Prevalence of blackleg (Leptosphaeria maculans) on canola (Brassica napus) in Western Australia

2001 ◽  
Vol 41 (1) ◽  
pp. 71 ◽  
Author(s):  
R. K. Khangura ◽  
M. J. Barbetti
Keyword(s):  
Western Australia ◽  
Disease Incidence ◽  
Leptosphaeria Maculans ◽  
Sowing Date ◽  
Blackleg Disease ◽  
The Mean ◽  
Seed Yields ◽  
Blackleg Fungus ◽  
Western Australian

Canola crops were monitored throughout the Western Australian wheatbelt during 1996–99 to determine the incidence and severity of crown cankers caused by the blackleg fungus (Leptosphaeria maculans). All crops surveyed had blackleg. The incidence of crown canker was 48–100%, 15–100%, 9–94% and 48–100% during 1996, 1997, 1998 and 1999, respectively. The mean incidence of crown cankers statewide was 85, 63, 55 and 85% in 1996, 1997, 1998 and 1999, respectively. The severity of crown canker (expressed as percentage disease index) ranged between 30 and 96%, 3 and 94%, 5 and 78% and 21 and 96% during 1996, 1997, 1998 and 1999, respectively. These high levels of blackleg can possibly be attributed to the accumulation of large amounts of infested canola residues. In 1999, there were effects of variety, application of the fungicide Impact, distance to last year’s canola residues and rainfall on the incidence and severity of blackleg. However, there were no effects of sowing date or region on the disease incidence or severity once the other factor effects listed above had been considered. In 1995, an additional survey of 19 sites in the central wheatbelt of Western Australia assessed the survival of the blackleg fungus on residues from crops grown in 1992–94. The residues at all sites carried blackleg. However, the extent of infection at any particular site varied from 12 to 100% of stems with the percentage of stems carrying pseudothecia containing ascospores varying between 7 and 96%. The high levels of blackleg disease found in commercial crops are indicative of significant losses in seed yields, making it imperative that management of blackleg be improved if canola is to remain a viable long-term cropping option in Western Australia.

Response of soybeans to sowing date during the wet season in the Ord Irrigation Area, Western Australia

1988 ◽  
Vol 28 (3) ◽  
pp. 357 ◽  
Author(s):  
DF Beech ◽  
AL Garside ◽  
IM Wood
Keyword(s):  
Western Australia ◽  
Cropping Systems ◽  
Plant Morphology ◽  
Sowing Date ◽  
Wet Season ◽  
Double Cropping ◽  
Affected Plant ◽  
Pod Development ◽  
Late Maturity ◽  
Seed Yields

The responses of 3 soybean cultivars to sowing date during the wet season in the Ord Imgation Area (OIA) in northern Western Australia are described. The cultivars, Buchanan, Ross and Durack, are classified as early, medium and late maturity respectively, when grown during the wet season in the OIA. The cultivars were grown 10 times between 22 December and 18 April during 2 wet seasons and we investigated the patterns of phenology, growth and seed production. Sowing date had no significant effect (P> 0.05) on the time to flowering (26-36 days) with cv. Buchanan, but the duration of flowering was curtaiied so that the period from sowing to maturity declined from 120 to 95 days as sowing was delayed from December to April. In contrast the time to flowering of cv. Durack declined in response to photoperiod from about 70 to 40 days and the time from sowing to maturity declined from about 160 to 100 days. The responses of cv. Ross were intermediate between those of Buchanan and Durack. The phenological responses to sowing date were consistent with responses to photoperiod rather than to temperature. Sowing date also affected plant morphology and yields and quality of seed. Delay in sowing after December led to declines in above-ground dry matter yields at flowering, in number of nodes on the main stem at flowering, crop height at maturity and seed yields. Mean individual seed weights increased with delay in sowing. Oil concentrations in the seed declined (from 23 to 17%) and protein concentrations increased (from 32 to 45%) as the period of pod development occurred later in the season. Phenology is a major determinant of the suitability of a cultivar for specific cropping systems. The early maturing cultivar, Buchanan, most closely meets the requirements for a system of double cropping in which the wet season soybean crop is followed by a May sown dry season crop. The late maturing cultivar, Durack, is suitable for a system involving a single wet-season crop.

