IBIS-Flora

Angiosperm Flora of India

Effect of defoliation by livestock on stem canker caused by Leptosphaeria maculans in Brassica napus

Publication Type:Journal Article
Year of Publication:2013
Authors:Sprague, SJ, Graham, JM, Hamblin, PJ, KIRKEGAARD, JA
Journal:Plant Pathology
Volume:62
Issue:2
Date Published:2013
ISBN Number:1365-3059
Keywords:blackleg, Brassica, canola, Grazing, Phoma lingam, phoma stem canker, Sheep
Abstract:

Brassica napus (canola, oilseed rape), an important break crop for cereals across the Australian wheat belt, is being rapidly adopted as a dual-purpose (forage and grain) crop in mixed farming systems. Stem canker caused by the fungus Leptosphaeria maculans is the most important disease of B. napus in Australia. The primary source of inoculum is airborne ascospores released during autumn/winter which coincides with the grazing of dual-purpose crops. Field experiments were defoliated by sheep to determine the effect of grazing on blackleg stem canker severity at plant maturity in B. napus cultivars differing in their resistance level and grazed at different times. One cultivar was sown on different dates to investigate the impact of grazing at the same time, but at different growth stages. Defoliation by mowing was compared to defoliation by livestock. Similar amounts of dry matter remained after defoliation by machinery (0·66 t ha−1) or livestock (0·52 t ha−1). However, stem canker severity was higher in the grazed (40% of crown cross-section diseased) compared with the mown (25%) treatment, which was higher than the ungrazed control (9%). Stem canker severity generally increased with grazing, but the increase was eliminated or reduced in cultivars with good resistance. Grazing during vegetative plant growth minimized the increase in stem canker severity compared with grazing during reproductive growth. Currently, cultivars with good L. maculans resistance are recommended in high disease situations. To avoid excessive yield loss in dual-purpose B. napus crops due to L. maculans it is recommended that such cultivars are grown even in low-moderate disease situations.

URL:http://dx.doi.org/10.1111/j.1365-3059.2012.02652.x
Short Title:Plant Pathology
Taxonomic name: 
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