Soilborne root disease pathogen complexes drive widespread decline of subterranean clover pastures across diverse climatic zones

2017 ◽  
Vol 68 (1) ◽  
pp. 33 ◽  
Author(s):  
Kevin Foster ◽  
Ming Pei You ◽  
Brett Nietschke ◽  
Nick Edwards ◽  
Martin J. Barbetti
Keyword(s):  
Lateral Root ◽  
Geographic Location ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Disease Index ◽  
Root Disease ◽  
Fusarium Spp ◽  
Soilborne Disease ◽  
Root Diseases ◽  
Rot Disease

Subterranean clover (Trifolium subterraneum L.) is an important pasture legume in many regions of Australia, and elsewhere. A survey was undertaken in 2014 to define the levels of soilborne disease and associated pathogens in annual subterranean clover pastures across southern Australia. Most of the 202 samples processed had very severe levels of taproot rot disease (disease index 60–80%) and extremely severe lateral root rot disease (disease index 80–100%). A complex of soilborne root pathogens including Aphanomyces trifolii, Phytophthora clandestina, and one or more of Pythium, Rhizoctonia and Fusarium spp. was found responsible for severe pre- and post-emergence damping-off and root disease. This is the first study to highlight the high incidence of A. trifolii across southern Australian pastures and the first to highlight the existence of natural synergistic associations in the field between Rhizoctonia and Pythium spp., Pythium and Fusarium spp., Pythium spp. and A. trifolii, and P. clandestina and A. trifolii. Nodulation was generally poor, mainly only in the 20–40% nodulation index range. There was no relationship between rainfall zone and tap or lateral root disease level, with root disease equally severe in lower (330 mm) and higher (1000 mm) rainfall zones. This dispels the previous belief that severe root disease in subterranean clover is an issue only in higher rainfall zones. Although overall the relationship between tap and lateral root disease was relatively weak, these two root-disease components were strongly positively expressed within each pathogen’s presence grouping, providing explanation for variability in this relationship across different field situations where soilborne root disease is a major problem. Most producers underestimated the levels and effect of root disease in their pastures. This study established that tap and lateral root diseases are widespread and severe, having devastating impact on the feed gap during autumn–early winter across southern Australia. Severe root disease was independent of the highly variable complex of soilborne pathogens associated with diseased roots, geographic location and rainfall zone. It is evident that soilborne root diseases are the primary factor responsible for widespread decline in subterranean clover productivity of pastures across southern Australia. Implications for disease management and options for extension are discussed.

Amelioration of root disease of subterranean clover (Trifolium subterraneum) by mineral nutrients

2012 ◽  
Vol 63 (7) ◽  
pp. 672 ◽  
Author(s):  
Tiernan A. O'Rourke ◽  
Megan H. Ryan ◽  
Tim T. Scanlon ◽  
Krishnapillai Sivasithamparam ◽  
Martin J. Barbetti
Keyword(s):  
Nutrient Solution ◽  
Lateral Root ◽  
Field Experiments ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Mineral Nutrients ◽  
Root Disease ◽  
Tap Root ◽  
Complete Nutrient Solution

Subterranean clover (Trifolium subterraneum) is a key pasture legume across southern Australia and elsewhere. Decline in subterranean clover pastures was first recognised in Australia during the 1960s and manifests as an increase in weeds and a decrease in desirable legume species. While both root disease and poor nutrition contribute to subterranean clover pasture decline, the relationships between root disease and nutrition have not been determined. The objective of this study was to define these relationships. Field experiments were undertaken to determine the nutritional and pathogen status of soils and subterranean clover from three Western Australian field sites. Subsequently, controlled environment experiments were undertaken to determine the relative severities of tap and lateral root disease and growth of plants when soil cores taken from these three field sites were amended with a complete nutrient solution or a range of individual macro- or micronutrient treatments. Application of a ‘Hoaglands’ complete nutrient solution decreased the severity of tap root disease by an average of 45% and lateral root disease by 32%. Amendment with K alone reduced the severity of tap root disease an average of 32%; while the application of N alone reduced the severity of tap root disease by 33% and lateral root disease by 27%. Application of Hoaglands, K, N or Zn increased shoot and root dry weight, while Mo only increased shoot dry weight. This is the first report to show that mineral nutrients can substantially ameliorate root disease in subterranean clover. The results demonstrate that while root disease limits plant growth, improvement in the nutritional status of nutrient-impoverished soils can significantly reduce root disease. There is significant potential to incorporate nutrient amendments into an integrated and more sustainable approach to better manage root disease and to increase productivity of pasture legumes where soils are inherently nutrient deficient in one or more nutrients.

