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Calonectria queenslandica: Causal agent of Eucalyptus leaf blight in Southern China

    Affiliations
    Authors and Affiliations
    • Ms. WenWen Li, Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa; wenwen.li@fabi.up.ac.za
    • Prof. ShuaiFei Chen, Research Institute of Fast-growing Trees (RIFT)/China Eucalypt Research Centre (CERC), Chinese Academy of Forestry (CAF), ZhanJiang, China; shuaifei.chen@gmail.com
    • Prof. Mike Wingfield, Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa; Mike.Wingfield@fabi.up.ac.za
    • Mr. Tuan A. Duong, Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa; tuan.duong@fabi.up.ac.za

      Published Online:https://doi.org/10.1094/PDIS-01-22-0196-RE

      Calonectria leaf blight caused by Calonectria spp. is amongst the most serious diseases affecting the health and sustainability of Eucalyptus plantations in Southern China. Recent outbreaks of this disease in GuangDong Province prompted a need to identify the species involved. Typical symptoms of Calonectria leaf blight were observed on 2-year-old E. urophylla × E. grandis trees in a plantation in the ZhaoQing region. Thirty-eight Calonectria isolates were collected from 32 diseased trees. All isolates were identified using DNA sequence analyses of the translation elongation factor 1-alpha (tef1), β-tubulin (tub2), calmodulin (cmdA) and histone H3 (his3) gene regions. Phylogenetic analyses revealed that C. queenslandica was the dominant species, accounting for 81.6% of the isolates collected. Other species isolated included C. pseudoreteaudii (10.5%), C. reteaudii (5.3%) and C. aconidialis (2.6%). This is the first report of C. queenslandica in China and all isolates had identical sequences in all four gene regions. PCR amplification using primers targeting the MAT1-1-1 and MAT1-2-1 genes in all C. queenslandica isolates revealed that only MAT1-2 idiomorph was present. The results suggest that C. queenslandica was introduced into the sampled area with very limited genetic diversity. Pathogenicity tests were conducted on two Eucalyptus genotypes widely planted in the GuangDong Province using isolates representing all species collected. The results showed that these species could all cause disease but the predominance of C. queenslandica on infected trees suggests that it is the major driver of the disease problem studied. Different Eucalyptus genotypes used in the pathogenicity tests differed in susceptibility to infection by the Calonectria spp. tested, providing opportunities to avoid leaf blight by deploying disease-tolerant planting stock.