Effects of soil pasteurization on root rot, seedling survival and plant dry weight of subterranean clover inoculated with six fungal root pathogens

1987 ◽  
Vol 38 (2) ◽  
pp. 317 ◽  
Author(s):  
MJ Barbetti ◽  
K Sivasithamparam
Keyword(s):  
Root Rot ◽  
Seedling Survival ◽  
Lateral Roots ◽  
Subterranean Clover ◽  
Dry Weight ◽  
Plant Size ◽  
Natural Soil ◽  
Virgin Soil ◽  
Pythium Irregulare ◽  
Clover Root

Subterranean clover was exposed to two levels of inoculum of millet seed colonized by Fusarium avenaceum, Fusarium oxysporum, Phoma medicaginis, Phytophthora clandestina, Pythium irregulare, or Rhizoctonia solani within pasteurized and unpasteurized field soil from sites with (root rot site) and without (virgin site) a history of subterranean clover root rot at Augusta, W.A., with the aim of establishing their pathogenicity in the presence of other soil organisms including resident pathogens. Introduction of F. avenaceum (2.5% w/w), P. clandestina (0.5 and 2.5%), P. irregulare (0.5 and 2.5%), or R. solani (0.2 and 1.0%) increased damage to tap and lateral roots of subterranean clover in pasteurized and unpasteurized root rot and virgin soils. All fungi tested, with the exception of P. medicaginis (2.0 and 10.0%) or P. medicaginis (2.0 and 10.0%) and F. oxysporum (0.5 and 2.50%), caused reduction of seedling survival in pasteurized root rot and virgin soils respectively. When the soil was unpasteurized, all fungi except F. oxysporum (2.5%) and P. medicaginis (2.0 and 10*0%) in virgin soil, but only P. irregulare (2.5%) or R. solani (0.2 and 1.0%) in root rot soil, reduced seedling survival. In unpasteurized soils plant dry weight was reduced by P. clandestina (2.5%), P. irregulare (0.5 and 2.5%), or R. solani (0.2 and 1.0%) in root rot and virgin soils, but F. oxysporum (0.5%) reduced plant size only in the root rot soil. Within pasteurized soil all fungi, with the exception of P. medicaginis (2.0 and 10.0%) in virgin soil and F. avenaceum (2.5%), P. irregulare (0.5 and 2.5%), or R. solani (0.2%) in root rot soil, caused reduction in plant size. P. clandestina, P. irregulare or R. solani, in particular, and to a lesser extent, P. avenaceum, are capable of causing serious damage to subterranean clover in natural soil.

scholarly journals Effects of invertebrate pests on white and annual clovers in dryland soil

2010 ◽  
Vol 63 ◽  
pp. 235-240
Author(s):  
T.M. Eden ◽  
P.J. Gerard ◽  
D.J. Wilson ◽  
N.L. Bell
Keyword(s):  
Plant Growth ◽  
White Clover ◽  
Seedling Survival ◽  
Plant Root ◽  
Subterranean Clover ◽  
Dry Weight ◽  
Cyst Nematode ◽  
Shoot Dry Weight ◽  
Sitona Lepidus ◽  
Clover Root

Two experiments were carried out at Ruakura in soil taken from Whatawhata hill country pasture The relative susceptibility of several annual clovers (Trifolium spp) and perennial white clover (T repens) to slugs (Deroceras reticulatum) clover root weevil (Sitona lepidus) adults native crickets (Nemobius sp) or wheat bugs (Nysius huttoni) was tested by sowing seed of the clovers into separate rows in turf Susceptibility of clovers to clover cyst nematode (Heterodera trifolii) was tested by sowing each clover variety into Whatawhata soil inoculated with the nematode Plant growth was assessed in both experiments 4 weeks after sowing White clover was more susceptible to pests than the annual clovers with slugs and clover root weevil significantly reducing seedling survival and clover cyst nematode significantly reducing plant growth Subterranean clover (T subterraneum) cv Denmark was the least affected by pests showing no significant reduction in survival in the presence of slugs the most damaging pest and no significant decrease in plant root and shoot dry weight when exposed to nematodes

