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51. Phytophthora megakarya and Phytophthora palmivora, Closely Related Causal Agents of Cacao Black Pod Rot, Underwent Increases in Genome Sizes and Gene Numbers by Different Mechanisms

Author

Ali, Shahin S., primary, Shao, Jonathan, additional, Lary, David J., additional, Kronmiller, Brent A., additional, Shen, Danyu, additional, Strem, Mary D., additional, Amoako-Attah, Ishmael, additional, Akrofi, Andrew Yaw, additional, Begoude, B.A. Didier, additional, ten Hoopen, G. Martijn, additional, Coulibaly, Klotioloma, additional, Kebe, Boubacar Ismaël, additional, Melnick, Rachel L., additional, Guiltinan, Mark J., additional, Tyler, Brett M., additional, Meinhardt, Lyndel W., additional, and Bailey, Bryan A., additional

Published
2017
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53. Cacao Diseases : A History of Old Enemies and New Encounters / edited by Bryan A. Bailey, Lyndel W. Meinhardt.

Author

Bailey, Bryan A. editor., Meinhardt, Lyndel W. editor., SpringerLink (Online service), Bailey, Bryan A. editor., Meinhardt, Lyndel W. editor., and SpringerLink (Online service)

Abstract

This book reviews the current state of knowledge concerning cacao pathogens and methods for their management. Topics discussed include the history, biology and genetic diversity of Moniliophthora (which causes witches’ broom and frosty pod rot) and Phytophthora species (which causes black pod rot) that cause diseases resulting in major losses to cacao production. Emerging pathogens such as Cacao swollen shoot virus and Ceratobasidium theobromae (which causes vascular streak dieback) are also discussed in detail, along with many pathogens of significant local concern. Most of these pathogens represent major risks to global cacao production should they expand into new areas, breaking out of their current limited distributions. By considering cacao diseases as a group, similarities in the available tools and techniques used in their management become apparent, as do their limitations. Gaps in our current knowledge of cacao pathogens and the management of the diseases they cause are detailed, and suggestions for future research directions are provided. This insight allows readers to consider cacao disease threats from a more comprehensive, global perspective and paves the way for an improved synergy of efforts between the various research programs, agencies, and industries, both private and public, with vested interests in cacao production, and cacao farmers.

Published
2016

55. Biology and genomics of Phytophthora spp.: fight against a potential global chocolate famine [W115]

Author

Ali, Shahin, Amoako-Attah, Ishmael, Shao, Jonathan, Bailey, Rebecca, Strem, Mary, Phillips, Wilbert, Surujdeo-Maharaj, Surendra, Marelli, Jean-Philippe, Ten Hoopen, Gerben Martijn, Goss, Erica, Villela Dias, Cristianao, Shen, Danyu, Tyler, Brett, Meinhardt, Lyndel W., Bailey, Bryan, Ali, Shahin, Amoako-Attah, Ishmael, Shao, Jonathan, Bailey, Rebecca, Strem, Mary, Phillips, Wilbert, Surujdeo-Maharaj, Surendra, Marelli, Jean-Philippe, Ten Hoopen, Gerben Martijn, Goss, Erica, Villela Dias, Cristianao, Shen, Danyu, Tyler, Brett, Meinhardt, Lyndel W., and Bailey, Bryan

Abstract

Theobroma cacao is currently under serious threat due to various diseases, of which Phytophthora pod rot, commonly called 'black pod' is one of the most economically important. Four fungal species of the same genus are primarily responsible for this disease: P. palmivora, P. megakarya, P. capsici and P. citrophthora. Among these, P. palmivora is the most common, being present in most cacao producing countries. P. palmivora can cause yield losses of 20-30% and tree mortality of 10% annually. P. megakarya occurs only in West African countries, but is the most virulent among the four species. In Africa it causes 30-90% annual crop losses and thus it poses a severe threat to the cacao industry and to producers in Africa. Both in vitro pod husk inoculation assays and in planta pod inoculation assays verified that P. megakarya was more aggressive. Studies suggest effective early penetration by P. megakarya makes it a more destructive pathogen. Since the Phytophthora species that cause disease on cacao differ so much in their virulence, we developed specific primers for QPCR identification of each species. At the same time we characterized the genetic diversity of P. palmivora and P. megakarya in Ghana, a major producer. Through further genetic analysis, we estimate the genome size of P. megakarya to be 116.9 Mb and the P. palmivora genome size to be 100 Mb. P. palmivora appears to be tetraploid whereas P. megakarya, despite its larger genome, is not. Comparative genome analysis between these two species shows that both species carry large numbers of plant-pathogen interaction proteins including the RxLR effectors. An in-depth comparative analysis of genomics and transcriptomics between these two closely related species is being carried out to highlight the molecular mechanism behind their virulence and support the development of effective control measures. This is critical since Phytophthora spp. in general and P. megakarya specifically, represent a significant threat to

