An Unusual Phytophthora Associated with Root Rot of Subterranean Clover.

Plant Disease ◽  
1984 ◽  
Vol 68 (1) ◽  
pp. 450e ◽  
Author(s):  
P. A. Taylor
Keyword(s):  
Root Rot ◽  
Subterranean Clover

The in vitro inhibition of Phytophthora clandestina by some rhizobia and the possible role of Rhizobium trifolii in biological control of Phytophthora root rot of subterranean clover

1999 ◽  
Vol 50 (8) ◽  
pp. 1469 ◽  
Author(s):  
S. Simpfendorfer ◽  
T. J. Harden ◽  
G. M. Murray
Keyword(s):  
Biological Control ◽  
Root Rot ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Root Disease ◽  
Rhizobium Trifolii ◽  
Biological Control Agents ◽  
Control Activity ◽  
Phytophthora Root Rot

The interaction between 29 isolates of Rhizobium and the in vitro growth of 3 strains of Phytophthora clandestina was investigated to determine the potential of these bacteria as biological control agents against root rot of subterranean clover (Trifolium subterraneum L.). The biological control activity of Rhizobium on the severity of root disease in seedlings was also investigated under glasshouse conditions. Thirteen of the 29 Rhizobium isolates caused significant reductions in the hyphal growth of the 3 P. clandestina isolates examined. Inoculation of seedlings with Rhizobium trifolii reduced the severity of root disease by 14–58% with corresponding increases in dry matter production of 20–73%. These results indicate that Rhizobium species have potential as biological control agents against the root rot of T. subterraneum seedlings caused by P. clandestina.

Infection of seed of subterranean clover and allied species by species of Fusarium

1980 ◽  
Vol 31 (2) ◽  
pp. 297 ◽  
Author(s):  
AW Kellock ◽  
LL Stubbs ◽  
DG Parbery
Keyword(s):  
Root Rot ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Scar Tissue ◽  
Seed Infection ◽  
Fusarium Spp ◽  
Blotting Paper ◽  
Optical Brighteners ◽  
First Time ◽  
Healthy Seed

Fusarium avenaceurn (Corda ex Fr.) Sacc. was shown for the first time to be carried in the hilum of subterranean clover (Trifolium Subterraneum L.) seed. Scanning electron microscopy and thin-section techniques showed that the fungus occurred only as dormant mycelium in parenchyma cells of funicle scar tissue. It emerged from these tissues after a 12 h incubation at 24�C and in 48 h penetrated internal parts of the seed through the hilum fissure. After 21 days on moist blotting paper, seedlings grown from infected seed developed lesions on their roots similar to those of root-rot of subterranean clover in the field. Fusarium spp. were also detected in the hilum of seeds of white (T. repens L.) and strawberry (T. fragiferum L.) clover and barrel medic (M. truncatula L.). It was demonstrated experimentally that all parts of the burr, incl~tding the funicle, became infected with F. avenaceuni when subterranean clover plants grown from healthy seed in pasteurized soil buried their burrs in soil inoculated with the fungus. Use of optical brighteners failed to trace seed infection because the compounds, although absorbed by the pathogen in culture, were not translocated.

Severity of root rot in mature subterranean clover and associated fungal pathogens in the wheatbelt of Western Australia

2009 ◽  
Vol 60 (1) ◽  
pp. 43 ◽  
Author(s):  
Tiernan A. O'Rourke ◽  
Tim T. Scanlon ◽  
Megan H. Ryan ◽  
Len J. Wade ◽  
Alan C. McKay ◽  
...  
Keyword(s):  
Western Australia ◽  
Root Rot ◽  
Fungal Pathogens ◽  
Lateral Roots ◽  
Subterranean Clover ◽  
Growing Season ◽  
Root Diameter ◽  
Root Disease ◽  
Soil Dna ◽  
Tap Root

