Brassica Production Research Articles

Oilseed brassica in India: Demand, supply, policy perspective and future potential

India is the largest agrarian subcontinent supporting 26% world’s agricultural population on 12% arable land. India is also the fifth largest vegetable oil economy accounting 7.4% oilseeds, 5.8% oils and 6.1% oil meal production, and 9.3% of edible oil consumption in the world. Oilseeds are the second most important agricultural economy in India next to cereals growing at a pace of 4.1% per annum in the last three decades. Oilseed brassica shares 23.5% area and 24.2% production of total oilseeds in the country. Despite being the third largest producer (11.3%) of oilseed brassica after Canada and China in the world, India meets 57% of the domestic edible oil requirements through imports and ranked 7th largest importer of edible oils in the world. Oilseed brassica achieved significant growth in India in the past, however, the productivity levels are still low owing to large cultivation under rainfed situation, biotic and abiotic stresses, and resources crunch. It is also facing the challenges of low genotypic potential, climate change and price fluctuation. Though, it embraces the immense scope to increase the production in traditional and non-traditional areas in India with proper inputs, technological interventions, and suitable policy framework. This needs to develop strategies in a well-planned, targeted manner with multi-scientific inputs, policy interface and stable price systems to bring the desired growth in oilseeds brassica production, and to reduce the import of edible oils in the country.

New sources of resistance to downy mildew in a collection of wild and cultivated brassicas

Brassica downy mildew (DM) is a foliar disease caused by the oomycete Hyaloperonospora brassicae (syn. Hyaloperonospora parasitica subs. brassica) that can affect plants at all stages including the nurseries and can limit the production of vegetable Brassica especially in temperate climates. Twenty-eight landraces and wild genotypes from different Brassica species, coming from Portuguese and Italian germplasm collections, were screened for DM resistance. Genotypes of B. oleracea (23 acc.), B. rupestris (3 acc.), B. incana (1 acc.), and B. villosa (1 acc.) were tested with four H. brassicae pathotypes from different geographical origin at the seedling stage. DM evaluation showed no differential responses to the four H. brassicae pathotypes but great differences in resistance were observed between accessions. Seven accessions including one B. villosa (UNICT3944), two B. oleracea var. acephala (BPGV4533 and UNICT4448), three B. oleracea var. costata (BPGV1773, BPGV1726, and BPGV1747), and one B. oleracea var. sabauda (UNICT4633) were resistant to DM infection at cotyledon stage. These accessions are potential sources of DM resistance to be genetically characterised and further exploited in breeding programmes.

Field evaluation of aqueous indigenous plant extracts against the diamondback moth, Plutella xylostella L. and the rape aphid, Brevicoryne brassicae L. in brassica production

Small-scale vegetable farmers in southern Africa are battling with increasing pressure from insect pests due to limited sustainable control options. Concerns are growing about human safety and environmental impact of conventional synthetic pesticides commonly used against the pests. Two experiments were therefore conducted to investigate the insecticidal efficacy of crude aqueous extracts of two indigenous plants, Maerua edulis and Bobgunnia madagascariensis in controlling the most damaging pests of cabbage and rape; Plutella xylostella and Brevicoryne brassicae, respectively. Experiment I was on-station in which aqueous extracts of M. edulis leaf and B. madagascariensis fruit powder were applied separately on rape and cabbages at 3–20% w/v compared to negative water control and synthetic pesticide positive controls. Concentrations of 5 and 10% w/v M. edulis and 15 and 20% w/v B. madagascariensis were further tested on-farm in Experiment II. On-station results showed that extracts from M. edulis and B. madagascariensis at 5–20% w/v and 15–20% w/v, respectively, showed significant insecticidal effect (P<0.05) compared to the negative control. In both experiments, there were no significant differences in pest counts between plant extracts and the positive controls. In both experiments, vegetable yields from plant extract treatments differed significantly (P<0.05) from the negative control at M. edulis 5–20% w/v and B. madagascariensis 15–20% w/v, but not from the positive controls. The commercial potential of local plant extract sprays for vegetable pest management on small-scale farms is discussed.