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.

Taxonomic and pathogenic characteristics of a new species Aphanomyces trifolii causing root rot of subterranean clover (Trifolium subterraneum) in Western Australia

2010 ◽  
Vol 61 (9) ◽  
pp. 708 ◽  
Author(s):  
Tiernan A. O'Rourke ◽  
Megan H. Ryan ◽  
Hua Li ◽  
Xuanli Ma ◽  
Krishnapillai Sivasithamparam ◽  
...  
Keyword(s):  
New Species ◽  
Western Australia ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Root Disease ◽  
Molecular Characteristics ◽  
Root Pruning ◽  
High Rainfall ◽  
South West ◽  
A New Species

Subterranean clover (Trifolium subterraneum) is grown extensively as a pasture legume in agronomic regions with Mediterranean-type climates in parts of Africa, Asia, Australia, Europe, North America and South America. Root diseases of subterranean clover, especially those caused by oomycete pathogens including Aphanomyces, Phytophthora and Pythium, greatly reduce productivity by significantly decreasing germination, seedling establishment, plant survival and seed set. For this reason, experiments were conducted to determine the species of Aphanomyces causing root disease on subterranean clover in the high-rainfall areas of south-west Western Australia. The effects of flooding, temperature and inoculum concentration on the development of root disease on subterranean clover caused by this Aphanomyces sp. were also investigated as was its host range. Morphological and molecular characteristics were used to identify the pathogen as a new species Aphanomyces trifolii sp. nov. (O’Rourke et al.), which forms a distinct clade with its nearest relative being A. cladogamus. A. trifolii caused significant lateral root pruning as well as hypocotyl collapse and tap root disease of subterranean clover. The level of disease was greater in treatments where soil was flooded for 24 h rather than for 6 h or in unflooded treatments. The pathogen caused more disease at 18/13oC than at lower (10/5oC) or higher (25/20oC) temperatures. The pathogen caused more disease at 1% inoculum than at 0.5 or 0.2% (% inoculum : dry weight of soil). In greenhouse trials, A. trifolii also caused root disease on annual medic (M. polymorpha and M. truncatula), dwarf beans (Phaseolus vulgaris) and tomatoes (Solanum lycopersicum). However, the pathogen did not cause disease on peas (Pisum sativum), chickpea (Cicer arietinum), wheat (Triticum aestivum), annual ryegrass (Lolium rigidium) or capsicum (Capsicum annuum). A. trifolii is a serious pathogen in the high-rainfall areas of south-west Western Australia and is likely a significant cause of root disease and subsequent decline in subterranean clover pastures across southern Australia.

Response of Italian elite subterranean clover genotypes to Fusarium avenaceum and Fusarium oxysporum under artificial conditions

2002 ◽  
Vol 42 (5) ◽  
pp. 557 ◽  
Author(s):  
E. Piano ◽  
L. Riccioni ◽  
L. Pecetti ◽  
A. M. Carroni ◽  
A. Porta-Puglia
Keyword(s):  
Root Rot ◽  
Disease Outbreaks ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Fusarium Spp ◽  
Seedling Vigour ◽  
Breeding Programs ◽  
Disease Response ◽  
Artificial Infestation ◽  
Growth Vigour

