Inheritance of disease resistant genes

[J Peazy]

If one crosses a disease resistant hybrid with an heirloom lacking those genes, how are the genes inherited? Do the progeny show muted resistance, or is it Mendelian like fruit color?

Thanks in advance.

[Fusion_power]

J, that depends on the gene(s) in question. Most of the disease tolerance genes are either recessive or penetrant. A few are described as incompletely dominant which is just a different way of saying they are penetrant. With a recessive, you don't get expression of the desired trait until they are homozygous. With penetrant genes, varying levels of expression occur, depending on the gene, but the gene is always expressed. The highest expression occurs when the gene is homozygous.

There are about 50 known disease tolerance genes that are commonly discussed in tomato breeding. Several of the genes have multiple variants so you will find a lot more than 50 genes in the list. This list covers about half of the genes that you can find mentioned in various literature.

http://tgrc.ucdavis.edu/Data/Acc/Genes.aspx

DarJones