Field Evaluation of Insecticides for Control of Cabbage Maggot (Diptera: Anthomyiidae) in Rutabaga in Canada.

At the time of this research, there were only two insecticides registered for control of cabbage maggot, Delia radicum L., in rutabaga in Canada, one of which (diazinon) will be deregistered by 2017, and resistance having been reported in some areas for the other (chlorpyrifos). To screen for chemistries to replace these organophosphates, and obtain efficacy data comparable between key vegetable brassica production areas in Canada, four small plot field studies were conducted concurrently in British Columbia, Saskatchewan, Ontario, and Quebec in 2009. These studies followed standardized protocols for seeding, application of insecticide drenches, sampling and damage assessment, and generally tested the same products. Of the insecticides evaluated, none provided maggot control comparable with the industry standard, chlorpyrifos. However, cyantraniliprole (Cyazypyr 200SC; registered in 2015 as Verimark) applied at 3 g AI (15.0 ml product)/100 m row of seeded rutabagas consistently provided the next highest reduction in % culls, suggesting the efficacy of this chemical may be improved if used at higher rates. The results of these studies are discussed in the context of current literature on D. radicum management in rutabaga. Future management strategies are also discussed, including a transplant plug treatment approach for increasing the dosage per plant and efficacy of chemistries such as Cyazypyr 200SC in the field.

Cultivar resistance offers the first opportunity for effective management of the emerging powdery mildew (Erysiphe cruciferarum) threat to oilseed brassicas in Australia

Powdery mildew of brassicas, caused by Erysiphe cruciferarum, is an emerging threat to oilseed Brassica production in Australia. Resistance to powdery mildew was assessed in 112 current and historic Australian Brassica napus canola cultivars and five cultivars of B. juncea mustard cultivars under controlled environmental conditions. Only 18% of leaf area was infested by the end of the test on the most resistant cultivars, compared with means of up to 70% for the most susceptible cultivars as well as severe stem and pod infection. For B. napus, cultivars with the greatest potential for reducing the impact of powdery mildew in the field were Trooper, Bravo TT, Summit, Tumby, Narendra and Hyola 650TT, all ranked in the 10% of cultivars with the lowest leaf infestation (Area Under The Disease Progress Curve (AUDPC) &lt;537) and with &lt;10% of stem area infested. For B. juncea, the level of leaf infestation was lowest for Sahara CL and Xceed X121 CL (AUDPC 303 and 380 respectively), but the high levels of stem infestation (42% and 28% respectively) in these cultivars may reduce their usefulness in the field. The most resistant cultivars identified can be immediately deployed into regions where powdery mildew is prevalent, providing the canola industry with an immediate and effective option for management of this increasingly troublesome disease.

Control of clubroot (Plasmodiophora brassicae) in oilseed rape using varietal resistance and soil amendments

Clubroot is a major threat to global brassica production. It has been an increasing problem in UK oilseed rape (OSR) crops due to the persistence of the soil-borne pathogen responsible for disease, Plasmodiophora brassicae, exacerbated by close rotations. Field surveys in the UK in the years 2007–2010 showed that clubroot was present in all areas of the UK where OSR was grown with 52% of the selected sites testing positive. Varietal resistance and soil amendment with calcium carbonate, calcium cyanamide and boron alone or in various combinations applied before sowing were assessed for the potential to manage clubroot. Soil amendments gave variable control between sites and years but showed some potential as part of a clubroot management strategy. Varietal resistance remained the more effective management option providing 50–95% disease control at three sites in England. However, this control was not consistently effective at sites in Scotland where resistant OSR varieties have been heavily used in rotations. Yield losses were demonstrated at 0.03tha−1 for every 1% increase in clubroot severity in the susceptible variety Kommando. Yield losses were only slightly lower per 1% increase in clubroot severity for the resistant variety Mendel at 0.028tha−1 despite lower disease levels. Losses in affected crops can therefore equate to over 50% of potential yield in severely infected crops. Soil testing for clubroot and lengthening rotations are important to the long term management of clubroot as varietal resistance and soil amendments can reduce clubroot severity but provide inconsistent results.

