Pathways of infection of Brassica napus roots by Leptosphaeria maculans

Abstract

Summary• Infection of Brassica napus cotyledons and leaves by germinating ascospores of Leptosphaeria maculans leads to production of leaf lesions followed by stem cankers (blackleg). Leptosphaeria maculans also causes root rot but the pathway of infection has not been described.• An L. maculans isolate expressing green fluorescent protein (GFP) was applied to the petiole of B. napus plants. Hyphal growth was followed by fluorescence microscopy and by culturing of sections of plant tissue on growth media. Leptosphaeria maculans grew within stem and hypocotyl tissue during the vegetative stages of plant growth, and proliferated into the roots within xylem vessels at the onset of flowering. Hyphae grew in all tissues in the stem and hypocotyl, but were restricted mainly to xylem tissue in the root.• Leptosphaeria maculans also infected intact roots when inoculum was applied directly to them and hyphae entered at sites of lateral root emergence. Hyphal entry may occur at other sites but the mechanism is uncertain as penetration structures were not observed.• Infection of B. napus roots by L. maculans can occur via above-and belowground sources of inoculum, but the relative importance of the infection pathways under field conditions is unknown.

Rhizosphere microbial community manipulated by 2 years of consecutive biofertilizer application associated with banana Fusarium wilt disease suppression

“…The biofertilizer treatment significantly (P<0.05) enriched the genera of Leptosphaeria and Phaeosphaeriopsis and decreased abundance of Lichtheimia across all soil samples. Leptosphaeria and Phaeosphaeriopsis are two fungal pathogens of the Ascomycota phylum causing blackleg disease on Brassica crops (Sprague et al 2007) and leaf spot and necrosis on Ruscus (Câmara et al 2003). However, no study has been conducted to evaluate their involvement in Fusarium wilt disease.…”

Root and shoot glucosinolates: a comparison of their diversity, function and interactions in natural and managed ecosystems

“…Based on this distribution of the GSL-myrosinase system in field grown B. napus roots, McCully et al (2008) speculate that the major defensive role in these mature plants appears to be related to the protection of large roots during the critical seed filling stages when these roots are acting as pipelines for nutrients and water absorbed by the fine roots. The same authors suggest that the root-rot fungus L. maculans, which first infects the leaves and enters the root via the xylem, may be confined to the vascular bundle by this ring of cells containing high levels of 2PE-GSL (Sprague et al 2007). The fine roots need less protection, since they are ephemeral and continuously replaced from meristems located in the outer regions of thickened roots (Table 4; M. McCully, personal communication).…”

The Arabidopsis Glucosyltransferase UGT76B1 Conjugates Isoleucic Acid and Modulates Plant Defense and Senescence

“…Consistent with these findings and its role in promoting the JA pathway, UGT76B1 was induced after wounding ( Figure 8J). The constitutive expression of UGT76B1 in hydathodes and young tissues ( Figures 8B and 8C) could be involved in the local enhancement of the JA pathway, providing protection against herbivores or necrotrophs at these more vulnerable sites (Hugouvieux et al, 1998;Sprague et al, 2007).…”