Seedling and adult plant resistance to downy mildew (Peronospora parasitica) in cauliflower (Brassica oleracea convar. botrytis var. botrytis)

Seedlings of six cauliflower cultivars ( Brassica oleracea convar. botrytis var. botrytis ) were assessed for resistance to a Danish isolate of Peronospora parasitica , under controlled conditions. Resistance, characterized by restricted sporulation and necrotic dark flecks at the inoculation site on the cotyledons, was expressed in the hybrids 9306 F1, 9311 F1, and the open pollinated cultivar Perfection. Testing of the parent lines and F2 generations of the two resistant hybrids suggested that resistance was a dominantly inherited trait controlled by a single gene. Inoculation of the cultivars with seven isolates, from different geographical origins, showed that the resistance was isolate specific. The two hybrid cultivars expressing cotyledon resistance and two hybrids expressing susceptibility were assessed for adult plant resistance under field conditions. The AUDPC (Area Under the Disease Progress Curve), based on disease incidence and severity, revealed significant differences between the cultivars. At harvest, the cultivars exhibited significantly different levels of defoliation and curd attack. The cultivars 9306 F1 and 9311 F1 showed high levels of resistance in all assessments, whereas the two cultivars exhibiting susceptibility at the seedling stage, 9304 F1 and 9305 F1, also exhibited susceptibility through the adult plant stage. Thus, the resistance exhibited under field conditions resembled that identified at the seedling stage under controlled conditions. The results suggest that cotyledon resistance similar to that described could provide resistance throughout the adult plant stage, including curds.     

The Distribution and Spread of Sorghum Downy Mildew in Sorghum and Maize Fields in Nigeria and Zimbabwe

Sorghum downy mildew (Peronosclerospora sorghi, SDM) is a damaging disease of sorghum and maize crops in Africa. Runs analysis was used to study the distribution of systemically infected sorghum and maize plants in Nigeria and Zimbabwe. The temporal and spatial development of local lesions of SDM on sorghum in Zimbabwe was investigated by assessing the local lesion symptoms caused by conidia in plots with a single point source of inoculum. With ordinary runs analysis, there was evidence of clustering of disease in some fields in the humid areas of Nigeria and the semi-arid areas of Nigeria and Zimbabwe. Clustering was found in two of the eight runs analyses performed on maize in the humid south of Nigeria, and in only one of the eight runs in Zimbabwe, which was interpreted as a predominance of random infection at the time of assessment and at the spatial scales assessed. Symptoms of local lesions of SDM developed rapidly across plots from an introduced point source of infection. After 9 days-exposure to the source of inoculum, the incidence of diseased leaves was 1.2%, and after 50 days it was 74.5%. A disease gradient which initially developed flattened as the plot became uniformly diseased. The predominant wind direction was NNE, and most rapid spread of disease was towards the SSW and WSW. In conclusion, local lesions can spread rapidly in sorghum crops, suggesting that they may be an important source of conidial inoculum for further local and systemic infections during the growing season.     

Ribonucleases in the Seedlings of Pearl Millet and their Involvement in Resistance Against Downy Mildew Disease

Tissue homogenates of pearl millet seedlings (cultivars HB 3, 843 B, ICMP 451 and IP 18292), with varying degree of resistance to downy mildew disease were tested for ribonuclease (RNase) enzyme activity and the profile of major RNase isozymes by substrate based gel assay. Polyacrylamide gel electrophoresis (PAGE) of the four pearl millet homogenates revealed 15–20 isozymes, varying in size from 6.5 to 121.0kDa. Most of the RNases were highly active between pH 6 and 8 with maximum activity at pH 7. Tissue specific expression of RNase was observed with more activity in the root, i.e., 38.84, 59.61, 39.90 and 49.23 units in HB 3, 843 B, ICMP 451 and IP 18292, respectively than in shoot 11.54, 9.95, 9.46 and 9.49 units in HB 3, 843 B, ICMP 451 and IP 18292, respectively. Effect of metal ions on the RNase profile indicates Zn⁺⁺ at 2, 20 and 200M concentrations to be inhibitory. Ca⁺⁺ and Mg⁺⁺ at 1mM concentration enhanced the enzyme activity while at 10mM inhibition of enzyme activity was observed. Inoculation with the downy mildew pathogen Sclerospora graminicola reduced RNase activity by 4–13% in compatible interactions while in incompatible combinations, the enzyme activity increased by 10–27%. The significance of RNase in pearl millet-downy mildew interaction and its involvement of in systemic acquired resistance of pearl millet against the downy mildew pathogen are discussed.     

