Pathogenicity of four <i>Phytophthora</i> species on kauri in vitro and glasshouse trials

Abstract

In kauri forest soils surveys Phytophthora taxon Agathis (PTA) P cinnamomi P multivora and P cryptogea were detected frequently In vitro and glasshouse studies determined that all four Phytophthora species produced lesions on excised kauri leaves and stems Lesion advance was significantly slower with P cinnamomi P multivora and P cryptogea than with PTA When 2yearold kauri seedlings were trunkinoculated lesion spread was rapid with PTA trunks were girdled and all trees died within 46 weeks Phytophthora cinnamomi P multivora and P cryptogea produced substantially smaller lesions than PTA no trees died and plant growth was only slightly suppressed Following soil inoculation with PTA all kauri seedlings died within 10 weeks There were no deaths following soil inoculation with P cinnamomi P multivora or P cryptogea although feeder root damage was observed and the respective pathogens were reisolated Results suggest that PTA is an aggressive pathogen and the other three species are weaker pathogens of kauri

Genome sequences of six Phytophthora species associated with forests in New Zealand

“…In New Zealand, P. multivora is found in exotic forests, natural ecosystems and horticultural settings [1] . Together with P. cinnamomi and Phytophthora cryptogea , it is also one of the multiple species commonly isolated from soil around Kauri trees exhibiting dieback, caused by P. agathidicida [6] , [11] .…”

Canker and decline diseases caused by soil- and airborne Phytophthora species in forests and woodlands

“…Other Phytophthora species like P. cryptogea , P. kernoviae , P. multivora and P. nicotianae are occasionally recovered from kauri soils, while P. cinnamomi is widespread in kauri forests. Although in general P. cinnamomi is not associated with kauri dieback it can be infrequently associated with scattered mortality of individual kauri trees under particularly favouring conditions for the pathogen ( Podger & Newhook 1971 , Beever et al 2009 , Waipara et al 2013 , Horner & Hough 2014 ). In both underbark inoculation and soil infestation trials, P. agathidicida showed much higher aggressiveness to A. australis than P. cinnamomi , P. cryptogea and P. multivora , causing large girdling lesions and high mortality ( Horner & Hough 2014 ).…”

“…Although in general P. cinnamomi is not associated with kauri dieback it can be infrequently associated with scattered mortality of individual kauri trees under particularly favouring conditions for the pathogen ( Podger & Newhook 1971 , Beever et al 2009 , Waipara et al 2013 , Horner & Hough 2014 ). In both underbark inoculation and soil infestation trials, P. agathidicida showed much higher aggressiveness to A. australis than P. cinnamomi , P. cryptogea and P. multivora , causing large girdling lesions and high mortality ( Horner & Hough 2014 ). Recent surveys demonstrated a wide distribution of collar rot, dieback and mortality of kauri throughout much of the natural range in the North Island, and P. agathidicida has been isolated at many sites from collar rot lesions confirming this pathogen being the causal agent of this epidemic ( Waipara et al 2013 , Scott & Williams 2014 ).…”

Phytophthora agathidicida: research progress, cultural perspectives and knowledge gaps in the control and management of kauri dieback in New Zealand

“…At the root surface, zoospores encyst and produce hyphae that penetrate and colonize the root (Bellgard et al , ). Phytophthora agathidicida hyphae colonize host vascular tissue with a delay between infection and visible lesion development (Horner & Hough, ; Herewini et al , ). An early symptomless stage of infection has similarly been identified across a range of Phytophthora species and host plants and may be associated with the pathogen suppressing the host defence response (Denman et al , ).…”