Mechanisms involved in control of Blumeria graminis f.sp. hordei in barley treated with mycelial extracts from cultured fungi

Abstract

Treatment with mycelial extracts, prepared from liquid cultures of Bipolaris oryzae , Pythium ultimum and Rhizopus stolonifer , protected barley ( Hordeum vulgare ) against powdery mildew disease caused by the fungus Blumeria graminis f.sp. hordei . The mechanisms of this protection were studied using histopathological methods and molecular analysis. Germination and appressorial formation of B. graminis were generally reduced after treatment with mycelial extracts. Although this reduction (between 12 and 62% depending on treatment and experiment) was inconsistent and only occasionally significantly different from the water-treated control, it indicated a direct antifungal effect of the extracts. In situations where the fungus succeeded in forming an appressorium, penetration efficiency and haustorium formation from these appressoria was not affected -no enhanced penetration resistance associated with papilla formation was detected. However, a post-penetration effect was observed, as B. graminis colonies on mycelial extracttreated leaves produced 50% fewer hyphae than on controls. Northern blot analyses showed earlier accumulation of defence-related gene transcripts following treatment with B. oryzae and P. ultimum mycelial extracts, and to a lesser extent R. stolonifer mycelial extract, compared with water-treated leaves. It is suggested that the protection mechanism of the mycelial extracts involves direct antifungal effects and possible induced resistance for the B. oryzae and P. ultimum mycelial extracts.

A review of fungal antagonists of powdery mildews and their potential as biocontrol agents

“…During the search for active metabolites, mycelial extracts of several other fungi ( Bipolaris oryzae (Breda de Haan) Shoem, B sorokiniana (Sacc) Shoem, Drechslera teres (Sacc) Shoem, Fusarium culmorum Sacc, Pythium ultimum Trow and Rhizopus stolonifer Lind) were also tested against barley powdery mildew ( Blumeria graminis (DC) Speer f sp hordei ) 59. 60 However, these fungi were not considered antagonists of powdery mildews, and therefore are not included in Table 1, because only their sterile mycelial extracts were applied against B graminis without testing the possible effects of the fungi themselves.…”

The durable wheat disease resistance gene Lr34 confers common rust and northern corn leaf blight resistance in maize

“…Each fungus uses a different mechanism to invade its host plant. Penetration can be direct, through the cuticle and the different layers of the cell wall, as this is the case for rice blast, NCLB and powdery mildew pathogens (Haugaard et al, 2002;Knox-Davies, 1974;Pederson et al, 2012;Wathaneeyawech et al, 2015;Zabka et al, 2008;Zhang et al, 2014). Other pathogens like the rusts use natural openings such as stomata on the leaf surface (Song et al, 2011).…”

“…Other pathogens like the rusts use natural openings such as stomata on the leaf surface (Song et al, 2011). Once inside the leaf, the obligate biotrophic rust and mildew fungi produce specialized feeding structures called haustoria for nutrient uptake and effector secretion (Haugaard et al, 2002;Pederson et al, 2012;Petre and Kamoun, 2014;Song et al, 2011;Zabka et al, 2008). The hemi-biotrophic fungi rice blast and NCLB also develop vesicles-like structures by differentiation of primary hyphae (Kankanala et al, 2007;Muiru et al, 2008;Wilson et al, 2012) that are very similar to haustoria and that are also surrounded by the host membrane (Levy and Cohen, 1983;Wilson and Talbot, 2009).…”

The resistance to leaf rust and powdery mildew of recombinant lines of barley (Hordeum vulgare L.) derived from H. vulgare × H. bulbosum crosses

“…Inoculation was carried out by blowing spores from the infected plants over the leaf segments using a settling tower. A glass slide was placed in the settling tower to monitor inoculum density, which was adjusted to give approximately 20 conidia/mm 2 (Spain) or 2–4 conidia/mm 2 (Germany; Haugaard et al. 2002).…”

“…Inoculation was carried out by blowing spores from the infected plants over the leaf segments using a settling tower. A glass slide was placed in the settling tower to monitor inoculum density, which was adjusted to give approximately 20 conidia/mm 2 (Spain) or 2-4 conidia/mm 2 (Germany; Haugaard et al 2002). After inoculation, Petri dishes were transferred to a growth chamber at 18-20°C (Spain) or 16°C (Germany) and incubated in darkness for 12 h. They were then transferred to a growth chamber with fluorescent lighting (12 h light/12 h dark -Spain, or continuous light -Germany) with temperatures as before (Edwards 1993).…”