Bremia lactucae Breeding Lines and Resistance Genes

Questions and Answers

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?

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?

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?

They prevent the expression of defense genes and stop the resistance reaction Signup and view all the answers

What is the genotype of the F1 offspring?

R1R1, Ss Signup and view all the answers

What is the ratio of resistant to susceptible phenotypes in the F2 generation?

1:1 Signup and view all the answers

What is the effect of the dominant gene for suppression of resistance?

It prevents the expression of resistance genes Signup and view all the answers

What is the genotype of one of the two parents?

R1R1, SS Signup and view all the answers

What is a consequence of high soil fertility on plants?

They become more succulent and more susceptible to disease development Signup and view all the answers

How does the age of a plant affect its response to a pathogen or insect pest?

The response varies with age, with some diseases being more intense at the early stage Signup and view all the answers

What is the term for a new variant of a parasite that overcomes the current resistance in the host?

New pathotypes or biotypes Signup and view all the answers

What is non-preference in the context of insect resistance?

A phytophagous species refusing a plant as a source of nutrients due to attractive alternatives Signup and view all the answers

What is antibiosis in the context of insect resistance?

An adverse effect of feeding on a host plant on the development and or reproduction of the insect pest Signup and view all the answers

What is the purpose of field screening in breeding for insect resistance?

To evaluate the performance of a crop under natural field conditions Signup and view all the answers

What is tolerance in the context of insect resistance?

The ability of a host plant to withstand damage from an insect pest Signup and view all the answers

What is the primary source of insect resistance?

All of the above Signup and view all the answers

Which cultivar(s) show a negative yield reduction due to lack of tolerance?

Cultivar D Signup and view all the answers

Which cultivar is the most tolerant to the infection?

Cultivar D Signup and view all the answers

Which cultivar(s) are most susceptible to the infection?

Cultivar A and Cultivar E Signup and view all the answers

Which cultivar(s) show a significant difference between the observed yield reduction and the yield reduction due to lack of resistance?

Cultivar B and Cultivar E Signup and view all the answers

Which cultivar(s) would be most suitable for breeding a new variety with high tolerance to the infection?

Cultivar B and Cultivar D Signup and view all the answers

Which line(s) show a high susceptibility to infection?

Line 1 and Line 6 Signup and view all the answers

Which line(s) show a high resistance to infection?

Line 3 and Line 7 Signup and view all the answers

Which line(s) would be most valuable for breeding a new variety with improved resistance to infection?

Line 3 and Line 7 Signup and view all the answers

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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Description

This quiz covers breeding lines and resistance genes of Bremia lactucae, including factors affecting expression of resistance genes and types of breeding lines. Questions test knowledge of specific breeding lines and their resistances to various isolates.