Preliminary Analyses on Diversity and Pathogenicity of Calonectria spp. on Eucalyptus in China
Calonectria leaf blight caused by Calonectria spp. is a serious disease on Eucalyptus trees in the world.The aims of the study were to clarify the species diversity and pathogenicity of Calonectria spp. on Eucalyptus trees in China. Species diversity of Calonectria were clarified based on comparisons of DNA sequences data of ITS, Histone H3, and TEF-1α gene regions, and combined with the fungal morphological characteristics and culture growth features. Research results indicated that six species of Calonectria were existed, these species included Ca. cerciana, Ca. crousiana, Ca. pauciramosa, Ca. pseudocolhounii, Ca. pseudoreteaudii and Ca. fujianensis. Six species could be distinguished by morphological characteristics. The six species resided in different phylogenetic groups. The culture growth features are different for the tested five Calonectria spp. The optimal growth temperature for Calonectria spp. is 25-30 ℃, no growth at 5 ℃ or 35 ℃. Leaf inoculations showed that all four Eucalyptus clones( Guang 1, Guang 4, DH32-29, OC14) tested were susceptible to infect by five tested Calonectria spp. Significant differences of virulence were observed among five Calonectria spp., with rank of Ca.cerciana Ca. pauciramosa Ca. pseudoreteaudii Ca. crousiana Ca. fujianensis. Significant differences of resistances were observed among four tested Eucalyptus clones. The paper revealed that species diversity of Calonectria on Eucalyptus trees in China, and provided prospects to select disease-tolerant planting stock for the disease management of Calonectria leaf blight on Eucalyptus trees in the future.