Publications by authors named "G E Pietersen"

South Africa has a small but growing olive industry. Until now, no virological research has been carried out on this crop locally. Seventeen samples were collected from various olive cultivars from a single producer in the Stellenbosch growing area of South Africa.

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Introduction: Citrus is one of the most important fruit crops worldwide, and the root-associated microbiota can have a profound impact on tree health and growth.

Methods: In a collaborative effort, the International Citrus Microbiome Consortium investigated the global citrus root microbiota with samples collected from nine citrus-producing countries across six continents. We analyzed 16S rDNA and ITS2 amplicon sequencing data to identify predominant prokaryotic and fungal taxa in citrus root samples.

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South Africa is associated with a centuries-old viticultural industry, accompanied by a diverse range of wine and table grape cultivars and an extensive history of pervasive introductions of vine material and associated viruses. The D2 collection in Stellenbosch represents the most comprehensive collection of species, hybrids, and cultivars in South Africa. We collected leaf petiole material from 229 accessions from this collection.

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Seven viroid species and one putative viroid species have been reported to infect grapevine namely, hop stunt viroid (HSVd), grapevine yellow speckle viroid 1 (GYSVd-1), grapevine yellow speckle viroid 2 (GYSVd-2), Australian grapevine viroid (AGVd), Japanese grapevine viroid (JGVd), grapevine latent viroid (GLVd), and citrus exocortis viroid (CEVd), as well as a grapevine hammerhead viroid-like RNA (GHVd), so far. In this study, RNA sequence (RNA-Seq) data, from 229 Vitis accessions from the field-maintained vineyard of the South African Vitis germplasm collection, were analysed to determine the diversity of the viroids present. Five of the seven known grapevine-infecting viroids and one putative grapevine-infecting viroid species were very commonly found, with 214 of the 229 samples containing at least one viroid species.

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The Asian citrus psyllid ( Kuwayama) is a key pest of sp. worldwide, as it acts as a vector for Liberibacter asiaticus, the bacterial pathogen that causes citrus Huanglongbing. has been reported in Kenya, Tanzania, and more recently in Ethiopia.

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