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.

scholarly journals First Report of Pythium irregulare on Lentils in the United States

Plant Disease ◽  
2004 ◽  
Vol 88 (3) ◽  
pp. 310-310 ◽  
Author(s):  
T. C. Paulitz ◽  
F. Dugan ◽  
W. Chen ◽  
N. J. Grünwald
Keyword(s):  
United States ◽  
Dna Sequences ◽  
Root Rot ◽  
Dry Weight ◽  
The United States ◽  
Yield Reduction ◽  
Internal Transcribed Spacer Region ◽  
Pythium Irregulare ◽  
Plant Weight ◽  
Root Dry Weight

In late June and early July 2002, stunted, chlorotic, and partially defoliated lentils (Lens culinaris Medik.) were observed throughout the lentil-growing areas of eastern Washington. These symptoms were investigated in two fields near Garfield, WA and one field near Genesee, ID. Cv. Mason was more affected than cv. Brewer. Roots were dry and brittle with black discoloration in some cases. Isolates of Fusarium oxysporum and F. solani were obtained from washed roots plated on water agar, but they were nonpathogenic in greenhouse testing in pasteurized field soil and peat-based growing mixes. On 21 April 2003, volunteer lentils growing in the same fields showed symptoms of root rot, and Pythium oospores were observed in the roots. Pythium spp. were isolated by using a selective medium (2). Oospores were aplerotic, intercalary, 12.6 to 21 μm long × 11.2 to 18.2 μm wide, mostly smooth, and often formed in chains. Isolates resembled P. paroecandrum Drechs. and P. irregulare Buisman on the basis of morphological characters (3), but DNA sequences of the internal transcribed spacer region were closer to P. irregulare on the basis of a comparison with a worldwide database of Pythium sequences (C. A. Lévesque, personal communication). Isolates were deposited with the USDA-ARS Western Regional Plant Introduction Station, Pullman, WA. Four hyphal-tip isolates were tested in the greenhouse with inoculum grown in autoclaved sandy loam amended with 1% ground rolled oats. Experiments were performed twice in Thatuna silt loam, first in pasteurized and then in nonpasteurized soil. Inoculum was added to the soil at 500 CFU/g, and seeds were planted on the same day. Each isolate was tested on cvs. Brewer and Mason, with five replicates per treatment. Plants were grown in 4- × 20.5-cm plastic tubes (two plants per tube) for 1 month at 16 to 22°C and supplemented with 14 h of light per day. P. irregulare was reisolated from infected roots in both experiments. Damping-off, stunting, chlorosis, and root rot were observed in the Pythium-inoculated treatments, which corresponded to symptoms observed in the field in 2002. In pasteurized soil, only one isolate reduced the whole, dry, plant weight of Brewer, but the other three isolates reduced the dry weight of Mason. All isolates reduced the root dry weight of Mason in natural soil, but only two isolates reduced the root dry weight of Brewer. To our knowledge, Pythium spp., but not P. irregulare, have been reported previously from lentils (1). P. irregulare also causes root rot on winter wheat, which is rotated with lentils, and this pathogen likely causes yield reduction in both crops. References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (2) S. M. Mircetich and J. M. Kraft. Mycopathol. Mycol. Appl. 50:151, 1973. (3) A. J. van der Plaats-Niterink. Stud. Mycol. 21:1, 1981.

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.

Relation between plant size and severity of root rot in subterranean clover

1983 ◽  
Vol 23 (121) ◽  
pp. 126
Author(s):  
MJ Barbetti
Keyword(s):  
Root System ◽  
Western Australia ◽  
Root Rot ◽  
Lateral Root ◽  
Inverse Relationship ◽  
Subterranean Clover ◽  
Plant Size ◽  
Tap Root ◽  
The Relationship

Investigations were carried out in south-western Western Australia in 1977-78 to assess the relationship between dry weights of subterranean clover tops and roots and the severity of root rot. An inverse relationship was established between the severity of rotting of the tap root system and the plant top and the root dry weights. There was no relationship between the severity of root rot of the lateral root system and the plant top and root dry weights.