Breeding programs of subterranean clover in southern Europe have traditionally set low priority on selection against major pathogens, in part because there have been no major disease outbreaks in this region. However, root-rot causing fungi, such as Fusarium spp., occur frequently on other crops and can therefore also represent a threat to clover. Thus, the breeding program carried out in Sardinia, Italy, took note of this disease. This study reports the results of 2 trials carried out in 2 consecutive years following artificial infestation with Fusarium spp. The first trial included 45 genotypes, of which 37 were Sardinian lines under advanced breeding and 8 were commercial varieties. To validate the variation observed in disease response, a subset of 27 genotypes was further evaluated in the second trial. In both trials, 3 pathogen treatments were applied, in addition to a control, uninoculated treatment - F. avenaceum, F. oxysporum, and an equal mixture of both fungi. One-month-old clover seedlings were scored in all treatments for shoot-growth vigour (1-9 scale), then excavated for scoring root-rot symptoms (1-5�scale), and finally weighed after oven drying. Analysis of variance tested differences among treatments, among genotypes, and between subsp. subterraneum and brachycalycinum of Trifolium subterraneum. On the common set of genotypes to both trials, a cluster analysis was applied using, as original variables, the average disease score across the 3 inoculated treatments in the 2 trials. Confirming previous evidence, F. avenaceum proved more pathogenic than F. oxysporum. The results suggested that high seedling vigour may play a role in limiting root-rot effects, and this may also contribute to the relatively better tolerance of subsp. brachycalycinum over subsp. subterraneum observed. Despite some inconsistency of response in the 2 trials both at the treatment and genotype level, some Sardinian genotypes demonstrated a consistent level of tolerance especially in relation to the performance of the commercial varieties tested. Among them were the lines `125 brachy C', `56 sub D', `22 brachy G', `56 sub B' (=Campeda), and `19 brachy E' (=Antas).

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.

Seed-borne Fusarium species on subterranean clover and other pasture legumes

1978 ◽  
Vol 29 (5) ◽  
pp. 975 ◽  
Author(s):  
AW Kellock ◽  
LL Stubbs ◽  
DG Parbery
Keyword(s):  
White Clover ◽  
Root Rot ◽  
Fusarium Species ◽  
Subterranean Clover ◽  
Fusarium Spp ◽  
Root Rot Disease ◽  
Pasture Legumes ◽  
Rot Disease ◽  
Clover Seed ◽  
First Time

Fusarium avenaceum (Corda ex. Fr.) Sacc. was detected for the first time on seed of strand medic (M. littoralis Rhode), lucerne (M. sativa L.), white clover (T. repens L.) and strawberry clover (T. fragiferum L.). The percentage of seed infected was 24% on medic seed, 2–3% on strawberry clover, 2–6% on white clover, and 10–14% on lucerne, compared with 1–42% on subterranean clover seed. The majority of infected seed lines were grown in the main seed-producing areas of Victoria. F. arthrosporioides Sherb., F. equiseti (Corda) Sacc., F, acuminatum Ellis & Everhart and F. culmorum (W. G. Sm.) Sacc. were isolated from subterranean clover seed for the first time, comprising between 1 and 8% of Fusarium spp. isolates, while F. oxysporum (Schlecht) and F. avenaceum comprised the remaining 55% and 35% of isolates respectively. In laboratory tests, isolates of F. avenaceum from each seed host were all strongly pathogenic on roots of subterranean clover, but there was no evidence of pathogenicity by other Fusarium spp. F. oxysporum had no effect on the severity of root rot disease either alone or in combination with F. avenaceum.

Meeting the Kyoto target: implications for the Australian livestock industries

1999 ◽  
Vol 50 (8) ◽  
pp. I
Keyword(s):  
Biological Control ◽  
Root Rot ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Hyphal Growth ◽  
Root Disease ◽  
Biological Control Agents ◽  
Control Activity ◽  
Matter Production

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.

