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.

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.

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.

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.

Effects of cultivation and cultural practice on root rot of subterranean clover

1984 ◽  
Vol 24 (127) ◽  
pp. 550 ◽  
Author(s):  
MJ Barbetti ◽  
GC MacNish
Keyword(s):  
Western Australia ◽  
Root Rot ◽  
Lateral Root ◽  
Field Experiments ◽  
Cultural Practices ◽  
Subterranean Clover ◽  
Cultural Practice ◽  
Second Year

Field experiments in 1975 and 1976 in south-western Western Australia investigated the effects of various cultivation and cultural practices on the level of root rot of subterranean clover. The treatments produced significant reductions in the levels of both tap and lateral root rot, but these reductions failed to persist beyond the second year after treatment. The best treatments were those of fallowing an area from August to March before cultivation and reseeding, or spring cultivation before sowing to oats followed by a March cultivation and reseeding.

scholarly journals Landslides and the Urban Forest

2011 ◽  
Vol 37 (5) ◽  
pp. 213-218
Author(s):  
Robert Loeb ◽  
Samuel King
Keyword(s):  
Root System ◽  
Lateral Root ◽  
Urban Forest ◽  
Basal Area ◽  
Natural Area ◽  
Species Classification ◽  
Slope Steepness ◽  
Tap Root ◽  
Area Survey ◽  
Root Plate

Trees and saplings were felled and killed by rockslides and soil slides formed during the record breaking rains of May 1–2, 2010, in Radnor Lake State Natural Area, Nashville, Tennessee, U.S. The losses were analyzed by species; stem basal area; root plate diameter and depth; percent slope; occurrence in a rockslide or soil slide as well as species classification as a lateral root system species versus tap or heart root system species. The number of stems lost for each species had a distribution similar to the results of the 2009 Natural Area survey but the number of saplings was significantly underrepresented at the landslide sites. Tree deaths were nearly five times greater than saplings lost. Although there were nearly equal numbers of tree and sapling stems classified as possessing a lateral root system versus tap or heart root system, 74% of the sapling losses were from surface root system species. The means for root plate diameter and depth were significantly larger in rockslides than soil slides even though the mean stem basal area did not differ significantly. For both slide types, slope steepness was not correlated with root plate depth, root plate diameter, or stem basal area. Similarly for both root system classi-fications, slope steepness was not significantly correlated except for surface root system trees with root plate depth. Planting tap root system trees reduces the risk of landslide, but advances in the cultivation of taxa, such as hickory (Carya spp.), are needed to assure tap root preservation during transplantation.

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.

Relationship of rainfall, cultural practices, soil and plant nutrients, and seedling survival with root disease and parasitic nematode numbers in annual Medicago spp. Pastures

1999 ◽  
Vol 50 (6) ◽  
pp. 977 ◽  
Author(s):  
M. P. You ◽  
I. T. Riley ◽  
K. Sivasithamparam ◽  
M. J. Barbetti
Keyword(s):  
Root Rot ◽  
Lateral Root ◽  
Cultural Practices ◽  
Seedling Survival ◽  
Root Disease ◽  
Plant Nutrients ◽  
Tap Root ◽  
Low Levels ◽  
Annual Medicago ◽  
Relationship Of

Surveys were conducted for annual Medicago spp. (medic) pastures in the grain belt of south-west Western Australia during spring 1996 and winter–spring 1997 to determine the relationship of rainfall, cultural practices, soil and plant nutrients, and seedling survival with severity of root disease and numbers of parasitic nematodes. Medic pasture was sampled on 116 farms. Most pastures consisted of a single medic variety, viz. Serena, Santiago, Cyprus, or Caliph, whereas about 33% of sites had mixed varieties. Regression analyses showed that high rainfall and application of phosphorus fertilisers were correlated with increased severity of rot in medic tap roots. Crop history and medic variety were not related to the level of root rot. Numbers of Pratylenchusin medic roots were not correlated with the level of tap or lateral root rot, medic variety, rainfall, or with the application of insecticide, fertilisers, or herbicides. Soil with relatively high levels of P, NO3-, or Fe was associated with an increased level of tap root rot. Soils with high pH were associated with reduced tap root rot. Soils with relatively high K were related to severe lateral root rot, whereas relatively high levels of P in soil were associated with reduced lateral root rot. Plants with high levels of tap root rot showed low levels of Mg, whilst low levels of Ca and NO3– in tissues were related to high levels of lateral root rot. High levels of tap root rot were associated with relatively high levels of total N, K, and S, Cu, Zn, Mn, and NO3- in plant tissues. Plants with relatively high levels of lateral root rot had relatively high levels of Cu in shoots. Of the 116 annual Medicago pastures sampled, only 1% had adequate Mg content and only 19% had adequate Ca content. However, 83% had higher than adequate levels of Cu, 70% had higher than adequate levels of Mn, and all samples showed more than adequate levels of chloride. Experimental sites of M. polymorpha cv. Serena at 6 farms showed that the percentage survival rate of seedlings was negatively correlated with the severity of tap and lateral root rot in the previous year. These results indicate that in the farms surveyed there is a serious threat to annual medic pastures from root rot fungi. The severity of the disease was partly determined by soil conditions and cultural practices.

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.

Naturalized subterranean clover strains in Western Australia: A preliminary agronomic examination

1967 ◽  
Vol 18 (5) ◽  
pp. 713 ◽  
Author(s):  
JS Gladstones
Keyword(s):  
Flowering Time ◽  
Western Australia ◽  
Morphological Characteristics ◽  
Subterranean Clover ◽  
Morphological Characters ◽  
Biochanin A ◽  
The Relationship

Ninety naturalized and four commercially introduced subterranean clover strains present in Western Australia were examined. Flowering time, hardseededness, contents of the oestrogenic isoflavones formononetin, genistein, and biochanin A, and plant morphological characteristics were measured in spaced plants. Probabilities of random relationships were calculated for all character pairs. Wide variation was found among strains for all characters measured. A number of strains had low oestrogenic isoflavone contents. Levels of the three isoflavones appeared to vary independently of each other and of all other characters. Hardseededness decreased with lateness of maturity, but evidence is adduced that the relationship was not causal. Correlations were recorded among several morphological characters. Some 20 naturalized, non-commercial strains were selected as worthy of further agronomic study.

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