of resistance. Across the four sets of isolates, adapted isolates infected higher proportions of root tips, produced more sporangia per infected root tip, and caused larger lesions than their respective non-adapted isolates of the same race and from the same resistance source. Adapted isolates also produced more aggressive zoospore progeny than the non-adapted isolates. Adaptation to partial resistance involves multiple aggressiveness components that results in the increased aggressiveness observed for P. nicotianae. These results improve our knowledge on the nature of P. nicotianae adaptation to partial resistance in tobacco and indicate that different resistance sources are likely to select for similar aggressiveness components in the pathogen.

scholarly journals Resistance to Phytophthora nicotianae in Tobacco Breeding Lines Derived from Variety Beinhart 1000

Plant Disease ◽  
2013 ◽  
Vol 97 (2) ◽  
pp. 252-258 ◽  
Author(s):  
Kestrel McCorkle ◽  
Ramsey Lewis ◽  
David Shew
Keyword(s):  
Partial Resistance ◽  
Phytophthora Nicotianae ◽  
Sources Of Resistance ◽  
Black Shank ◽  
Breeding Lines ◽  
Stem Resistance ◽  
Race 1 ◽  
Low Levels ◽  
Dh Lines ◽  
Rapid Emergence

Black shank, caused by Phytophthora nicotianae, is managed primarily by host resistance. The rapid emergence of race 1 eliminated the usefulness of available complete resistance, leading breeders to search for new sources of resistance. Cigar tobacco ‘Beinhart 1000’ (BH) is highly resistant to all races of P. nicotianae. Doubled-haploid (DH) lines from a cross of BH and the susceptible ‘Hicks’ were evaluated for black shank resistance, and quantitative trait loci (QTL) on linkage groups (LGs) 4 and 8 accounted for >43% of the phenotypic variation in resistance. Forty-three DH lines and parents were evaluated, and genotypes with one or both QTL from BH on LGs 4 and 8 had increased incubation periods and decreased root rot but higher final inoculum levels than genotypes with neither QTL. A low level of stem resistance was observed in BH and DH lines with the QTL from BH on LG 4 but not LG 8. Low levels of leaf resistance were seen for Hicks, BH, and DH lines with both QTL from BH on LG 4 and 8. The partial resistance from BH has not been used commercially and may provide an increase in level of partial resistance in future tobacco varieties.

scholarly journals Managing the Race Structure of Phytophthora parasitica var. nicotianae with Cultivar Rotation

Plant Disease ◽  
2005 ◽  
Vol 89 (12) ◽  
pp. 1285-1294 ◽  
Author(s):  
M. J. Sullivan ◽  
T. A. Melton ◽  
H. D. Shew
Keyword(s):  
Partial Resistance ◽  
Disease Incidence ◽  
Single Gene ◽  
Growing Season ◽  
Phytophthora Parasitica ◽  
Black Shank ◽  
Complete Resistance ◽  
Race 1 ◽  
High Level ◽  
Different Levels

Deployment of tobacco cultivars with single-gene, complete resistance to race 0 of the tobacco black shank pathogen, Phytophthora parasitica var. nicotianae, has resulted in a rapid increase in the occurrence of race 1 of the pathogen in North Carolina. Cultivar-rotation studies were conducted in three fields to assess how different levels and types of resistance affected the race structure and population dynamics of the pathogen when deployed in fields initially containing single or mixed races of the pathogen. In a field with both races present, a high level of partial resistance in cv. K 346 was most effective in reducing disease and decreasing the proportion of race 1 in the pathogen population. The deployment of complete resistance in cv. NC 71 resulted in intermediate levels of disease control and race 1 became the predominate race. The cv. K 326, with a low level of partial resistance, had the highest levels of disease, and race 0 was the dominant race recovered. In a field where no race 1 was detected initially, disease incidence was high with the use of partial resistance. Complete resistance was very effective in suppressing disease, but race 1 was recovered after only one growing season. By the end of the third growing season, race 1 was recovered from most treatments where single-gene resistance was deployed. A high level of partial resistance was most effective in suppressing disease in a field where race 1 initially was the predominant race. A rotation between cultivars with single-gene resistance and cultivars with a high level of partial resistance should provide the most effective approach to black shank management. This rotation will reduce disease incidence and minimize race shifts in the pathogen and, over time, should prolong the usefulness of the Ph gene for black shank control in commercial production of tobacco.