Assessment of Partial Resistance to Powdery Mildew (Podosphaera pannosa) in a Tetraploid Rose Population Using a Spore-suspension Inoculation Method

Powdery mildew (Podosphaera pannosa) is the most important fungal disease in greenhouse roses and is in practice controlled by fungicides. The creation of novel cultivars with durable resistance to powdery mildew is highly desirable. To understand the inheritance of mildew resistance, a tetraploid rose population with a size of 181 seedlings was obtained by crossing two tetraploid genotypes each having partial resistance. The population and its parents were tested under greenhouse conditions with two well-defined monospore isolates (2 and F1) using artificial inoculation with spore suspensions. Disease score at 11 days post-inoculation, latent period and rate of symptom development were used to describe seedling resistance. The tests for both isolates exhibited a wide and significant variation among genotypes for resistance. The distribution of the genotypic means of the disease scores was continuous and showed a considerable transgression. Statistical analysis, scatter plot of disease scores for the isolates, and correlation analyses indicated that the two isolates differed in pathogenicity. The outcome of the tests showed that the inoculation assay with spore suspensions was a reliable and effective way to screen large numbers of genotypes under greenhouse conditions for genetic and breeding studies. This is the first report on spore-suspension inoculation to be used successfully in rose.     

A Greenhouse Test for Screening Sugar Beet (Beta Vulgaris) for Resistance to Rhizoctonia Solani

Rhizoctonia solani Kühn is a serious plant pathogenic fungus, causing various types of damage to sugar beet (Beta vulgaris L.). In Europe, the disease is spreading and becoming a threat for the growing of this crop. Plant resistance seems to be the most practical and economical way to control the disease. Experiments were carried out to optimise a greenhouse procedure to screen plants of sugar beet for resistance to R. solani. In the first experiment, two susceptible accessions were evaluated for root and leaf symptoms, after being grown in seven different soil mixtures and inoculated with R. solani. The fungus infected all plants. It was concluded that leaf symptoms were not reliable for the rating of disease severity. Statistically significant differences between the soil mixtures were observed, and there were no significant differences between the two accessions. The two soil mixtures, showing the most severe disease symptoms, were selected for a second experiment, including both resistant and susceptible accessions. As in the first experiment, root symptoms were recorded using a 1–7 scale, and a significant expression of resistance was observed. The average severity of the disease in the greenhouse experiment generally was comparable with the infection in field experiments, and the ranking of the accessions was the same in the two types of experiments. It was concluded that evaluation procedures in the greenhouse could be used as a rapid assay to screen sugar beet plants for resistance to R. solani.     

Interaction of Root-knot Nematodes (RKN) and the Bacterium Agrobacterium Tumefaciens in Roots of Prunus Cerasifera: Evidence of the Protective Effect of the Ma RKN Resistance Genes Against Expression of Crown Gall Symptoms

Agrobacterium tumefaciens (AT) is the causal agent of crown gall, a major problem in the family Rosaceae and particularly for Prunus spp. Crown gall symptoms result from the bacterial infection of the cells damaged mechanically at the collar or by root parasitic nematodes. Myrobalan plum (P. cerasifera) is susceptible to AT and is not a host for the root-knot nematode (RKN), M. hapla. Some clones of this plum carry single Ma resistance genes that control M. arenaria, M. incognita and M. javanica. The four above mentioned RKN and Myrobalan progenies segregating for Ma were used in experiments aimed at obtaining a better knowledge of the interaction between AT and RKN in relation to the RKN resistance genes. Prunus rooted cuttings, naturally infected with the bacterium were repotted, grown and inoculated individually with RKN. In a first experiment, Prunus plants were (i) either inoculated with 10,000 juveniles (J2s) of M. arenaria to provide a short inoculum pressure (SIP) or (ii) inoculated by association with one M. arenaria-galled tomato root system that produced a high and durable inoculum pressure of the same nematode species. Four months after RKN inoculation, plants were rated for nematode and bacterial root galling symptoms. RKN and AT galls were more numerous and more homogenous under DIP than under SIP. Nevertheless, for both inoculum regimes, AT galls were present in the RKN-susceptible clones (= carrying none of the Ma genes) and absent in the RKN-resistant clones. Subsequent experiments, conducted under DIP with M. arenaria, M. incognita, M. javanica and M. hapla, also showed, for the three first species, the presence of AT galls only in RKN-susceptible clones whereas Prunus plants inoculated with M. hapla and nematode-free controls were free of AT galls. Consequently RKN act as a wound agent in the AT infection process of Myrobalan plum only when the plant develops a compatible reaction (i.e. when it lacks the Ma resistance genes). Considering that J2s do penetrate the roots of resistant plants, the absence of crown gall symptoms on this material even under durable inoculum pressure strengthens the hypothesis that this nematode stage has a very weak effect on plant cells during the infection process. This is the first evidence of the protective effect of a RKN resistance gene against the expression of root crown gall consecutive to RKN infection. The protective effect of Ma and presumably of other RKN resistance genes against AT is a strong argument for their introgression into Prunus and other Rosaceae or bacterium-susceptible crops.     

