Identification and Pathogenicity of Fungal Dieback Disease on Sengon (Paraserianthes falcataria (L.) Nielsen) Seedling and Rice (Oryza sativa)

Nicotiana benthamiana as a model for studying Cryptococcus-plant interaction

Cryptococcus gattii, an environmental yeast isolated from plants, is one of the agents of cryptococcosis. Here, we aimed to develop a plant model to study C. gattii-plant interaction, since it is unclear how it affects the plant and the yeast. We tested three inoculation methods (scarification, infiltration, and abrasion) in three plant species: Arabidopsis thaliana, Nicotiana tabacum, and N. benthamiana. Cryptococcus gattii was able to grow in all three models, with a peak of yeast cell burden after 7 days, without any pathological effects. Furthermore, the fungal burden was reduced later, confirming that C. gattii is not a phytopathogen. Cryptococcus gattii proliferation was higher in N. benthamiana, which presented an increase in the hydrogen peroxide content, antioxidant system activity, and indoleacetic acid (IAA) production. Cryptococcus gattii colonies recovered from N. benthamiana presented lower ergosterol content, reduced capsule, and increased growth rate in vitro and inside macrophages. In vitro, IAA altered C. gattii morphology and susceptibility to antifungal drugs. We hypothesize that C. gattii can temporarily colonize plant living tissues, which can be a potential reservoir of yeast virulence, with further dissemination to the environment, birds, and mammals. In conclusion, N. benthamiana is suitable for studying C. gattii-plant interaction.

In vitro biological control of Ceratobasidium ramicola by using tannin extracts from Acacia villosa, Myristica fragrans, Acacia mangium, and Calliandra calothyrsus leaves

Ceratobasidium ramicola is a fitopathogenic fungus that harmful and causes various levels of damage on several types of forestry and horticultural crops. The purpose of this study was to examine the effect of Acacia villosa, Myristica fragrans, Acacia mangium and Calliandra calothyrsus leaf extracts as tannin sources related to the in vitro inhibition of Ceratobasidium ramicola growth. The in vitro inhibition was performed by employing solid potato dextrose agar (PDA) medium to obtain the radial inhibition, while liquid potato dextrose broth (PDB) medium was used to obtain the biomass inhibition. Experimental design was based on in time nested-completely randomized design and statistical analysis was carried out with SAS software version 9.1. The result of radial growth inhibition of Ceratobasidium ramicola showed that tannin extracts of A. mangium and M. Fragrans were not significantly different to each other. Treatment of tannin extracts from A. villosa, M. fragrans, A. mangium and C. Calothyrsus with a concentration of 1% were significantly different with other concentrations and resulted the greatest inhibition values. Tannin extract of A. Mangium at 1% concentration produced the greatest radial inhibition by 33.2%. In most cases, the effective inhibition from tannin extract occurred at the 24h of incubation. The greatest biomass inhibition was produced on 1% tannin extract of A. mangium by 64.3%, while the lowest was produced from 1% tannin extract of M. fragrans by 27.0%.