English

Oilseed brassicas also known as rapeseed-mustard is an important group of oilseed crop in the world. These crops are susceptible to a number of diseases caused by biotic and mesobiotic pathogens. Among various diseases, Alternaria leaf blight also known as Alternaria dark spot is the most destructive disease of oilseed brassicas species in all the continents. This disease is known to be incited by Alternaria brassicae, Alternaria brassicicola and Alternaria raphani singly or by mixed infection. Alternaria leaf spot pathogens are necrotrophs and produces lesions surrounded by chlorotic areas on leaves, stems and siliquae causing reduction in the photosynthetic areas, defoliation, and early induction of senescence. Alternaria blight causes considerable reduction in quantity and quality of harvested brassica products. The Alternaria leaf blight pathogens are seedborne, soilborne and airborne. The pathogens are greatly influenced by weather with the highest disease incidence reported in wet seasons and in areas with relatively high rainfall. The concentration of conidia, age of the host plants, and wetness period on leaves also influence the severity of the disease. This paper reviews the research and development of Alternaria blight in the oilseed brassicas (rapeseed-mustard) during the past years in relation to pathogen taxonomy, biology, epidemiology, host pathogen interaction and management through chemicals, botanicals, biological, cultural, and biotechnological approaches. The paper also attempts to present future outlook and strategy for Alternaria blight of rapeseed-mustard research. Key words: Alternaria blight, rapeseed-mustard, symptoms, variability, pathogen, survival, management.

The Fate of Chromosomes and Alleles in an AllohexaploidBrassicaPopulation

Production of allohexaploid Brassica (2n = AABBCC) is a promising goal for plant breeders due to the potential for hybrid heterosis and useful allelic contributions from all three of the Brassica genomes present in the cultivated diploid (2n = AA, 2n = BB, 2n = CC) and allotetraploid (2n = AABB, 2n = AACC, and 2n = BBCC) crop species (canola, cabbages, mustards). We used high-throughput SNP molecular marker assays, flow cytometry, and fluorescent in situ hybridization (FISH) to characterize a population of putative allohexaploids derived from self-pollination of a hybrid from the novel cross (B. napus × B. carinata) × B. juncea to investigate whether fertile, stable allohexaploid Brassica can be produced. Allelic segregation in the A and C genomes generally followed Mendelian expectations for an F2 population, with minimal nonhomologous chromosome pairing. However, we detected no strong selection for complete 2n = AABBCC chromosome complements, with weak correlations between DNA content and fertility (r(2) = 0.11) and no correlation between missing chromosomes or chromosome segments and fertility. Investigation of next-generation progeny resulting from one highly fertile F2 plant using FISH revealed general maintenance of high chromosome numbers but severe distortions in karyotype, as evidenced by recombinant chromosomes and putative loss/duplication of A- and C-genome chromosome pairs. Our results show promise for the development of meiotically stable allohexaploid lines, but highlight the necessity of selection for 2n = AABBCC karyotypes.

Root traits and microbial community interactions in relation to phosphorus availability and acquisition, with particular reference to Brassica.

Brassicas are among the most widely grown and important crops worldwide. Phosphorus (P) is a key mineral element in the growth of all plants and is largely supplied as inorganic rock-phosphate, a dwindling resource, which is likely to be an increasingly significant factor in global agriculture. In order to develop crops which can abstract P from the soil, utilize it more efficiently, require less of it or obtain more from other sources such as soil organic P reservoirs, a detailed understanding the factors that influence P metabolism and cycling in plants and associated soil is required. This review focuses on the current state of understanding of root traits, rhizodeposition and rhizosphere community interaction as it applies to P solubilization and acquisition, with particular reference to Brassica species. Physical root characteristics, exudation of organic acids (particularly malate and citrate) and phosphatase enzymes are considered and the potential mechanisms of control of these responses to P deficiency examined. The influence of rhizodeposits on the development of the rhizosphere microbial community is discussed and the specific features of this community in response to P deficiency are considered; specifically production of phosphatases, phytases and phosphonate hydrolases. Finally various potential approaches for improving overall P use efficiency in Brassica production are discussed.

