A strain (X) of tomato characterized by the ability to grow at low temperatures carries a gene (t) for this character that is recessive. Strain X, however, has no resistance to a serious wilt disease.

A second strain (Y) is characterized by resistance to the wilt disease: this resistance is the result of a recessive gene (r).

A certain area in Wyoming is characterized by low temperatures during the growing season and also by the prevalence of the wilt disease; the common tomato cannot be grown there for both reasons.

You are given: a strain X plant: homozygous for ability to grow at low temperatures and for lack of resistance to wild and a strain Y plant, homozygous for resistance to wilt and for lack of ability to grow at low temperature.

You wish to produce strain Z, which will can be grown successfully in the Wyoming area.

By means of diagrams (or Punnett Square), indicate the necessary crosses and point out the genotype of strain Z. Assume no linkage.