Improved Resistance Management for Durable Disease Control: A Case Study of Phoma Stem Canker of Oilseed Rape (Brassica napus)

Specific resistance loci in plants are generally very efficient in controlling development of pathogen populations. However, because of the strong selection pressure exerted, these resistances are often not durable. The probability of a resistance breakdown in a pathosystem depends on the evolutionary potential of the pathogen which is affected by: (i) the type of resistance (monogenic and/or polygenic), (ii) the type of reproduction of the pathogen (sexual and/or asexual), (iii) the capacity of the pathogen for dispersal, (iv) the resistance deployment strategy (pyramiding of specific resistances, mixture of cultivars, spatio-temporal alternation), (v) the size of the pathogen population, which is affected by control methods and environmental conditions. We propose the concept of Integrated Avirulence Management (IAM) to enhance the durability of specific resistances. IAM involves a strategy to limit the selection pressure exerted on pathogen populations and, at the same time, reduce the size of pathogen populations by combining cultural, physical, biological or chemical methods of control. Several breakdowns of resistance specific to Leptosphaeria maculans, the causal agent of phoma stem canker have occurred in Europe and in Australia. This review paper examines control methods to limit the size of L. maculans populations and discusses how this limitation of population size can enhance the durability of specific resistances. It proposes pathways for the development of a spatially explicit model to define IAM strategies. Simulation results are presented to demonstrate the potential uses of such a model for the oilseed rape/L. maculans pathosystem.     

Major gene resistance in Brassica napus (oilseed rape) is overcome by changes in virulence of populations of Leptosphaeria maculans in France and Australia

Resistance of Brassica napus (oilseed rape, canola) conferred by three different major resistance genes has been overcome by changes in virulence of Leptosphaeria maculans populations in France and Australia. In South Australia where B. napus cultivars with major gene resistance derived from Brassica rapa ssp. sylvestris were grown extensively, resistance was rendered ineffective within 3 years of commercial release of the cultivar. Disease severity was higher on cultivars with sylvestris-derived resistance than cultivars with polygenic resistance. This Australian situation is compared to that in France, where resistance conferred by the Rlm1 gene was overcome nation-wide in 5 years under commercial cropping practices, and also where a source of resistance introgressed into B. napus from B. juncea was rendered inefficient in 3 years in experimental field plots near Rennes.     

Enhancement of Postharvest Disease Resistance in Ya Li Pear (Pyrus bretschneideri) Fruit by Salicylic Acid Sprays on the Trees during Fruit Growth

The Ya Li pear (Pyrus bretschneideri) trees were sprayed three times with 2.5 mM salicylic acid (SA) around 30, 60 and 90 days after full flowering. The fruit were harvested at commercial maturity (about 120 days after full flowering), inoculated with Penicillium expansum, and incubated at 20 °C, 95–100% RH. The results showed that resistance to the pathogen of the mature pear fruit was remarkably enhanced by the SA sprays. Disease incidence in the SA-treated fruit was 58.0% or 26.5%, and lesion diameter on SA-treated fruit was 58.4% or 29.0% lower than that in/on fruit without SA treatment (control) on day 12 or 17 after incubation, respectively. The SA spray applied to the trees around 30 days after full flowering notably enhanced accumulation of hydrogen peroxide in the young fruit. Meanwhile, activities of defense enzymes, including peroxidase, phenylalanine ammonia-lyase (PAL), chitinase or β-1,3-glucanase in the young fruit from SA-treated trees was 29.5%, 60.0%, 24.4% or 35.7% higher than that in the control fruit 4 days after the SA spraying. Furthermore, after harvest, activities of PAL, chitinase and β-1,3-glucanase were still significantly higher in the mature pear fruit from the trees sprayed three times with SA than those of the control fruit. Activities of the antioxidant enzymes including catalase and ascorbate peroxidase in the young fruit were significantly reduced by SA spraying. However, the activity of another antioxidant enzyme, glutathione reductase in the young fruit was significantly enhanced by SA spraying. These results suggest that enzymes exerting their functions in different ways may be coordinately regulated by SA in the pear fruit. Our study indicates that treatment of SA sprays on the trees may provide further protection against postharvest disease of Ya Li pear fruit in practice and could be used as an alternative and economical approach to reduce application of chemical fungicides.     

