MDMV and HPV: Two Virus Diseases of Sweet Corn PNVA Meeting Kennewick, WA Nov. 13, 2007 Steve Grier Sweet Corn Breeder Stanton, MN

MDMV and HPV MDMV

Maize Dwarf Mosaic Virus

High Plains Virus

An important disease of sweet corn outside of the PNW

Impacts sweet corn in the PNW and CO

– Midwest – Northeast – Hungary – Chile

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HPV

Symptoms MDMV

HPV

Bob Forster, U.ID, Kimberly, 1996 www.uidaho.edu/ag/plantdisease/index.htm

http://www.ipm.ucdavis.edu/PMG/C/D-CN-CMDV-FO.002.html

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Symptoms, con’t MDMV

http://hgic.clemson.edu/factsheets/Graphics/corndis/mdmv.htm

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HPV

http://utahpests.usu.edu/plantdiseases/files/uploads/PestMonitorin g/high_plains_virus.pdf

Symptoms, con’t MDMV

HPV

http://www.udel.edu/IPM/cca/diseaseslides/sld019.htm

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http://utahpests.usu.edu/plantdiseases/files/up loads/PestMonitoring/high_plains_virus.pdf

Symptoms, con’t MDMV

HPV

http://www.udel.edu/IPM/cca/diseaseslides/sld023.htm

http://nematode.unl.edu/PPATHPER/photo6.jpg

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Symptoms, con’t MDMV

HPV

http://ohioline.osu.edu/ac-fact/0024.html

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http://www.ento.okstate.e du/ddd/diseases/wsmvhpv.pdf

Symptoms, con’t MDMV

http://nu-distance.unl.edu/Homer/disease/agron/corn/CoMDMV.html

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HPV

http://www.ento.okstate.edu/ddd/diseases/wsmv-hpv.pdf

Symptoms from 2007

HPV

NE

MDMV

MN

WA

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Symptoms MDMV – Maize Dwarf Mosaic Virus Mosaic pattern of leaf mottling Chlorosis/reddening of infected leaf tissue Stunting

HPV – High Plains Virus Chlorotic spots (foliar mosaic pattern) that parallel the leaf veins Spots merge to give a generalized chlorosis –

Necrosis if severe infection

Stunting Symptoms vary greatly with different: – – – –

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Host genotypes Environments Plant growth stage Combination with other infecting viruses

Economic consequences MDMV

Yield loss due to: – Kernel abortion, particularly at the butt of the ear. – Plant stress and/or death.

Quality loss due to: – Higher ratio of pericarp to endosperm. – Reduced sugar level in kernels.

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HPV

Same as MDMV – Except for the kernel abortion at the butt of the ear?

Diagnosis MDMV

HPV

Difficult based on field symptoms (visual diagnosis). Send infected leaf samples for ELISA or PCR assay: – State Dep’t Agric / Extension Service / Plant Pathology Lab – Third party testing service http://www.agdia.com/

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Same as MDMV

Pathogen MDMV

Group: Potyvirus Virus: flexous, filamentous particle, ss-RNA. Strains: – MDMV-A, C, D, E, F – SCMV-MDMV-B (now a strain of SCM potyvirus) Host range: Corn, sorghum, and many grasses – MDMV-A overwinters in johnsongrass – MDMV-B does not infect johnsongrass 13

HPV

Group: Unclassified dsRNA – Same group as wheat spot mosiac, fig mosaic, thistle mosaic, rose rosette, and redbud yellow ringspot. Virus: 32 kDa protein; large spherical to ovoid double membrane bound particle; ds-RNA. Strains: Five (Seifers, 2004) Host range: Maize, wheat, barley, oats, rye, foxtail, several grasses.

Transmission MDMV

HPV

Primary means of transmission is via insect vector: –

Aphids (over 20 species)

Seed transmission: Yes, but rare (0.007 to 0.4%) Mechanical transmission: Leaf rub

Primary means of transmission is via insect vector: – – – –

Wheat Curl Mite (Aceria tosichella Keifer) The WCM also vectors WSMV, so mixed infections often occur. WSMV is a potyvirus, like MDMV WCM are wingless and depend on wind for dispersal

Seed transmission: Yes, but rare (0.0008% to 4%). Mechanical transmission: Vascular punch 14

Vector MDMV

Aphid Over 20 species – Corn leaf aphid

HPV Wheat curl mite (WCM)

Same vector as WSMV Small and hard to see

– Greenbug – Green peach aphid

http://www.ento.okstate.edu/ddd/diseases/wsmv-hpv.pdf

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Distribution and Occurance MDMV

More common in the MW

More common in the PNW

MDMV-A: coincides with the distribution of johnsongrass, its overwintering host.

TX, KS, CO, NE, SD, ID, WA, Brazil, Chile, and Israel

MDMV-B: spread north during the summer by “aphid rains” causing isolated outbreaks.

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HPV

First reported in WA in 1998.

Control MDMV

HPV

No curative measures –

No post-infection contol

Insecticides generally won’t kill the insect fast enough to prevent infection. Destroy johnsongrass (reservoir of inoculum) Plant resistant varieties

No curative measures Break the “green bridge”; limit WCM infestations –

–

Control volunteer wheat and corn in fall wheat plantings to break the bridge. Plant fall wheat 14-21 days after volunteer wheat and corn has been killed. Control grassy weeds and volunteer wheat and corn in sweet corn fields.

Plant corn early - or late - to avoid having corn at the 5- to 7leaf stage when WCM are migrating out of wheat. Plant resistant varieties. 17

Genetic Map of Resistance Loci – MDMV and HPV

Kaeppler, S. et al., 1997. http://www.intl-pag.org/5/abstracts/p-5d-192.html

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Artificial Inoculation (breeding nurseries and variety screening) MDMV

Mechanical inoculation at Stanton, MN

HPV

Dependent on natural infection – Infestation by viruliferous WCM – We are working to establish screening at a Syngenta research site in Nebraska

Individual plant inoculation with viruliferous WCM or vascular punch is prohibitively difficult for large scale screening. 19

Disease Resistant Varieties MDMV

HPV

See listing from Dr. Pataky’s sweet corn disease trials at the Univ. Illinois: – http://sweetcorn.uiuc.edu/ report-index.html

See variety fact sheets.

GH6462 GSS1477 20

Published list from 1996 is outdated – http://www.uidaho.edu/ag/ plantdisease/hpdcorn.htm

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