Characterization of histological changes at the tillering stage (Z21) in resistant and susceptible wheat plants infected by Tilletia controversa Kühn

Abstract

Background Dwarf bunt, which is caused by Tilletia controversa Kühn, is a soilborne and seedborne disease that occurs worldwide and can lead to 70% or even total losses of wheat crops. However, very little information is available about the histological changes that occur in dwarf bunt-resistant and dwarf bunt-susceptible wheat plants at the tillering stage (Z21). In this study, we used scanning electron microscopy and transmission electron microscopy to characterize the histological changes at this stage in resistant and susceptible wheat cultivars infected by T. controversa. Results Using scanning electron microscopy, the root, stem, and leaf structures of resistant and susceptible cultivars were examined after T. controversa infection. The root epidermal and vascular bundles were more severely damaged in the susceptible T. controversa-infected plants than in the resistant plants. The stem cell and longitudinal sections were much more extensively affected in susceptible plants than in resistant plants after pathogen infection. However, slightly deformed mesophyll cells were observed in the leaves of susceptible plants. With transmission electron microscopy, we found that the cortical bundle cells and the cell contents and nuclei in the roots were more severely affected in the susceptible plants than in the resistant plants; in the stems and leaves, the nuclei, chloroplasts, and mesophyll cells changed significantly in the susceptible plants after fungal infection. Moreover, we found that infected susceptible and resistant plants were affected much more severely at the tillering stage (Z21) than at the seedling growth stage (Z13). Conclusion Histological changes in the wheat roots, stems and leaves were much more severe in T. controversa-infected susceptible plants than in infected resistant plants at the tillering stage (Z21).

Characteristics of the Infection of Tilletia laevis Kühn (syn. Tilletia foetida (Wallr.) Liro.) in Compatible Wheat

“…Scanning electron microscopy could be used to observe the teliospores in wheat tissues, and transmission electron microscopy could be used to directly observe the distribution of pathogens in plant tissues, organs and the ultrastructural changes caused by the infection of the pathogen. Particularly, we used WGA-AF 488 to label T. laevis hyphae and used PI to label wheat tissues with laser scanning confocal microscopy, which was much simpler and produced clearer results than using the traditional tissue sectioning technique ( Xu et al, 2021 ).…”

“…Based on the protocols used by Xu et al (2021) , we modified with the following details; three infected wheat leaves and three mock inoculated leaves in each stage were used, for each stage of the one-leaf (Z11), two-leaf (Z12), three-leaf (Z13), tillering (Z21), jointing (Z31), and mature stages (92), 10 samples were used for scanning electron microscopy observation. For the mature stage samples, we also checked the roots, stems, leaves, glumes and awns of the infected wheat.…”

“…The samples were chosen as the same method mentioned for scanning electron microscopy. We followed the protocol published previously by Xu et al (2021) , briefly; the surface of the plant tissue was cleaned, cut it into small pieces with a blade, and immediately put in a 3% glutaraldehyde solution for 48 h, and a vacuum was used to remove the bubbles in the plant tissue. With this method, when the plant sample sinks, the glutaraldehyde is completely infiltrated into the plant tissues.…”

“…Therefore, laser scanning confocal microscopy is a powerful tool for the research of molecular cell biology, genetics, immunology, and pathology ( Muhae-Ud-Din et al, 2020 ). It can be used to observe the cellular morphological changes in host tissues after pathogen infection and study the infection of pathogens and the interactions between pathogens and hosts ( Xu et al, 2021 ). Gao et al (2013) used laser scanning confocal microscopy to investigate the impact of corn smut pathogen on maize anther development.…”

Toward Understanding the Molecular Recognition of Fungal Chitin and Activation of the Plant Defense Mechanism in Horticultural Crops

“…that prevents pathogens and predators from invading the plant cell [23]. When plants become infected, several changes in the cuticle take place, which causes the activation of defense responses [24]. Once pathogens overcome the first line of defense, the second line of defense is initiated based on the cellular innate immunity, which allows the plant to resist or block the pathogen [25].…”