Azoxystrobin and propiconazole offer significant potential for rice blast (<Emphasis Type="Italic">Pyricularia oryzae</Emphasis>) management in Australia     

Dolar Pak  Ming Pei You  Vincent Lanoiselet  Martin J. Barbetti 《European journal of plant pathology / European Foundation for Plant Pathology》2017,148(2):247-259

Fungicides are the preferred rice blast (Pyricularia oryzae) control option by farmers. However, no fungicides are yet registered for this purpose in Australia. Hence, it is important to test the baseline sensitivity of P. oryzae isolates collected from blast-affected regions across northern Australia, which have not yet been exposed to the fungicides, as part of a resistance management strategy. Further, it is also important to investigate and compare effect of application timing of fungicides on conidial development, including germination and germ tube growth, and penetration on susceptible rice. The EC₅₀ of a collection of fungicide-sensitive blast isolates were within the range of 0.02–2.02 and 0.06–1.91 mg L^?1 for azoxystrobin and propiconazole, respectively. Azoxystrobin was shown to have greater inhibitory effect on conidial germination than propiconazole. In addition, for pre-inoculation application, only germ tubes in the presence of external nutrients continued to grow from 24 to 48 hpi. On susceptible seedlings, both fungicides completely controlled blast disease when applied the same day as inoculation. However, for pre- or post-inoculation application of fungicide, the extent of disease control was reduced, with azoxystrobin more efficacious than propiconazole. A stimulatory effect of both fungicides at low dose was observed on certain P. oryzae isolates. This is the first study to assess the baseline sensitivity of the P. oryzae population in Australia and the first to report a stimulatory effect of low azoxystrobin concentration on growth of P. oryzae. The study highlights, for the first time, the critical role of external nutrients in promoting germ tube growth under fungicide stress conditions. Lastly, it demonstrates the high degree of efficacy of the fungicides and their potential for future rice blast management in Australia.  相似文献   

First report of the recently introduced,destructive powdery mildew <Emphasis Type="Italic">Erysiphe corylacearum</Emphasis> on hazelnut in Turkey     

Arzu Sezer  F. Sara Dolar  Stuart J. Lucas  Çiğdem Köse  Ebru Gümüş 《Phytoparasitica》2017,45(4):577-581

Hazelnut (Corylus avellana) is Turkey’s most valuable agricultural export, and an essential source of income for many families in the Black Sea Region. In spring 2013, hazelnut leaves, fruit clusters and shoots showing powdery mildew infection symptoms different from those observed previously were discovered in Giresun, Ordu and Trabzon provinces of Turkey. The disease has become epidemic throughout all hazelnut production areas spreading from east to west of the Black Sea Region over the subsequent years. Erysiphe corylacearum was identified as the causal agent of this new and highly destructive powdery mildew based on its morphological characteristics and analyses of DNA sequences of the internal transcribed spacer (ITS) and 28S regions of the ribosomal DNA. Pathogenicity of this species was examined in an infection test and proven for the first time. To our knowledge, this is the first report of E. corylacearum on Corylus avellana worldwide.  相似文献   

Management of rice blast (Pyricularia oryzae): implications of alternative hosts     

Pak  Dolar  You  Ming Pei  Lanoiselet  Vincent  Barbetti  Martin J. 《European journal of plant pathology / European Foundation for Plant Pathology》2021,161(2):343-355

Rice blast (Pyricularia oryzae) has become a serious disease on commercial rice (Oryza sativa) crops in northern Australia and is present there on wild rice (O. australiensis). Characterisation of the host range of P. oryzae is fundamental to both reducing disease spread and to preventing development of epidemics via better management of Poaceae inoculum reservoirs in Australia. Studies on response of three different wild O. australiensis sources toward four isolates of P. oryzae showed all genotypes very susceptible to three isolates [WAC13466 (race IA-1), BRIP53376 (race IB-3), NT2014a (race unknown)], but resistant to isolate BRIP39772 (race IA-3). Studies to investigate levels of blast disease development following inoculation on a range of Poaceae hosts showed both P. oryzae isolates (WAC13466, BRIP53376) were highly virulent on barley (disease index, DI?=?100%), and on Phalaris and O. australiensis (DI?=?70%). However, isolate BRIP53376 showed a significantly higher level of aggressiveness (DI ~80%) on ryegrass, wild oat and rice. Of the two wheat cultivars tested, only one cultivar showed disease and only from WAC13466 (DI ~30%). Sweet corn and goosegrass were also susceptible to both blast isolates, but DI was <50%. That P. oryzae was virulent across these diverse Poaceae hosts, highlights, for Australia, the possibility for these species in, first, harbouring P. oryzae isolates highly virulent to commercial rice, second, fostering spread of rice-attacking P. oryzae strains into regions currently free of rice blast, and third, potential for these alternative host species to encourage development of more virulent host-specific strains of P. oryzae. The current study is an important step towards facilitating improved crop protection in the medium and long term from reducing P. oryzae disease epidemics via a better understanding and management of inoculum reservoirs in Australia.

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Comparative colonisation by virulent versus avirulent <Emphasis Type="Italic">Pyricularia oryzae</Emphasis> on wild <Emphasis Type="Italic">Oryza australiensis</Emphasis>     

Dolar Pak  Ming Pei You  Vincent Lanoiselet  Martin J. Barbetti 《European journal of plant pathology / European Foundation for Plant Pathology》2018,151(4):927-936

Pyricularia oryzae (rice blast) conidial development at pre-penetration stage determines success or otherwise of infection inside the rice host plants. Studies on conidial germination and growth on the leaf surface in commercial rice (Oryza sativa) report differently, dependent upon host type and level of blast resistance. Although wild rice (O. australiensis) is known to be an alternative host of blast, the interaction between P. oryzae conidia and wild O. australiensis on its leaf surface has not been previously studied. We found significant (P?<?0.001) differences in conidial development between two blast isolates with different virulence in terms of conidial germination, germ tube growth and appressoria formation on both wild and cultivated rice. Conidial germination at 6 h post-inoculation (hpi) for the virulent isolate was significantly (P?<?0.001) delayed. Germ tubes of the avirulent isolate conidia grew significantly (P?<?0.001) faster and with significantly (P?<?0.001) longer germ tubes than from virulent conidia. Appressoria development for the virulent isolate was significantly (P?<?0.001) faster at its later growth stages of 12 and 18 hpi when approximately 100% of germ tubes formed appressoria. In contrast, formation rate of appressoria for the avirulent isolate was significantly (P?<?0.001) slower and only reached 76% of germ tubes forming appressoria. Appressoria formation on O. australiensis was significantly (P?<?0.001) greater than the formation on O. sativa for both virulent and avirulent P. oryzae at 12 hpi, a clear indication that host type influences the extent of appressoria formation.  相似文献