Agriculture Reference
In-Depth Information
11.3.1
Experimental design, analytical procedures and
interpretation modules
Cross-talk between nutrients is a well-known phenomenon in plant nutrition and in terms
of SIR, interactions between S metabolism and other nutrients should be considered in
experimentation. A promising approach seems to be cross-talk between manganese (Mn)
and S metabolic pathways. Mn is a redox-active nutrient and the oxidation of Mn
2+
is a
characteristic of virulent pathogens (Thompson & Huber, 2007). A suffi cient content of
reduced Mn may be essential for the activation of resistance mechanisms in plants and it
might be hypothesised further that the ascorbate/GSH cycle plays a key role in reducing
Mn
4+
to Mn
2+
.
Further research on the interactions between S nutritional status and the local/systemic
release of H
2
S in relation to infection, together with fumigation studies on fungal cultures
will fi nally unravel the role of H
2
S in SIR.
For an early, quantitative diagnosis before appearance of fungal mycelia, enzyme-
linked immunosorbent assays (ELISA) are required. Visual rating of disease incidence
and severity is regularly applied to follow up development of the disease in fi eld exper-
iments. While a close relationship was found between ELISA test and visual scoring
(Lind, 1992; Newton & Reglinski, 1993), other authors found visual scoring to be more
sensitive than the ELISA test (Delapena & Murray, 1994), or vice versa (Balesdent
et al.
,
1995; ForoughiWehr
et al.
, 1996). For the identifi cation of metabolites and pathways
underlying SIR, it is crucial to analyse the infected plant tissue during the initial phase
when resistance mechanisms are activated, which is, however, diffi cult to achieve under
fi eld conditions.
Common fi eld experimentation, together with routine statistical treatment of results,
might not be appropriate to uncover general interactions between host and pathogen
(Salac
et al.
, 2003). Geostatistics has been successfully applied for the evaluation of the
spatial distribution and spatial simulation of insects (Ribes-Dasi
et al.
, 2001), the progno-
sis for the spread of plant viruses (Nelson
et al.
, 1994) and the spatial distribution of plant
diseases at plot and fi eld scale (Chellemi
et al.
, 1988; Larkin
et al.
, 1995; Wu
et al.
, 2001;
Morgan
et al.
, 2002). With regard to SIR, Salac
et al.
(2003) showed in a fi eld experiment
that elevated levels of GSH coincided with a high risk of strong fungal infections of oil-
seed rape with black leg (
Leptosphaeria maculans
), whereby initiation of GSH synthesis
appeared to be dependent on some threshold infection. In contrast, interpretation of ana-
lytical results by employing standard statistical procedures revealed no signifi cant effect.
11.4
References
Anon, 1988. Pilzkrankheiten des Rapses.
Aktuelles aus Acker- und Pfl anzenbau
. Kiel: Landwirtschaftskammer
Schleswig-Holstein, 58-63.
Anon, 2003. Verordnung über das Inverkehrbringen von Düngemitteln, Bodenhilfsstoffen, Kultursubstraten
und Pfl anzenhilfsmitteln. Düngemittelverordnung - DüMV vom 26. November 2003.
Anon, 2006.
Statistisches Jahrbuch über Ernährung, Landwirtschaft und Forsten der Bundesrepublik
Deutschland 2006
. Münster-Hiltrup: Landwirtschafts-Verlag.
Balesdent MH, Desthieux I, Gall C, Robin P, Rouxel T, 1995. Quantifi cation of
Leptosphaeria maculans
growth in cotyledons of
Brassica napus
using ELISA.
Journal of Phytopathology
143
, 65-73.
Ball L, Accotto GP, Bechtold U, Creissen G, Funck D, Jimenez A, Kular B, Leyland N, Mejia-Carranza
J, Reynolds H, Karpinski S, Mullineaux PM, 2004. Evidence for a direct link between glutathione
biosynthesis and stress defense gene expression in Arabidopsis.
Plant Cell
16
, 2448-2462.
