Window of opportunity for root infection leading to foliar symptoms of soybean sudden death syndrome

Sudden death syndrome (SDS) is an economically important soybean disease caused by F. virguliforme. Foliar symptoms typically develop after flowering in field conditions, but can sometimes appear on young plants. Fungal colonization of the root vascular system is essential for expression of foliar s...

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Bibliographic Details
Published in:Phytopathology 2008-06, Vol.98 (6), p.S60-S60
Main Authors: Gongora-Canul, C, Leandro, L
Format: Article
Language:English
Online Access:Get full text
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Summary:Sudden death syndrome (SDS) is an economically important soybean disease caused by F. virguliforme. Foliar symptoms typically develop after flowering in field conditions, but can sometimes appear on young plants. Fungal colonization of the root vascular system is essential for expression of foliar symptoms since these are caused by a toxin translocated from the roots to the leaves. Our objective was to define the window of opportunity for effective root infection resulting in the development of SDS foliar symptoms. Soybean seeds were planted staggered over a five week period to obtain plants of different ages (1 day, 4 days, and 1, 2, 3, 4, and 6 weeks old) at inoculation. Plants were inoculated by drenching a spore suspension of 6 x 10 super(3) conidia/ml into each pot and incubated for 7 days at 17C, followed by 31 days at 24C. Root rot and foliar severity were assessed at 18 and 38 days after inoculation (DAI). Root rot developed on plants inoculated at all ages, but plants inoculated 1-day after planting had the highest (P < 0.01) root rot severity, 76.8% at 18 DAI and 90% at 38 DAI respectively, compared to those inoculated at all other ages. Root rot severity did not differ among plants inoculated 1 to 5 weeks after planting and ranged between 12-32%. Foliar symptoms only developed on plants inoculated 1-day after planting, but not on any other age. Foliar severity on these plants was 21% at 18 DAI and 80% at 38 DAI. Frequency of root colonization by F. virguliforme was consistent with root rot severity. This study reveals that soybean roots are susceptible for infection at all ages but that root infection at the seedling stage is critical for foliar symptom development. The effectiveness of management practices aimed at protecting seedling roots at the stage should be investigated.
ISSN:0031-949X