Abstract
The fungus Leptosphaeria maculans (anamorph Phoma lingam) causes blackleg in canola (Brassica napus). Infection of all above-ground parts of the plant has been described, but there are no reports of infection of roots. In a recent review West et al. (1999) described the common plant symptoms, but did not mention root infection. Canola plants at the flowering and pod-filling stages, with foliar symptoms of blackleg, were collected from commercial crops in South Australia, Victoria and New South Wales, Australia in November and December 2000. Some plants had lodged and had the basal cankers commonly described for blackleg, however, many plants had died prematurely during late pod fill. Cankers and other external symptoms were not present on the lower stems of these plants and many could be pulled easily from the ground. The lateral roots had blackened areas. Taproots had extensive internal tissue necrosis. In some plants, the pith of the stem was also necrotic, although there were no external symptoms. In another case, a distinct black band was seen around the circumference of the taproot below the crown. Samples of discoloured tissue were surface-sterilized and cultured on quarter-strength potato dextrose agar. Phoma lingam was isolated from all samples, identified as described by Punithalingham & Holliday (1972). All isolates were virulent (A-group) according to PCR-based tests carried out by the Root Disease Testing Service, South Australian Research and Development Institute (Sosnowski et al., 2001). Phytophthora and Rhizoctonia spp. were not isolated from the discoloured tissues. Pycnidiospore suspensions (106 spores mL−1) were prepared from two isolates of P. lingam (66/97 and 208/00) obtained from leaves and roots, respectively, of diseased plants. These suspensions were used to inoculate (i) lateral roots severed with surface-sterilized scissors; and (ii) hypocotyls wounded with sterile toothpicks on otherwise healthy canola seedlings in the glasshouse. Three weeks after inoculation, stem and crown cankers appeared on plants inoculated with either isolate on either roots or hypocotyls and root tissue was necrotic, whereas control plants, wounded as described above and inoculated with sterile water, remained healthy. Phoma lingam was the only pathogen isolated from diseased root tissue. This confirms the occurrence of the blackleg fungus in the roots of canola plants, and reveals its ability to infect through wounds in the roots. This is the first record of symptoms of blackleg on canola roots in Australia. However, there is anecdotal evidence that such symptoms have occurred in the past (D. Ballinger, Dovuro Pty Ltd, Horsham, Victoria, Australia, personal communication; M. Barbetti, Agriculture Western Australia, South Perth, Western Australia, Australia, personal communication). Initially it was assumed that the infection had spread from the crown into the roots, but new evidence suggests that the disease can also be soilborne. This may have important ramifications for understanding the blackleg disease cycle. This aspect will be investigated further in the current project entitled ‘Investigating resistance and management of blackleg in canola’, which is funded by the Australian Research Council, the South Australian Grains Industry Trust Fund and the South Australian Research and Development Institute.
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Claims 11
Claim · model-written summary
Some blackleg-affected canola plants lodged and developed basal cankers, while many died during late pod fill.
- Taxon
- canola
.jpg?width=60)
Brassica napus var. napust0 - Interactor
- Leptosphaeria maculans
Plenodomus lingamt1pathogen - Outcome
- lodged and had the basal cankerse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“Some plants had lodged and had the basal cankers commonly described for blackleg, however, many plants had died prematurely during late pod fill.”
t0“canola”
t1“Leptosphaeria maculans”
Claim · model-written summary
Affected canola lateral roots had blackened areas.
- Taxon
- canolaBrassica napus var. napust0
- Organ / stage
- lateral rootse0
- Outcome
- blackened arease0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The lateral roots had blackened areas.”
t0“canola”
Claim · model-written summary
Affected canola taproots had extensive internal necrosis.
- Taxon
- canolaBrassica napus var. napust0
- Organ / stage
- Taprootse0
- Outcome
- internal tissue necrosise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Taproots had extensive internal tissue necrosis.”
t0“canola”
Claim · model-written summary
Some canola stems had necrotic pith without external symptoms.
- Taxon
- canolaBrassica napus var. napust0
- Organ / stage
- pith of the steme0
- Outcome
- necrotice0
- Qualifier
- there were no external symptomse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In some plants, the pith of the stem was also necrotic, although there were no external symptoms.”
t0“canola”
Claim · model-written summary
One canola taproot showed a black band below the crown.
- Taxon
- canolaBrassica napus var. napust0
- Organ / stage
- taproote0
- Outcome
- black bande0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a distinct black band was seen around the circumference of the taproot below the crown”
t0“canola”
Claim · model-written summary
Phoma lingam was isolated from all discoloured tissue samples.
- Taxon
- canolaBrassica napus var. napust0
- Interactor
- Phoma lingamPlenodomus lingame0pathogen
- Outcome
- isolated from all samplese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Phoma lingam was isolated from all samples”
t0“canola”
Claim · model-written summary
PCR tests identified all recovered isolates as virulent A-group.
- Taxon
- canolaBrassica napus var. napust0
- Interactor
- Phoma lingamPlenodomus lingame1pathogen
- Outcome
- virulent (A-group)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“All isolates were virulent (A-group) according to PCR-based tests”
e1“Phoma lingam was isolated from all samples”
t0“canola”
Claim · model-written summary
Neither Phytophthora nor Rhizoctonia was isolated from discoloured tissue.
- Taxon
- canolaBrassica napus var. napust0
- Interactor
- Phytophthora and Rhizoctonia spp.
Phytophthora.jpg?width=60)
Rhizoctoniae0pathogen - Outcome
- not isolated from the discoloured tissuese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“Phytophthora and Rhizoctonia spp. were not isolated from the discoloured tissues.”
t0“canola”
Claim · model-written summary
Both leaf- and root-derived P. lingam isolates caused stem and crown cankers and root necrosis after wound inoculation.
- Taxon
- canolaBrassica napus var. napuse1
- Treatment
- inoculated with either isolate on either roots or hypocotylse0
- Outcome
- stem and crown cankerse0
- Direction
- appearede0
- Comparator
- control plants, wounded as described above and inoculated with sterile watere0
- Setting
- glasshousee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Three weeks after inoculation, stem and crown cankers appeared on plants inoculated with either isolate on either roots or hypocotyls and root tissue was necrotic, whereas control plants, wounded as described above and inoculated with sterile water, remained healthy.”
e1“canola seedlings in the glasshouse”
Claim · model-written summary
The authors establish the first Australian record of blackleg symptoms on canola roots.
- Taxon
- canolaBrassica napus var. napuse0
- Organ / stage
- rootse0
- Outcome
- symptoms of blacklege0
- Qualifier
- first recorde0
- Setting
- Australiae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This is the first record of symptoms of blackleg on canola roots in Australia.”
Claim · model-written summary
The fungus can infect canola through wounds in roots.
- Taxon
- canolaBrassica napus var. napust1
- Organ / stage
- rootse0
- Interactor
- Leptosphaeria maculansPlenodomus lingamt0pathogen
- Outcome
- infecte0
- Qualifier
- through woundse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reveals its ability to infect through wounds in the roots”
t0“Leptosphaeria maculans”
t1“canola”
The same questions in other papers
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2 papers in the same direction as this paper · 11 in the opposite direction
- positive
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See all 14 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.