Introgressed Allele Conferring Cucumber Mosaic Virus Resistance in Pepper
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Solution Overview
Problem
Current methods for breeding pepper plants with resistance to cucumber mosaic virus (CMV) strains, particularly resistance-breaking CMV (rbCMV) strains, face challenges due to a lack of specific markers and linkage drag, leading to incomplete resistance and undesirable plant quality.
Innovation Solution
Introduction of an introgressed allele on chromosome 8 flanked by Marker1 and Marker4, which confers increased resistance to rbCMV strains, utilizing marker-assisted selection and backcrossing to develop a Capsicum annuum plant with improved resistance, including the resistance haplotype HAS-ZF17-4448, deposited under ATCC Accession Number PTA-124434.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If marker-assisted selection is used to select plants based on genetic markers linked to CMV resistance traits, then selection accuracy is improved, but the availability of accurate markers is frequently unavailable even if a gene associated with the trait has been characterized
Solution Approach 1:
The patent performs preliminary action by developing and validating specific molecular markers (SNP markers) linked to the cmr-1 resistance locus before they are needed for selection. The markers are characterized and tested in advance against known resistance alleles, making them immediately available for marker-assisted selection programs. This preliminary marker development resolves the availability issue by ensuring accurate markers exist before breeding programs begin.
Solution Approach 2:
The patent uses molecular markers as intermediaries to connect the resistance gene to the selection process. These SNP markers serve as detectable proxies for the cmr-1 allele, allowing breeders to indirectly select for resistance without directly observing the trait. The markers act as mediators that bridge the gap between the hidden genetic resistance and the visible selection decision.
2Reliability
If disease resistance alleles are introduced into cultivated pepper lines, then resistance to CMV strains is improved, but linkage drag leads to unacceptable plant quality
Solution Approach 1:
The patent extracts only the desired resistance allele (cmr-1) from its original genetic background through precise marker-assisted backcrossing. By using flanking markers to track the resistance locus, the breeding process removes the allele while leaving behind the superior quality traits of the cultivated parent. This extraction eliminates linkage drag by separating the resistance gene from unwanted linked genes.
Solution Approach 2:
The patent applies local quality by introducing only the specific chromosomal region containing the cmr-1 resistance allele while maintaining the rest of the genome from the cultivated parent. The marker-assisted selection ensures that only the local region of interest (the resistance locus and minimal flanking regions) is transferred, while the majority of the genome retains the high-quality traits of the elite cultivated line.
3Reliability
If backcrossing is used to introgress resistance alleles, then resistance is improved, but the number of generations required increases production time
Solution Approach 1:
The patent implements feedback by using molecular markers to continuously monitor the presence and purity of the resistance allele during each backcross generation. This feedback allows breeders to make informed decisions at each step, selecting only those plants that have successfully recovered the resistance locus while minimizing the number of backcrosses needed. The marker data provides real-time information that accelerates the breeding process.
Solution Approach 2:
The patent replaces the traditional mechanical/phenotypic selection system with a molecular marker-based selection system. Instead of growing multiple generations and visually assessing resistance (a slow mechanical process), the patent uses DNA marker analysis to rapidly identify plants with the resistance allele. This substitution of molecular detection for phenotypic evaluation dramatically reduces the time required for each selection cycle.
Data Source
AI summary
The present disclosure provides Capsicum annuum plants exhibiting increased resistance to resistance-breaking cucumber mosaic virus (rbCMV) strains. Such plants comprise novel introgressed genomic regions associated with disease resistance on chromosome 8. In certain aspects, compositions and methods for producing, breeding, identifying, and selecting plants or germplasm with an increased disease resistance phenotype are provided.