Cytological aspects of incompatible and compatible interactions between rice, wheat and the blast pathogen Pyricularia oryzae

Abstract

Blast, caused by the fungus Pyricularia oryzae, is an important disease affecting rice and wheat yield worldwide. This study investigated the cytological aspects of incompatible (non-host resistance) and compatible (host resistance) rice-(R_Po) and wheat-(W_Po) Pyricularia oryzae isolate interactions. Inoculations of rice and wheat with the R_Po and W_Po isolates of P. oryzae, respectively, were expected to be compatible interactions (host resistance), whereas inoculations of rice and wheat with the W_Po and R_Po isolates of P. oryzae, respectively, were considered to be incompatible interactions (non-host resistance). For the compatible interactions (rice-R_Po and wheat-W_Po), fungal hyphae penetrated and colonized the epidermal cells and also invaded many neighboring cells. By contrast, in the case of the incompatible interactions (rice-W_Po and wheat-R_Po), fungal hyphae were not able to penetrate nor colonize the epidermal cells, but when penetration did occur, the hyphae were restricted to the first-invaded epidermal cell. The frequency of appressorial sites exhibiting infection hyphae within the epidermal cell underlying an appressorium was greater in the case of the compatible interactions. By contrast, unsuccessful penetrations with cytoplasmic granulation occurred with high frequency in the incompatible wheat-R_Po and rice-W_Po interactions and the number of necrotic epidermal cells underlying the appressorium was low for the rice-W_Po interaction as well as for the wheat-R_Po interaction, where no symptoms of necrosis were exhibited. However, the opposite was observed for the compatible interactions. The present study presents cytological features associated with incompatible and compatible rice-and wheat-P. oryzae interactions that may be useful to studies involving variability, coevolution, diagnosis, and regulation of quarantine or even in a rice or wheat breeding program whose aim is to transfer genes involved in non-host resistance to host resistance due to similarities in downstream mechanisms.

Hydrogen Peroxide Detoxifying Enzymes Showed Different Activities at Different Timing in Host and Nonhost Plants Interactions with Wheat Blast Fungus Magnaporthe Oryzae Triticum Pathotype

“…However, MoT isolate did not produce any symptom on rice plant, thus considered as resistant to MoT isolate. Our result is consistent with the result reported by Araujo et al [38] that the rice plant did not produce any necrosis or hypersensitive response cell death when inoculated with wheat-infecting M. oryzae isolates (non-host). In Bangladesh, maize is the third important cereals crops after rice and wheat [39] and barley is a non-major cereal but widely grown in north Bengal of Bangladesh [40].…”

Wheat blast disease: danger on the move

“…Initial cytological studies of "non-host resistance" have compared infection outcomes on the adapted and non-adapted hosts using M. oryzae isolates from the Oryza, Triticum, and Eleusine pathotypes and M. grisea isolates from Digitaria species. Fungal strains often failed to penetrate non-adapted hosts, and if penetration occurred, they induced post-penetration cytoplasmic-granulation or hypersensitive-like responses characteristic of genefor-gene interactions in rice (Heath et al 1990;FaivreRampant et al 2008;Tufan et al 2012;Araujo et al 2016). …”

Wheat blast: A review from a genetic and genomic perspective

“…Appressoria that form in water droplets, such as dew, generate extremely high turgor pressure to penetrate and colonize the host leaf surface. In non-adapted hosts, fungal strains frequently failed to penetrate, and when they did, they elicited cytoplasmic granulation or hypersensitive-like reactions suggestive of gene-for-gene exchanges ( Araujo et al, 2016 ).…”