Downy Mildew-Resistant Interspecific Hybrid Cucumber Breeding
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Solution Overview
Problem
Conventional Cucumis sativus breeding methods for downy mildew resistance are inefficient, time-consuming, and susceptible to environmental factors, with low target trait transfer efficiency and unstable resistance in cultivated varieties.
Innovation Solution
A breeding method involving hybridization of Cucumis sativus with Cucumis hystrix using InDel molecular markers linked to the downy mildew-resistant major effect QTLdm5.2, followed by backcrossing and molecular marker-assisted selection to create a new downy mildew-resistant interspecific hybrid variety with stable resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional natural inoculation method is used for phenotype identification, then downy mildew-resistant varieties can be selected, but the breeding process takes a long time and requires large quantity of manpower and material resources
Solution Approach 1:
The patent replaces the conventional mechanical phenotypic observation method with molecular marker-assisted selection. Specifically, InDel markers linked to downy mildew resistance genes are used to detect genotypes directly, substituting the time-consuming natural inoculation and visual assessment process with rapid DNA-based detection, thereby dramatically reducing breeding period while maintaining selection accuracy
Solution Approach 2:
The patent introduces molecular markers as an intermediary between the resistance gene and phenotype expression. The InDel markers serve as genetic markers that indirectly indicate the presence of downy mildew resistance genes, allowing selection to be performed at the molecular level rather than waiting for phenotypic expression, thus accelerating the breeding process
2Measurement precision
If conventional natural inoculation method is used, then downy mildew-resistant varieties can be identified, but the efficiency of phenotype selection is low and the bred varieties have unstable resistance
Solution Approach 1:
The patent replaces phenotypic resistance assessment with genotypic detection using molecular markers. By directly detecting the presence of resistance genes through InDel markers rather than observing disease resistance phenotypes, the method ensures more accurate and stable resistance identification that is not affected by environmental variations or gene expression variability
Solution Approach 2:
The patent performs molecular marker detection at early generations during the breeding process, allowing selection of plants carrying resistance genes before phenotypic expression occurs. This preliminary genetic screening ensures that only plants with the desired resistance genes advance to subsequent breeding stages, guaranteeing stable resistance in final varieties
3Productivity
If molecular marker technology is used for selection, then selection speed and accuracy are greatly increased, but the requirement for DNA quality and detection complexity increases
Solution Approach 1:
The patent employs InDel markers that can be detected using simple, inexpensive PCR-based methods rather than requiring complex sequencing or specialized equipment. The markers are designed to be easily detectable with standard molecular biology techniques, making the system accessible and cost-effective while maintaining high selection speed and accuracy
Solution Approach 2:
The patent optimizes the molecular marker characteristics to match the detection capabilities of standard laboratories. The InDel markers are designed with appropriate amplification efficiencies and detection characteristics that work well with routine PCR and gel electrophoresis or simple capillary electrophoresis, balancing detection complexity with selection productivity
Data Source
AI summary
The present invention discloses a breeding method and application of a new downy mildew-resistant interspecific hybrid Cucumis sativus variety. The breeding method comprises the following steps: performing hybridization to obtain F1 with the high-generation inbred line CCMC of ‘Changchun dense thorn Cucumis sativus’ as a female parent and a Cucumis sativus-Cucumis hystrix introgression line material IL52 as a male parent, selfing the hybrid F1 to obtain F2, and continuously constructing an F6 recombinant inbred line by the single seed transfer method; and by identifying of phenotypes of the recombinant inbred line populations during the natural inoculation of downy mildew at the adult plant stage in the field for 4 years, recombinant individuals with high resistance and good fruit marketability will be screened; and utilizing backcrossing and molecular marker-assisted selection to obtain the individuals as the new downy mildew-resistant interspecific hybrid Cucumis sativus variety in which the genotype in the dm5.2 region coincides with the banding pattern of IL52 and the other chromosome regions are the banding pattern of ‘Changchun dense thorn Cucumis sativus’. The new variety has a high downy mildew-resistant trait, high yield and excellent fruit quality.