Published
2015

56. Molecular markers for cacao traits

Author

Motilal, Lambert A., Zhang, Dapeng, Umaharan, Pathmanathan, Boccara, Michel, Meinhardt, Lyndel W., and Lanaud, Claire

Subjects
F60 - Physiologie et biochimie végétales, food and beverages, F30 - Génétique et amélioration des plantes
Abstract

Seventy-one microsatellites and 82 SNP markers were examined for their association with flush colour, shell content, seed butterfat content, fruit butterfat content, dry mass of cotyledons in a seed and dry mass of cotyledons from a fruit in 145 cacao accessions drawn from Refractario and Forastero groups. The more reliable markers were obtained when a vector matrix of multidimensional similarities rather than a matrix of population composition was utilised as a system screen. Fifteen markers (five SNPs and 10 SSRs) were found over six linkage groups (chromosomes 1, 2, 4, 5, 7 and 9). Each marker accounted for 10 - 43% of the phenotypic variation. Three markers (mTcCIR250, mTcCIR251 and SNP836) appeared fairly robust. The microsatellite mTcCIR250, present on chromosome nine, accounted for a substantial 34.1% of variation in the cotyledonary mass of a fruit. The microsatellite mTcCIR251, located on the same chromosome, tagged both the cotyledonary mass and butterfat content of a fruit explaining 43.4% and 41.7% of the variation respectively. The marker SNP836, present on chromosome 2, tagged both fruit butterfat content and cotyledonary dry mass in a seed explaining 12% and 11% of the total variation respectively. (Texte intégral)

Published
2012

63. Genome and secretome analysis of the hemibiotrophic fungal pathogen, Moniliophthora roreri, which causes frosty pod rot disease of cacao: mechanisms of the biotrophic and necrotrophic phases

Author

Meinhardt, Lyndel W, primary, Costa, Gustavo Gilson, additional, Thomazella, Daniela PT, additional, Teixeira, Paulo José PL, additional, Carazzolle, Marcelo, additional, Schuster, Stephan C, additional, Carlson, John E, additional, Guiltinan, Mark J, additional, Mieczkowski, Piotr, additional, Farmer, Andrew, additional, Ramaraj, Thiruvarangan, additional, Crozier, Jayne, additional, Davis, Robert E, additional, Shao, Jonathan, additional, Melnick, Rachel L, additional, Pereira, Gonçalo AG, additional, and Bailey, Bryan A, additional

Published
2014
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65. Genetic analyses of Rhizoctonia solani isolates from Phaseolus vulgaris grown in the Atlantic Rainforest Region of São Paulo, Brazil

Author

MEINHARDT, LYNDEL W., WULFF, NELSON A., BELLATO, CLÁUDIA M., and TSAI, SIU M.

Subjects
telomere, genetic biodiversity, soil-borne fungi, Mata Atlântica, food and beverages, ITS
Abstract