Pasture decline is considered to be a serious challenge to agricultural productivity of subterranean clover across southern Australia. Root disease is a significant contributing factor to pasture decline. However, root disease assessments are generally carried out in the early part of the growing season and in areas predominantly sown to permanent pastures. For this reason, in spring 2004, a survey was undertaken to determine the severity of root disease in mature subterranean clover plants in pastures located in the wheatbelt of Western Australia. DNA-based soil assays were used to estimate population density in the soil of a variety of soil-borne pathogens known to commonly occur in the Mediterranean-type environments of southern Australia. The relationships between severity of disease on tap and lateral roots and root diameter, root length, nodulation, and total rainfall were determined. The survey showed, for the first time, that severe root disease is widespread in spring across the wheatbelt of Western Australia. There was a positive correlation between rainfall and tap root disease, and between tap root disease and average root diameter of the entire root system. Despite the high levels of root disease present across the sites, the DNA of most root disease pathogens assayed was detected in trace concentrations. Only Pythium Clade F showed high DNA concentrations in the soil. DNA concentrations in the soil, in particular for Phytophthora clandestina and Rhizoctonia solani AG 2.1 and AG 2.2, were higher in the smaller autumn sampling in 2006. This study suggests that the productivity of subterranean clover-based pastures is severely compromised by root rot diseases throughout the growing season in the wheatbelt of Western Australia.

Occurrence of Phytophthora clandestina in Trifolium subterraneum paddocks in Australia

2001 ◽  
Vol 41 (2) ◽  
pp. 187 ◽  
Author(s):  
R. Aldaoud ◽  
W. Guppy ◽  
L. Callinan ◽  
S. F. Flett ◽  
K. A. Wratten ◽  
...  
Keyword(s):  
Western Australia ◽  
Root Rot ◽  
New South ◽  
New South Wales ◽  
South Australia ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Soil Samples ◽  
South Wales ◽  
Differential Cultivars

In 1995–96, a survey of soil samples from subterranean clover (Trifolium subterraneum L.) paddocks was conducted across Victoria, South Australia, New South Wales and Western Australia, to determine the distribution and the prevalence of races of Phytophthora clandestina (as determined by the development of root rot on differential cultivars), and the association of its occurrence with paddock variables. In all states, there was a weak but significant association between P. clandestina detected in soil samples and subsequent root rot susceptibility of differential cultivars grown in these soil samples. Phytophthora clandestina was found in 38% of the sampled sites, with a significantly lower prevalence in South Australia (27%). There were significant positive associations between P. clandestina detection and increased soil salinity (Western Australia), early growth stages of subterranean clover (Victoria), mature subterranean clover (South Australia), recently sown subterranean clover (South Australia), paddocks with higher subterranean clover content (Victoria), where herbicides were not applied (South Australia), irrigation (New South Wales and Victoria), cattle grazing (South Australia and Victoria), early sampling dates (Victoria and New South Wales), sampling shortly after the autumn break or first irrigation (Victoria), shorter soil storage time (Victoria) and farmer’s perception of root rot being present (Victoria and New South Wales). Only 29% of P. clandestina isolates could be classified under the 5 known races. Some of the unknown races were virulent on cv. Seaton Park LF (most resistant) and others were avirulent on cv. Woogenellup (most susceptible). Race 1 was significantly less prevalent in South Australia than Victoria and race 0 was significantly less prevalent in New South Wales than in South Australia and Western Australia. This study revealed extremely wide variation in the virulence of P. clandestina. The potential importance of the results on programs to breed for resistance to root rot are discussed. in South Australia.

Studies on Phytophthora clandestina, the cause of taproot rot in subterranean clover. 1. Evidence for physiological specialisation in Phytophthora clandestina

1994 ◽  
Vol 34 (8) ◽  
pp. 1125 ◽  
Author(s):  
SP Flett
Keyword(s):  
Root Rot ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Resistant Cultivar ◽  
Greenhouse Experiments ◽  
Temperate Pastures ◽  
Serious Disease

Root rot caused by Phytophthora clandestina Taylor, Pascoe & Greenhalgh is a serious disease of subterranean clover (Trifolium subterraneum), an important leguminous component of Australia's temperate pastures. Previous reports have shown that P. clandestina causes severe taproot rot in cv. Woogenellup, while cvv. Larisa and Trikkala remain highly resistant. In this study, 3 greenhouse experiments were conducted to determine the effects of P. clandestina isolates collected between 1983 and 1990 on different subterranean clover cultivars. Woogenellup was consistently susceptible while Meteora was less affected by all isolates tested. Trikkala, a previously known root rot resistant cultivar, was as susceptible as Woogenellup when tested with a recently collected isolate from Katamatite, northern Victoria. This study provides the first evidence for variation in virulence between isolates of P. clandestina and for physiological specialisation in this species.

