Download Mechanisms involved in spatial and temporal mobility of disease

Mechanisms involved in spatial and temporal mobility of disease patches caused
by Rhizoctonia solani in sugar beet field: Induction of antagonists within disease
patch
Muhammad Anees (1), Arne Tronsmo (2), Véronique Edel-Hermann (1), Nadine Gautheron (1)
Vincent Faloya (3) and Christian Steinberg (1)
(1) INRA, Université de Bourgogne, UMR 1229 Microbiologie du Sol et de l’Environment, CMSE,
17 rue Sully, BP86510, F-21065 Dijon, France ; (Phone: +33-3-80-69-30-50; E-mail:
[email protected])
(2) Department of chemistry, biotechnology and food science, PO box 5003, NO-1432 Aas,
Norway
(3) Unité Expérimentale de Bretenière, INRA, BP86510, F-21065 Dijon, France
Rhizoctonia solani AG 2-2 causes damping off and root rot in sugar beet in patches which are
highly mobile both on spatial and temporal scales. They never occur in the same place where they
were in the last season. The present study was to uncover the mechanisms underlying the dynamics
of disease patches. Soil was sampled from within diseased patch, healthy area and in between the
two regions in sugar beet field, previously inoculated with R. solani AG 2-2 and tested for inoculum
potential and soil suppressiveness towards the pathogen as well as genetic and physiological
structure of bacteria and fungi. Potential antagonists, Trichoderma were isolated from within and
outside the disease patch and studied for their antagonistic ability against the pathogen both in vitro
and in vivo in two different soils. It was observed that soil inoculum potential was higher within
diseased patch than in healthy area. However, the dormant pathogen in healthy area was stimulated
by addition of buckwheat meal more than that in diseased patch. In addition soil from diseased area
was more suppressive towards the pathogen. We did not observe significant differences in bacterial
genetic structure between different treatments. However, diseased area could be easily distinguished
from healthy area by their bacterial physiological fingerprints. Diseased patch and healthy area were
distinguishable both on the fungal genetic and physiological structures. In addition to this,
Trichoderma isolates from diseased patch were more antagonistic than the ones from outside the
patch both in vitro and in vivo in both types of soils. These results suggest that R. solani when
active may stimulate the development of antagonistic organisms. Their presence may inhibit the
formation of patches in the subsequent season in that part of the field.