Rhizoctonia solani isolates obtained from common beans (Phaseolus vulgaris) grown in the mountainous Atlantic Rainforest (Mata Atlântica) region of São Paulo, Brazil, were analyzed to determine their genetic diversity using internal transcribed spacer (ITS), microsatellite and telomere sequence-based PCR primers. Restriction digestion of the ITS1/5.8S/ITS2 ribosomal regions yielded unique banding patterns specific for AG4 and its subgroups. The ITS restriction digestion (ITS/RFLP), telomere and microsatellite primers identified five to 11 genotypes within the isolates of R. solani. While all isolates were pathogenic on beans, there was no correlation found between genotypic differences and pathogenicity. The different PCR primers revealed a number of isolates that were genetically similar. Some of these genetic groups were supported by more than one of the primers utilized in this study, thus confirming their relationship. A diversidade genética de 18 isolados de Rhizoctonia solani de feijoeiro (Phaseolus vulgaris) cultivado na Mata Atlântica de São Paulo, Brasil foi avaliada através da análise do espaçadores transcritos internos (ITS), microssatélites e iniciadores ("primers") específicos para sequências teloméricas. A análise de restrição da região ribossomal ITS1/5,8S/ITS2 produziu um padrão de bandas específico para o grupo de anastomose 4 (GA 4) e seus subgrupos. O padrão obtido com ITS/RFLP, microsatélites e os iniciadores teloméricos permitiram identificar cinco a 11 genótipos entre os isolados de R. solani. Enquanto todos os isolados foram patogênicos em feijoeiro, não houve correlação entre patogenicidade e diferenças genotípicas. Os diferentes iniciadores para PCR revelaram que muitos isolados são geneticamente similares, análise esta que pode ser confirmada por mais de um conjunto de iniciadores, fortalecendo a relação deste agrupamento.

Published
2002

66. Global analyses of Ceratocystis cacaofunesta mitochondria: from genome to proteome

Author

Ambrosio, Alinne Batista, primary, do Nascimento, Leandro Costa, additional, Oliveira, Bruno V, additional, L Teixeira, Paulo José P, additional, Tiburcio, Ricardo A, additional, Toledo Thomazella, Daniela P, additional, Leme, Adriana F P, additional, Carazzolle, Marcelo F, additional, Vidal, Ramon O, additional, Mieczkowski, Piotr, additional, Meinhardt, Lyndel W, additional, Pereira, Gonçalo A G, additional, and Cabrera, Odalys G, additional

Published
2013
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68. A potential role for an extracellular methanol oxidase secreted by Moniliophthora perniciosa in Witches’ broom disease in cacao

Author

de Oliveira, Bruno V., primary, Teixeira, Gleidson S., additional, Reis, Osvaldo, additional, Barau, Joan G., additional, Teixeira, Paulo José P.L., additional, do Rio, Maria Carolina S., additional, Domingues, Romênia R., additional, Meinhardt, Lyndel W., additional, Paes Leme, Adriana F., additional, Rincones, Johana, additional, and Pereira, Gonçalo A.G., additional

Published
2012
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71. The mitochondrial genome of Moniliophthora roreri, the frosty pod rot pathogen of cacao

Author

Costa, Gustavo G.L., primary, Cabrera, Odalys G., additional, Tiburcio, Ricardo A., additional, Medrano, Francisco J., additional, Carazzolle, Marcelo F., additional, Thomazella, Daniela P.T., additional, Schuster, Stephen C., additional, Carlson, John E., additional, Guiltinan, Mark J., additional, Bailey, Bryan A., additional, Mieczkowski, Piotr, additional, Pereira, Gonçalo A.G., additional, and Meinhardt, Lyndel W., additional

Published
2012
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72. The hemibiotrophic cacao pathogen Moniliophthora perniciosa depends on a mitochondrial alternative oxidase for biotrophic development

Author

Thomazella, Daniela P. T., primary, Teixeira, Paulo José P. L., additional, Oliveira, Halley C., additional, Saviani, Elzira E., additional, Rincones, Johana, additional, Toni, Isabella M., additional, Reis, Osvaldo, additional, Garcia, Odalys, additional, Meinhardt, Lyndel W., additional, Salgado, Ione, additional, and Pereira, Gonçalo A. G., additional

Published
2012
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73. Regulation of Lysine Metabolism and Endosperm Protein Synthesis by the Opaque-5 and Opaque-7 Maize Mutations.

