PERMANENT GENETIC RESOURCES: Development of microsatellite markers for the guava rust fungus, Puccinia psidii

Abstract A description is provided for Puccinia psidii. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Pimenta officinalis and Psidium guajava, also on Callistemon speciosus, Eucalyptus citriodora, Eugenia jambos, E. malaccensis, E. uvalha, Marlierea edulis, Myrcia spp., Myrciaria jaboticaba and Pimenta acris. DISEASE: Guava rust. Attacks foliage, inflorescences and young succulent twigs of pimento and Eucalyptus, and foliage and fruit of guava, causing severe defoliation under certain conditions. GEOGRAPHICAL DISTRIBUTION: Central America and Caribbean (Cuba, Dominica, Dominican Republic, Jamaica, Puerto Rico, Trinidad); South America (Argentina, Brazil, Colombia, Ecuador, Paraguay, Uruguay, Venezuela). (CMI Map 181, Ed. 2, 1949 & Herb. IMI.) TRANSMISSION: Urediospores disseminated by rain-splash in Jamaica (41: 569).

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Microsatellite Markers in Olives (Olea europaea L.): Utility in the Cataloging of Germplasm, Food Authenticity and Traceability Studies

Foods ◽

10.3390/foods10081907 ◽

2021 ◽

Vol 10 (8) ◽

pp. 1907

Author(s):

Shambhavi Yadav ◽

Joana Carvalho ◽

Isabel Trujillo ◽

Marta Prado

Keyword(s):

Molecular Markers ◽

Oleic Acid ◽

Microsatellite Markers ◽

Genetic Resources ◽

Mediterranean Region ◽

Food Authenticity ◽

Food Authentication ◽

Organoleptic Characteristics ◽

Olive Cultivars ◽

Molecular Information

The olive fruit, a symbol of Mediterranean diets, is a rich source of antioxidants and oleic acid (55–83%). Olive genetic resources, including cultivated olives (cultivars), wild olives as well as related subspecies, are distributed widely across the Mediterranean region and other countries. Certain cultivars have a high commercial demand and economical value due to the differentiating organoleptic characteristics. This might result in economically motivated fraudulent practices and adulteration. Hence, tools to ensure the authenticity of constituent olive cultivars are crucial, and this can be achieved accurately through DNA-based methods. The present review outlines the applications of microsatellite markers, one of the most extensively used types of molecular markers in olive species, particularly referring to the use of these DNA-based markers in cataloging the vast olive germplasm, leading to identification and authentication of the cultivars. Emphasis has been given on the need to adopt a uniform platform where global molecular information pertaining to the details of available markers, cultivar-specific genotyping profiles (their synonyms or homonyms) and the comparative profiles of oil and reference leaf samples is accessible to researchers. The challenges of working with microsatellite markers and efforts underway, mainly advancements in genotyping methods which can be effectively incorporated in olive oil varietal testing, are also provided. Such efforts will pave the way for the development of more robust microsatellite marker-based olive agri-food authentication platforms.

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Transcriptome Analysis of Eucalyptus grandis Implicates Brassinosteroid Signaling in Defense Against Myrtle Rust (Austropuccinia psidii)

Frontiers in Forests and Global Change ◽

10.3389/ffgc.2021.778611 ◽

2021 ◽

Vol 4 ◽

Author(s):

Shae Swanepoel ◽

Caryn N. Oates ◽

Louise S. Shuey ◽

Geoff S. Pegg ◽

Sanushka Naidoo

Keyword(s):

Disease Resistance ◽

Rna Sequencing ◽

Plant Disease Resistance ◽

Rust Fungus ◽

Eucalyptus Grandis ◽

Post Inoculation ◽

Puccinia Psidii ◽

Myrtle Rust ◽

Brassinosteroid Signaling ◽

Austropuccinia Psidii

Eucalyptus grandis, in its native Australian range, varies in resistance to Austropuccinia psidii (syn. Puccinia psidii). The biotrophic rust fungus, A. psidii is the causal agent of myrtle rust and poses a serious threat to Australian biodiversity. The pathogen produces yellow pustules of urediniospores on young leaves and shoots, resulting in shoot tip dieback, stunted growth, and death. Dissecting the underlying mechanisms of resistance against this pathogen will contribute to improved breeding and control strategies to mitigate its devastating effects. The aim of this study was to determine the molecular dialogue between E. grandis and A. psidii, using an RNA-sequencing approach. Resistant and susceptible E. grandis seedlings grown from seed collected across its natural range were inoculated with the pandemic biotype of A. psidii. The leaf tissue was harvested at 12-h post inoculation (hpi), 1-day post inoculation (dpi), 2-dpi and 5-dpi and subjected to RNA-sequencing using Illumina 50 bp PE reads to a depth of 40 million reads per sample. Differential gene expression and gene ontology enrichment indicated that the resistant seedlings showed controlled, coordinated responses with a hypersensitive response, while the susceptible seedlings showed no systemic response against myrtle rust. Brassinosteroid signaling was apparent as an enriched term in the resistant interaction at 2-dpi, suggesting an important role of this phytohormone in defense against the pathogen. Brassinosteroid mediated signaling genes were also among the candidate genes within two major disease resistance loci (Puccinia psidii resistance), Ppr3 and Ppr5. While brassinosteroids have been tagged as positive regulators in other plant disease resistance interactions, this is the first report in the Eucalyptus – Austropuccinia psidii interaction. Furthermore, several putative resistance genes, underlying known resistance loci and implicated in the interaction have been identified and highlighted for future functional studies. This study provided further insights into the molecular interactions between E. grandis and A. psidii, contributing to our understanding of this pathosystem.

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