Simulated soil and plant management effects on root rots of subterranean clover

1986 ◽  
Vol 37 (6) ◽  
pp. 633 ◽  
Author(s):  
RW Smiley ◽  
PA Taylor ◽  
RG Clarke ◽  
FC Greenhalgh ◽  
P Trutmann
Keyword(s):  
Root Rot ◽  
Subterranean Clover ◽  
Plant Management ◽  
Root Rots ◽  
Root Diseases ◽  
Organic Debris ◽  
Pasture Soil ◽  
Management Procedures ◽  
Controlled Environments ◽  
Management Effects

Pasture productivity in southern Australia is often limited by root diseases of complex etiology. The influences of simulated plant and soil management procedures on subterranean clover (Trifolium subterranean cv. Woogenellup) root rots were evaluated in controlled environments, using a soil from an irrigated and from a dryland pasture. Root rot incidence and severity were high in soils collected and used as intact cores, and low to moderate in soils disturbed while being collected. Simulated cultivation of soil in cores also reduced root rots in the dryland pasture soil that had little surface litter, but not in the irrigated pasture soil which had high levels of organic debris (and pathogen inocula) distributed through the surface 0-11 cm. Root rot was mild on plants in continually moist cores at 10�C, and severe in cyclically wetted and dried cores at 10, 15 and 20�C, and in continually moist cores at 15 and 20�C. Root rots were reduced by treatment of seeds with Rhizobium, fungicides, or both, by drenching soils with fungicides, and by planting the resistant T. yanninicum cvv. Larisa, Meteora and Trikkala. Removal of seedling leaves, to simulate grazing, accentuated root rot severity. The identified pathogens included species of Pythium, Fusarium, Rhizoctonia, and nematodes. Integrated strategies for controlling root rots of subterranean clover are considered promising in view of these studies with cores of pasture soils.

scholarly journals Characterization and Pathogenicity of Rhizoctonia Species on Canola

Plant Disease ◽  
1999 ◽  
Vol 83 (8) ◽  
pp. 714-721 ◽  
Author(s):  
Ravjit K. Khangura ◽  
Martin J. Barbetti ◽  
Mark W. Sweetingham
Keyword(s):  
Root Rot ◽  
Seedling Emergence ◽  
Subterranean Clover ◽  
Enzyme Electrophoresis ◽  
Nuclear Staining ◽  
Damping Off ◽  
Weed Species ◽  
Bare Patch ◽  
Hyphal Morphology ◽  
Leguminous Crops