scholarly journals RNAseq Reveals Differential Gene Expression Contributing to Phytophthora nicotianae Adaptation to Partial Resistance in Tobacco

Agronomy ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 656
Author(s):  
Jing Jin ◽  
Rui Shi ◽  
Ramsey Steven Lewis ◽  
Howard David Shew
Keyword(s):  
Partial Resistance ◽  
Molecular Mechanisms ◽  
Biological Activities ◽  
Effective Means ◽  
Phytophthora Nicotianae ◽  
Economic Losses ◽  
Black Shank ◽  
Differential Gene ◽  
Go Terms

Phytophthora nicotianae is a devastating oomycete plant pathogen with a wide host range. On tobacco, it causes black shank, a disease that can result in severe economic losses. Deployment of host resistance is one of the most effective means of controlling tobacco black shank, but adaptation to complete and partial resistance by P. nicotianae can limit the long-term effectiveness of the resistance. The molecular basis of adaptation to partial resistance is largely unknown. RNAseq was performed on two isolates of P. nicotianae (adapted to either the susceptible tobacco genotype Hicks or the partially resistant genotype K 326 Wz/Wz) to identify differentially expressed genes (DEGs) during their pathogenic interactions with K 326 Wz/Wz and Hicks. Approximately 69% of the up-regulated DEGs were associated with pathogenicity in the K 326 Wz/Wz-adapted isolate when sampled following infection of its adapted host K 326 Wz/Wz. Thirty-one percent of the up-regulated DEGs were associated with pathogenicity in the Hicks-adapted isolate on K 326 Wz/Wz. A broad spectrum of over-represented gene ontology (GO) terms were assigned to down-regulated genes in the Hicks-adapted isolate. In the host, a series of GO terms involved in nuclear biosynthesis processes were assigned to the down-regulated genes in K 326 Wz/Wz inoculated with K 326 Wz/Wz-adapted isolate. This study enhances our understanding of the molecular mechanisms of P. nicotianae adaptation to partial resistance in tobacco by elucidating how the pathogen recruits pathogenicity-associated genes that impact host biological activities.

scholarly journals Effects of Chemical Control, Cultivar Resistance, and Structure of Cultivar Root System on Black Shank Incidence of Tobacco

Plant Disease ◽  
2010 ◽  
Vol 94 (5) ◽  
pp. 613-620 ◽  
Author(s):  
Dimitrios F. Antonopoulos ◽  
Thomas Melton ◽  
Asimina L. Mila
Keyword(s):  
Partial Resistance ◽  
Adventitious Roots ◽  
Early Stage ◽  
Laboratory Studies ◽  
Critical Factors ◽  
Cultivar Resistance ◽  
Black Shank ◽  
Initial Application ◽  
Race 1 ◽  
Tobacco Growth

Black shank, caused by the hemibiotrophic oomycete Phytophthora parasitica var. nicotianae, is a major disease of tobacco (Nicotiana tabacum). The rise of race 1 in the late 1990s, after extensive cropping of cultivars possessing the Php gene, confirming immunity to race 0 of P. parasitica var. nicotianae, imposed new challenges to black shank management. The effects of tobacco cultivars and chemical controls with mefenoxam (Ridomil Gold) on black shank incidence were investigated in naturally infested fields. Twenty-five cultivars were tested and the highest resistance for races 0 and 1 of P. parasitica var. nicotianae was provided by RJR 75 and SP 227 based on field and laboratory studies. When race 1 was prevalent, mefenoxam was effective to control black shank. An initial application at an early stage of tobacco growth, such as a few days before or after transplant, was essential to successfully control the disease. In greenhouse experiments, cultivars carrying the Php gene produced fewer and shorter adventitious roots than cultivars possessing only partial resistance to all races of P. parasitica var. nicotianae. Strategies such as use of mefenoxam, especially at an early stage, when adventitious roots are emerging, and planting a cultivar with high partial resistance or possessing the Ph gene when race 1 or race 0, respectively, predominates are critical factors in reducing loss due to P. parasitica var. nicotianae.

scholarly journals Characterization of Capsicum chinense Cultigens for Resistance to Meloidogyne arenaria, M. hapla, and M. javanica

