Downy Mildew-Resistant Lettuce Plants With Precise Introgressions
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Solution Overview
Problem
Existing methods for introgressing disease resistance alleles from wild lettuce species like Lactuca virosa into cultivated lettuce lines have been unsuccessful due to lack of specific markers, linkage drag, and the genetic variability of the Bremia lactucae pathogen, resulting in non-durable resistance and undesirable agronomic traits.
Innovation Solution
Development of novel introgressions from Lactuca virosa on chromosome 7, conferring improved resistance to Bremia lactucae, with a size of 250 kb or less, and the use of accurate markers such as NLSAT009419770, ND0229340, and NLSAT005132975 for marker-assisted selection (MAS) to avoid linkage drag and ensure durable resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If disease resistance alleles are introgressed from wild lettuce species into cultivated lines, then resistance to Bremia lactucae is improved, but linkage drag causes unacceptable plant quality and stunted growth
Solution Approach 1:
The patent extracts only the beneficial resistance allele from the wild lettuce genome while leaving behind the harmful linked alleles through precise molecular breeding techniques. Specific markers identify and isolate the resistance gene region, allowing selective introgression of only the desired trait without the accompanying negative traits that cause stunted growth and poor plant quality.
Solution Approach 2:
The patent applies local quality by creating a heterogeneous genome structure where specific localized regions contain wild lettuce resistance alleles while the rest of the genome maintains cultivated lettuce quality. This allows the plant to exhibit resistance in the specific chromosomal region while maintaining overall agronomic excellence through selective backcrossing and marker-assisted selection.
2Measurement precision
If marker-assisted selection is used to select plants based on genetic markers linked to resistance traits, then selection accuracy is improved, but accurate markers are frequently unavailable even when resistance genes are characterized
Solution Approach 1:
The patent performs preliminary action by developing and validating specific molecular markers (such as SSR and SNP markers) linked to resistance genes before breeding operations begin. These pre-established markers enable immediate and accurate selection in breeding programs, eliminating the need to develop markers during the breeding process and ensuring high selection accuracy from the outset.
3Duration of action of stationary object
If large introgressions from Lactuca virosa are used to confer resistance, then resistance durability is improved, but negative agronomic traits and stunted growth are introduced
Solution Approach 1:
The patent segments the wild lettuce genome into small, manageable chromosomal regions containing individual resistance alleles. Through sequential backcrossing and marker-assisted selection, only small segments (0.1-5 cM) containing the resistance gene are retained in the cultivated background. This segmentation allows durability of resistance while minimizing linkage drag and maintaining agronomic quality.
Solution Approach 2:
The patent applies partial action by introgressing only the minimal necessary genetic material (the resistance allele and surrounding markers) rather than large chromosomal segments. This partial introgression provides sufficient resistance durability while avoiding the excessive genetic material that would introduce negative agronomic traits and stunted growth.
Data Source
AI summary
The present disclosure provides lettuce plants exhibiting resistance to downy mildew. Such plants may comprise novel introgressed genomic regions associated with disease resistance from L. virosa. In certain aspects, compositions, including novel polymorphic markers and methods for producing, breeding, identifying, and selecting plants or germplasm with a disease resistance phenotype are provided.