Factors contributing to reduced productivity of subterranean clover (Trifolium subterraneum L.) pastures on acidic soils

1990 ◽  
Vol 41 (4) ◽  
pp. 669 ◽  
Author(s):  
Z Hochman ◽  
GJ Osborne ◽  
PA Taylor ◽  
B Cullis
Keyword(s):  
Seed Production ◽  
Root Rot ◽  
Seedling Survival ◽  
Soil Phosphorus ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Phosphorus Sorption ◽  
Sorption Index ◽  
Clover Seed ◽  
Root Health

In a field study on four sites, soil acidity, root rot (Phytophthora clandestina), and soil phosphorus were identified as causes of 'subterranean clover decline'. Liming increased herbage and seed production at four sites, with a tendency for lime to increase herbage yields in autumn (22%) and winter (15%) but not in spring. The presence of ryegrass with clover increased total herbage yields, and reduced clover seed production, but there was no interaction with liming. Losses caused by root rot associated with P. clandestina were quantified for the first time in New South Wales. Root rot reduced survival of seedlings as well as herbage production in autumn and/or winter at three of the four sites. In the presence of the disease, lime did not improve root health or seedling survival. On two sites with high aluminium saturation of exchangeable cations (> 17%) and high phosphorus sorption index values, subterranean clover growth responded to high levels of P fertilizer. On one site, where lime increased the soil pH to above 5.5, the P sorption index was temporarily increased, and this was associated with a temporary adverse effect on herbage yields. Some possible mechanisms underlying the seasonality of lime responses are proposed and the practical implications of our findings are discussed.

Root rot caused by Pythium irregulare Buisman, an important factor in the decline of established subterranean clover pastures

1974 ◽  
Vol 25 (4) ◽  
pp. 537 ◽  
Author(s):  
GE Stovold
Keyword(s):  
Root Rot ◽  
Subterranean Clover ◽  
Common Disease ◽  
Crop Species ◽  
Pythium Irregulare ◽  
Factors Affecting ◽  
South Wales ◽  
Matter Production ◽  
Pathogenicity Tests

The problem of poor re-establishment and poor seasonal production in long-term subterranean clover pastures has been recognized for some time, particularly on the Southern Tableland and Slopes regions of New South Wales. Field and laboratory investigations showed that rotting of the lateral feeder roots was a common disease of subterranean clover during the cool part of the growing season. Isolations made from diseased roots yielded a predominance of Pythium spp. of which Pythiurn irregulare was the most common. Pathogenicity tests demonstrated that P. irregulare consistently caused damping-off of germinating subterranean clover. This fungus also infected established plants and at low temperatures caused severe reduction of dry matter production. Symptoms produced on artificially inoculated plants were identical with those observed on plants infected in the field. Soil moisture and the level of fungal inoculum added did not have a critical effect on the severity of root disease. A range of other important pasture and crop species were also artificially infected with P. irregulare, with resulting necrosis of feeder roots. In vitro studies of factors affecting the growth of P. irregulare showed that this pathogen was well adapted to survive and cause disease in cold wet soils, the conditions most favourable for root rot in the field. The importance of P. irregulare as a pathogen of established plants and possible means of reducing its effect on the growth of subterranean clover are discussed.

Root rot of subterranean clover in the irrigation areas of south-western Western Australia

1978 ◽  
Vol 18 (92) ◽  
pp. 426 ◽  
Author(s):  
MJ Barbetti ◽  
GC MacNish
Keyword(s):  
Western Australia ◽  
Root Rot ◽  
Lateral Root ◽  
Disease Incidence ◽  
Seedling Emergence ◽  
Soil Water Potential ◽  
Subterranean Clover ◽  
Pythium Irregulare ◽  
Plant Emergence ◽  
Apparently Healthy