Competition among seedlings of perennial grasses, subterranean clover, white clover, and annual ryegrass in replacement series mixtures

2000 ◽  
Vol 51 (3) ◽  
pp. 377 ◽  
Author(s):  
G. M. Lodge
Keyword(s):  
White Clover ◽  
Plant Competition ◽  
Perennial Grass ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Perennial Grasses ◽  
Maximum Likelihood Estimates ◽  
Annual Ryegrass ◽  
Replacement Series ◽  
Successful Establishment

Seedlings of 3 perennial grasses, Danthonia linkii Kunthcv. Bunderra, D. richardsonii Cashmore cv. Taranna(wallaby grasses), and Phalaris aquatica L. cv. Sirosa,were each grown in replacement series mixtures with seedlings ofTrifolium repens L. (white clover),Trifolium subterraneum L. var. brachycalycinum (Katzn.et Morley) Zorahy & Heller cv. Clare (subterraneanclover), and Lolium rigidum L. (annual ryegrass). Plantswere sown 5 cm apart in boxes (45 by 29 by 20 cm) at a density of 307plants/m2. Maximum likelihood estimates were usedto derive parameters of a non-linear competition model using the dry matterweights of perennial grasses and competitors at 3 harvests, approximately 168,216, and 271 days after sowing. Intra-plant competition was examined inmonocultures of each species, grown at plant spacings of 2, 5, and 8 cm apartwith plants harvested at the above times.Competition occurred in all perennial grass–competitor mixtures, exceptin those of each perennial grass with white clover and thephalaris–subterranean clover mixture (Harvest 1) and those withD. richardsonii and phalaris grown with white clover(Harvest 2). For D. richardsonii (Harvests 1 and 2) andD. linkii (Harvest 1 only) grown with white clover andthe phalaris–subterranean clover (Harvest 1), the two species in themixture were not competing. In the phalaris–white clover mixture, eachspecies was equally competitive (Harvests 1 and 2). These differences incompetition and aggressiveness reflected differences in individual plantweights in monocultures where there was an effect (P < 0.05) of species ondry matter weight per box, but no significant effect of plant spacing.These data indicated that for successful establishment,D. richardsonii and D. linkiishould not be sown in swards with either subterranean clover or white clover,or where populations of annual ryegrass seedlings are likely to be high.Phalaris was more compatible with both white clover and subterranean clover,but aggressively competed with by annual ryegrass.

scholarly journals Host plant recognition by the root feeding clover weevil, Sitona lepidus (Coleoptera: Curculionidae)

2004 ◽  
Vol 94 (5) ◽  
pp. 433-439 ◽  
Author(s):  
S.N. Johnson ◽  
P.J. Gregory ◽  
P.J. Murray ◽  
X Zhang ◽  
I.M. Young
Keyword(s):  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Plant Roots ◽  
Grass Species ◽  
Movement Rates ◽  
Sitona Lepidus ◽  
Macro Scale ◽  
Significant Difference ◽  
Invasive Techniques ◽  
Root Feeding

AbstractThis study investigated the ability of neonatal larvae of the root-feeding weevil, Sitona lepidus Gyllenhal, to locate white clover Trifolium repens L. (Fabaceae) roots growing in soil and to distinguish them from the roots of other species of clover and a co-occurring grass species. Choice experiments used a combination of invasive techniques and the novel technique of high resolution X-ray microtomography to non-invasively track larval movement in the soil towards plant roots. Burrowing distances towards roots of different plant species were also examined. Newly hatched S. lepidus recognized T. repens roots and moved preferentially towards them when given a choice of roots of subterranean clover, Trifolium subterraneum L. (Fabaceae), strawberry clover Trifolium fragiferum L. (Fabaceae), or perennial ryegrass Lolium perenneL. (Poaceae). Larvae recognized T. repens roots, whether released in groups of five or singly, when released 25 mm (meso-scale recognition) or 60 mm (macro-scale recognition) away from plant roots. There was no statistically significant difference in movement rates of larvae.

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