Development of rice conidiation media for Ustilaginoidea virens

Abstract

Rice false smut, caused by the ascomycete Ustilaginoidea virens, is a serious disease of rice worldwide. Conidia are very important infectious propagules of U. virens, but the ability of pathogenic isolates to produce conidia frequently decreases in culture, which influences pathogenicity testing. Here, we developed tissue media with rice leaves or panicles that stimulate conidiation of U. virens. Among the tested media, 0.10 g/ml panicle medium was most efficient for conidiation. Whereas, some rice leaf media more effectively increased conidiation than panicle media except 0.10 g/ml panicle medium, and certain non-filtered tissue media were better than their filtered counterparts. Although the conidia induced in rice tissue media were smaller, they were able to germinate on potato sucrose agar medium and infect rice normally. The rice tissue medium is also workable in inducing conidia for conidiation-defective isolates. This method provides a foundation for the production of conidia by U. virens that will be widely applicable in pathogenicity testing as well as in genetic analyses for false smut resistance in rice cultivars.

UvKmt6-mediated H3K27 trimethylation is required for development, pathogenicity, and stress response in Ustilaginoidea virens

“…In order to survive and complete infection, U. virens fungus needs to adapt to various stresses from the host and environment [ 35 ]. By RNA-seq analysis, we found that a lot of stress response-related genes were affected extensively when UvKMT6 was deleted (Table S3 and S4).…”

“…In this study, an epigenetic regulator UvKmt6 was found to contribute to the virulence of U. virens in several ways. First, disruption of UvKMT6 resulted in drastic decrease in conidiation, which usually leads to reduced pathogenicity in U. virens [ 35 ]. For example, UvAtg8 is an autophagy marker, and its gene deletion mutant is significantly reduced in pathogenicity due to the decrease of conidia production [ 32 ].…”

Culture media promoting sporulation of rice kernel smut fungus Tilletia barclayana

“…Unfortunately, such knowledge is not available in the literature. Traditionally, sufficient secondary sporidia are collected from PDA after 3 or more weeks of incubation because the fungus grows slowly, and the colonies are small even after 2 or 3 weeks of growth (Wang et al 2019). The results of our study demonstrated that the incubation time effect was significant on the production of secondary sporidia and that the most effective incubation time to produce greatest secondary sporidia was at 2 weeks, as conidial production significantly declined after 2 weeks of incubation.…”

“…Carbon source is essential for the growth and sporulation of fungi, and different carbon sources affect their ability to grow and sporulate. In previous studies, dextrose or sucrose amended liquid medium was the most common culture media used to promote fungal conidial production for inoculation preparations (Ghahal et al 1993;Wang et al 2019). Other than dextrose, however, there have been no reports on the effects of carbon sources on mycelium growth and spore production of T. barclayana.…”

UvVelC is important for conidiation and pathogenicity in the rice false smut pathogen Ustilaginoidea virens

“…For conidiation tests, five mycelial plugs were incubated in 50 mL YT (YTA without agar) medium, with or without rice tissue. Media containing rice tissue was prepared as previously described [ 25 ]. In brief, flag leaves and panicles of rice cultivars “LYP9” were collected at the late booting stage.…”