Author

Azevedo, Ricardo A., Lea, Peter John, Damerval, Catherine, Landry, Jacques, Bellato, Cláudia M., Meinhardt, Lyndel W., Le Guilloux, Martine, Delhaye, Sonia, Varisi, Vanderlei A, Gaziola, Salete A., Gratão, Priscila Lupino, Toro, Alejandro A., Azevedo, Ricardo A., Lea, Peter John, Damerval, Catherine, Landry, Jacques, Bellato, Cláudia M., Meinhardt, Lyndel W., Le Guilloux, Martine, Delhaye, Sonia, Varisi, Vanderlei A, Gaziola, Salete A., Gratão, Priscila Lupino, and Toro, Alejandro A.

Abstract

Two high lysine maize endosperm mutations, opaque-5 (o5) and opaque-7 (o7), were biochemically characterized for endosperm protein synthesis and lysine metabolism in immature seeds. Albumins, globulins, and glutelins, which have a high content of lysine, were shown to be increased in the mutants, whereas zeins, which contain trace concentrations of lysine, were reduced in relation to the wild-type lines B77xB79+ and B37+. These alterations in the storage protein fraction distribution possibly explain the increased concentration of lysine in the two mutants. Using two-dimensional polyacrylamide gel electrophoresis of proteins of mature grains, variable amounts of zein polypeptides were detected and considerable differences were noted between the four lines studied. The analysis of the enzymes involved in lysine metabolism indicated that both mutants have reduced lysine catabolism when compared to their respective wild types, thus allowing more lysine to be available for storage protein synthesis.

Published
2004

74. Genetic control of lysine metabolism in maize endosperm mutants.

Author

Azevedo, Ricardo A., Damerval, Catherine, Lea, Peter J., Landry, Jacques, Bellato, Cláudia M., Meinhardt, Lyndel W., Le Guilloux, Martine, Delhaye, Sonia, Toro, Alejandro A., Gaziola, Salete A., Varisi, Vanderlei A., Gratão, Priscila Lupino, Azevedo, Ricardo A., Damerval, Catherine, Lea, Peter J., Landry, Jacques, Bellato, Cláudia M., Meinhardt, Lyndel W., Le Guilloux, Martine, Delhaye, Sonia, Toro, Alejandro A., Gaziola, Salete A., Varisi, Vanderlei A., and Gratão, Priscila Lupino

Abstract

The capacity of three maize endosperm opaque mutants (o10, o11 and o13) to accumulate soluble lysine in the seed in relation to their wildtype counterpart, W22+, was investigated. The W22o13 and W22o11 mutants exhibited 278% and 186% increases in soluble lysine, respectively, while for W22o10, a 36% decrease was observed, compared with the wildtype. A quantitative and qualitative study of the N constituents of the endosperm has been conducted and data obtained for the total protein, non-protein N, soluble amino acids, albumins / globulins, zeins and glutelins present in the seed of the mutants. Following 2D–PAGE, a total of 38 different forms of zein polypeptides were detected and considerable differences were noted between the three mutant lines. The metabolism of lysine was also studied by analysis of the enzymes aspartate kinase, homoserine dehydrogenase, lysine 2-oxoglutarate reductase and saccharopine dehydrogenase, which exhibited major changes in activity, depending on the genotype, suggesting that the mutant genes may have distinct regulatory activities.

Published
2004

78. Genes Acquired by Horizontal Transfer Are Potentially Involved in the Evolution of Phytopathogenicity in Moniliophthora perniciosa and Moniliophthora roreri, Two of the Major Pathogens of Cacao

Author

Tiburcio, Ricardo Augusto, primary, Costa, Gustavo Gilson Lacerda, additional, Carazzolle, Marcelo Falsarella, additional, Mondego, Jorge Maurício Costa, additional, Schuster, Stephen C., additional, Carlson, John E., additional, Guiltinan, Mark J., additional, Bailey, Bryan A., additional, Mieczkowski, Piotr, additional, Meinhardt, Lyndel W., additional, and Pereira, Gonçalo Amarante Guimarães, additional

Published
2009
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79. A genome survey of Moniliophthora perniciosa gives new insights into Witches' Broom Disease of cacao