Selecting the right parasitoid for the environment in classical biological control programmes: the case of Diadegma semiclausum (Hymenoptera: Ichneumonidae) and Plutella xylostella (Lepidoptera: Plutellidae) in the Kofele highland of Ethiopia

The careful selection of parasitoids with a track record of success in similar environmental conditions may increase the likelihood of effective biocontrol. Diamondback moth (DBM) population and level of parasitism were assessed for three years prior to the release of Diadegma semiclausum (Hellén) in June 2008. Thereafter, the DBM population and severity of crop damage and the occurrence of D. semiclausum and indigenous DBM parasitoids were monitored by monthly surveys during the main production season of June to December for three years. Before release, DBM numbers fluctuated between 4.2 and 11.2 per plant and parasitism ranged between 6.5 and 24.7%. DBM density declined to 2.8, 0.9 and 0.7 per plant whilst parasitism levels increased successively to 21, 39 and 38% in 2008, 2009 and 2010, respectively. A significant shift in parasitoid guild was observed after D. semiclausum release: it comprised 18.6, 80.3 and 88.6% of total parasitism in the first, second and third year, respectively. The decline of DBM density following the release of the introduced parasitoid and its establishment will ensure production of Brassica spp. without pesticide use against DBM in the affected area.

Xanthomonas campestris pv. campestris race 1 is the main causal agent of black rot of Brassicas in Southern Mozambique

Severe outbreaks of bacterial black rot caused by Xanthomonas campestris pv. campestris (Xcc) were observed in Brassica production fields of Southern Mozambique. The causal agent of the disease in the Mahotas and Chokwe districts was identified and characterised. In total, 83 Xanthomonas -like strains were isolated from seed samples and leaves of cabbage and tronchuda cole with typical symptoms of the disease. Forty-six out of the 83 strains were found to be putative Xcc in at least one of the tests used: Classical biochemical assays, enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies, Biolog identification system, polymerase chain reaction (PCR) with specific primers and pathogenicity tests. The ELISA tests were positive for 43 strains. Biolog identified 43 strains as Xanthomonas , but only 32 as Xcc. PCR tests with primers targeting a fragment of the hrpF gene were positive for all 46 strains tested. Three strains were not pathogenic or weakly pathogenic and all other strains caused typical black rot symptoms in brassicas. Race type differentiation tests revealed the Xcc strains from Mozambique as members of race 1. The prevalence of this pathogenic race of the Xcc pathogen in Mozambique should be considered when black rot resistant cultivars are evaluated or introduced into the production regions of this country. Keywords : Cole crops, cabbage, tronchuda, landraces, seeds, black rot, enzyme-linked immunosorbent assay (ELISA), Biolog, polymerase chain reaction (PCR), race-type African Journal of Biotechnology Vol. 12(6), pp. 602-610

Genetics of resistance to downy mildew in Brassica oleracea and breeding towards durable disease control for UK vegetable production

Downy mildew resistance was previously identified from screening a Brassica oleracea collection against two standard UK isolates of Hyaloperonospora parasitica. Sources of resistance were chosen from this material and developed further in this study by generating doubled haploid (DH) and inbred lines. Seedlings from the new lines were tested for resistance to a larger collection of H. parasitica isolates collected in 2001–2002 and 2007–2008 from the main broccoli and cauliflower production regions of the UK. Three lines (derived from borecole or summer cabbage) were broadly resistant to the pathogen isolates. Three of the remaining lines exhibited strong isolate‐specific resistance; several examples of weak or basal level of resistance to some isolates were observed. A new H. parasitica variant collected in 2008 was virulent in the broadly resistant lines, but was avirulent in a line with narrow specificity of resistance. The F2 and BC1 seedlings derived from outcrossing each of the three broadly resistant lines to susceptible broccoli and cauliflower lines segregated in a manner indicating that the resistance was controlled by a single dominant gene. No susceptibility was observed amongst F2 seedlings derived from intercrossing the three resistant lines, indicating that they all share the same or closely linked broad‐spectrum resistance gene(s). DH lines were produced from F1 plants, and resistant plants were further backcrossed to produce broccoli and cauliflower‐like lines that could be useful pre‐breeding material. A combination of resistance from lines with broad and narrow specificity is recommended for controlling downy mildew in UK brassica production.

