High Humidity Causes Abnormalities in the Process of Appressorial Formation of Blumeria graminis f. sp. hordei

Abstract

High humidity decreases the penetration rate of barley powdery mildew Blumeria graminis f. sp. hordei. However, the mechanism is not well understood. In this study, the morphological and cytochemical analyses revealed that substances containing proteins leaked from the tip of the appressorial germ tube of conidia without the formation of appressorium under a high humidity condition. In addition, exposure to high humidity prior to the formation of appressorium caused the aberrant formation of the appressorial germ tube without appressorium formation, resulting in failure to penetrate the host cell. These findings suggest that the formation and maturation of the appressorium requires a low humidity condition, and will be clues to improve the disease management by humidity control.

Nicotinamide Mononucleotide Potentiates Resistance to Biotrophic Invasion of Fungal Pathogens in Barley

“…Therefore, it would not be only physical forces that penetrate the cell wall [ 21 ]. Bgh may secrete proteins necessary for penetration from the tip of the appressorium [ 18 ]. Likewise, F. graminearum probably secretes proteins such as cell-wall-degrading enzymes from the tips of the appressoria-like structures in order to penetrate host cells.…”

“…The coleoptiles were incubated on a Kimwipe paper moistened with a 1 mM CaCl 2 solution containing NMN 12 h before inoculation. The coleoptiles were then inoculated with Bgh conidia using a brush and incubated at 20 °C in dark conditions for about 30 h. The penetration rate was calculated by counting the number of conidia developing a haustorium per the number of interactions between an epidermal cell and a conidium attacking the cell with an appressorium as described in Sugai et al [ 18 ]. When studying the effect of NMN on leaves, seeds were grown on filter paper containing NMN solution for 12 days, transferred to vermiculite, and grown for 20 days.…”

“…Therefore, further detailed analysis of Stage I and Stage II was performed by confocal fluorescence microscopy using an F. graminearum strain expressing GFP constitutively and the epidermis of wheat coleoptiles, which are more easily observed due to its single-cell layer [ 17 ]. The coleoptile epidermal cells have been used as a suitable material to observe the morphogenesis of Bgh , which occurs relatively synchronously on time [ 18 ]. For example, the primary germ tube emerges within 2 h after the conidium comes into contact with the host’s epidermal cell, and the second germ tube, the appressorial germ tube (AGT), forms 8–10 h later.…”

RACE1, a Japanese Blumeria graminis f. sp. hordei isolate, is capable of overcoming partially mlo-mediated penetration resistance in barley in an allele-specific manner

“…In this study, the isolate formerly known as “Race I” is described as RACE1 as the genomically analysed culture strain according to Frantzeskakis et al [ 27 ]. Leaves were inoculated with Bgh as described by Sugai et al [ 28 ]. After inoculation, the seedlings were incubated in the chamber (NK system LH-60FL3-DT, Nippon Medical & Chemical Instruments, Osaka, Japan).…”