Author

Mondego, Jorge MC, primary, Carazzolle, Marcelo F, additional, Costa, Gustavo GL, additional, Formighieri, Eduardo F, additional, Parizzi, Lucas P, additional, Rincones, Johana, additional, Cotomacci, Carolina, additional, Carraro, Dirce M, additional, Cunha, Anderson F, additional, Carrer, Helaine, additional, Vidal, Ramon O, additional, Estrela, Raíssa C, additional, García, Odalys, additional, Thomazella, Daniela PT, additional, de Oliveira, Bruno V, additional, Pires, Acássia BL, additional, Rio, Maria Carolina S, additional, Araújo, Marcos Renato R, additional, de Moraes, Marcos H, additional, Castro, Luis AB, additional, Gramacho, Karina P, additional, Gonçalves, Marilda S, additional, Neto, José P Moura, additional, Neto, Aristóteles Góes, additional, Barbosa, Luciana V, additional, Guiltinan, Mark J, additional, Bailey, Bryan A, additional, Meinhardt, Lyndel W, additional, Cascardo, Julio CM, additional, and Pereira, Gonçalo AG, additional

Published
2008
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80. The mitochondrial genome of the phytopathogenic basidiomycete Moniliophthora perniciosa is 109kb in size and contains a stable integrated plasmid

Author

Formighieri, Eduardo F., primary, Tiburcio, Ricardo A., additional, Armas, Eduardo D., additional, Medrano, Francisco J., additional, Shimo, Hugo, additional, Carels, Nicolas, additional, Góes-Neto, Aristóteles, additional, Cotomacci, Carolina, additional, Carazzolle, Marcelo F., additional, Sardinha-Pinto, Naiara, additional, Thomazella, Daniela P.T., additional, Rincones, Johana, additional, Digiampietri, Luciano, additional, Carraro, Dirce M., additional, Azeredo-Espin, Ana M., additional, Reis, Sérgio F., additional, Deckmann, Ana C., additional, Gramacho, Karina, additional, Gonçalves, Marilda S., additional, Moura Neto, José P., additional, Barbosa, Luciana V., additional, Meinhardt, Lyndel W., additional, Cascardo, Júlio C.M., additional, and Pereira, Gonçalo A.G., additional

Published
2008
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82. Differential Gene Expression Between the Biotrophic-Like and Saprotrophic Mycelia of the Witches' Broom Pathogen Moniliophthora perniciosa

Author

Rincones, Johana, primary, Scarpari, Leandra M., additional, Carazzolle, Marcelo F., additional, Mondego, Jorge M. C., additional, Formighieri, Eduardo F., additional, Barau, Joan G., additional, Costa, Gustavo G. L., additional, Carraro, Dirce M., additional, Brentani, Helena P., additional, Vilas-Boas, Laurival A., additional, de Oliveira, Bruno V., additional, Sabha, Maricene, additional, Dias, Robson, additional, Cascardo, Júlio M., additional, Azevedo, Ricardo A., additional, Meinhardt, Lyndel W., additional, and Pereira, Gonçalo A. G., additional

Published
2008
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83. Characterization of necrosis and ethylene-inducing proteins (NEP) in the basidiomycete Moniliophthora perniciosa, the causal agent of witches' broom in Theobroma cacao

Author

Garcia, Odalys, primary, Macedo, Joci A.N., additional, Tibúrcio, Ricardo, additional, Zaparoli, Gustavo, additional, Rincones, Johana, additional, Bittencourt, Livia M.C., additional, Ceita, Geruza O., additional, Micheli, Fabienne, additional, Gesteira, Abelmon, additional, Mariano, Andréa C., additional, Schiavinato, Marlene A., additional, Medrano, Francisco J., additional, Meinhardt, Lyndel W., additional, Pereira, Gonçalo A.G., additional, and Cascardo, Júlio C.M., additional

Published
2007
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84. Genetic variability and chromosome-length polymorphisms of the witches' broom pathogen Crinipellis perniciosa from various plant hosts in South America

Author

RINCONES, Johana, primary, MAZOTTI, Gabriel D., additional, GRIFFITH, Gareth W., additional, POMELA, Alan, additional, FIGUEIRA, Antonio, additional, Leal, Gildemberg A., additional, QUEIROZ, Marisa V., additional, PEREIRA, Jorge F., additional, AZEVEDO, Ricardo A., additional, PEREIRA, Gonçalo A.G., additional, and MEINHARDT, Lyndel W., additional

