Oplismenopsis najada new host of Pyricularia spp.

doi:10.21203/rs.3.rs-1408361/v1

Download PDF

Short Report

Oplismenopsis najada new host of Pyricularia spp.

https://doi.org/10.21203/rs.3.rs-1408361/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted

You are reading this latest preprint version

Pyricularia spp is a fungal complex whose best known representative is Pyricularia oryzae. It also affects other weeds that grow alongside the rice culture, posing greater risk of contribute as primary inoculum for development, survival and dissemination of pathogen. During monitoring of species weeds near of rice culture in Corrientes (Argentina), were observed symptoms of blast on leaf blades of Oplismenopsis najada, known as “canutillo” (Poaceae). It is a perennial species that inhabits flooded and rice-growing areas of argentinian NE. Koch's postulates were applied to determine the etiology confirming O. najada as a new host of Pyricularia spp, but incapable of causing disease in rice. This is the first report of Oplismenopsis najada as new host of Pyricularia spp in Argentina.

blast

Koch

Magnaporthe

weeds

The genus Pyricularia comprises large group of species hose best known representative is Pyricularia oryzae (teleomorph Magnaporthe oryzae B. Couch) named by Cavara in Italy in 1891 (Ou 1985). Is the causal agent of the rice blast disease (Oryza sativa), considered as the most widespread and destructive disease worldwide (Couch and Kohn 2002; Ou 1985; Bastida et al. 2019) and is a threatening global food security (Asibi et al. 2019).

The genus Pyricularia It affects more than 50 species of the Poaceae family, among them crops like rice, wheat and accompanying weeds (Ou 1985; Scheuerman et al. 2012; Webster and Gunnell 1992). In rice crops it attacks from seedling to grain filling; though most damage is observed from tillering stage onward (Bastida et al. 2019).

In monitoring of species weeds near of rice culture in Corrientes (Argentina) plants of Oplismenopsis najada (Hack, et Arech) Parodi, commonly known as canutillo (Poaceae), were observed, whose leaf blast symptoms were typical as shown in Fig. 1.

INSERT Fig. 1 Symptoms of blast on O. najada in natural infection

The primary inoculum of Pyricularia spp survives in crop residue, seeds and secondary hosts as conidia and mycelium. Despite having been identified in different plants, the role of the different hosts of the pathogen on rice is still controversial (Scheuerman et al. 2012).

In this regard several authors cross-inoculated isolated from rice and grass-weeds and were able to show cross-infection. Results from some cross-inoculation studies shown that Pyricularia spp from Bromus catharticus infect Oryza sativa (Bastida et al. 2019). Also Mackill and Bonman (1986) showed pathogenicity cross between of Pyricularia spp from Rottboellia exalta on O. sativa. These researches suggests that each pathosystem should be evaluated in particular, being that most of the pathogenicity tests of Pyricularia spp isolated on grass weeds, does not show positive results in cross inoculations with rice (Ou 1985) which is the most important extensive crop in Argentina, confirming that cross pathogenicity is a rare phenomenon (Scheuerman et al. 2012).

Our hypothesis holds that the inoculation of Pyricularia spp strains of O. najada in rice will be negative. However, it constitutes a new host for Pyricularia spp.

In order to update the host range of Pyricularia spp and to contribute to the clarification of the pathogenic role of rice weeds as potential sources of primary inoculum, the present work was carried out.

The study was carried out in the Laboratory of Plant Pathology, Faculty of Agronomy, National University of North East (FCA-UNNE) (Corrientes Province). Botanical identification was carried out at the Weed Center FCA-UNNE.

Lesions on leaves were measured with a ruler. Micromorphometric characteristics were determined by measuring conidia and conidiophores obtained from lesions, using an ENOSA 40x microscope with micrometer eyepiece.

To obtain Pyricularia spp isolates, sowings were made from leaf pieces taken from the border between healthy and diseased tissue of the lesions, which were disinfected in 2.5% NaCl one minute, and transferred to Petri dishes with 1.5% potato glucose agar (PGA) 1.5%, pH 6. Colonies were grown in a 12 h light − 12 h dark illumination hood for 8 days (Philips TL-D 36W/54–765 1SL/25 lamp) at 25 ± 2°C. Cultural characteristics were determined on PGA.

Pathogen inoculations were performed by spraying a suspension of 10⁶ conidia mL^− 1 with the addition of Tween 20, on healthy plants of O. najada (Fig. 2) and rice (GURI INTA CL variety) with 3–4 leaves, grown in greenhouses. Inoculated plants remained in humid chamber conditions for 7 days (25 ± 2°C) (Verzignassi et al. 2012).

INSERT Fig. 2 Pyricularia spp on O. najada leaves inoculated in the laboratory

The genus Pyricularia was identified on leaf blades of O. najada causing fusiform lesions with brown edges surrounded by a chlorotic halo measuring 7.3 x 2.15 cm. Numerous spots tended to coalesce to form blight. In young lesions a green efflorescence was observed, becoming gray in older ones; with sympodially growing conidiophores with 10 to 18 conidia at their extremity, pyriform, biseptate, of 16.8 x 5.4 µ.

