Question

3. Two varieties—A (susceptible) and B (resistant)—of a particular squash were used to characterize the genetics of resistance to a necrotizing plant pathogen. Eight thousand plants from each variety were inoculated, and the average number of necrotic lesions produced per leaf was recorded. Variety A averaged 52 lesions per leaf, whereas variety B averaged six lesions per leaf. The F? progeny from a cross between variety A and variety B plants averaged 21 lesions per leaf, with a phenotypic variance of 13.7. Of the F? progeny, 8000 were again tested by inoculation, and a total of four plants were produced that were phenotypically similar to the original parental plants—2 plants for each extreme (i.e., parental) phenotype. Overall, the F? plants averaged 18 lesions per leaf with a phenotypic variance of 56.3. (4 pts.) a) How many gene pairs control resistance to this pathogen? b) Determine the broad-sense heritability of resistance to this particular pathogen among the F? plants, assuming that there is no genetic-environmental interaction variance for this trait.

          3. Two varieties—A (susceptible) and B (resistant)—of a particular squash were used to characterize the
genetics of resistance to a necrotizing plant pathogen. Eight thousand plants from each variety were
inoculated, and the average number of necrotic lesions produced per leaf was recorded. Variety A averaged
52 lesions per leaf, whereas variety B averaged six lesions per leaf. The F? progeny from a cross between
variety A and variety B plants averaged 21 lesions per leaf, with a phenotypic variance of 13.7. Of the F?
progeny, 8000 were again tested by inoculation, and a total of four plants were produced that were
phenotypically similar to the original parental plants—2 plants for each extreme (i.e., parental) phenotype.
Overall, the F? plants averaged 18 lesions per leaf with a phenotypic variance of 56.3. (4 pts.)
a) How many gene pairs control resistance to this pathogen?
b) Determine the broad-sense heritability of resistance to this particular pathogen among the F? plants,
assuming that there is no genetic-environmental interaction variance for this trait.

3. Two varieties—A (susceptible) and B (resistant)—of a particular squash were used to characterize the
genetics of resistance to a necrotizing plant pathogen. Eight thousand plants from each variety were
inoculated, and the average number of necrotic lesions produced per leaf was recorded. Variety A averaged
52 lesions per leaf, whereas variety B averaged six lesions per leaf. The F? progeny from a cross between
variety A and variety B plants averaged 21 lesions per leaf, with a phenotypic variance of 13.7. Of the F?
progeny, 8000 were again tested by inoculation, and a total of four plants were produced that were
phenotypically similar to the original parental plants—2 plants for each extreme (i.e., parental) phenotype.
Overall, the F? plants averaged 18 lesions per leaf with a phenotypic variance of 56.3. (4 pts.)
a) How many gene pairs control resistance to this pathogen?
b) Determine the broad-sense heritability of resistance to this particular pathogen among the F? plants,
assuming that there is no genetic-environmental interaction variance for this trait.

Added by Michael B.

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