Analysis of seed-bank data confirms suitability of international seed-storage standards for the Australian flora

2007 ◽  
Vol 55 (1) ◽  
pp. 18 ◽  
Author(s):  
Andrew D. Crawford ◽  
Kathryn J. Steadman ◽  
Julie A. Plummer ◽  
Anne Cochrane ◽  
Robin J. Probert
Keyword(s):  
Western Australia ◽  
Seed Bank ◽  
Seed Storage ◽  
Storage Conditions ◽  
International Standards ◽  
Australian Flora ◽  
Western Australian

The suitability of applying international standards for long-term seed storage to the Australian flora was examined by reviewing seed-storage data from the Western Australian Threatened Flora Seed Centre. The 375 collections examined represented 176 taxa from 44 genera and 16 families. A high proportion of collections, representative of some of the most common genera in Australia, maintained viability in the short (<5 years) and medium (5–12 years) term. Declines in germination were evident for a small number of collections, representing 10 taxa, stored for 5–12 years. However, many of the declines were collection-specific and other collections of the same taxon did not decline. Five taxa showing germination declines were represented by a single collection so it was not possible to determine whether the germination decline was directly related to the taxa, storage conditions or to other factors. Only the closely related Stylidium coroniforme and S. amabile exhibited germination declines in all collections, but cut tests of seeds remaining from germination testing indicated that viability of the collections had not declined, just the proportion to germinate; for these species a change in germination conditions is a more likely explanation for the reduction in germination. The results illustrate the successful application of these seed-storage standards to threatened flora in Western Australia and highlight their suitability for the Australian flora.

scholarly journals Breakdown of a Brassica rapa subsp. sylvestris Single Dominant Blackleg Resistance Gene in B. napus Rapeseed by Leptosphaeria maculans Field Isolates in Australia

Plant Disease ◽  
2003 ◽  
Vol 87 (6) ◽  
pp. 752-752 ◽  
Author(s):  
H. Li ◽  
K. Sivasithamparam ◽  
M. J. Barbetti
Keyword(s):  
Brassica Napus ◽  
Resistance Gene ◽  
Disease Severity ◽  
Brassica Rapa ◽  
Oilseed Rape ◽  
Leptosphaeria Maculans ◽  
Blackleg Disease ◽  
Field Isolates ◽  
Western Australian ◽  
Lower Stem

Blackleg, caused by Leptosphaeria maculans, is a major disease of oilseed rape (Brassica napus) grown in Canada, Europe, and Australia. Cv. Surpass 400 was released in Australia in 2000 as the most resistant cultivar to L. maculans. It carries a single dominant resistance gene from B. rapa subsp. sylvestris. This cultivar usually shows a hypersensitive response to L. maculans characterized by small, dark brown lesions that are necrotic, localized, and without pycnidia on cotyledons, leaves, and stems. However, in 2001 on a Western Australian experimental farm, a small proportion of the lesions on the lower stem and crown region of cv. Surpass 400 were typical of those observed in susceptible cultivars, which were brown, necrotic lesions with a darker margin, but they contained fewer pycnidia. Forty seedlings of cv. Surpass 400 and susceptible cv. Westar were inoculated with pycnidiospore suspensions (106/ml) of each of 18 isolates taken from lesions on cv. Surpass 400. All 18 isolates caused collapse of cotyledons of susceptible cv. Westar. Four of these isolates caused large cotyledon lesions with some pycnidia on cv. Surpass 400. Three of these four isolates were subsequently inoculated onto 60 seedlings per isolate, at each of the four cotyledon lobes of each seedling of the two cultivars. Inoculated plants were assessed for disease severity on cotyledons and transplanted to the field 14 days after inoculation. The cotyledons of inoculated cv. Surpass 400 showed characteristic large, necrotic lesions with pycnidia, while the cotyledons of cv. Westar had collapsed and contained a mass of pycnidia. Blackleg disease severity in the crown region of the stem was assessed at 2 weeks before harvest. Fifty-four percent of the cv. Surpass 400 transplanted inoculated plants subsequently developed susceptible symptoms of crown cankers on stems. These symptoms were deep, girdling, brown lesions on the plant crowns with some pycnidia. One hundred percent of cv. Westar plants were infected and dead at this stage. This confirmed the ability of these field isolates to overcome the single dominant resistance gene present in cv. Surpass 400. To our knowledge, this is the first report of breakdown of a single dominant B. rapa subsp. sylvestris gene based resistance to blackleg in oilseed rape in the field.

scholarly journals Efficacy of Fungicide Seed Treatments in Controlling Blackleg of Canola