Direct pathogenicity was tested in O. najada plants reproducing the lesions of the natural infection. The natural and micromorphometric characteristics of the reisolate coincided with the pure isolate, complying with Koch's postulates. Pathogenicity in rice was negative.

According to our studies this is the first report of Oplismenopsis najada as a new host of Pyricularia spp. in Argentina however, pathogenicity studies should continue to determine if it plays a role as a reservoir of the disease capable of making other hosts sick.

Oplismenopsis najada, commonly known as “canutillo” is found inhabiting canals, drains, flooded sites and rice fields in the province of Corrientes. Although it is a host of Pyricularia spp, it does not represent a source of inoculum for rice blast.

Several authors have verified the cross-pathogenicity of Pyricularia spp obtained from different hosts on rice plants (Bastida et al. 2019; Gutiérrez and Cúndom 2015; Ou 1985; Mackill and Bonman 1986; Perelló et al. 2017) however, it is still a rare phenomenon as Scheuerman et al. (2012) argue, which is why each pathosystem should continue to be studied individually.

The direct pathogenicity of Pyricularia spp from O. najada in the same host, but with negative results in rice plants, indicates that it does not represent a direct inoculum source of blast disease confirming our hypothesis, despites be a Pyricularia spp hosts.

All this points to the need to continue exploring the pathogenic combinations among the different hosts deepening the studies in botanically related plants and of other families, in order to clarify the role of the weeds as potential sources or rice blast inoculum to contribute to the knowledge of this disease of worldwide distribution.

Funding. This work was financed through the granting of a doctoral scholarship to the first author by CONICET (National Commission for Scientific and Technological Research) Resolution No. 4869 and contributes to project 20A015 of the General Secretary of Science and Technology of the National University of Northeast (UNNE).

Ethics declarations. This research article is not submitted elsewhere for publication and this manuscript complies with the Ethical Rules applicable for this journal.

Human and animal rights. This research did not involve any animal and/ or human participants. Conflict of interest. The authors declare that they have no conflict of interest.

Contributions

Bastida LM has conceived the idea, carried out plant sampling, trials, writing and general supervision. Quiroga JA has contributed with sampling, trials, photographic registration and editing of the text. Gutiérrez SA and Carmona MA have contributed to the revision and final editing of the text.

Acknowledgments

We thank the National Commission for Scientific and Technological Research (CONICET) for granting a doctoral fellowship to the first author and the Weed Center of de Faculty of Agronomy of the National University of the Northeast for botanical identification of O. najada.

Asibi AE, Chai Q, Coulter JA (2019) Rice Blast: A Disease with Implications for Global Food Security. Agronomy 9(8):451. https://doi.org/10.3390/agronomy9080451
Bastida LM, Gutierrez SA, Carmona MA (2019) Aislamiento y caracterización sintomática de Pyricularia spp en arroz y otros hospedantes en la provincia de Corrientes (Argentina). Summa Phytopathologica 45(2):200–203. https://doi.org/10.1590/0100-5405/190957
Couch BC, Kohn LM (2002) A multilocus gene genealogy concordant with host preference indicates segregation of a new species, Magnaporthe oryzae, from M. grisea. Mycologia 94:683– 693. https://doi.org/10.1080/15572536.2003.11833196
Gutiérrez SA, Cúndom MA (2015) Pyricularia oryzae en cultivos de cebada en Corrientes (Argentina). Summa Phytopathologica 41(4):318–320. https://doi.org/10.1590/0100-5405/2063
Mackill AO, Bonman JM (1986) New hosts of Pyricularia oryzae. Plant Dis 70(2):125–127. https://doi.org/10.1094/PD-70-125
Ou SH (1985) Rice Diseases. Commonwealth Mycological Institute
Perelló AE, Martinez I, Sanabria A, Altamirano R, Sibole JV (2017) Pathogenicity of isolates of Magnaporthe spp from wheat and grasses infecting seedlings and mature wheat plants in Argentina. Plant Pathol 66:1149–1161. https://doi.org/10.1111/ppa.12658
Scheuerman K, Raimondi J, Marschalek R, De Andrade A, Wickert E (2012) Magnaporthe oryzae Genetic Diversity and Its Outcomes on the Search for Durable Resistance. In: Çalışkan M (ed) The molecular basis of plant genetic diversity, 1th edn. InTech, Croatia, pp 331–356. https://doi.org/10.5772/2639
Verzignassi JR, Poltronieri LS, Benchimol RL, Santos De França SK, Arruda Carvalho E, Dornelas Fernandes C (2012) Pyricularia grisea: novo patógeno em Brachiaria brizantha cv. Marandu no Pará. Summa Phytopathologica 38(3):254. https://doi.org/10.1590/S0100-54052012000300016
Webster RK, Gunnell PS (1992) Compendium of rice diseases. The American Phytopathological Society, Saint Paul MN

Download PDF

Version 1

posted

You are reading this latest preprint version

Oplismenopsis najada new host of Pyricularia spp.

Status:

Version 1

Abstract

Figures

Introduction

Materials And Methods

Results

Discussion

Declarations

References

Status:

Version 1