Watermelon Virus Resistance via Citrullus colocynthis Introgression
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Solution Overview
Problem
Current methods fail to introduce reliable monogenic resistance to Watermelon Chlorotic Stunt Virus (WmCSV) and Squash Leaf Curl Virus (SLCV) in Citrullus lanatus plants without compromising flesh quality traits, due to complex genetic mechanisms and undesirable traits associated with resistance sources.
Innovation Solution
Introgression of specific DNA sequences from Citrullus colocynthis into Citrullus lanatus, conferring monogenic and recessive resistance to WmCSV and SLCV, which are unlinked to negative traits like flesh quality, and are identifiable through molecular genetic markers such as SNPs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistance genes are introgressed from wild Citrullus species into cultivated watermelon, then virus resistance is improved, but undesirable traits such as poor flesh quality are also introduced
Solution Approach 1:
The patent extracts only the specific resistance gene (wmCSV-R) from the wild Citrullus colocynthis genome, separating it from the undesirable traits. Through precise molecular breeding techniques, only the resistance conferring DNA sequence is introgressed into the cultivated watermelon genome, leaving the poor flesh quality traits behind. This selective extraction resolves the contradiction by obtaining resistance without the associated negative traits.
Solution Approach 2:
The patent applies local quality by introducing the resistance gene into a specific chromosomal location in the cultivated watermelon, rather than throughout the entire genome. The resistance trait is localized to specific heterozygous loci, allowing the rest of the genome to maintain its desirable flesh quality characteristics. This localized introgression enables resistance without compromising overall fruit quality.
2Reliability
If complex genetic mechanisms are used to achieve resistance, then resistance reliability is improved, but breeding complexity and time required increase
Solution Approach 1:
The patent replaces traditional mechanical breeding methods (crossing, selection, and phenotyping over multiple generations) with molecular-based detection methods. Specific molecular markers are used to directly detect the presence and zygosity of the resistance gene at the DNA level, eliminating the need for complex phenotypic screening and reducing breeding complexity while maintaining resistance reliability.
Solution Approach 2:
The patent changes the detection parameter from phenotypic expression (visual symptom scoring) to genotypic expression (molecular marker detection). By using molecular markers that directly detect the resistance gene sequence and its zygosity state, the breeding process becomes simpler and more predictable, reducing the time and complexity required to develop resistant varieties.
3Strength
If dominant resistance mechanisms are used, then resistance expression is stronger, but resistance is more difficult to breed and stabilize
Solution Approach 1:
The patent implements feedback through molecular marker detection that provides information about the zygosity state of the resistance gene. Breeders can detect whether plants are homozygous or heterozygous for the resistance allele, allowing them to make informed breeding decisions. This feedback mechanism simplifies the breeding process by enabling selective propagation of homozygous resistant plants, making resistance stabilization easier despite the gene's recessive nature.
Data Source
AI summary
The present invention is directed to watermelon plant and seed, namely of C. lanatus, which are resistant to geminiviruses, especially to begomoviruses including WmCSV, comprising in their genome introgressed sequences from C. colocynthis conferring resistance to said viruses, when present homozygously. The introgressed sequences are preferably characterized by defined alleles of SNPs on chromosome 6. The introgressed sequences can be chosen from those present in the genome of a plant of Citrullus lanafus-WMCSVR accession number NCIMB 42197. The invention is also directed to parts of these resistant plants, as well as progeny, to the use of these plants for introgressing the resistance in another genetic background, as well as to different methods for obtaining resistant watermelon plants or seeds.