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Questions and Answers
What is the characteristic of breeding line A?
What is the characteristic of breeding line A?
- Race specific and susceptible for isolate 1
- Race non-specific and resistant for all isolates (correct)
- Race non-specific and susceptible for all isolates
- Race specific and resistant for isolate 2
What is the characteristic of breeding line D?
What is the characteristic of breeding line D?
- Race specific and resistant for isolate 1
- Race non-specific and resistant for all isolates
- Race specific and resistant for isolate 2
- Race specific and comparatively more susceptible (correct)
What factors can influence the expression of resistance genes?
What factors can influence the expression of resistance genes?
- Genotype of the pathogen and developmental stage of the plant
- Environmental factors like temperature and genetic background of cultivars
- Genetic background of cultivars and genotype of the pathogen
- All of the above (correct)
What is the role of suppressors in plant defense?
What is the role of suppressors in plant defense?
What is the genotype of the F1 offspring?
What is the genotype of the F1 offspring?
What is the ratio of resistant to susceptible phenotypes in the F2 generation?
What is the ratio of resistant to susceptible phenotypes in the F2 generation?
What is the effect of the dominant gene for suppression of resistance?
What is the effect of the dominant gene for suppression of resistance?
What is the genotype of one of the two parents?
What is the genotype of one of the two parents?
What is a consequence of high soil fertility on plants?
What is a consequence of high soil fertility on plants?
How does the age of a plant affect its response to a pathogen or insect pest?
How does the age of a plant affect its response to a pathogen or insect pest?
What is the term for a new variant of a parasite that overcomes the current resistance in the host?
What is the term for a new variant of a parasite that overcomes the current resistance in the host?
What is non-preference in the context of insect resistance?
What is non-preference in the context of insect resistance?
What is antibiosis in the context of insect resistance?
What is antibiosis in the context of insect resistance?
What is the purpose of field screening in breeding for insect resistance?
What is the purpose of field screening in breeding for insect resistance?
What is tolerance in the context of insect resistance?
What is tolerance in the context of insect resistance?
What is the primary source of insect resistance?
What is the primary source of insect resistance?
Which cultivar(s) show a negative yield reduction due to lack of tolerance?
Which cultivar(s) show a negative yield reduction due to lack of tolerance?
Which cultivar is the most tolerant to the infection?
Which cultivar is the most tolerant to the infection?
Which cultivar(s) are most susceptible to the infection?
Which cultivar(s) are most susceptible to the infection?
Which cultivar(s) show a significant difference between the observed yield reduction and the yield reduction due to lack of resistance?
Which cultivar(s) show a significant difference between the observed yield reduction and the yield reduction due to lack of resistance?
Which cultivar(s) would be most suitable for breeding a new variety with high tolerance to the infection?
Which cultivar(s) would be most suitable for breeding a new variety with high tolerance to the infection?
Which line(s) show a high susceptibility to infection?
Which line(s) show a high susceptibility to infection?
Which line(s) show a high resistance to infection?
Which line(s) show a high resistance to infection?
Which line(s) would be most valuable for breeding a new variety with improved resistance to infection?
Which line(s) would be most valuable for breeding a new variety with improved resistance to infection?
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Study Notes
Breeding Line and Isolate of Bremia lactucae
- A is a non-specific and resistant breeding line for all isolates
- B, C, D, and E are race-specific breeding lines, with B resistant to isolate 2 and E resistant to isolates 1 and 2
- Among B, C, D, and E, D is relatively more susceptible
Expression of Resistance Gene
- Factors affecting expression of resistance gene:
- Resistance allele (incomplete or complete)
- Genetic background of cultivars
- Genotype of the pathogen (homozygous or heterozygous state)
- Developmental stage of the plant
- Environmental factors like temperature
Suppressors
- Suppressors prevent the expression of defense genes and stop the resistance reaction
- Suppressors can be dominant or recessive
- Example of suppressor genes in two homozygous host plants
Breeding for Resistance to Insects
- Mechanisms of resistance:
- Non-preference: refusing a plant as a source of nutrients
- Non-acceptance: refusing a plant as a source of nutrients due to unattractive features
- Antibiosis: adverse effect of feeding on a host plant on the insect's development and reproduction
- Tolerance: similar to disease tolerance
- Avoidance: same as disease escape, not true insect resistance
- Sources of insect resistance:
- Cultivated cultivar
- Commercial cultivars
- Other varieties
- Landraces
- Related species
- Germplasm collection
- Breeding methods for insect resistance are similar to breeding methods for disease resistance
Breeding for Abiotic Resistance
- Phenotypic performance of a population is determined by genotype, environment, and G x E interaction
- Optimal environment: no interference by environmental factors (stress-free environment)
Interpretation of Data
- Higher figures indicate susceptibility or sensitivity
- Negative values indicate tolerance or resistance
- Cultivar D is the most tolerant, and Cultivar F is the most resistant
- Cultivars B and E are the most sensitive, and Cultivar A is the most susceptible
Breeding Material and Infection
- Infection types: S (susceptible) and R (resistant)
- Line 1 is susceptible, Line 3 is resistant, and Lines 2, 6, 7, and 10 are interesting for breeding programs for resistance
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