Task 3

Creation of mapping populations (read Supplementary information 7.1.1 and 7.2.1.)

For mapping we need a population, composed of plants from the same genetic background, that segregates for bitter and sweet plants. Such a population can be used to determine the genes underlying the trait. To develop such a mapping population crossing “bitter” and a “sweet” quinoa line is required to obtain a F1 hybrid.

To obtain true hybrids, with alleles of both parents combined, we have to prevent self-pollination. In several crops emasculation (removal of the pollen/stamen of the female parent) is performed to prevent self-pollination. However, due to the abundance of small flowers, manual emasculation has proven very difficult in Quinoa.

Two crosses were made between a bitter and a sweet Quinoa line. The seeds that develop on the female parent are the F1 seeds: Atlas (sweet) x Carina Red (bitter) and 0654 (bitter) x Kurmi (sweet)

Read section 7.2.1. plant material.

• Q: Describe how the cross Atlas (sweet) x Carina Red (bitter) was made and how first generation true F1s were identified

• Q: How were the true F1 hybrids selected in this case?

• Q: How many of the offspring proved to be from a real cross?

Phenotyping is done on seed tissue. Saponins taste bitter and can cause foaming in aqueous solution (see figure of foaming test).

Open

The F1 population is 100% heterozygous. A few of the true F1 plants were then selected to produce F2 seeds (by self-pollination) and one of these F2 families was selected as the mapping population (742 F2-plants).

• Q: What is the segregation rate of  “sweet” compared to “bitter” in the this F2 population and how was this determined?

• Q: Is the sweet trait determined by a recessive or dominant gene? Explain.

• Q: Are sweet plants homozygous or heterozygous for the sweet trait?