Published
2006
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87. Regulation of Lysine Metabolism and Endosperm Protein Synthesis by the Opaque-5 and Opaque-7 Maize Mutations

Author

Azevedo, Ricardo A., primary, Lea, Peter J., additional, Damerval, Catherine, additional, Landry, Jacques, additional, Bellato, Cláudia M., additional, Meinhardt, Lyndel W., additional, Le Guilloux, Martine, additional, Delhaye, Sonia, additional, Varisi, Vanderlei A., additional, Gaziola, Salete A., additional, Gratão, Priscila L., additional, and Toro, Alejandro A., additional

Published
2004
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88. Genetic control of lysine metabolism in maize endosperm mutants

Author

Azevedo, Ricardo A., primary, Damerval, Catherine, additional, Lea, Peter J., additional, Landry, Jacques, additional, Bellato, Cláudia M., additional, Meinhardt, Lyndel W., additional, Guilloux, Martine Le, additional, Delhaye, Sonia, additional, Toro, Alejandro A., additional, Gaziola, Salete A., additional, Varisi, Vanderlei A., additional, and Gratão, Priscila Lupino, additional

Published
2004
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95. Utilization of the Etest Assay for Comparative Antibiotic Susceptibility Profiles of Citrus Variegated Chlorosis and Pierce’s Disease Strains of Xylella fastidiosa.

Author

de P. M. A. Ribeiro, Milena, de T. F. Dellias, Marina, Tsai, Siu M., Bolmströn, Anne, Meinhardt, Lyndel W., and de M. Bellato, Cláudia

Subjects
ANTIBIOTICS, CHLOROSIS (Plants), PIERCE'S disease, PATHOGENIC bacteria, GRAPE diseases & pests, CITRUS diseases & pests
Abstract

Xylella fastidiosa has a wide host range. Isolates of this bacterium that cause diseases in citrus (CVC) and grapes (PD) share 98% genome homology, and 95.7% amino acid identity. Drug resistance genes show a higher level of divergence and may be involved in the X. fastidiosa–host interaction. Antibiotic susceptibility of CVC and PD strains were compared utilizing the Etest strip method (AB Biodisk). Etest is applicable for fastidious slow-growing organisms due to its reproducibility. Results showed that the CVC strain was resistant to bacitracin, cefotaxime, and trimethoprim, and susceptible to chloramphenicol, erythromycin, gentamicin, kanamycin, streptomycin, and tetracycline. The PD strain was susceptible to all tested antibiotics, except kanamycin and trimethoprim. Both isolates produced a class C β-lactamase. These data support previous antibiotic studies and gene discrepancies found in the sequencing data of PD and CVC strains. These results demonstrate the efficacy of utilizing Etest assays for X. fastidiosa strains. [ABSTRACT FROM AUTHOR]

Published
2005
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96. Population Structure and Genetic Diversity of the Trinitario Cacao (Theobroma cacaoL.) from Trinidad and Tobago

Author

Johnson, Elizabeth S., Bekele, Frances L., Brown, Steven J., Song, Qijian, Zhang, Dapeng, Meinhardt, Lyndel W., and Schnell, Raymond J.

Abstract

Population structure of the old Trinitario cacao (Theobroma cacaoL.) in Trinidad was evaluated from the 35‐microsatellite multilocus profile of 32 relict clones from abandoned cocoa estates in Trinidad (TRD) and 88 Imperial College selections (ICS) clones conserved in the International Cocoa Genebank, Trinidad. Ancestry was derived by comparison to 34 representative genotypes of Criollo, Central American, and Lower and Upper Amazon origin. The 154 individuals separated into four populations in this study, labeled Population 1—Upper Amazon; Population 2—Ecuadorian; Population 3—Lower Amazon; and Population 4—Trinitario. Over 90% of the individuals demonstrated 70 to 99% membership to their respective populations. The ICS and TRD clones formed a genetically homogenous group, 84% of which clustered in Population 4 with clones of pure Criollo descent. Another 10% clustered in Population 1 containing clones of Upper Amazon descent. The cacao population of Trinidad is genetically different from clones of Ecuadorian and Lower Amazon descent, Populations 2 and 3, respectively. The 10 most discriminating loci for each population were different as shown by polymorphism information content values for each of the 35 microsatellite loci. This is the first report to provide a strong genetic basis for the industry flavor distinction of Trinitario and Ecuadorian cacaos. These findings significantly impact germplasm fingerprinting and curatorship and maintenance of industry flavor classes while breeding for disease resistance in cacao.