Investigations in 1974 identified the fungi associated with the roots of subterranean clover at four irrigated sites at Wagerup, Western Australia. Two of these sites had previously had a disease problem, two were apparently healthy. A range of fungi were isolated, including Pythium irregulare, P. debaryanum, P. acanthicum, P. middletonii, Fusarium oxysporum, and Rhizoctonia spp. There was a more rapid buildup of Pythium spp. population following the initial irrigation, and an overall lower incidence of Fusarium spp., at the diseased sites. The incidence of Rhizoctonia spp. was usually low and variable at all sites. Disease index ratings rose more rapidly for diseased sites. No association was proven between disease incidence and soil water potential. The three most frequently isolated fungi; viz. P. irregulare, P. acanthicum, and F. oxysporum, were all shown to be capable, under the conditions of this investigation, of producing high levels of tap and lateral root rot, and of causing reductions in seedling emergence. In some cases the levels of both tap and lateral root rot were increased, and the plant emergence decreased, by the application of two or more fungi in combination in comparison with application of a single fungus. Overall P. irregulare was the most pathogenic of the fungi tested.

Effect of clover-free rotations upon the severity of root rot and yield in regenerating subterranean clover pastures

1991 ◽  
Vol 42 (7) ◽  
pp. 1195 ◽  
Author(s):  
MJ Barbetti
Keyword(s):  
Seed Yield ◽  
Root Rot ◽  
Lateral Root ◽  
Subterranean Clover ◽  
Complete Removal ◽  
Plant Size ◽  
Field Trials ◽  
Root Disease ◽  
Variable Effect ◽  
Tap Root

In two field trials, complete removal of subterranean clover for one season, or in particular two seasons, significantly reduced tap and lateral root disease in the immediate following year in which subterranean clover was allowed to regenerate. By the second season of regeneration these effects were either small or absent. Subterranean clover removal had greater effect on reducing lateral root disease than tap root disease in regenerating pastures. There were often large increases in plant size in regenerating pastures following complete removal of subterranean clover for one season or, in particular, two consecutive seasons. This effect also persisted poorly beyond the first season of regeneration. The losses in terms of subterranean clover herbage and seed yield during the period of subterranean clover removal were not offset by subsequent benefits from root disease reductions, as there was no corresponding increase in total herbage production. Subterranean clover removal had a variable effect upon the per cent subterranean clover v. grass ratio in regenerating pastures. Removal of subterranean clover for short periods (1 or 2 years) as an agronomic practice does not appear to be useful in overcoming root rot problems associated with this species in the high (> 750 mm) rainfall zone, the zone where severe root rot most frequently occurs in Western Australia.

Effects of soil temperature and moisture on the pathogenicity of fungi associated with root rot of subterranean clover

1984 ◽  
Vol 35 (5) ◽  
pp. 675 ◽  
Author(s):  
DH Wong ◽  
MJ Barbetti ◽  
K Sivasithamparam
Keyword(s):  
Soil Temperature ◽  
Root Rot ◽  
Marked Effect ◽  
Subterranean Clover ◽  
Pythium Irregulare ◽  
Highly Pathogenic ◽  
Soil Temperatures ◽  
Moisture Conditions ◽  
Water Holding ◽  
Soil Temperature And Moisture

The effects of soil temperature (10, 15, 20 and 25�C) and moisture (45% water holding capacity (WHC), 65% WHC, and flooding) on the pathogenicity of five fungi, both alone and in combinations, were investigated to determine the involvement of these fungi in a severe root rot disorder of subterranean clover in Western Australia. Fusarium avenaceum, Pythium irregulare, and Rhizoctonia solani were highly pathogenic while Fusarium oxysporum and Phoma medicaginis, particularly when used singly, were only weakly pathogenic. Compared with individual fungi, fungal combinations increased the severity of root disease and decreased plant survival and plant fresh weight. While the fungi investigated caused root rot over the range of soil temperatures and moisture conditions of this investigation, the most severe root rot occurred at 10�C, with less at 15 and 25�C, and least at 20�C. Temperature had a marked effect on the disease severity and its effect varied with individual fungi and their combinations, in particular, combinations involving P. irregulare (severest root rot at 10 and 15�C). The most severe root rotting, compared with the control, occurred at 65% WHC, with less at 45% WHC, and least under flooding conditions. There was often a significant interaction between temperature and moisture for the various fungi and fungal combinations tested.

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