Question

An agricultural breeder seeks to build a bigger green bean. Truncation selection is applied to a population and the intensity of selection on bean size is measured as (i = 0.15). In the next generation the response to selection is measured as 0.08. What is the realized heritability of the trait “bean size” in the population?

A) 0.15 B) 0.08 C) 0.082 D) 0.012 E) none of the above

PLEASE show your work/how you got the answer!

Thank you!

Answer 1

answer: {Some theory detailed below to give an overview of few technical terms}

In truncation selection, only a fixed proportion of the population is chosen to reproduce and find the next generation, Individuals are selected as parents only if their index values are higher than a certain cutoff value; ie the truncation point.

Selection Differential {S} is equal to the difference in mean trait values between the selected individuals and the entire population.

Selection Differential {S} = ISELECTED - IPOPULATION

Where I selected is the mean index of the selected parents and I population the mean index of the population.

The selection differential can be standardized by dividing it with standard deviation of the index ( S1 ). The standardized selection differential is called selection intensity, and is expressed as i.

   Given, i =  Selection Differential {S} / σ = 0.15

R, response to selection = 0.08 for next generation

as per Breeders’ Equation,

Realized heritability, h2 =  response to selection / Selection Differential {S}

   i.e h2 = R / S

   = 0.08 / {0.15 x σ}

   = 0.53333 / σ

Since the standard deviation value isnt directly given, nor it can be assumed from the details, the question can be termed as incomplete. Hence answer is option E : none of these