Ustilago esculenta is a biotrophic smut fungus that parasitizes Zizania latifolia, an edible aquatic vegetable of the southern China region. Infection results in swelling of the upper parts of the Z. latifolia culm which are called jiaobai and have a unique flavor and delicacy and are popular among Chinese. The infection process of Z. latifolia by U. esculenta was investigated with light and electron microscopy. Distribution of hyphae was uneven in plants; hyphae were mainly present in the swollen upper parts (jiaobai), the nodal regions of mature culms and old rhizomes and buds or shoots. Hyphae were rare in the internodes of mature culms and were fewer in the internodes of old rhizomes. All new buds produced on the nodes of culms and rhizomes were infected by hyphae in November before and in March after overwintering. The hyphae grew into the buds from the parent nodes via intervascular tissues only or via parenchyma tissues and vascular bundles. Hyphae extended within and between the host cells and frequently formed hyphal aggregations or clusters, not only in the mature tissues but also in developing tissues. The typical interface between the fungal hyphal wall and invaginated host plasma membrane comprised a sheath. The sheath surrounding a hyphae comprised an outer electron-opaque matrix and an inner electron-dense layer. The electron-opaque matrix layers were thicker in jiaobai tissues, ranging from 0.28 to 0.85 μm. The electron-dense hyphal coatings were more conspicuous in the young buds or shoots and mature culms than in the jiaobai. The intercellular hyphae caused large cavity formation between the cells or rupture of host cell walls, for gaining entry into host cells. The broken host cell wall fused with the electron-opaque matrix of the hyphal sheath as an interactive interface. The teliospore wall and wall ornamentation development was the same in postmature jiaobai tissues with sporadic sori and in the huijiao (jiaobai tissues containing the massive sori), but a sheath enveloping the teliospore was more transparent in the process of teliospore development in the jiaobai than in the huijiao.

Cytology and ultrastructure of interactions between Ustilago esculenta and Zizania latifolia

Ustilago maydis is a biotrophic fungus that induces formation of tumors in maize (Zea mays L). In a recent study we identified See1 (Seedling efficient effector 1) as an U. maydis organ-specific effector required for tumor formation in leaves. See1 is required for U. maydis induced reactivation of plant DNA synthesis during leaf tumor progression. The protein is secreted from biotrophic hyphae and localizes to the cytoplasm and nucleus of plant cell. See1 interacts with maize SGT1, a cell cycle and immune regulator, interfering with its MAPK-triggered phosphorylation. Here, we present new data on the conservation of See1 in other closely related smuts and experimental data on the functionality of See1 ortholog in Ustilago hordei, the causal agent of barley covered smut disease.

Conservation of the Ustilago maydis effector See1 in related smuts

The development of ecological circular agriculture has been highly encouraged by the Chinese government to recycle agricultural wastes, reduce mineral fertilizer input, and protect the environment. Biogas slurry, a byproduct of biogas engineering developed in rural areas of China, could be used as N fertilizer for crop growth. The field experiments were conducted in 2014 and 2015 to study the plant growth responses and environmental impacts of applying biogas slurry to two-season Zizania aquatica Turcz. growth. The potential factors that restrict the rational use of biogas slurry were also clarified. Mineral N fertilizer can be completely or partly substituted by N fertilizer from biogas slurry to satisfy Z. aquatica plant growth. It was not at the cost of sacrificing yield, dry matter accumulation, N accumulation and physiological N use efficiency in the above-ground parts. However, the growth inhibition occurs when the N quantity in biogas slurry was 2 or 2.7 times higher than that of mineral N fertilizer. Vitamin C in non-shell swollen culms (as edible part) of Z. aquatica significantly increased after biogas slurry application. Biogas slurry application substantially increased the N concentrations, i.e., total N, NH4
 +–N, and NO3
 −–N in floodwater and delayed the time to reach national discharge standards. However, biogas slurry application did not affect the N concentrations in percolating water compared with the treatment with mineral N fertilizer only. Applying biogass slurry did not generate potential pollution risks by trace elements (Cu, Zn, Pb, Cr, Cd, As, and Hg) in the non-shell swollen culm and soil, and did not increase the nitrate content in non-shell swollen culm. We found the NH4
 +–N concentration in biogas slurry can account for 77–93% of total N and reflects the N level in biogas slurry to a great degree. Semi-quantitative color-based colorimetric methods possessing simple and fast characteristics should be developed to determine the NH4
 +–N concentration with the purpose of promoting reasonable use of biogas slurry in area of crop cultivation. Otherwise, excessive use of biogas slurry can adversely affect crops and increase environmental risks.

Biogas slurry use as N fertilizer for two-season Zizania aquatica Turcz. in China

Plant growth and photosynthetic performance of Zizania latifolia are altered by endophytic Ustilago esculenta infection

Successful and efficient dispersal of fungi is crucial to the survival of the fungi, balance of ecosystems, and stability of biodiversities. Dispersal strategies of microfungi and other fungi are reviewed in detail based on the literature published in the last four decades. It covers the latest development of research on the dispersal process: liberation, transporation, deposition, resuspension, and survival of fungal spores and other propagules from microscale to macroscale. The characters of dispersal strategies of fungi from different habitats are elucidated. The fungal habitats include litter, soil, plants, insects, other animals, aquatic and marine environments, etc. For each strategy, the associated mechanisms are discussed for their ecological significance. The significance of the new technology used in the recent studies on dispersal strategies is presented. At the same time, current and future applications of dispersal strategies of microfungi are discussed in the chapter.

Dispersal Strategies of Microfungi

Zizania latifolia (Manchurian wild rice), native to eastern Asia, is often infected by the smut fungus, Ustilago esculenta, causing culm enlargement and failure to produce flowers. The enlarged infected culms have been used as a vegetable (gau sun) in China since the 10th century. The occasionally-used nameZ. Caduciflora is shown to be only a synonym. To facilitate identification of the host, a taxonomic key shows thatZ. Latifolia differs from and is fully distinct from the American species ofZizania. The nature and structure of the fungus and the history and cultivation of the vegetable are described. As a precaution we propose quarantine of the host and fungus to prevent possible disastrous widespread infection of American wild rices by the fungus.

https://www.jstor.org/stable/pdfplus/4254397.pdf

L. R. Batra

Papers

Zizania latifolia andUstilago esculenta, a Grass-Fungus Association