Effect of the insect growth regulator novaluron on diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), and its indigenous parasitoids

Research to evaluate effective and selective insecticides through periodic screening is needed to strengthen diamondback moth (DBM) ( Plutella xylostella L.) management. The efficacy of the insect growth regulator novaluron on DBM and effects on the parasitoids Diadegma sp. (Hym.: Ichneumonidae), Apanteles sp. (Hym.: Braconidae) and Oomyzus sokolowskii Kurdjumov (Hym.: Eulophidae) were evaluated. Novaluron was compared with the microbial insecticide Bacillus thuringiensis ( Bt) var. aizawai, the pyrethroid insecticide λ - cyhalothrin and the organophosphate insecticide profenofos. Two replicated experiments were conducted on head cabbage, Brassica oleracea var. capitata, planted in March and May 2007 at Wonji in the Central Rift Valley of Ethiopia. Infestation by DBM was less with novaluron and Bt compared with other treatments for both planting dates. Infestation with λ-cyhalothrin and profenofos was comparable with the untreated control. Yields were greatest with novaluron and were 80 and 32.5% (12.4 and 7.4 t ha −1) greater than the untreated treatment for the first and second plantings, respectively. Diadegma sp. accounted for 91% of the parasitoid complex observed. Parasitism of DBM by Diadegma sp. ranged between 10 and 43% among treatments. Parasitism was less with λ-cyhalothrin and profenofos compared with other treatments. Owing to its efficacy against DBM and relative safety to its parasitoid, Diadegma sp., novaluron can be used in integrated DBM management for low elevation brassica production in the Central Rift Valley of Ethiopia.

Validation of the Forage Brassica Calculator: A fertiliser forecasting system for forage brassica crops grown in New Zealand. Pasja and bulb turnips

Forage brassica calculators can be used to assist fertiliser consultants and farmers plan nitrogen (N) and phosphorus (P) applications for site-specific brassica production. The cost of each nutrient and the predicted productivity are used to recommend both economic and environmentally sound application rates. In this study, simulated yield was that modelled by PARJIB (a model that analyses and forecasts yield responses to nutrients) from the soil available nutrient levels, the potential yield and the fertiliser rates. The actual (observed) yields are those measured from the field. Simulations for ePasjaf (R2=0.96; root mean square of the deviation (RMSD) .3% (0.25 t/ha)) followed observed data closely with individual harvests at 60 and 90 days after sowing, consistent with observed data (R2&gt;0.93; RMSD.4% (0.20 t/ha)). The ePasjaf model is sufficiently robust to predict site specific N and P fertiliser requirements. However, the model may need to be extended to more than two grazing events. Simulations for bulb turnips (R2=0.10; RMSD.28.1% (2.70 t/ha)) was poor. Simulations predicted the same yield for different treatments within sites, while observed yields differed widely (4.12 t/ha). This was because experiments included establishment and seeding method treatments which are not currently accounted for by the calculators. Thus, practical use of the brassica calculators for assisting with fertiliser rates currently depends on other agronomic factors being managed optimally. Key words: agro-ecological, leachate, supplementary feed, water-holding capacity

Cloning and Characterization of a Constitutive Lysophosphatidic Acid Acyltransferase 2 (LPAT2) Gene from Tropaeolum majus L~!2009-07-22~!2009-09-25~!2010-03-12~!

The cloning and characterization of a lyso-phosphatidic acid acyltransferase (LPAT2; EC 2.3.1.51) from Tropaeolum majus from a 20,000 EST collection is described. The 1358 bp TmLPAT2 gene encodes a 42.6 kD polypep- tide; the primary sequence has a membrane bound O-acyltransferase, MBOAT, Box I motif, and Boxes II, III and IV typical of LPATs from various species. Unlike many LPAT2s, the gene was constitutively expressed in all tissues. The TmLPAT2 functionality was confirmed by expression in a yeast LPAT deletion (SLC1 - ) mutant. The TmLPAT2 could use a range of acyl-CoAs as acyl donor, including 22:1-CoA and 20:1-CoA and either 18:1-LPA or 22:1-LPA as acyl acceptor. This new LPAT2 could enable the production of Brassica seed oils with enhanced levels of very long-chain fatty acids.

