30 research outputs found
Development and evaluation of robust molecular markers linked to disease resistance in tomato for distinctness, uniformity and stability testing
Molecular markers linked to phenotypically important traits are of great interest especially when traits are difficult and/or costly to be observed. In tomato where a strong focus on resistance breeding has led to the introgression of several resistance genes, resistance traits have become important characteristics in distinctness, uniformity and stability (DUS) testing for Plant Breeders Rights (PBR) applications. Evaluation of disease traits in biological assays is not always straightforward because assays are often influenced by environmental factors, and difficulties in scoring exist. In this study, we describe the development and/or evaluation of molecular marker assays for the Verticillium genes Ve1 and Ve2, the tomato mosaic virusTm1 (linked marker), the tomato mosaic virus Tm2 and Tm22 genes, the Meloidogyne incognita Mi1-2 gene, the Fusarium I (linked marker) and I2 loci, which are obligatory traits in PBR testing. The marker assays were evaluated for their robustness in a ring test and then evaluated in a set of varieties. Although in general, results between biological assays and marker assays gave highly correlated results, marker assays showed an advantage over biological tests in that the results were clearer, i.e., homozygote/heterozygote presence of the resistance gene can be detected and heterogeneity in seed lots can be identified readily. Within the UPOV framework for granting of PBR, the markers have the potential to fulfil the requirements needed for implementation in DUS testing of candidate varieties and could complement or may be an alternative to the pathogenesis tests that are carried out at present
Suppression of Plant Resistance Gene-Based Immunity by a Fungal Effector
The innate immune system of plants consists of two layers. The first layer, called basal resistance, governs recognition of conserved microbial molecules and fends off most attempted invasions. The second layer is based on Resistance (R) genes that mediate recognition of effectors, proteins secreted by pathogens to suppress or evade basal resistance. Here, we show that a plant-pathogenic fungus secretes an effector that can both trigger and suppress R gene-based immunity. This effector, Avr1, is secreted by the xylem-invading fungus Fusarium oxysporum f.sp. lycopersici (Fol) and triggers disease resistance when the host plant, tomato, carries a matching R gene (I or I-1). At the same time, Avr1 suppresses the protective effect of two other R genes, I-2 and I-3. Based on these observations, we tentatively reconstruct the evolutionary arms race that has taken place between tomato R genes and effectors of Fol. This molecular analysis has revealed a hitherto unpredicted strategy for durable disease control based on resistance gene combinations
Identification of an OsPR10a promoter region responsive to salicylic acid
Orysa sativa pathogenesis-related protein 10a (OsPR10a) was induced by pathogens, salicylic acid (SA), jasmonic acid (JA), ethephon, abscisic acid (ABA), and NaCl. We tried to analyze the OsPR10a promoter to investigate the transcriptional regulation of OsPR10a by SA. We demonstrated the inducibility of OsPR10a promoter by SA using transgenic Arabidopsis carrying OsPR10a:GFP as well as by transient expression assays in rice. To further identify the promoter region responsible for its induction by SA, four different deletions of the OsPR10a promoter were made, and their activities were measured by transient assays. The construct containing 687-bp OsPR10a promoter from its start codon exhibited a six-fold increase of induction compared to the control in response to SA. Mutation in the W-box like element 1 (WLE 1) between 687 and 637-bp from TGACA to TGAAA completely abolished induction of the OsPR10a promoter by SA, indicating that the WLE 1 between −687 and −637 of OsPR10a promoter is important in SA-mediated OsPR10a expression. We show for the first time that the W-box like element plays a role in SA mediated PR gene expression
Overproduction of salicylic acid in plants by bacterial transgenes enhances pathogen resistance
After a hypersensitive response to invading pathogens, plants show elevated accumulation of salicylic
acid (SA), induced expression of plant defense genes, and systemic acquired resistance (SAR) to further
infection by a broad range of pathogens. There is compelling evidence that SA plays a crucial role in triggering
SAR. We have transformed tobacco with two bacterial genes coding for enzymes that convert
chorismate into SA by a two-step process. When the two enzymes were targeted to the chloroplasts, the
transgenic (CSA, constitutive SA biosynthesis) plants showed a 500- to 1,000-fold increased accumulation
of SA and SA glucoside compared to control plants. Defense genes, particularly those encoding
acidic pathogenesis-related (PR) proteins, were constitutively expressed in CSA plants. This expression
did not affect the plant phenotype, but the CSA plants showed a resistance to viral and fungal infection resembling SAR in nontransgenic plants.Ministry of Economic Affairs, the Ministry of
Education, Culture and Science, and the Ministry of Agriculture, Nature
Management and Fishery in the framework of a research program of the
Association of Biotechnology Centres in the Netherlands (ABON)Peer reviewe