Plant Disease ◽  
2001 ◽  
Vol 85 (3) ◽  
pp. 267-270 ◽  
Author(s):  
Judy A. Thies ◽  
Richard L. Fery
Keyword(s):  
High Resistance ◽  
Meloidogyne Incognita ◽  
Capsicum Chinense ◽  
Sources Of Resistance ◽  
Alternative Source ◽  
Highly Pathogenic ◽  
Habanero Pepper ◽  
Race 1 ◽  
Race 2

Four Capsicum chinense cultigens with known reactions to Meloidogyne incognita were characterized for resistance to M. arenaria races 1 and 2, M. hapla, and M. javanica, in greenhouse and growth-chamber tests. The M. incognita-resistant cultigens PA-353, PA-398, and PA-426 exhibited high resistance to M. arenaria race 1; the M. incognita-susceptible PA-350 was susceptible to M. arenaria race 1. M. arenaria race 2 and M. javanica were not highly pathogenic to any of the C. chinense cultigens. PA-353, PA-398, and PA-426, however, supported an average of 98.1 and 94.8% fewer (P < 0.05) M. arenaria race 2 and M. javanica eggs per gram fresh root, respectively, than PA-350. M. hapla was pathogenic to all four C. chinense cultigens. PA-353, PA-398, and PA-426 will be useful sources of resistance to M. arenaria races 1 and 2, M. javanica, and M. incognita, for developing resistant habanero pepper cultivars; however, an alternative source of resistance must be identified for M. hapla.

scholarly journals Population Structure, Mating Type, and Mefenoxam Sensitivity of Phytophthora nicotianae in Virginia Tobacco Fields

Plant Disease ◽  
2010 ◽  
Vol 94 (11) ◽  
pp. 1361-1365 ◽  
Author(s):  
V. Parkunan ◽  
C. S. Johnson ◽  
B. C. Bowman ◽  
C. X. Hong
Keyword(s):  
United States ◽  
Population Structure ◽  
Mating Type ◽  
Single Gene ◽  
The United States ◽  
Phytophthora Nicotianae ◽  
Species Identity ◽  
Single Strand Conformational Polymorphism ◽  
Black Shank ◽  
Major Mechanism

Black shank is an important disease of tobacco (Nicotiana tabacum) caused by the fungus-like organism, Phytophthora nicotianae. Three physiological races (0, 1, and 3) have been documented in the United States. Shifts in the pathogen population structure have become a concern due to the widespread use of cultivars possessing resistance to race 0 arising from a single gene (Php or Phl). A comprehensive statewide survey conducted throughout major tobacco-growing areas during summer 2006 and supplemented by additional isolates in 2007 and 2008 yielded 217 isolates from flue-cured, burley, and dark fire-cured tobacco fields. After determining species identity using a single-strand conformational polymorphism fingerprinting technique, the race identity of isolates was assessed via greenhouse tests using three differential cultivars (Hicks, L8, and NC1071). Approximately 76% of the isolates belonged to race 1, 21% to race 0, and the remaining 3% were race 3. This race structure was comparable with those in the other tobacco-producing states in the United States. Approximately 94% of isolates belonged to A2 mating type and merely 6% were A1. These data suggest that it is unlikely that sexual recombination serves as a major mechanism enhancing the genetic diversity of the pathogen in Virginia. All isolates were also evaluated against mefenoxam at 5 μg/ml. None were insensitive; 98% of isolates were either highly sensitive or sensitive and the remaining 2% were intermediately sensitive. These results indicate that mefenoxam remains effective for control of black shank in Virginia. The results of this study can assist breeders to develop cultivars possessing the most appropriate set of disease resistance traits, as well as extension specialists, county agents, and tobacco growers in their decision-making process to manage tobacco black shank in Virginia.

scholarly journals Characterization of the Black Shank Pathogen, Phytophthora nicotianae, Across North Carolina Tobacco Production Areas

Plant Disease ◽  
2018 ◽  
Vol 102 (6) ◽  
pp. 1108-1114 ◽  
Author(s):  
Courtney A. Gallup ◽  
Kestrel L. McCorkle ◽  
Kelly L. Ivors ◽  
David Shew
Keyword(s):  
North Carolina ◽  
Natural Populations ◽  
Hyphal Growth ◽  
The United States ◽  
The State ◽  
Phytophthora Nicotianae ◽  
Mating Types ◽  
Black Shank ◽  
Nuclear Regions

