Behaviour of the fungus Rhizoctonia solani Kiihn in the soil

Abstract

Rhigoctaia so&& was found able to grow 0s a saprophyte through natural unsterilized soil. Its rate of growth under different soil conditions in glass tumblers was studied by the Rossi-Cholodny soil-plate method. Growth was most rapid at the lowest soil-moisture content tested, viz. 30 yo saturation, and was accelerated by for& aeration of the soil. The maximum distance to which mycelial growth could be suppofied on the food reserves of the agar inoculum alone was some 5 ~n . , as shown by extent of growth through tubes of moist sand, but in 23 days the fungus grew 21-24 crn. through tubes of soil. Removal of the agar disk 2 days after inoculation of the tubes reduced growth through sand by more than half, but through soil by only a small proportion. In soil, Rhizoctonk was able to cause 100% darnping-off of radish seedlings planted at a radial distance of 4 un. from the agar inocdum, and some 40 yo darnping-off at a distance of 9 an. The depressing effect of additions of I % ground-wheat straw or dried grass to the soil upon growth of the fungus was attributed to (I) the negligible cellulosedecomposing ability of Rhizoctoniu, (2) nitrogen starvation of the mycelium, through rapid utilization of the available soil nitrogen by the cellulose-decomposing micro-organisms multiplying upon the fresh organic material, (3) fungistatic action on Rhizoctonia of the respiratory carbon dioxide produced by the cellulose-decomposers.

Spatial heterogeneity of soil water around single roots: use of CT‐scanning to predict fungal growth in the rhizosphere

“…Bars represent standard errors of the mean of three replicates. {b) Tbe saprophytic growth of Rhizoctonia solani in a sandy loam soil (Woburn) from Blair (1943); symbols represent five isolates. Growth of isolates was assessed by the Rossi-Gholodny method and shows the mean growth of hyphae on 12 slides buried in the soil for 5 d. The moisture contents of tbe original data were converted to kPa from a moisture characteristic curve of this soil (data not shown), assuming the characteristics not to have changed.…”

“…These results are preliminary and much work still needs to be done on the analysis of these regions m field soiL (a) Figure 9. Heterogeneity of the regions of favourable and unfavourable sites for the saprophytic growth of R. solani around radish based on the data of Blair (1943). The two-dimensional representations are of the volumetric water contents (cm^ water cm"^ soil) in a 50 x 50 ROI around single roots of 8-d-old radish seedlings observed under ' drier' conditions (-10 kPa) at depths of (o) 15 nim and (6) 3 5 mm and ' wetter^ conditions (-4 kPa) at depths of (c) 1 5 mm and {d) 3 5 mm; tbe y-axis is volumetric water content (cm^ cm'').…”

“…For Rhizoctonia solani, data from Blair (1943) (Fig. Ib) were used in the same way as the data for G. graminis to estimate the regions of growth around roots suitable for R. solani, using the CT-scanning data for radish and cotton, which are both hosts of this fungus.…”

“…V. Arx & Olivier and Rhizoctonia solani Kiihn were examined. Both fungi are capable of saprophytic growth through the soil when provided with a food base (Blair, 1943;Grose, Parker & Sivasithamparam, 1984), and there is limited information about their saprophytic growth at conditions of controlled matric water potential in soil (Blair, 1943;Benson & Baker, 1974;Glenn et aL, 1987). We asked if the changes in soil water measured through CT-scanning were such that favourable and unfavourable water sites for the saprophytic growth of these two pathogens might occur over small distances.…”

Interaction of Meloidogyne hapla and Rhizoctonia solani in alfalfa

“…causing stem rot of Dianthus caryophyllus was above 88°F and at soil mois tures unsuitable for best derelopraent of the plsj^t, Blair (1943) found that H. solani grew fastest at 30 per cent saturation which was the lovrest soil moisture content tested. Papavizas and Davey (1961) observed the saprophytic activity of Rhizoctonia sp.…”