Antagonism of the endophytic insect pathogenic fungus Metarhizium robertsii against the bean plant pathogen Fusarium solani f. sp. phaseoli

Figures & data

Fig. 1. Images of dual plate cultures of Metarhizium robertsii (M.r) and Fusarium solani (F.s) and biocontrol of F. solani by M. robertsii on bean root. (a) Dual plate assays showing antagonistic activity of M. robertsii on F. solani on day 7 and 14. In each photo, a zone of F. solani clearing is evident at the colony interface. (b) Images of bean root rot caused by F. solani after four weeks. Roots were obtained from control plants, F. solani treatment and M. robertsii + F. solani treatments.

Fig. 2. Inhibition of Fusarium solani in Metarhizium robertsii cell-free culture extracts. (a) Germination of F. solani conidia in M. robertsii cell-free culture extract. Fusarium solani conidia were suspended in different concentrations (100%, 90%, 50% and 10%) of 4-day-old and 10-day-old M. robertsii cell-free culture filtrates. Con = control, no cell-free extract. Germination of 100 F. solani conidia was counted (N = 4) after 24 h (light bars) and 48 h (dark bars). Each bar represents mean % germination ± S. E. (b) Fusarium solani biomass yield in M. robertsii cell-free culture filtrate (autoclaved – light bars and non-autoclaved – dark bars) after four days of growth. Data represents the mean ± S.E. of dry weights of F. solani grown under different concentrations (100%, 90% and 50%) of M. robertsii autoclaved and not autoclaved cell-free extract and the control (Con = control, no cell-free extract).

Table 1.  The effect of M. robertsii (M.r) as an antagonist of Fusarium solani (F.s) infection of bean plants

	Root rot and colour intensity^b	Disease index based on necrotic lesions on roots and hypocoty
Control^a	0.25 ± 0.03	1.73 ± 0.28
F.s	0.69 ± 0.03	3.93 ± 0.07
F.s + M.r	0.35 ± 0.03	2.31 ± 0.11
^aControls represent plants grown without F. solani or M. robertsii. Values are mean (±S.E.).
^bThe indices are described in the Materials and methods. The root rot indices (±S.E.) and colour intensities are according to Dar et al. (1997) and disease indices based on necrotic lesions on the roots and hypocotyl are as described by Filion et al. (2003).

Dar , G.H.H. , Zargar , M.Y. and Beigh , G.M. 1997 . Biocontrol of Fusarium root rot in the common bean (Phaseolus vulgaris L.) by using symbiotic Glomus mosseae and Rhizobium leguminosarum . Microb. Ecol. , 34 : 74 – 80 .

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Filion , M. , St-Arnaud , M. and Jabaji-Hare , S.H. 2003 . Quantification of Fusarium solani f. sp. phaseoli in mycorrhizal bean plants and surrounding mycorrhizosphere soil using real-time polymerase chain reaction and direct isolations on selective media . Phytopathology , 93 : 229 – 235 .

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