RESUMO
LepR3, found in the Brassica napus cv 'Surpass 400', provides race-specific resistance to the fungal pathogen Leptosphaeria maculans, which was overcome after great devastation in Australia in 2004. We investigated the LepR3 locus to identify the genetic basis of this resistance interaction. We employed a map-based cloning strategy, exploiting collinearity with the Arabidopsis thaliana and Brassica rapa genomes to enrich the map and locate a candidate gene. We also investigated the interaction of LepR3 with the L. maculans avirulence gene AvrLm1 using transgenics. LepR3 was found to encode a receptor-like protein (RLP). We also demonstrated that avirulence towards LepR3 is conferred by AvrLm1, which is responsible for both the Rlm1 and LepR3-dependent resistance responses in B. napus. LepR3 is the first functional B. napus disease resistance gene to be cloned. AvrLm1's interaction with two independent resistance loci, Rlm1 and LepR3, highlights the need to consider redundant phenotypes in 'gene-for-gene' interactions and offers an explanation as to why LepR3 was overcome so rapidly in parts of Australia.
Assuntos
Ascomicetos/fisiologia , Brassica napus/genética , Brassica napus/microbiologia , Resistência à Doença/genética , Proteínas Fúngicas/metabolismo , Proteínas de Membrana/genética , Doenças das Plantas/microbiologia , Ascomicetos/patogenicidade , Brassica napus/imunologia , Mapeamento Cromossômico , Cromossomos de Plantas/genética , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Estudos de Associação Genética , Loci Gênicos/genética , Marcadores Genéticos , Proteínas de Membrana/metabolismo , Fenótipo , Doenças das Plantas/genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Sintenia/genética , Transformação Genética , VirulênciaRESUMO
Isolated microspore culture techniques are being widely used in Brassica breeding programs to generate haploid and doubled haploid plants. A number of factors influence regeneration response in vitro including genotype. In order to assess the effect of genotype on microspore embryogenesis in B. rapa L. var. oleifera, 17 cultivars and breeding lines were evaluated. Embryos developed from all but one genotype when using NLN medium with 17% sucrose, followed by a reduction in sucrose concentration to 10%, 48 h later. The number of embryos /100 buds differed between genotypes, ranging from 0 to 70. Further studies indicated that sucrose concentration and incubation time influenced embryogenesis. Selection studies carried out with an Agriculture and Agri-Food Canada breeding line have resulted in the identification of a highly embryogenic B. rapa line. This line produced thousands of microspore-derived embryos /100 buds and will be useful in mutant selection and gene transfer as well as biochemical and developmental studies.
RESUMO
A protocol previously developed for B. napus microspore culture was modified to produce embryos from several lines of Brassica campestris. Bud size, genotype, media constituents, and incubation time and temperature were examined. Donor plants were grown in a growth cabinet at a day/night temperature of 10/5°C. Microspores were isolated from buds 2.0 - 2.9 mm in length and cultured in modified Lichter (1982) medium containing 17% sucrose, pH 6.2. After 48 h at 32°C, the incubation medium was replaced with NLN (Lichter 1982) medium containing 10% sucrose. Microspores were cultured at 24°C in darkness and embryos developed after three weeks. More than 1000 plants have thus far been regenerated. Genotypic differences were observed for microspore embryogenesis. The majority of the regenerants were haploid, however colchicine could be effectively used to achieve chromosome doubling.
RESUMO
The economic impact of locating small group homes in various single-family residential neighborhoods was assessed. Sales within 229 m of 19 homes, which occurred 24 months prior and subsequent to licensing, were examined using a computer assisted mass appraisal model and an adaptive estimation procedure. The findings confirm earlier studies that refute the notion that such homes adversely impact real estate values of adjacent properties. An extensive review of relevant literature and litigation was provided.
