1,720,967 research outputs found
Identification of Brassica accessions with enhanced resistance to Verticillium longisporum under controlled and field conditions
No full textVerticillium longisporum (VL) is a soil-borne vascular fungal pathogen with host-specificity to cruciferous plants such as oilseed rape, threatening its production particularly in the Northern European countries. In a comprehensive screening conducted under greenhouse conditions, 1348 accessions of Brassica napus as well as the progenitor species B. oleracea and B. rapa (syn. campestris) were tested for their resistance to VL. While most of the tested B. napus accessions showed a susceptible to moderate resistant phenotype and the majority of the B. rapa genotypes were highly susceptible, an elevated level of resistance was found in the B. oleracea pool. Resynthesized oilseed rape lines produced on the basis of these data by interspecific hybridization of B. oleracea and B. rapa also exhibited enhanced resistance to VL. In order to verify the greenhouse data, a subset of B. napus breeding lines was further tested for resistance in the field at different sites in North and Northeast Germany. Overall, there was no statistically significant relationship, neither between greenhouse and field data nor between results of different field sites. However, genotypes highly resistant in the greenhouse generally performed well also in the field. Thus, the combination of resistance tests conducted under controlled as well as field conditions is a powerful and reliable approach in the practical selection of resistant breeding lines
Verticillium longisporum - identifying resistance to a new threat to winter oilseed rape
No full textComparative histological studies on the interaction of Verticillium longisporum and Verticillium dahliae with roots of Brassica napus
No full textInternal Resistance in Winter Oilseed Rape Inhibits Systemic Spread of the Vascular Pathogen Verticillium longisporum
No full textVerticillium longisporum is a vascular fungal pathogen presently threatening oilseed rape production in Europe. Systemic spread and vascular responses were studied in a susceptible ('Falcon') and a resistant genotype (SEM 05-500256) of Brassica napus. Colonization of both genotypes after dip-inoculation of the roots followed by quantitative polymerase chain reaction revealed similarities only in the initial stages of root penetration and colonization of the hypocotyl, while a substantial invasion of the shoot was only recorded in 'Falcon'. It is concluded that the type of resistance represented in SEM 05-500256 does not prevent the plant base from being invaded as it is internally expressed well after root penetration and colonization of the plant base. The morphological and biochemical nature of barriers induced in the hypocotyl tissue upon infection was studied with histochemical methods accompanied by biochemical analyses. Histochemical studies revealed the build-up of vascular occlusions and the reinforcement of tracheary elements through the deposition of cell wall-bound phenolics and lignin. Furthermore, the accumulation of soluble phenolics was observed. Although these responses were found in vascular tissues of both genotypes, they occurred with a significantly higher intensity in the resistant genotype and corresponded with the disease phenotype. In the resistant genotype phenols were differentially expressed in a time-dependent manner with preformed soluble and cell wall-bound phenolics at earlier time points and de novo formation of lignin and lignin-like polymers at later stages of infection. This is the first study identifying a crucial role of phenol metabolism in internal defense of B. napus against V. longisporum and locating the crucial defense responses in the plant hypocotyl
Interactions of Verticillium spp. with Brassica: root invasion, systemic spread and plant response
No full textBroadening the genetic basis of Verticillium longisporum resistance in Brassica napus by interspecific hybridization
