Plant Breeding Methods (CS, HS 541)

Exercise 4 – Heterosis, Populations, Inbreds

Give complete answers, but be brief and specific. Show your work.

20 points total

1. Explain Lonnquist’s selection study to improve yield of 2 maize inbreds using (a new technique at that time) convergent improvement. How does that study affect our 2 theories (over-dominance and dominance) for explaining inbreeding depression and heterosis?


2a. Diagram Gardner’s procedure of modified mass selection using blocks of 50 plants in a population of 1000.

2b. What is k (selection intensity) if you keep the best 10%?

2c. What is k for normal mass selection?


3a. In Lonnquist’s modified ear-to-row selection system, is selection on the male parent, female parent, or both?

3b. What is a composite pollenizer (CP), and why use one?