Recticladiella inexpectata gen. et sp. nov. (Nectriaceae) Pathogenic to Native Cinnamomum camphora (Lauraceae) Trees in Southeastern China.

Abstract

The ascomycete family Nectriaceae includes soil-borne saprobes, plant pathogens and human pathogens, biodegraders, and biocontrol agents for industrial and commercial applications. Cinnamomum camphora is a native tree species that is widely planted in southern China for landscaping purposes. During a routine survey of Eucalyptus diseases in southern China, disease spots were frequently observed on the leaves of Ci. camphora trees planted close to Eucalyptus. The asexual fungal structures on the leaf spots presented morphological characteristics typical of the Nectriaceae. The aim of this study is to identify these fungi and determine their pathogenic effect on Ci. camphora. Of the isolates obtained from 13 sites in the Fujian and Guangdong Provinces, 54 isolates were identified based on the DNA phylogeny of the tef1, tub2, cmdA, and his3 regions and morphological features. Two isolates were identified as Calonectria crousiana, and fifty-two isolates were described as a new genus, including a single species. These fungi were named Recticladiella inexpectata gen. et sp. nov. The identification of the new genus was based on strong DNA base differences in each of the four sequenced gene regions. The conidiophores of this fungus had several avesiculate stipe extensions tapering toward a straight, occasionally slightly curved terminal cell, distinguishing it from other phylogenetically close Nectriaceae genera. The results indicate that R. inexpectata is distributed in wide geographic regions in southern China. Inoculation showed that R. inexpectata and Ca. crousiana caused lesions on the leaves of Ci. camphora seedlings within 6 days of inoculation, indicating that they are pathogenic to native Ci. camphora in China.