Published
2009
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98. Biology and genomics of #Phytophthora# spp.: fight against a potential global chocolate famine [W115]

Author

Ali, Shahin, Amoako-Attah, Ishmael, Shao, Jonathan, Bailey, Rebecca, Strem, Mary, Phillips, Wilbert, Surujdeo-Maharaj, Surendra, Marelli, Jean-Philippe, Gerben Martijn ten Hoopen, Goss, Erica, Villela Dias, Cristianao, Shen, Danyu, Tyler, Brett, Meinhardt, Lyndel W., and Bailey, Bryan

Subjects
H20 - Maladies des plantes
Abstract

Theobroma cacao is currently under serious threat due to various diseases, of which Phytophthora pod rot, commonly called 'black pod' is one of the most economically important. Four fungal species of the same genus are primarily responsible for this disease: P. palmivora, P. megakarya, P. capsici and P. citrophthora. Among these, P. palmivora is the most common, being present in most cacao producing countries. P. palmivora can cause yield losses of 20-30% and tree mortality of 10% annually. P. megakarya occurs only in West African countries, but is the most virulent among the four species. In Africa it causes 30-90% annual crop losses and thus it poses a severe threat to the cacao industry and to producers in Africa. Both in vitro pod husk inoculation assays and in planta pod inoculation assays verified that P. megakarya was more aggressive. Studies suggest effective early penetration by P. megakarya makes it a more destructive pathogen. Since the Phytophthora species that cause disease on cacao differ so much in their virulence, we developed specific primers for QPCR identification of each species. At the same time we characterized the genetic diversity of P. palmivora and P. megakarya in Ghana, a major producer. Through further genetic analysis, we estimate the genome size of P. megakarya to be 116.9 Mb and the P. palmivora genome size to be 100 Mb. P. palmivora appears to be tetraploid whereas P. megakarya, despite its larger genome, is not. Comparative genome analysis between these two species shows that both species carry large numbers of plant-pathogen interaction proteins including the RxLR effectors. An in-depth comparative analysis of genomics and transcriptomics between these two closely related species is being carried out to highlight the molecular mechanism behind their virulence and support the development of effective control measures. This is critical since Phytophthora spp. in general and P. megakarya specifically, represent a significant threat to cacao production and the chocolate industry worldwide. (Texte intégral)

99. Accurate Differentiation of Green Beans of Arabica and Robusta Coffee Using Nanofluidic Array of Single Nucleotide Polymorphism (SNP) Markers.

Author

Dapeng Zhang, Vega, Fernando E., Infante, Francisco, Solano, William, Johnson, Elizabeth S., and Meinhardt, Lyndel W.

Abstract

Green (unroasted) coffee is one of the most traded agricultural commodities in the world. The Arabica (Coffea arabica L.) and Robusta (Coffea canephora Pierre ex A. Froehner) species are the two main types of coffees for commercial production. In general, Arabica coffee is known to have better quality in terms of sensory characteristics; thus, it has a higher market value than Robusta coffee. Accurate differentiation of green beans of the two species is, therefore, of commercial interest in the coffee industry. Using the newly developed single nucleotide polymorphism(SNP) markers, we analyzed a total of 80 single green bean samples, representing 20 Arabica cultivars and four Robusta accessions. Reliable SNP fingerprints were generated for all tested samples. Unambiguous differentiation between Robusta and Arabica coffees was achieved using multivariate analysis and assignment test. The SNP marker panel and the genotyping protocol are sufficiently robust to detect admixture of green coffee in a high-throughput fashion. Moreover, the multilocus SNP approach can differentiate every single bean within Robusta and 55% of Arabica samples. This advantage, together with the single-bean sensitivity, suggests a significant potential for practical application of this technology in the coffee industry. [ABSTRACT FROM AUTHOR]

Published
2020
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