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Biology & Management of Brown Root Rot of Alfalfa. F.A. Gray, C.R. Hollingsworth, D.W. Koch. R.W. Groose and R.C. Larsen. Fungal Taxonomy. Anamorphic (asexual) stage: Phoma sclerotioides (syn. Plenodomus meliloti & Plenodomus sclerotioides ). 8-wk-old culture on PDA.

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Biology & Management of

Brown Root Rot of Alfalfa

F.A. Gray, C.R. Hollingsworth, D.W. Koch

R.W. Groose and R.C. Larsen


Fungal Taxonomy

Anamorphic (asexual) stage: Phoma sclerotioides

(syn. Plenodomus meliloti & Plenodomus sclerotioides)

8-wk-old culture on PDA

Pycnidia (SEM, 110x)

Hyaline, single-celled conidia (400x)


History

1933-1st reported on sweet clover in Canada

1984 – widespread on alfalfa in the Peace River Valley of Alberta

1996 – 1st reported on alfalfa in the U.S. in Wyoming

Host Range

(J.G.N Davidson)

Alfalfa

Alsike Clover

Bird’s-Foot Trefoil

Red Clover

Sainfoin

Sweet Clover


Survival & Spread

(J.G.N Davidson)

  • Survival: in plant debris & in soil

- Spread: by wind & grazing animals


Diagnosis

a. Plant Symptoms

Diseased

Severe Winterkill

Dead

Close up of dead and dying plants

Farson, Wyoming Spring of 1996

Plants removed showing severe root rot


Diagnosis

b. Root isolation

Root isolation on PDA at 500 F. after 8 weeks

Note white mycelium, black pycnidia and yellow spore masses

c. PCR-based SCAR markers (R.C. Larsen, USDA-ARS, Prosser, WA)


Distribution

Indigenous Fungus

CANADA

USA

Currently known distribution in the U.S.

(Idaho, Montana, Wisconsin, Wyoming)


Recommended Control Practices in Canada

  • Crop rotation – Grow annual crops such as oats or barley for 3 years between alfalfa crops. Avoid rotation with other forage legume crops especially sweet clover.

  • Harvesting/Grazing Management

  • Avoid excessive cutting

  • Avoid late fall cutting

  • Avoid overgrazing & grazing in the fall before the ground is frozen.


  • 3. Maintain proper soil fertility

  • 4. Plant a resistant variety

  • The variety Anik

  • (Medicago falcata) is

  • partially resistant.

  • The variety Peace is the

  • least susceptible of the

  • M. sativa varieties

  • J.G.N Davidson.

Farson, Wyoming

Peace

Anik


Recommended Control

Practices in the USA

  • Same as for Canada (items 1, 2, and 3)

  • Reaction of most U.S. varieties to BRR is currently unknown

  • The variety “Peace” performed well in the presence of BRR at Farson, Wyoming but may be susceptible to other major stand decline diseases in the U.S.

  • Other varieties performing well in the presence of BRR at Farson include: Ranger, Avalanche + Z and Spreador 3


Other available information on Brown Root Rot:

  • University of Wyoming Bulletin, B-1136, “Brown Root Rot of Alfalfa”

  • b. BRR Evaluation Protocol for, “Standard Tests to Characterize Alfalfa Cultivars” (pending final approval)

  • [email protected]


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