No full textVerticillium wilt caused by the vascular fungal pathogen Verticillium longisporum is one of the most important pathogens of oilseed rape (Brassica napus sp. oleifera) in northern Europe. Because production of this major oilseed crop is expanding rapidly and no approved fungicides are available for V longisporum, long-term control of the disease can only be achieved with cultivars carrying effective quantitative resistance. However, very little resistance to V longisporum is available within the gene pool of oilseed rape, meaning that interspecific gene transfer from related species is the only possibility for broadening levels of resistance in current varieties. The amphidiploid species B. napus can be resyn-thesized by crossing the two progenitor species Brassica oleracea and Brassica rapa, hence resistant accessions of these two diploid species can be used as resistance donors. In this study a total of 43 potential B. rapa and B. oleracea resistance donors were tested with regard to their reaction to a mixture of two aggressive V longisporum isolates, and resistances from diverse lines were combined by embryo rescue-assisted interspecific hybridization in resynthesized rapeseed lines. Progenies from crosses of the two B. rapa gene bank accessions 13444 and 56515 to the B. oleracea gene bank accessions BRA 1008, CGN 14044, 8207, BRA 1398, and 7518 showed a broad spectrum of resistance in pathogenicity tests. Of 45 tested resynthesized lines, 41 lines exhibited a significantly higher level of resistance than the moderately V longisporum-tolerant oilseed rape cultivar Express. These lines represent a promising basis for the combination of different resistance resources in new varieties
Differential interactions of Verticillium longisporum and V-dahliae with Brassica napus detected with molecular and histological techniques
No full textThe differential interactions of V. longisporum (VL) and V. dahliae (VD) on the root surface and in the root and shoot vascular system of Brassica napus were studied by confocal laser scanning microscopy (CLSM), using GFP tagging and conventional fluorescence dyes, acid fuchsin and acridin orange. VL and VD transformants expressing sGFP were generated by Agrobacterium-mediated transformation. GFP signals were less homogenous and GFP tagging performed less satisfactory than the conventional fluorescence staining when both were studied with CLSM. Interactions of both pathogens were largely restricted to the root hair zone. At 24 h post-inoculation (hpi), hyphae of VL and VD were found intensely interwoven with the root hairs. Hyphae of VL followed the root hairs towards the root surface. At 36 hpi, VL hyphae started to cover the roots with a hyphal net strictly following the grooves of the junctions of the epidermal cells. VL started to penetrate the root epidermal cells without any conspicuous infection structures. Subsequently, hyphae grew intracellularly and intercellularly through the root cortex towards the central cylinder, without inducing any visible plant responses. Colonisation of the xylem vessels in the shoot with VL was restricted to individual vessels entirely filled with mycelium and conidia, while adjacent vessels remained completely unaffected. This may explain why no wilt symptoms occur in B. napus infected with VL. Elevated amounts of fungal DNA were detectable in the hypocotyls 14 days post-inoculation (dpi) and in the leaves 35 dpi. Root penetration was also observed for VD, however, with no directed root surface growth and mainly an intercellular invasion of the root tissue. In contrast to VL, VD started ample formation of conidia on the roots, and was unable to spread systemically into the shoots. VD did not form microsclerotia in the root tissue as widely observed for VL. This study confirms that VD is non-pathogenic on B. napus and demonstrates that non-host resistance against this fungus materializes in restriction of systemic spread rather than inhibition of penetration
Bioclimatic analysis of potential worldwide production of spring-type camelina [Camelina sativa (L.) Crantz] seeded in the spring
Full text linkCamelina [Camelina sativa (L.) Crantz] is a Brassicaceae oilseed that is gaining interest
worldwide as low-maintenance
crop for diverse biobased applications. One of
the most important factors determining its productivity is climate. We conducted a
bioclimate analysis in order to analyze the relationship between climatic factors and
the productivity of spring-type
camelina seeded in the spring, and to identify regions
of the world with potential for camelina in this scenario. Using the modelling tool
CLIMEX, a bioclimatic model was developed for spring-seeded
spring-type
camelina
to match distribution, reported seed yields and phenology records in North America.
Distribution, yield, and phenology data from outside of North America were used
as independent datasets for model validation and demonstrated that model projections
agreed with published distribution records, reported spring-seeded
camelina
yields, and closely predicted crop phenology in Europe, South America, and Asia.