Breaching by a new strain of Leptosphaeria maculans of anatomical barriers in cotyledons of Brassica napus cultivar Surpass 400 with resistance based on a single dominant gene

Infection processes were examined to investigate the breach by a strain of Leptosphaeria maculans of anatomical barriers in cv. Surpass 400, a cultivar containing single dominant gene-based resistance (SDGBR). Two strains, UWA 192 and UWA P11, were used to inoculate cvs. Surpass 400 and Westar. The pre-penetration and penetration behaviour of both strains was similar in both cultivars. However, they differed significantly after penetration. When UWA P11 infected cv. Surpass 400 through stomata, guard cells rapidly died within a few hours and the surrounding mesophyll cells became necrotic, constituting a hypersensitive reaction (HR). Hyphal growth continued, albeit slowly, through the intercellular palisade mesophyll and spongy mesophyll spaces, but hyphae rarely spread beyond the HR region, and did not sporulate. Polyphenolic compounds accumulated in the area bordering the HR. However, when UWA 192 infected through stomata, symptoms were not evident until 10–12 days postinoculation (dpi) and were typically characterized by pale tan to grey circular lesions in which abundant pycnidia were produced by 14 dpi. Subsequently, hyphae extensively spread beyond the lesion border, reaching the veins and progressing down the petiole towards the stem. Where the SDGBR remained effective (i.e. against strain UWA P11) death of cells was restricted to a few palisade cells within the HR, even though hyphae were present in the lower tissue layers of the cotyledon. In contrast, where the SDGBR was not present (cv. Westar) or was overcome (cv. Surpass 400 with UWA 192), extensive death of epidermal and upper and lower palisade cells occurred throughout infected areas of the cotyledon, with subsequent abundant production of pycnidia. Polyphenolic compounds, which are also associated with resistance, did not accumulate in this instance. It was evident that the ability of the host to instigate the HR mechanism displayed by cv. Surpass 400 was lost with UWA 192 resulting in a “normal” susceptible response. This is the first study of the specific processes involved in the breaching of the HR in cv. Surpass 400.     

北京地区粘虫对5种杀虫剂的抗药性

采用浸叶法测定了北京地区6个粘虫Mythimna separata(Walker)田间种群对5种不同类型杀虫剂的抗药性。结果表明:与相对敏感品系相比,6个田间种群对5种杀虫剂均表现出不同程度的抗性水平。其中,对氯虫苯甲酰胺(抗性倍数为1.314~4.213)、甲氨基阿维菌素苯甲酸盐(抗性倍数为1.000~4.385)和毒死蜱(抗性倍数为1.083~5.936)表现为敏感至低水平抗性;对虫螨腈(抗性倍数为1.355~20.80)和氯氟氰菊酯(抗性倍数为1.748~13.98)表现为敏感至中等水平抗性。因此,北京地区的粘虫防治应注重将氯虫苯甲酰胺、甲氨基阿维菌素苯甲酸盐和毒死蜱与虫螨腈或氯氟氰菊酯交替或轮换使用,以延缓抗药性的产生与发展。     

