No abstract

Background: Tea, which is produced from new shoots of existing tea plants (Camellia sinensis), is one of the most popular, non-alcoholic, healthy beverages worldwide. Colletotrichum camelliae is one of the dominant fungal pathogens of tea. The interaction of C. camelliae with tea could be a useful pathosystem to elucidate various aspects of woody, medicinal plant-fungal interactions. Currently, many studies characterizing resistance or virulence and aggressiveness use lesion size at the infection sites on the leaves to quantify the growth of the pathogen. However, this method does not offer the sensitivity needed for the robust quantification of small changes in aggressiveness or the accurate quantification of pathogen growth at the early stages of infection. Results:A quantitative real-time polymerase chain reaction (qRT-PCR) assay was developed for the quantification of C. camelliae growth on tea plant. This method was based on the comparison of fungal DNA in relation to plant biomass. This assay was used to investigate the phenotypes of tea plant cultivars in response to C. camelliae infection. Two cultivars, Zhongcha 108 (ZC108) and Longjing 43 (LJ43), were tested with this method. ZC108 was previously reported as an anthracnose-resistant cultivar against C. camelliae, while LJ43 was susceptible. The traditional lesion measurement method showed that both cultivars were susceptible to a virulent strain of C. camelliae, while the qRT-PCR approach indicated that very little fungal growth occurred in the anthracnose-resistant cultivar ZC108. The observed results in this study were consistent with previously published research. In addition, the DNA-based real-time PCR method was applied for analysis of pathogenic differences in general C. camelliae isolates and among several Colletotrichum spp that infect tea. Conclusions:This study showed that the DNA-based qRT-PCR technique is rapid, highly sensitive and easily applicable for routine experiments and could be used in screening for resistant tea plant cultivars or to identify differences in pathogen aggressiveness within and among Colletotrichum species.

Botrytis cinerea is a necrotrophic microbe that causes gray mold disease in a broad range of hosts. In the present study, we conducted molecular microbiology and transcriptomic analyses of the host–B. cinerea interaction to investigate the plant defense response and fungal pathogenicity. Upon B. cinerea infection, plant defense responses changed from activation to repression; thus, the expression of many defense genes decreased in Arabidopsis thaliana. B. cinerea Zn(II)2Cys6 transcription factor BcSpd1 was involved in the suppression of plant defense as ΔBcSpd1 altered wild-type B05.10 virulence by recovering part of the defense responses at the early infection stage. BcSpd1 affected genes involved in the fungal sclerotium development, infection cushion formation, biosynthesis of melanin, and change in environmental pH values, which were reported to influence fungal virulence. Specifically, BcSpd1 bound to the promoter of the gene encoding quercetin dioxygenase (BcQdo) and positively affected the gene expression, which was involved in catalyzing antifungal flavonoid degradation. This study indicates BcSpd1 plays a key role in the necrotrophic microbe B. cinerea virulence toward plants by regulating pathogenicity-related compounds and thereby suppressing early plant defense.