2019 ◽  
Vol 20 (3) ◽  
pp. 160-164
Author(s):  
Sudha GC Upadhaya ◽  
Venkataramana Chapara ◽  
Mukhlesur Rahman ◽  
Luis E. del Río Mendoza
Keyword(s):  
Seed Treatment ◽  
Leaf Growth ◽  
Disease Incidence ◽  
Leptosphaeria Maculans ◽  
Field Trials ◽  
Management Tool ◽  
Blackleg Disease ◽  
Seed Treatments ◽  
Spring Canola ◽  
Plant Stand

The efficacy of five fungicide seed treatments as a management tool against blackleg on spring canola was evaluated under greenhouse and field conditions in North Dakota. Blackleg, caused by Leptosphaeria maculans, inflicts the greatest yield losses when infecting seedlings before they reach the six-leaf growth stage. In greenhouse studies, 10-day-old seedlings were inoculated with L. maculans spore suspensions and evaluated 12 days later and at maturity or inoculated 12, 20, or 28 days after planting and evaluated at maturity. In field trials conducted in 2017 and 2018, severity was assessed at maturity. In the greenhouse, all fungicide seed treatments reduced (P = 0.05) disease severity at the seedling stage, but only the protection provided by Obvius (fluxapyroxad + pyraclostrobin + metalaxyl) and Helix Vibrance (mefenoxam + fludioxonil + sedaxane + difenoconazole + thiamethoxam) reduced (P < 0.05) severity at the adult stage; however, none of them provide effective protection when plants were inoculated 20 days after planting or later. In field trials, none of the treatments significantly (P > 0.05) improved plant stand and yield or reduced disease incidence and severity. Although fungicide seed treatment is a valuable tool, it should not be used as the only method to manage blackleg disease.

Reliability of canola production in different rainfall zones of Western Australia

2007 ◽  
Vol 58 (4) ◽  
pp. 326 ◽  
Author(s):  
Imma Farré ◽  
Michael Robertson ◽  
Senthold Asseng
Keyword(s):  
Soil Water ◽  
Western Australia ◽  
Soil Type ◽  
Oil Content ◽  
Sowing Date ◽  
Soil Types ◽  
Minor Effect ◽  
High Rainfall ◽  
History Of

The area of canola in the wheat-based farming systems of the wheatbelt of Western Australia (WA) expanded rapidly during the 1990s and has subsequently decreased. Due to the short history of canola production in WA, there is little information on yield and oil content expectations in relation to rainfall, location, and soil type. In this paper we: (1) present the recent history of canola production in the context of the long-term climate record; (2) assess the effect of location, rainfall, soil type, and soil water at sowing on yield and oil content; and (3) determine cut-off sowing dates for profitable canola production. Simulations were run using the APSIM-Canola model with long-term climate records for 3 selected locations from the low-, medium-, and high-rainfall zones and different soil types. Analysis of recent trends in canola area showed that poor seasons and price volatility in the last few years have contributed to farmers’ perception of risk and hence the decline in area sown. Long-term simulations showed the importance of location, sowing date, soil type, and stored soil water at sowing on grain yield. Yield was negatively related to sowing date. Light-textured soils had lower yields and larger yield penalties with delayed sowing than heavy-textured soils. Soil water at sowing gave a yield advantage in most years in all locations studied, but especially in low- and medium-rainfall locations. Variation in oil content was most strongly affected by sowing date and location, while soil type and soil water at sowing had a minor effect. Long-term simulation analysis can be used as a tool to establish the latest possible sowing date to achieve profitable canola for different locations and soil types, given different canola prices and growing costs. Given the vulnerability of profitability to seasonal conditions, in the low- and medium-rainfall zone, the decision to grow canola should be tactical depending on stored soil water, sowing opportunities, seasonal climate outlook, prices, and costs. In contrast, in the high-rainfall zone, canola production is relatively low risk, and could become a reliable component of rotations.