Effects of 5-Aminolevulinic Acid on Oilseed Rape Seedling Growth under Herbicide Toxicity Stress

Weeds are one of the major constraints in oilseed Brassica production. Use of effective herbicides to control weeds in the fields is one of the major objectives of agronomists. To improve weed control efficacy and minimize the application costs, complex combinations of 5-aminolevulinic acid (ALA) and a new postemergence herbicide, propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate (ZJ0273), were used to investigate their combined effects in relation to seedling growth and development of oilseed rape (Brassica napus cv. ZS 758). Brassica seeds were treated with different concentrations of ZJ0273 [100 (normal dose for rape), 200, 500, and 1000 mg/L] and ALA (0.1, 1, 10, and 50 mg/L). ALA was applied as pre- and post-treatment alone and in combination with ZJ0273. We found that ZJ0273 stress imposed negative effects on rape seedling growth. Shoot fresh weight, shoot length, and root fresh weight were inhibited significantly under ZJ0273 stress, and the rate of decline increased consistently with increased ZJ0273 concentration. Root oxidizability was also inhibited significantly under ZJ0273 stress conditions, and the higher the concentration of the herbicide ZJ0273, the lower the oxidizability. Herbicide ZJ0273 treatment produced a gradual decrease in antioxidant enzymes (peroxidase, superoxide dismutase, and ascorbate peroxidase) and an increase in peroxidation substance (malondialdehyde accumulation). The increase and decrease were consistent with the ZJ0273 dosage. Our results indicated that pre- and post-treatments with a lower dosage of ALA (1 mg/L) improved rape seedling growth and root oxidizability parameters, whereas a higher concentration of ALA (50 mg/L) depressed growth. We also found that plants treated with 1 mg/L ALA produced the highest shoot fresh weights, shoot lengths, root fresh weights, and root oxidizability when the seeds were treated with different concentrations of ZJ0273. Lower dosages of ALA improved the activities of antioxidant enzymes, whereas the highest dosage of ALA increased the accumulation of peroxidation substance. These results indicate that ALA has promotive effects in the recovery of growth and development of rape seedlings under herbicide ZJ0273 toxicity stress.

Spatial distribution of Diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), at the field and the regional level in Ethiopia

Pheromone trap catches were used to study the spatial distribution of Diamondback moth (DBM), Plutella xylostella L., at both single field and regional levels. At the field level, the DBM population tended to remain within the cabbage field. At the regional level, DBM captures were highly influenced by geographic location and cropping systems. In highland areas, daily maximum temperatures positively influenced the aggregation index, whereas in the lowland areas, rainfall had a negative influence on the aggregation index. The implications for integrated DBM managements are as follows: at the local level, knowledge on spatial dynamics allows the delimitation of areas with high DBM infestations for consideration in both monitoring and biological control programmes. At the regional level, areas with year-round production of Brassica spp. and intensive use of pesticides should receive priority in the design and implementation of integrated DBM management systems.

Glucosinolates in Brassica foods: bioavailability in food and significance for human health

Glucosinolates are sulphur compounds that are prevalent in Brassica genus. This includes crops cultivated as vegetables, spices and sources of oil. Since 1970s glucosinolates and their breakdown products, have been widely studied by their beneficial and prejudicial biological effects on human and animal nutrition. They have also been found to be partly responsible for the characteristic flavor of Brassica vegetables. In recent years, considerable attention has been paid to cancer prevention by means of natural products. The cancer-protective properties of Brassica intake are mediated through glucosinolates. Isothyocianate and indole products formed from glucosinolates may regulate cancer cell development by regulating target enzymes, controlling apoptosis and blocking the cell cycle. Nevertheless, variation in content of both glucosinolates and their bioactive hydrolysis products depends on both genetics and the environment, including crop management practices, harvest and storage, processing and meal preparation. Here, we review the significance of glucosinolates as source of bioactive isothiocyanates for human nutrition and health and the influence of environmental conditions and processing mechanisms on the content of glucosinolate concentration in Brassica vegetables. Currently, this area is only partially understood. Further research is needed to understand the mechanisms by which the environment and processing affect glucosinolates content of Brassica vegetables. This will allow us to know the genetic control of these variables, what will result in the development of high quality Brassica products with a health-promoting activity.

