Published on November 25, 2008
Kauri (Agathis australis) under threat from Ross E. Beever1*, Sarah Tsai1, Nick W. Waipara 1,4, Tod D. Ramsfield2, Ian J. Horner3 1 Landcare Research, Private Bag 92170, Auckland 1142, New Zealand Phytophthora? 2 Scion, Private Bag 3020, Rotorua, New Zealand 3 HortResearch, Private Bag 1401, Havelock North, New Zealand 4 present adddress: Auckland Regional Council, Auckland, New Zealand *Correspondence: BeeverR@landcareresearch.co.nz Introduction The genus Agathis (Araucariaceae) includes about 13 species of tropical to warm temperate 175°E Japan China trees found from Malesia through Australia to New Zealand (Fig 1). Kauri (Agathis australis), is a Fig 1 Map showing PACIFIC OCEAN PACIFIC OCEAN Taiwan dominant tree of lowland forests in northern New Zealand (Ecroyd 1982). Giant individual trees natural range of Natural distribution Waipoua the genus Agathis Philippines of Agathis Forest Great Barrier Island Fig 2 The (Fig 2), which can reach over 4.5m in trunk diameter and exceed 1000 years age, are cultural icons. (left) and that 0° Yakas tree, a of kauri (Agathis 0 100km giant kauri In 1972, a Phytophthora was associated with dead and dying trees in a forest stand on Great australis), restricted Indonesia Papua New Guinea Coromandel in Waipoua Auckland to northern New Peninsula Forest Barrier, an island off the northern New Zealand coast (Gadgil 1974). We have now found this Zealand (right). Australia Waitakere Ranges 37°S same Phytophthora, here referred to as Phytophthora taxon Agathis (PTA), is more widespread New Zealand Southern natural limit of kauri with isolates recovered from the Waitakere Ranges near Auckland and Trounson Park, near the TASMAN SEA 0 2000kms Waipoua Forest in Northland. Symptoms Affected trees show foliage yellowing, canopy thinning and tree death (Fig 3), associated with bleeding lower trunk lesions extending to the major roots and sometimes girdling the trunk as a ‘collar rot’ (Fig 4). PTA has been isolated from the margin of bleeding lesions (Fig 5) and from soil under affected and healthy trees. Additionally, giant trees have been observed with large collar rots extending around the circumference associated with large dead sectors on the trunk and dead ‘stag heads’. Fig 3 Kauri stand showing yellowing of crowns Fig 4 Bleeding resin (‘kauri gum’) associated with collar rot of the lower trunk. Fig 5 Bleeding lesion exposed to show damage and and death of young trees. staining in cambial region and outer xylem. What species? Fig 6 Neighbour joining phylogenetic tree of Clade 5 based The organism was first identified as P. heveae (Gadgil 1974), but on ITS sequences of selected Phytophthora strains obtained Host Region the recent revolution in Phytopthora taxonomy warrants a re- in this study (ICMP cultures using species names as supplied P. katsurae AF266771 Cocos Ivory Coast by depositors), along with representative GenBank sequences examination of its affinities. While our molecular studies (Fig 6) used by Cooke et al. (2000) (underlined), and gametangia of P. katsurae ICMP16948 Cocos Hawaii confirm it is related to this species, they suggest it is more closely reprentative strains. P. katsurae ICMP16950 Cocos Hawaii related to P. katsurae, and indeed has an identical ITS sequence to an P. katsurae ICMP16951 Cocos Hawaii PTA EF067922 ICMP16471 Agathis New Zealand authentic strain of this species (ICMP 16915). However it differs from 0.01 PTA ICMP17021 Agathis New Zealand P. katsurae in the strict sense in its smooth, as opposed to strongly P. katsurae ICMP16915 soil Taiwan bullate (blister-like), oogonia (Fig 6). We propose that PTA is an as yet P. heveae AF266770 Hevea Malaysia unnamed species. Further, we suggest that it is introduced to New P. heveae ICMP16691 soil under Eucalytpus Australia Zealand, in view of its relatively recent recognition and the cultural P. heveae ICMP16914 Theobroma Malaysia P. citricola AF266788 and ITS sequence similarity of isolates recovered to date. Pathogenicity tests Table 1. Responses of various woody tree species found in association Kauri seedlings and a selection of other woody species from kauri ecosystems were inoculated (5 replicates) by cutting a flap of tissue from the stem (c. 1–2 cm with kauri to PTA and Phytophthora cinnamomi long), inserting an agar plug (colonised with PTA, P. cinnamomi, or with water as a control), folding the flap down, binding it with parafilm and covering with Lesion length ratio* aluminium foil. Kauri inoculated with PTA showed severe wilting at 3 weeks and were were dead at 7 weeks (Fig 7), whereas those inoculated with P. cinnamomi Species PTA P. cinnamomi Agathis australis (Araucariaceae) - Kauri DEAD ++ and the controls appeared showed no external symptoms even after 4 months. Beilschmiedia tawa (Lauraceae) - Tawa 0 + Stem lesion length was measured at 3–4 months (Table 1). None of the other woody species showed any response to PTA, whereas some showed a response to Beilshmiedia tarairi (Lauraceae) - Taraire 0 + Coprosma robusta (Rubiaceae) - Karamu – 0 +++ P. cinnamomi. P. cinnamomi is known to be common in kauri forests and has been implicated in occasional tree death (Beever at al. 2008) and may limit seedling Corynocarpus laevigata (Corynocarpaceae) - Karaka 0 ++ recruitment (Johnston et al. 2003). The two species most affected by P. cinnamomi were Knightia excelsa (Proteaceae) (Fig 8) and Coprosma robusta (Rubiaceae). Dacrycarpus dacrydioides (Podocarpaceae) - Kahikatea 0 0 Dacrydium cuppressinum (Podocarpaceae) - Rimu 0 0 Hebe stricta (Plantaginaceae) - Koromiko 0 0 Knightia excelsa (Proteaceae) - Rewarewa 0 +++ – Kunzea ericoides (Myrtaceae) - Ka nuka 0 0 – Leptospermum scoparium (Myrtaceae) - Ma nuka 0 0 – Metrosideros excelsa (Myrtaceae) - Po hutukawa 0 ++ – Myrsine australis (Myrsinaceae) - Ma pou 0 ++ Olearia albida (Asteraceae) - Tanguru 0 0 – – – Pittosporum tenuifolium (Pittosporaceae) - Ko hu hu 0 0 – Podocarpus hallii (Podocarpaceae) - To tarakotukutuku 0 0 – Podocarpus totara (Podocarpaceae) - To tara 0 0 A B C D Pseudopanax arboreus (Araliaceae) - Whauwhaupaku 0 ++ – Weinmannia racemosa (Cunoniaceae) - Ka mahi 0 + Fig 7 Plants inoculated with PTA (A), P. cinnamomi (B), water agar Fig 8 Examples of lesions on Knightia excelsa inoculated 4 months previously with PTA (left) or P. cinnamomi (right). control (C) and unwoulded control (D) at 3 weeks *lesion length relative to water control: 0 < 2.0, + >2<4, ++ >4<8, +++ >8 Impact of PTA Conclusions 40 The health of kauri was assessed (Fig 7) in a natural Many questions remain to be answered about the biology of PTA. However, we conclude 35 forest stand in the Waitakere Ranges where there is sufficient a priori evidence to propose that this pathogen poses a threat to kauri. 30 Dead Its long term effect may be to change the composition of kauri-dominated forests to symptomatic trees were abundant (Fig 3). PTA Gummosis forests dominated by podocarps, thus altering biodiversity values. Additionally, infection Number of trees was obtained from both trunk lesions and apple 25 Healthy baiting of soil. The vegetation at this site includes 20 of giant kauri may lead to premature death and loss of these cultural icons. – senescent trees of Kunzea ericoides (ka nuka) and 15 is interpreted as a seral successional site following References 10 Beever RE, Waipara NW, Ramsfield TD, Dick MA, Horner IJ. Kauri (Agathis australis) under threat from Phytophthora? Proceedings 4th IUFRO Working Party on Phytophthoras in timber extraction and fire about 100 years ago Forests and Native Ecosystems, 26–31 August 2007, Monterey, California, USA. (submitted) Cooke, D.E.L.; Drenth, A.; Duncan, J.M.; Wagels, G.; Brasier, C.M. 2000. A molecular phylogeny of Phytophthora and related oomycetes. Fungal Genetics and Biology 30: 17–32. 5 (Ogden 1983). The death of kauri at this site is likely Ecroyd, C.E. 1982. Biological flora of New Zealand 8. Agathis australis (D. Don) Lindl. (Araucariaceae) kauri. New Zealand Journal of Botany 20: 17–36. Gadgil, P.D. 1974. Phytophthora heveae, a pathogen of kauri. New Zealand Journal of Forestry Science 4: 59–63. to lead to a community shift towards dominance 0 Johnston, P.R.; Horner, I.J.; Beever, R.E. 2003. Phytophthora cinnamomi in New Zealand’s indigenous forests. In: McComb, J.A.; StJ Hardy, G.E.; Tommerup, I.C., eds Phytophthora in <2.5 5 10 15 20 25 30 35 40 40< Forests and Natural Ecosystems. 2nd International IUFRO Working Party Meeting, 30 Sept–5 Oct 2002, Albany, Western Australia. Perth: Murdoch University Print: pp 41–48. by podocarp tree species such as Dacrydium Size class - DBH (cm) Ogden, J. 1983. The scientific reserves of Auckland University. II Quantitative vegetation studies. Tane 29: 163–180. cupressinum (rimu). This species is present at the site, Fig 9 Size class distribution of Agathis australis (kauri) in a collar rot- Acknowledgements Maureen Fletcher, Duckchul Park, Nicolette Faville (Landcare Research), Mark Braithwaite, Mark Bullians and Heather Pearson (MAF Biosecurity), Jenni Stanley and Asher but appears unaffected and was not susceptible to affected forest stand in the Waitakere Ranges in 2007. In total, 156 trees Jones (Auckland University) assisted with laboratory and field work and figure preparation. Alex Nathan (Te Iwi O Te Roroa), Stephen King (Waipoua Forest Trust), and Dept of were scored. Health status was assessed as: healthy, showing gummosis Conservation (Northland) facilitated our sampling at Waipoua and Trounson. David Cooke (Scottish Crop Research Institute, Scotland), Janice Uchida (University of Hawaii, US) PTA in our pathogenicity tests (Table 1). (lesions oozing gum) or dead. and Michael Priest (Orange Agricultural Institute, Australia) supplied cultures. This work was funded by New Zealand’s Foundation for Research, Science and Technology, Ministry of Research, Science and Technology, and MAF Biosecurity New Zealand. w w w . l a n d c a r e r e s e a r c h . c o . n z
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Title: JAN22-09, Author: The Monitor Inc, Name: jan22-09, Length: 20 pages, Published: 2009-09-08T00:00:00.000Z.