A total of 112 Rhizoctonia isolates were collected from various canola (Brassica napus) growing areas of Western Australia. Pectic enzyme electrophoresis differentiated these isolates into six distinct zymogram groups: R. solani, 54% ZG5 (AG2-1), 8% ZG6 (AG2-1), and 1% ZG9 (AG10); binucleate Rhizoctonia, 12% CZG1 (CAG1), 4% CZG4, and 6% CZG5 (AGK); and the remainder unidentified binucleate groups (15%). Binucleate groups were also confirmed by fluorescent nuclear staining and hyphal morphology. One or more isolates from each of the above zymogram groups (including four unidentified binucleate groups) and an isolate of ZG1-1 (AG8) that causes bare patch in cereals and legumes were tested for their pathogenicity on canola. Isolates of ZG5 and ZG1-1 were highly pathogenic on canola, delayed seedling emergence, and caused severe hypocotyl and root rot, respectively. ZG5 also induced postemergence damping-off. Increasing the depth of sowing from 1 to 3 cm significantly delayed seedling emergence and increased disease severity. Four unidentified binucleate isolates (WAC9316, WAC9297, WAC9307, and WAC9290) were moderately pathogenic to canola, while two isolates (WAC9307 and WAC9316) caused significant preemergence damping-off. Two CZG5 isolates were weakly pathogenic. Isolates of ZG5 and ZG1-1 were also tested for their pathogenicity on other rotational crops (narrow-leafed lupin, subterranean clover, wheat, oats, barley, and mustard) and two weed species (wild radish and annual ryegrass). ZG5 caused a severe hypocotyl rot on mustard and mild symptoms of hypocotyl rot on narrow-leafed lupin and clover, but failed to infect any of the cereal hosts, such as wheat, oats, barley, and ryegrass. In contrast, all crops tested were highly susceptible to ZG1-1 except mustard, which was only moderately susceptible. Results indicate that ZG5 is most pathogenic to crucifers and is a mildly virulent pathogen of the leguminous crops but not of cereal crops tested. ZG1-1, known to cause bare patch in legumes and cereals, also can cause severe root rot in canola. This is the first report of hypocotyl rot and pathogenicity of ZG5 on canola in Australia.

Effect of short chemical fallow on Rhizoctonia bare patch and root rot of wheat at Esperance, Western Australia

1987 ◽  
Vol 27 (5) ◽  
pp. 671 ◽  
Author(s):  
GC MacNish ◽  
CS Fang
Keyword(s):  
Grain Yield ◽  
Western Australia ◽  
Root Rot ◽  
Subterranean Clover ◽  
Research Station ◽  
Annual Ryegrass ◽  
Bare Patch ◽  
Rhizoctonia Root Rot ◽  
Mixture Prior ◽  
Chemical Fallow

The effects of short chemical fallows after ryegrass pasture on rhizoctonia bare patch and root rot ofwheat were studied in 2 experiments at the Esperance Downs Research Station, 35 km north of Esperance, W.A. In 1 experiment the subterranean-clover dominant pasture was sprayed with a paraquat-diquat mixture prior to resowing with annual ryegrass at densities ranging from 3 to about 400 plants m-2. The ryegrass was allowed to grow for either 42 or 63 days prior to treatment with a desiccant herbicide (paraquat-diquat) followed by a short chemical fallow of 26 or 5 days, respectively, before sowing with wheat using minimum tillage. Some treatments were cultivated twice to 10 cm. Neither the ryegrass density nor the length of chemical fallow had any effect (P=0.05) on rhizoctonia bare patch score or incidence or severity of root rot. However, cultivation caused 76% reduction in mean patch score and a 38 and 68% reduction in mean rhizoctonia incidence and severity respectively. Yield was negatively correlated with rhizoctonia incidence and severity: each 1% increase in incidence percentage resulted in 17 kg ha-1 reduction in grain yield of wheat. In another experiment, chemical fallow periods of 66, 52, 24 or 1 day prior to sowing wheat had no effect (P= 0.05) on rhizoctonia root rot incidence.

Nodulation of subterranean clover growing in permanent pastures on acid soils in North-Central Victoria

1986 ◽  
Vol 26 (1) ◽  
pp. 31 ◽  
Author(s):  
HR Jones ◽  
BC Curnow
Keyword(s):  
Root Rot ◽  
Acid Soils ◽  
Subterranean Clover ◽  
Rhizobium Trifolii ◽  
Soil Factors ◽  
North Central ◽  
Exchangeable Calcium ◽  
Central Victoria ◽  
Clover Root

A survey ofclover at 44 sites in permanent dryland pastures in North-Central Victoria, highlighted poor nodulation of subterranean clover.In 1982 and 1983 respectively only 40 and 62% of plants were effectively nodulated 8-10 weeks after germination of the clover. Clover root rot was also present in both years, 64% of plants being affected in 1982 and 14% in 1983. Nodulation was negatively correlated with the incidence of root rot and with the percentage of exchangeable aluminium in the soil and positively correlated with the percentage of exchangeable calcium in the soil. The number of Rhizobium trifolii in the soil was not correlated with any of the soil factors measured.

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