Screening Kauri for resistance to Phytophthora agathidicida

Transcription

1 Screening Kauri for resistance to Phytophthora agathidicida Echo Herewini Supervisors Scion: Peter Scott, Nari Williams, Otago University: Phillip Wilcox Massey University: Rosie Bradshaw, Terry Stewart

2 Kauri (Agathis australis) Known as one of the largest and longest living trees in the world. Araucariaceae. Keystone species. Culturally and ecologically significant. One of the only ecosystems with trees known to pre-date human settlement. Tāne-mahuta, lord of the forest in Waipoua Forest in Northland (Hague, 2010)

3 Kauri Dieback Disease Host: Kauri (Agathis australis) Pathogen: Phytophthora agathidicida (formally known as Phytophthora taxon Agathis - PTA) Oospores (sexual) (Waipara, 2005) Sporangia (asexual) (Weir et al., 2015) Colony morphology

4 Main Aim To develop an assay to identify resistance in kauri seedlings to Phytophthora agathidicida. A lab-based assay to identify resistant kauri to regenerate infested forests. Rapid and efficient. Kauri stand displaying progressive dieback of crown (Weir et al., 2015)

5 Kauri Tissue Culture Library

6 Comparing: Root & Foliar Inoculations Root inoculations (WinRhizo) Foliar inoculations (WinFolia)

7 Exp 1: Foliar Screening Assay Aim: Compare different foliar inoculation methods 3 P. agathidicida isolates. 3 kauri clones. 7 inoculation methods.

8 Exp 1: Results Figure 1. Average lesion length on kauri leaves using seven different inoculation methods.

9 Exp 2: Foliar Inoculation on 5 year old Kauri Trees Aim: Test foliar inoculation on six kauri trees

10 Average disease area (%) Exp 2: Results Average disease area on leaves for six Agathis australis (kauri) trees infected with three Phytophthora agathidicida isolates Control P. agathidicida (1) P. agathidicida (2) P. agathidicida (3) * Tree 1 Tree 2 Tree 3 Tree 4 Tree 5 Tree 6 Agathis australis trees Figure 2. Average disease area on leaves for six kauri trees infected with three Phytophthora agathidicida isolates.

11 Exp 3: Foliar Inoculation single Kauri clone Aim: Upscale foliar inoculation method. Test the impact of leaf age on susceptibility. Do foliar inoculations on plants for comparison to root inoculations.

12 Average disease area (%) Exp 3. Results Average disease area on Agathis australis (kauri) leaves infected with six Phytophthora isolates * old middle young Possibly cross-contamination Isolates Figure 3. Average disease area on young, middle, and old aged leaves for 105 kauri glasshouse seedlings infected with four P. agathidicida, one P. cinnamomi, and one P. multivora isolate.

13 Exp 4: Glasshouse Root Inoculations Aim: Carry out root inoculations on same kauri plants used for foliar inoculations.

14 Root length (cm) Exp 4: Results Root length (0-0.5mm diameter) * Isolates Figure 4. Root length between 0-0.5mm in diameter for 105 kauri glasshouse seedlings infected with four P. agathidicida, one P. cinnamomi, and one P. multivora isolate.

15 Exp 3 and 4 Comparison P. agathidicida isolates vary in virulence to kauri roots and leaves Experiment 3 (Foliar) Experiment 4 (Roots) P. agathidicida 1 appears to be more virulent to leaves. P. agathidicida 2 appears to be more virulent to roots, resulting in the least amount of fine root Younger leaves are more susceptible. length.

16 Exp 5: Foliar Inoculation of 50 kauri Clones 2775 leaves inoculated

17 Average lesion length (mm) Exp 5: Preliminary Results 16 Average lesion length on Agathis australis (kauri) leaves infected with Phytophthora agathidicida Clones Figure 5. Subset of average foliar lesion length for 50 kauri clones infected with Phytophthora agathidicida. Blue line = base line from 5mm agar plug Red bar = Highest lesion length (clone 29), Green bar = lowest lesion length (clone 31).

18 Correlate to Field Performance Validate assay for predicting resistance in forests. Canopy thinning of kauri (Scott, 2012) Compare symptoms seen in assay to symptoms in the kauri forests. Bleeding resin of kauri trunk (Scott, 2012)

19 Summary/Next steps Summary: Variation observed in the susceptibility of kauri clones to foliar and root inoculations by different Phytophthora isolates. The relationship between root and foliar inoculation is unclear. Next steps: Do root inoculations on the same 50 kauri clones. Test resistant and susceptible clones identified from assay in natural environments.

20 Acknowledgements Supervisors Peter Scott (Scion) Rosie Bradshaw (Massey University) Nari Williams (Scion) Terry Stewart (Massey University) Phillip Wilcox (Otago University) Team Shannon Hunter Keiko Gough Catherine Baham Pam Taylor Sarah Orton Scholarship Funding BioProtection Research Centre Te Pūrehuroa Award

21 Keep Kauri Standing Whatu ngarongaro te tangata, toitū te whenua People will perish, but the land is permanent