Phyllode inoculation provides a rapid protocol for preliminary screening of Acacia species for tolerance to Ceratocystis wilt and canker disease

Aswardi Nasution,Morag Glen,Kathy Evans,Caroline Mohammed,Heru Indrayadi,Jeremy Brawner,Abdul Gafur,David Ratkowsky

doi:10.1007/s10658-022-02479-w

Aswardi Nasution, Morag Glen + Show 6 more

Open Access

https://doi.org/10.1007/s10658-022-02479-w

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Abstract

Ceratocystis wilt and canker disease has devastated Acacia mangium plantations in south-east Asia. Current screening methodologies to identify resistant or tolerant germplasm use potted plants in a greenhouse as a preliminary screening to select material for field trials, but these tests are time-consuming, motivating a search for rapid screening protocols. In this study, inoculation procedures were tested on three species of Acacia, viz. A. mangium, A. crassicarpa and a hybrid of A. auriculiformis and A. mangium, using three isolates of Ceratocystis manginecans. Mycelial plugs were compared with spore suspensions as inoculum to infect artificial wounds on the stems of A. mangium potted plants. The rapid screening protocols involved inoculation of stem segments with mycelial plugs and detached phyllodes with a spore suspension, with susceptibility measured by lesion length on the stems or necrosis length on the phyllodes. Both mycelial plugs and spore suspensions produced a similar level of disease incidence, so either inoculum form can be used for an assay. The stem segments were prone to contamination by other fungi and to desiccation, while results from the potted plant and phyllode protocols showed similar trends of susceptibility among the Acacia clones and species. The ease, rapidity, and reproducibility of the phyllode inoculation protocol makes it a potential replacement for inoculation of potted plants as a preliminary screening protocol to identify disease tolerant A. mangium germplasm prior to field screening.

Highlights

With accelerating pest impacts on forest productivity (Jactel et al, 2020), the incorporation of selection for tolerance or resistance to pests and/or diseases is receiving increasing recognition as a vital component of tree breeding programs (Woodcock et al, 2019)
No lesions emerged on the stems of whole potted plants of five clones of A. mangium which were inoculated with sterile distilled water or sterile water agar plugs and these results were excluded from the statistical analysis
Field trials are an important component of breeding programs, but rapid preliminary screening can expedite selection of plant accessions that are less susceptible to disease by excluding the most susceptible germplasm before the field trial stage

Summary

Introduction

With accelerating pest impacts on forest productivity (Jactel et al, 2020), the incorporation of selection for tolerance or resistance to pests and/or diseases is receiving increasing recognition as a vital component of tree breeding programs (Woodcock et al, 2019). Have been planted in 25.6 million hectares of forest plantations, mainly in China, India, Indonesia, Malaysia, Thailand and Vietnam (Harwood & Nambiar, 2014b) These fast-growing exotic hardwoods were established to meet the demand of raw materials for pulp and paper production which, on a global scale, rose substantially from 280 to 500 million tons per annum from 1980 to 2008 (Asia-Pacific Forestry Commission, 2010). The global market for printing and writing papers has been impacted by a consistent decline in production in developed regions such as North America and Europe; this has been offset by the increase in the supply of writing paper in other markets, especially the Asia Pacific (Wright, 2014)

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