安徽省部分地区冬小麦田日本看麦娘Alopecurus japonicus对精噁唑禾草灵的抗性发生现状及ACCase基因突变研究

日本看麦娘Alopecurus japonicus是中国冬小麦田和油菜田主要恶性禾本科杂草之一。为了明确安徽省部分地区日本看麦娘对精齅唑禾草灵抗性发生情况及可能存在的抗性机制,本研究在安徽省天长市日本看麦娘发生严重区域冬小麦田共采集10个种群,采用温室盆栽法在整株水平上测定了不同种群对精齅唑禾草灵的抗性水平,扩增并比对了抗性和敏感种群之间靶标酶乙酰辅酶A羧化酶 (Acetyl-CoA carboxylase,ACCase) 基因部分序列的差异。结果显示,与敏感种群相比,10个抗性种群对精齅唑禾草灵均产生了高水平抗性,抗性指数在30.50~58.55之间。不同抗性种群均发生了ACCase基因突变,其中8个种群发生了第1 781位异亮氨酸 (Ile) 到亮氨酸 (Leu) 突变,2个种群发生了第2 027位色氨酸 (Trp) 到半胱氨酸 (Cys) 突变。此外,各种群均具有较高的ACCase基因突变频率 (≥80%)。研究表明,抗性日本看麦娘在安徽省部分地区发生较为严重,ACCase基因突变是导致不同日本看麦娘种群对精齅唑禾草灵产生抗性的重要原因之一。相对于第2 027位,日本看麦娘ACCase基因更倾向于在第1 781位产生突变以表现靶标抗性。     

Study of Resistance to Orobanche ramosa in Host (Oilseed Rape and Carrot) and Non-host (Maize) Plants

Orobanche ramosa is a parasitic Angiosperm responsible for severe yield losses in several economical crops. It is a serious threat in oilseed rape in France and Morocco and is appearing in carrot crops in Morocco. In this study, several varieties of oilseed rape and carrot were screened in order to identify resistant cultivars and to characterize the resistance mechanisms involved. All the 15 oilseed rape varieties tested were susceptible. In carrot, the varieties 'Colmar à coeur rouge' and 'Nantaise demi-longue' were susceptible, whereas 'Palaiseau' and 'Buror' were resistant. In the susceptible 'Colmar à coeur rouge' carrot no defence reactions were found and the development of the parasite inhibited carrot tap root formation. In the resistant carrot varieties, the parasite germinated, became attached to the host root but became necrotic before emergence. In 'Buror' carrot, formation of a mechanical barrier was associated with the restriction to the cortex of the parasite. In maize cv. 'Vigni', a non-host of O. ramosa, thickening of xylem vessels, cell divisions in the central cylinder and formation of an encapsulation layer were observed in association with restricted development of Orobanche haustoria.     

Characterisation of a Quantitative Resistance to Vector Transmission of Tomato yellow leaf curl virus in Lycopersicon pimpinellifolium

Two wild genotypes from the same species Lycopersicon pimpinellifolium, WVA106 (susceptible) and INRA-Hirsute (so-called ‘resistant’), were compared with respect to their reaction to Tomato yellow leaf curl virus isolate Réunion (TYLCV-Mld[RE]), using both whitefly-mediated inoculation and graft inoculation. Disease incidence and symptom severity were scored. Presence and quantification of viral DNA were assessed by dot blot hybridisation. Upon insect inoculation, accession INRA-Hirsute showed a moderate resistance against TYLCV that was overcome by a high inoculation pressure obtained by increasing the cumulative number of inoculative whiteflies. Temporal analyses of the disease progress in relation to this criterion exhibited that the protection was quantitative, mainly reducing the TYLCV-Mld[RE] incidence by at maximum 50% at low inoculation pressure. When graft inoculated, the final TYLCV-Mld[RE] disease incidence was 100% in both susceptible and resistant genotypes with severe symptoms, suggesting a reduction of virus transmission by a vector resistance as a possible mechanism. Implications of using such type of resistance in breeding programmes are discussed.     

Methods for Sampling and Assessment in Relation to the Spatial Pattern of Phoma Stem Canker (Leptosphaeria maculans) in Oilseed Rape

A sound assessment of phoma stem canker symptoms is needed to develop epidemiological, agronomical and physiological studies on the pathosystem. A specific analysis was therefore carried out to: (i) compare four methods of crown canker assessment; (ii) test the among and within assessor repeatability of one of the methods compared; (iii) characterise the spatial pattern of the disease; and (iv) define the sample size required to achieve a given level of disease assessment precision. The methods compared examined the symptoms with different procedures and graded the plants observed into six severity classes. A disease index (DI) summarised the severity distribution observed. Examination of crown cross-sections was the most precise method for assessing crown cankers. The method was repeatable, though an 'assessor effect' was apparent. The disease generally had a random pattern although significant spatial correlations were detected for four out of the fifteen plots studied at the scales examined. A relationship between the coefficient of variation of the DI and the sample size was established, evaluated with experimental field data and exemplified for typical severity distributions.     

