Subject: Rhizoctonia Infestation method?

From: [email-masked]
Date: 19 AUG 96 20:45:40 GMT

Hallo Netters!

        I'm looking for a successful way to infest soil with Rhizoctonia for
trials.  I have tried Baker and Cook's method of infecting by placing an agar
plug in the corner of the tray but couldn't get infection.

        All suggestions welcome

        Susan :->

E-mail : [email-masked]

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From: "A. Phillips" <[email-masked]>
Date: Tue, 20 Aug 1996 23:49:18 -0700

> plug in the corner of the tray but couldn't get infection.

I have used two methods to infest soil with Rhizoctonia solani.  For pot experiments, I 
use inoculum in the form of mycelium grown in liquid cultures and added to soil at the 
rate of 0.25 g fresh weight of mycelium per kg of soil.  Details of this method are 
described in Annals of Applied Biology vol 118, pp 9-17 (1991) and the influence of the 
concentration of the inoculum in Canadian Journal of Microbiology vol 35, pp 1132-1140 
(1991).

For field experiments, a rather more vigorous inoculum is needed and I favour the green 
bean inoculum described by Van Bruggen & Arnesson (Plant Disease 69, 966-969; 1985).  In 
field experiments on fungicides I have used 5g of inoculum for each 4 m of row length 
and hoed this in to a depth of about 2 cm (TAC 11, pp 40-41, Annals of Applied Biology 
116, Supplement; 1983).  This amount of inoculum gave good levels of disease without 
wiping out the crop.

Of course, these methods work only if your isolate of R. solani is virulent and your 
host is susceptible.  I have always worked with a light sandy loam soil and have no idea 
how soil type affects the success of inoculation.

Let me know if these methods work for you; I suspect that they should be universally 
useful.  If you run into problems please let me know.

Alan J.L. Phillips

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From: [email-masked]
Date: Fri, 23 Aug 1996 05:19:49 GMT

>E-mail : [email-masked]

For both field and pot trials involving AG-8 we use colonised sterile
millet seed.  The seed is soaked overnight, drained, autoclaved,
inoculated, incubated at 25 C, and when fully colonised (about 2
weeks) is dried in a laminar flow and stored in a freezer where is is
normally stable for at least 12 months.

Advantages are that 
-it is easily quantifiable
-it is a small inoculum source 
-it can be spread easily and evenly by machine

The only warning is to be carefull of moisture levels in the
autoclaving grain so that you dont produce porridge.

See McDonald and Rovira,  pp174-174 in Ecology and Management of
Soilborne Plant Pathogens  C.A. Parker et al eds 1985 APS Press.

And now for a blatant plug, I hope you are recieving  International
Plant Pathology, Rhizoctonia newsletter.  If not email me regarding
details.

Stephen Neate 
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