Effect of benomyl on 'blackleg' disease of rape in Western Australia

1976 ◽  
Vol 16 (79) ◽  
pp. 276 ◽  
Author(s):  
AGP Brown ◽  
MJ Barbetti ◽  
PM Wood
Keyword(s):  
Western Australia ◽  
Maximum Rate ◽  
Field Experiments ◽  
Natural Infection ◽  
Leptosphaeria Maculans ◽  
Blackleg Disease ◽  
Seed Treatments ◽  
Poor Control ◽  
Rape Seedlings

Seed treatments using the fungicide benomyl at 1.1 and 2.2 per cent w/w protected seedling rape from infection by Leptosphaeria maculans under glasshouse conditions but in field experiments with natural infection no worthwhile control of the disease was obtained. Benomyl applied as a spray to rape seedlings in field experiments gave variable but mainly poor control At the maximum rate tried it increased yields at only three out of eight experiment sites.

scholarly journals Factors affecting growth and yield of short-duration pigeonpea and its potential for multiple harvests

1987 ◽  
Vol 109 (3) ◽  
pp. 519-529 ◽  
Author(s):  
Y. S. Chauhan ◽  
N. Venkataratnam ◽  
A. R. Sheldrake
Keyword(s):  
Short Duration ◽  
Dry Matter ◽  
Total Yield ◽  
Sowing Date ◽  
Growth And Yield ◽  
First Flush ◽  
Factors Affecting ◽  
Northern India ◽  
The Mean ◽  
Seed Yields

SummaryEnvironmental and cultural factors that may limit the yield of short-duration pigeonpea were investigated over three seasons. Plants in the peninsular Indian environment at Patancheru grew less and produced less dry matter by first-flush maturity than at Hisar, a location in northern India where the environment is considered favourable for the growth of short-duration pigeonpea. However, with a similar sowing date in June, the mean seed yields of three genotypes, ICPL 4, ICPL 81 and ICPL 87, were very similar, at about 2·3 t/ha, in both environments. This was mainly due to the higher ratio of grain to above-ground dry matter at Patancheru. In addition to the first harvest, all genotypes showed a potential for two more harvests owing to the warm winters at Patancheru. The potential for multiple harvests was particularly high in ICPL 87, which yielded 5·2 t/ha from three harvests in 1982–3, 3·6 t/ha from two harvests in 1983–4, and 4·l t/ha from three harvests in 1984–5. The optimum plant population density at Patancheru was 25–35 plants/m2 for ICPL 87, but was higher for the other two genotypes.At Patancheru, the total dry-matter and seed yield of first and subsequent harvests were significantly reduced by delaying sowing beyond June. Generally, the second- and the third-harvest yields were lower on vertisol than on alfisol under both irrigated and unirrigated conditions.The total yield of ICPL 87 from two harvests was far higher than that of a well-adapted medium-duration genotype BDN 1, grown over a similar period. The yield advantage was greater on the alfisol because of the better multiple harvest potential of this soil. The results of this study demonstrate that properly managed short-duration genotypes of pigeonpea may have considerable potential for increased yield from multiple harvests in environments where winters are warm enough to permit continued growth.

Growth and Habits of the Sea Mullet, Mugil dobula Gnnther, in Western Australia

1951 ◽  
Vol 2 (2) ◽  
pp. 193 ◽  
Author(s):  
JM Thomson
Keyword(s):  
Fresh Water ◽  
Western Australia ◽  
Age Groups ◽  
Age Determination ◽  
River System ◽  
The Mean ◽  
Pass Through ◽  
Considerable Individual Variation ◽  
Incomplete Sampling ◽  
Western Australian

Morphologically and physiologically, the sea mullet of Western Australia seems to be identical with that of the eastern Australian coast. No raciation can be detected either within Western Australian waters or between the stocks of eastern and Western Australia. However, the mean growth rate varies from one estuary to another and from year to year within any particular river system. Growth is isometric and shows considerable individual variation though tending to a mean rate. Increase in length is seasonal, practically stopping in midwinter and reaching a peak in midsummer. The seasons of fish and scale growth are contemporaneons. The annuli form at the end of September or the beginning of October, when growth recommences after the winter cessation. Mullet mature at a size of 31–35 cm. (12 1/2-13 3/4 in. length to caudal fin) at the end of their third year. The movement of mullet from the fishing grounds as they increase in size leads to an incomplete sampling of the population so that Petersen's method of age determination is inappIicable owing to the apparent nonprogression of the modes. Of 7110 mullet tagged, only 97 or 1.35 per cent. were returned. The return for separate tagging operations varied from nil to 25 per cent. and according to localities from nil to 16 per cent. Only three fish were retaken outside the rivers in which they were tagged. These showed a northerly movement. Inside the rivers the young fish spread out over the estuary and into the fresh water; but the older age-groups remain in the slightly brackish or fresh water except during the migration season, when they pass through the saline estuaries on the way to the sea.