2017—2019年江西省二化螟种群对四种杀虫剂的抗性

为明确近年来江西省二化螟种群对常用杀虫剂的抗性水平,提出合理化用药建议,本研究采用人工饲料浸药法测定2017—2019年江西省13个县(市)二化螟田间种群对氯虫苯甲酰胺、阿维菌素、三唑磷和杀虫单的抗性。结果表明,13个二化螟种群对氯虫苯甲酰胺的抗性水平整体为中等至高水平抗性,其中有11个二化螟种群对氯虫苯甲酰胺的抗性水平整体为上升趋势,在对氯虫苯甲酰胺抗性水平增加的种群中,都昌种群的抗性倍数从2017年的44.1倍上升至2018年的65.1倍,在2019年激增至高水平抗性,抗性倍数为283.5倍,为供试种群的最高抗性倍数。13个二化螟种群对阿维菌素的抗性水平整体为中等偏下,在对阿维菌素抗性水平增加的种群中,南昌种群的抗性倍数最高,2017—2019年分别为74.8倍、108.7倍和80.6倍。13个二化螟种群对三唑磷的抗性水平整体为中等偏下,其中新干、永修、万安、大余、上高和都昌这6个种群对三唑磷的抗性水平呈波动上升的趋势,而其他7个种群对三唑磷的抗性水平为波动性变化,偶有下降。13个二化螟种群对杀虫单的抗性水平整体为中等偏下并且有明显下降趋势,其中大余、永修、泰和、会昌、新干和上高这...     

广东省149个油茶品种（系）对炭疽病的抗性及其病原菌鉴定

为明确广东省油茶品种（系）对炭疽病的抗性及引起油茶炭疽病的病原菌种类,对广东省肇庆市、广州市和韶关市的149个油茶品种（系）进行田间抗性调查,从发病组织中分离纯化致病菌,观察菌株形态学特征,并结合3-磷酸甘油醛脱氢酶（glyceraldehyde-3-phosphate dehydrogenase,GAPDH）基因扩增序列进行分子生物学鉴定。结果显示,有93.29%的油茶品种（系）发生炭疽病,3个调查地油茶炭疽病的平均发病率为18.86%~24.25%,较抗病的油茶品种（系）占调查总数的53.02%,感病油茶品种（系）占调查总数的46.98%。其中,海南3号、长林400号和湘林89号等10个品种（系）表现为近免疫,揭阳5号、桂14号和湘林350号等16个品种（系）表现为高抗,赣5190号、湘林27号和岑软11号等53个品种（系）表现为中抗,赣兴46号、赣州S4号和赣州R10号等36个品种（系）表现为中感,岑软11-3000号、长林53号和湘林67号等34个品种（系）表现为高感,其中岑软11-19号发病率高达65.00%。共分离获得油茶炭疽病致病菌25株,结合形态学特征和基于GAPDH序列的系统发育树分析,将其中24株鉴定为果生炭疽菌Colletotrichum fructicola,1株鉴定为为暹罗炭疽菌C. siamense。筛选的油茶抗病品种（系）可作为广东省油茶良种选育材料,且该省油茶炭疽病主要由果生炭疽菌引起。     

Dissemination of Information About Management Strategies and Changes in Farming Practices for the Exploitation of Resistance to Leptosphaeria maculans (Phoma Stem Canker) in Oilseed Rape Cultivars

The management of phoma stem canker (blackleg disease, caused by Leptosphaeria maculans) is an integral component of oilseed rape production. In this paper, we discuss the information about management strategies that is disseminated in Europe and Australia. New cultivars have been introduced with improved resistance to disease, but sometimes this resistance has been overcome as new races of the pathogen have emerged. When cultivars with single major gene resistance have been introduced into areas with high inoculum concentrations, significant economic damage has been caused by new races of L. maculans within 2–3 years. Quantitative or polygenic resistance has also been used successfully against stem canker and offers more durable disease resistance if plant breeders and farmers deploy this resistance more effectively. Strategies to improve the durability of resistance need to be developed and tested in practice. New information on the occurrence of virulence and avirulence genes in populations of Leptosphaeria maculans and modelling of the durability of resistance provide opportunities for plant breeders, specialist technical organisations, cooperatives, advisory services and farmers to collaborate and better exploit cultivar resistance. Changing economic and environmental factors influence cropping practices and, if to be considered successful, management strategies must show clear financial benefits. Technology transfer will need to address all aspects of managing stem canker and other diseases of oilseed rape and using effective written, verbal and electronic methods of communication.