Sensitivity analysis, used to quantify the response of camelina to changes in precipitation
and temperature, indicated that crop performance was more sensitive to
moisture than temperature index parameters, suggesting that the yield potential
of spring-seeded
camelina may be more strongly impacted by water-limited
conditions
than by high temperatures. Incremental climate scenarios also revealed
that spring-seeded
camelina production will exhibit yield shifts at the continental
scale as temperature and precipitation deviate from current conditions. Yield data
were compared with indices of climatic suitability to provide estimates of potential
worldwide camelina productivity. This information was used to identify new areas
where spring-seeded
camelina could be grown and areas that may permit expanded
production, including eastern Europe, China, eastern Russia, Australia and New
Zealand. Our model is the first to have taken a systematic approach to determine
suitable regions for potential worldwide production of spring-seeded
camelina.Camelina [Camelina sativa (L.) Crantz] is a Brassicaceae oilseed that is gaining in-terest worldwide as low- maintenance crop for diverse biobased applications. One of the most important factors determining its productivity is climate. We conducted a bioclimate analysis in order to analyze the relationship between climatic factors and the productivity of spring- type camelina seeded in the spring, and to identify regions of the world with potential for camelina in this scenario. Using the modelling tool CLIMEX, a bioclimatic model was developed for spring- seeded spring- type camelina to match distribution, reported seed yields and phenology records in North America. Distribution, yield, and phenology data from outside of North America were used as independent datasets for model validation and demonstrated that model projec-tions agreed with published distribution records, reported spring- seeded camelina yields, and closely predicted crop phenology in Europe, South America, and Asia. Sensitivity analysis, used to quantify the response of camelina to changes in pre-cipitation and temperature, indicated that crop performance was more sensitive to moisture than temperature index parameters, suggesting that the yield potential of spring- seeded camelina may be more strongly impacted by water- limited con-ditions than by high temperatures. Incremental climate scenarios also revealed that spring- seeded camelina production will exhibit yield shifts at the continental scale as temperature and precipitation deviate from current conditions. Yield data were compared with indices of climatic suitability to provide estimates of potential worldwide camelina productivity. This information was used to identify new areas where spring- seeded camelina could be grown and areas that may permit expanded production, including eastern Europe, China, eastern Russia, Australia and New Zealand. Our model is the first to have taken a systematic approach to determine suitable regions for potential worldwide production of spring- seeded camelina
Combination of resistance to Verticillium longisporum from zero erucic acid Brassica oleracea and oilseed Brassica rapa genotypes in resynthesized rapeseed (Brassica napus) lines
No full textResynthesized (RS) forms of rapeseed (Brassica napus L.; genome AACC, 2n = 38) generated from interspecific hybridization between suitable genotypes of its diploid progenitors Brassica rapa L. (syn. campestris; genome AA, 2n 20) and Brassica oleracea L. (CC, 2n 18) represent a potentially useful resource to introduce resistance against the fungal pathogen Verticillium longisporum into the gene pool of oilseed rape. Numerous cabbage (B. oleracea) accessions are known with resistance to V. longisporum; however, B. oleracea generally has high levels of erucic acid and glucosinolates in the seed, which reduces the suitability of resulting RS rapeseed lines for oilseed rape breeding. In this study resistance against V. longisporum was identified in the cabbage accession Kashirka 202 (B. oleracea convar. capitata), a zero erucic acid mutant, and RS rapeseed lines were generated by crossing the resistant genotype with two spring turnip rape accessions (B. rapa ssp. olerifera) with zero erucic acid. One of the resulting zero erucic acid RS rapeseed lines was found to have a high level of resistance to V. longisporum compared with both parental accessions and with B. napus controls. A number of other zero erucic acid RS lines showed resistance levels comparable to the parental accessions. In the most resistant RS lines the resistance and zero erucic acid traits were combined with variable seed glucosinolate contents. Erucic acid-free RS rapeseed with moderate seed glucosinolate content represents an ideal basic material for introgression of quantitative V. longisporum resistance derived from B. oleracea and B. rapa into elite oilseed rape breeding lines
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