scholarly journals Seasonal and Diurnal Patterns of Spore Dispersal by Leptosphaeria maculans from Canola Stubble in Relation to Environmental Conditions

Plant Disease ◽  
2005 ◽  
Vol 89 (1) ◽  
pp. 97-104 ◽  
Author(s):  
X. W. Guo ◽  
W. G. D. Fernando
Keyword(s):  
Relative Humidity ◽  
Environmental Conditions ◽  
Disease Incidence ◽  
Leptosphaeria Maculans ◽  
Blackleg Disease ◽  
Spore Dispersal ◽  
The North ◽  
Diurnal Patterns ◽  
Air Temperatures ◽  
Rain Events

Seasonal and diurnal patterns of spore dispersal by Leptosphaeria maculans, which causes blackleg disease of canola, were studied in two consecutive field seasons using a 7-day Burkard spore sampler and rotorod impaction spore samplers. Ascospores of L. maculans were trapped from mid-June to the end of July, whereas pycnidiospores were trapped from mid-July until the end of July or early August. Ascospores and pycnidiospores were trapped between 9:00 P.M. and 4:00 A.M., when air temperatures were 13 to 18°C and relative humidity was >80%. Peak ascospore and pycnidiospore dispersal was associated with rain events. Peak ascospore dispersal was found to occur several hours after rainfall ≥2 mm, and ascospore dispersal continued for approximately 3 days after such events. Peak pycnidiospore dispersal occurred during the same hours as rain events. More ascospores and pycnidiospores were carried in the direction of prevailing winds than in other directions. To the south of the inoculated area, the gradients of disease incidence and stem disease severity were -19.2 and -0.8 m-1, respectively. Disease incidence and stem severity declined by 50% 12.5 and 5.5 m from the inoculated area, respectively. To the north of the inoculated area, the gradients of disease incidence and stem severity were -21.5 and -0.7 m-1, respectively. Disease incidence and stem severity declined by 50% 14.0 and 5.2 m from the inoculated area, respectively. In 2001, ascospores and pycnidiospores were trapped within 25 m of the inoculated area, whereas pycnidiospores were trapped up to 45 m from the inoculated area.

The profitability of short-duration canola and pea rotations in western Canada

2013 ◽  
Vol 93 (5) ◽  
pp. 933-940 ◽  
Author(s):  
E. G. Smith ◽  
H. R. Kutcher ◽  
S. A. Brandt ◽  
D. Ulrich ◽  
S. S. Malhi ◽  
...  
Keyword(s):  
Field Study ◽  
Short Duration ◽  
Production Systems ◽  
Disease Incidence ◽  
Economic Incentive ◽  
Western Canada ◽  
Blackleg Disease ◽  
Long Term Impact ◽  
Term Field

Smith, E. G., Kutcher, H. R., Brandt, S. A., Ulrich, D., Malhi, S. S. and Johnston, A. M. 2013. The profitability of short-duration canola and pea rotations in western Canada. Can. J. Plant Sci. 93: 933–940. A long-term field study of canola and pea interval in rotations was used to determine the most profitable canola production systems. The duration between canola crops has been declining with most canola grown more often than the recommended once every 4 yr. Producers could be reducing their long-term profitability if the short-duration canola rotation results in increased disease and lower yield. A field study was conducted from 1998 to 2007 at Scott and from 1999 to 2006 at Melfort in Saskatchewan, Canada, to examine the long-term impact of shorter-duration canola and pea rotations. Canola and pea were grown continuously, or in rotations with wheat or flax for 2, 3, or 4 yr. Two canola types were used, one was a blackleg-susceptible conventional cultivar and the other a blackleg-resistant hybrid. The returns above variable costs for the production systems were determined over the last 4 yr of the study, the period of time when rotation impacts should be most evident in this study. The continuous canola and pea rotations were the least profitable rotations. Blackleg-susceptible canola had higher return when in rotations of 3 or 4 yr, compared with continuous or 2 yr. Blackleg-resistant hybrid canola had statistically similar returns for 2, 3 and 4-yr rotations, which were superior to continuous canola. Even with increased blackleg disease incidence and severity after several years of a short-duration canola rotation, the short-duration canola rotation was more profitable when growing the disease-resistant hybrid. With high canola prices, the returns from the short-duration canola rotations were as high, or higher, than rotations with more years between canola crops. The canola industry must recognize that producers have an economic incentive to use short-duration canola rotations and new systems (disease resistance and rotations) need to be developed within this context.

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