Efeito do pré-plantio com plantas medicinais e aromáticas no controle de Plasmodiophora brassicae

A "hérnia das crucíferas" é a principal doença na produção de brássicas na Região Metropolitana de Curitiba-PR. Fatores ambientais favoráveis, ausência de cultivares resistentes e de controle químico eficiente, aliados ao plantio sucessivo de espécies da mesma família, têm colaborado para sua disseminação. Com o objetivo de controlar a doença com menor impacto ambiental, o presente estudo verificou o efeito do pré-plantio de plantas medicinais e aromáticas na redução de inóculo de Plasmodiophora brassicae. Dois experimentos foram conduzidos em casa de vegetação no Setor de Ciências Agrárias da Universidade Federal do Paraná, nos períodos de junho a novembro de 2003 e julho a dezembro de 2004. O delineamento foi inteiramente casualizado com nove tratamentos e seis repetições. As plantas utilizadas nos tratamentos foram: menta (Mentha piperita L.); alfavaca (Ocimum basilicum L.); bardana (Arctium minus Hill); calêndula (Calendula officinalis L.); cebolinha (Allium fistulosum L.); salsa (Petroselinum hortense Hoffm) e sálvia (Salvia officinalis L.), e como testemunhas foram utilizados solos sem patógeno e solo infestado, ambos em pousio. Utilizaram-se vasos contendo 3 Kg de solo esterilizado via vapor e como inóculo de P. brassicae foram utilizados 2,5 g de galhas por vaso. A rúcula (Eruca sativa Mill) foi o hospedeiro suscetível utilizado. Após 45 dias do plantio da rúcula foram determinadas a massa aérea fresca, incidência de galhas galhas e o índice de severidade. A maior massa aérea fresca e as menores severidades foram obtidas no experimento de 2003, nos tratamentos com o pré-plantio das medicinais bardana, salsa, menta, alfavaca e cebolinha.

Expression and relationships of resistance to white rust (Albugo candida) at cotyledonary, seedling, and flowering stages in Brassica juncea germplasm from Australia, China, and India

White rust (Albugo candida) is a highly destructive disease of oilseed Brassicas such as Brassica juncea and B. rapa. Most commercial B. juncea or B. rapa varieties are highly susceptible and yield losses from combined infection of leaves and inflorescences can be up to 20% or 60% in Australia and India, respectively. In Australia, canola-quality B. juncea has been developed to extend oilseed Brassica production into lower rainfall areas, with the first commercial B. juncea canola-quality variety planned for release in 2006. It is essential to identify useful sources of host resistance in B. juncea as breeding and/or selection of material for resistance is the most cost-effective method of delivering control for farmers. Three experiments were undertaken under controlled-environmental conditions to identify the best methods of characterising host resistance and to identify sources of resistance in B. juncea germplasm from Australia, China, and India. Forty-four B. juncea genotypes, viz. 22 from India, 12 from Australia, and 10 from China, were tested. Four Chinese genotypes (CBJ-001, CBJ-002, CBJ-003, CBJ-004) and one Australian genotype (JR049) consistently showed high resistance to A. candida across the different plant growth stages against a pathotype prevailing in Australia. Similarly, the most susceptible genotypes (viz. Indian genotypes RH781, RL1359, RH819) were extremely susceptible irrespective of the plant growth stage. Overall, although disease severity on cotyledons and leaves at the different growth stages was significantly and positively correlated, there was, however, no significant correlation between the number of stagheads and any of the other disease parameters measured. Our study demonstrates that controlled-environmental conditions are suitable for rapid identification of resistant genotypes and that genotypes with high levels of resistance can be reliably identified at the cotyledonary, seedling, or flowering stages.