Comparison of the Infection Biology of Teratosphaeria destructans and Teratosphaeria epicoccoides on Eucalyptus

Abstract

Leaf blight caused by Teratosphaeria destructans is one of the most important diseases of Eucalyptus planted in the sub-tropics and tropics. In contrast, the better-known Teratosphaeria epicoccoides, while also a primary pathogen of Eucalyptus, causes less damage to trees in these areas. Although T. destructans is an aggressive pathogen, nothing is known about its infection biology. In this study, the conditions for infection and disease development caused by T. destructans and T. epicoccoides were evaluated and compared on a Eucalyptus grandis x Eucalyptus urophylla hybrid clone. The optimal temperature for the germination of T. destructans ranged from 25 to 30 oC and 15 to 20 oC for T. epicoccoides. The germination of these pathogens was favored under conditions of light and high levels of relative humidity. Penetration by T. destructans and T. epicoccoides occurred via stomata and the hyphae colonized the intercellular spaces of infected leaves. Symptoms were clearly visible three weeks after inoculation by both pathogens and reproductive structures started to develop in substomatal cavities at four weeks after inoculation. The results of this study will facilitate the establishment of rapid screening trials based on artificial inoculations aimed at reducing the impact of disease caused by T. destructans.

Wide Distribution of Teratosphaeria epicoccoides and T. destructans Associated with Diseased Eucalyptus Leaves in Plantations in Southern China

“…Both species are widely distributed in Eucalyptus plantations that are mainly distributed across regions of southern China. Although previous studies have indicated that T. epicoccoides and T. destructans are widely distributed on Eucalyptus leaves globally [ 41 , 44 ], research on these species on diseased Eucalyptus leaves specifically in China is limited. During the sampling process in the current study, we found that the severity caused by each species of T. epicoccoides and T. destructans on different genotypes of E. urophylla × E. grandis were different.…”

“…At present, on a global scale, methods for assessing the pathogenicity of Mycosphaerellaceae and Teratosphaeriaceae species isolated from diseased Eucalyptus leaves include spraying ascospore suspensions, conidial suspensions, hyphal fragment suspensions, or a mixture of spores and hyphal fragment suspensions onto Eucalyptus seedlings in controlled environments. Additional inoculation methods involve applying ascospore masses or lesions from diseased leaf areas onto Eucalyptus seedling leaves [44,57,64]. Conidial suspensions are considered to be a typical method for evaluating the pathogenicity of Mycosphaerellaceae and Teratosphaeriaceae species; however, this is not possible for species that do not sporulate sufficiently in culture.…”

“…Based on previous research results, DNA sequences of the internal transcribed spacer regions and intervening 5.8S nrRNA gene (ITS), partial translation elongation factor 1-alpha ( tef1 ) gene, and partial β-tubulin ( tub2 ) gene were used as reliable DNA barcodes to clearly distinguish species in Mycosphaerellaceae and Teratosphaeriaceae , especially species of Teratosphaeria [ 25 , 26 , 43 , 44 ]. The three partial gene regions of T. epicoccoides were amplified using the primer pairs V9G /ITS-4 [ 45 ], EF1-728F/EF2 [ 46 , 47 ] and BT2a/BT2b [ 48 ], respectively.…”