植物科学

Phytophthora infestans is a hemibiotroph oomycete that primarily infects potato and tomato. It infects stems, leaves, and tubers and fruits of potato and tomato. High throughput and reproducible infection assays are prerequisites to find sources of resistance in any crop. In this protocol, we describe a detached leaf assay (DLA) for conducting the virulence assay of P. infestans in potato leaves. A late blight infection assay using a potato detached leaf is a semi-high throughput assay in which hundreds of plants can be screened in a laboratory setting.

Virus inoculation is a basic experimental procedure to evaluate the resistance of a rice variety or a transgenic material upon virus infection. We recently demonstrated that Rice Ragged Stunt Virus (RRSV), an oryzavirus that is transmitted by brown planthopper (BPH), can suppress jasmonic acid-mediated antiviral defense through the induction of microRNA319 and facilitate virus infection in rice. To verify this, we performed virus inoculation experiments on wild-type rice plants and miR319-TCP21-associated transgenic rice plants through a modified group inoculation method. Here, we presented the detailed procedure of RRSV propagation and infection process on rice plants.

Fusarium graminearum, the major causal agent of Fusarium head blight (FHB), causes serious wheat yield losses and a threat to human and animal health. The main efforts to combat the disease are the research of pathogenesis mechanisms and breeding for disease resistance plants. The efficiency of these actions could be evaluated by reliable inoculation assay, which is performed by accurate and repeatable inoculation methods. Hence, a standard procedure of effective wheat inoculation should improve the accuracy of pathogenicity evaluation. Here, we present a protocol for wheat spike inoculation with fungal conidial suspensions or fungus agar discs. These methods show highly reproducibility and accuracy on wheat infection experiment in laboratory conditions.

Rice yellow mottle virus (RYMV), a mechanically transmitted virus that causes serious damage to cultivated rice plants, is endemic to Africa. Varietal selection for resistance is considered to be the most effective and sustainable management strategy. Standardized resistance evaluation procedures are required for the identification and characterization of resistance sources. This paper describes a protocol for mechanical inoculation of rice seedlings with RYMV and two methods of resistance evaluation – one based on a symptom severity index and the other on virus detection through double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA).

Botrytis cinerea (B. cinerea) attacks many crops of economic importance, represents one of the most extensively studied necrotrophic pathogens. Inoculation of B. cinerea and phenotypic analysis of plant resistance are key procedures to investigate the mechanism of plant immunity. Here we describe a protocol for B. cinerea inoculation on medium and planta based on our study using the tomato-B. cinerea system.

Field-grown maize is inoculated with Cochliobolus heterostrophus, causal agent of southern leaf blight disease, by dropping sorghum grains infested with the fungus into the whorl of each maize plant at an early stage of growth. The initial lesions produce secondary inoculum that is dispersed by wind and rain, causing multiple cycles of infection that assures a high uniform disease pressure over the entire field by the time of disease scoring, which occurs after anthesis. This method, with slight modifications, can also be used to study the maize fungal diseases northern leaf blight (caused by Exserohilum turcicum) and gray leaf spot (Cercospora zeae-maydis).

We describe a protocol to measure the electrolyte leakage from plant tissues, resulting from loss of cell membrane integrity, which is a common definition of cell death. This simple protocol is designed to measure the electrolyte leakage from a tissue sample over a time course, so that the extent of cell death in the tissue can be monitored dynamically. In addition, it is easy to handle many tissue samples in parallel, which allows a high level of biological replication. Although the protocol is exemplified by cell death in Arabidopsis in response to pathogen challenge, it is easily applicable to other types of plant cell death.

Bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most serious bacterial diseases and a major impediment to the increase of rice yield. Appropriate methods for inoculation of Xoo and disease scoring are necessary to investigate the nature of the disease and the mechanism of plant resistance to the pathogen. As the most-widely grown crop in the worldwide, rice yield plays an important role in food security. Uncovering mechanisms of plant-pathogen interaction of rice and Xoo will help develop rice plants that are more resistant to disease caused by Xoo. Here we describe our validated and efficient methods for inoculation of Xoo and disease scoring.

The ascomycete fungus Fusarium graminearum is a destructive fungal pathogen of wheat, barley and maize. Although reverse genetics and homologous recombination gene deletion methods have generated thousands of gene deletion mutants of F. graminearum, evaluating virulence of these fungal mutants is still a rate-limiting step. Here we present a protocol for inoculation of wheat coleoptiles with conidial suspensions for large-scale phenotypic analysis, and describe how it can also be used to assess fungal infectious growth and symptom developmentat a cellular scale. The inoculation method described in this protocol provides highly reproducible results in wheat coleoptile infection by F. graminearum.

Ustilago bromivora is a biotrophic smut fungus infecting Brachypodium sp. It is closely related to the barley-infecting smut Ustilago hordei, and related to the well-studied, gall-inducing model pathogen Ustilago maydis. Upon flowering, the spikelets of U. bromivora-infected plants are filled with black fungal spores. While it is possible to directly use this spore material to infect Brachypodium seeds, in many cases it is more useful to isolate individual strains of U. bromivora for a genetically homogenous population. This protocol describes how to collect and germinate the spores of U. bromivora on plate in order to obtain strains derived from a single cell.