Phytophthora podocarpi sp. nov. from Diseased Needles and Shoots of Podocarpus in New Zealand

Kiryn Dobbie,Preeti Panda,Pam Taylor,Margaret Dick,Peter Scott,Rebecca Mcdougal,Diya Sen

doi:10.3390/f13020214

Kiryn Dobbie, Preeti Panda + Show 5 more

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https://doi.org/10.3390/f13020214

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Abstract

Foliage samples from Podocarpus totara with severe needle browning and needle loss in the lower part of the crown were observed in 2011 in the Gisborne region of New Zealand. A Phytophthora genus-specific test applied directly to the needles gave a strong positive result, and subsequent isolations yielded colonies of a slow-growing oomycete. Morphological examination in vitro revealed a Phytophthora species. Preliminary comparisons of the rDNA (ITS), and ras-related protein (Ypt) gene regions with international DNA sequence revealed low sequence similarity to species from the downy mildew genus Peronospora, as well as clade 3 Phytophthora species. Other studies have also demonstrated the close relationship with Peronospora. The species was given the interim designation Phytophthora taxon tōtara pending further examination. Here, we formally describe Phytophthora podocarpi sp. Nov. and its associated disease, tōtara needle blight.

Highlights

Foliage samples from Podocarpus totara with severe needle browning and needle loss in the lower part of the crown were examined in 2011
Affected tōtara trees were growing in the remnants of the native forest, remaining in steep gullies in a plantation of exotic Pinus radiata in the East Cape back-country of the North Island
Further to the typical symptoms on needles and shoots, dark bands were occasionally observed on the Podocarpus totara needles, as seen with infection of other conifers with Phytophthora species [18]

Summary

Introduction

Foliage samples from Podocarpus totara with severe needle browning and needle loss in the lower part of the crown were examined in 2011. Subsequent genome sequencing indicated that it was phylogenetically distinct from other Phytophthora species at that time It was given the interim designation Phytophthora taxon totara (PTT) [1]. The genome sequence was made publicly available on the NCBI database and was subsequently used in studies by McCarthy and Fitzpatrick [2] and Bourret, Choudhury [3]. These phylogenetic studies showed it had both (i) a close relationship to Phytophthora agathidicida [2], the causal agent of kauri (Agathis australis) dieback, which is another Phytophthora disease of a New Zealand native species, and (ii) strong phylogenetic links to the downy mildew genus Peronospora

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