Black shank disease of tobacco, caused by the oomycete Phytophthora nicotianae, is a major threat to production in the United States and tobacco-producing areas worldwide. In a statewide survey of North Carolina, the rapid shift from race 0 to race 1 was documented. Collected pathogen isolates were characterized phenotypically for mating type and mefenoxam sensitivity, and genotypically by comparing sequences from three cytoplasmic and two nuclear regions. Both the A1 and A2 mating types were found throughout the state. When both mating types were recovered from the same field, pairings of isolates yielded viable oospores, indicating for the first time the potential for sexual sporulation by P. nicotianae in natural populations. Because the loss of complete resistance required a renewed use of the fungicide mefenoxam, a subset of the survey isolates was screened for sensitivity to the fungicide. All isolates were sensitive, with a mean effective concentration to inhibit 50% of hyphal growth of 0.4 μg/ml that was similar across mating types and races. Molecular characterization of 226 isolates revealed that the pathogen exists as multiple clonal types within the state. Genetic diversity among the pathogen population and the potential for sexual recombination may help explain the ability of the pathogen to rapidly adapt to host resistance genes.

scholarly journals Southern Blight (Sclerotium rolfsiiSacc.) of Cowpea: Genetic Characterization of Two Sources of Resistance

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Richard L. Fery ◽  
Philip D. Dukes
Keyword(s):  
Resistance Genes ◽  
Sclerotium Rolfsii ◽  
Field Studies ◽  
Sources Of Resistance ◽  
Frequency Distributions ◽  
Southern Blight ◽  
Segregation Data ◽  
Cowpea Cultivars ◽  
Dominant Genes

Field studies were conducted to characterize the genetic nature of resistance to southern blight (caused bySclerotium rolfsiiSacc.) exhibited by the cowpea [Vigna unguiculata(L.) Walp.] cultivars Carolina Cream and Brown Crowder and to determine if a genetic relationship exists for this resistance between the two cultivars. Examination of the comparative frequency distributions of the parental and progeny populations of the “Carolina Cream” x “Magnolia Blackeye” and “Brown Crowder” x “Magnolia Blackeye” crosses and the corresponding segregation data indicates that the southern blight resistances exhibited by “Carolina Cream” and “Brown Crowder” are conditioned by single dominant genes. Examination of the segregation data from the parental and progeny populations of the “Carolina Cream” x “Brown Crowder” cross suggests that the two resistance genes are not allelic. The availability of each of the resistance genes in cultivar-type genetic backgrounds should allow for rapid incorporation of southern blight resistance genes into other cowpea cultivars by the application of conventional plant breeding methodologies.

scholarly journals Characterization of Phytophthora nicotianae Resistance Conferred by the Introgressed Nicotiana rustica Region, Wz, in Flue-Cured Tobacco

Plant Disease ◽  
2018 ◽  
Vol 102 (2) ◽  
pp. 309-317 ◽  
Author(s):  
Kestrel L. McCorkle ◽  
Katherine Drake-Stowe ◽  
Ramsey S. Lewis ◽  
David Shew
Keyword(s):  
Lesion Size ◽  
Resistance Mechanisms ◽  
Phytophthora Nicotianae ◽  
Slight Reduction ◽  
Additional Source ◽  
Black Shank ◽  
Initial Inoculum ◽  
Complete Resistance ◽  
Host Generation

Black shank, caused by Phytophthora nicotianae, is one of the most important diseases affecting tobacco worldwide and is primarily managed through use of host resistance. An additional source of resistance to P. nicotianae, designated as Wz, has been introgressed into Nicotiana tabacum from N. rustica. The Wz gene region confers high levels of resistance to all races, but has not been characterized. Our study found Wz-mediated resistance is most highly expressed in the roots, with only a slight reduction in stem-lesion size in Wz genotypes compared with susceptible controls. No substantial relationships were observed between initial inoculum levels and disease development on Wz genotypes, which is generally consistent with qualitative or complete resistance. Isolates of P. nicotianae adapted for five host generations on plants with the Wz gene caused higher disease severity than isolates adapted on Wz plants for only one host generation. Wz-adapted isolates did not exhibit increased aggressiveness on genotypes with other sources of partial resistance, suggesting pathogen adaptation was specific to the Wz gene. To reduce potential for pathogen population shifts with virulence on Wz genotypes, Wz should be combined with other resistance sources and rotation of varying black shank resistance mechanisms is also recommended.

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