Question about Estimating Heritability and BLUPs for Traits Using Tomato Phenotypic Data tutorial

Asked February 12, 2019, 3:39 AM EST

First of all, I would like to thank the author, Heather L. Merk for this great tutorial. She might not know it, but she is helping a lot of passionate farmers/amateurstudents like me to understand how Linear Mix Models works and how to apply the theoterical knowledge into the practical real one.

Afte that, I would like to ask two things:

  1. Why do you select Lines as Random effects?
  2. Do you have more tutorials like this one for calculating variance components or how to estimate GCA/SCA in real variety trials? If so, could you share them?
As a farmer myself, I really find interesting to understand how researchers develop new varieties and I would love to have some more real case tutorials, not just theoretical.

Thanks again! Hope Heather finds out about this message :)


Outside United States

1 Response


Thank you for your kind words. I'll let Heather know about your message and your thanks!

In the tutorial, lines are considered Random Effects because we are interested in estimating the variance associated with genetics (lines). We could also estimate this using a fixed effect framework by setting the expected mean squares equal to the estimated mean squares and solving. To do this you need to be able to write out the expected MS for an experiment. I can send you a paper describing how to do the first step. The estimated MS then come from the ANOVA. It would be better to private message me using francis.77 "at" where "at" = @ if you want the paper.

Regarding tutorials for GCA and SCA, we do not have any and given eXtension's new direction we do not anticipate creating any. I will ask if the National Association of Plant Breeder's Education Committee may be planning to develop such resources.

Yours, David F.