This past year (2014) we are started the process of making some of our very own varieties of tomatoes and winter squash!

The process begins with crossing two different varieties of a vegetable. Most vegetables have been bred to be homozygous (like AA or  aa instead of Aa… remember Mendel’s Punnett squares from Bio?) so that when you save seed from the plant after self pollination, all the seeds make the same kind of plant with same kind of fruit (same shape, size, color, and taste). However, some varieties are hybrids (Aa) that are the result of crosses from two different varieties, and when you self-pollinate these you get seeds that make plants that are all different from each other. We are choosing not to use hybrids, so all of the seeds that result from the first crosses that we make this year will all be the same (called the F1 generation). When we self pollinate that F1 generation plant we will get seeds that make plants that are all different from each other (F2 generation), which is where this gets fun! We will grow 20-30 plants from this F2 generation that will all be different from each other, then we will compare the plants and fruits and select our favorites based on what traits we want our new variety to have. We’ll be looking for traits like strong growth, resistance to diseases common in our region, amount of fruit produced, and especially taste! That’s right, we’ll be TASTE TESTING the fruit from all the F2 plants to decide which one has the flavor we like the most (For all of you squash or tomato enthusiasts, I will be looking for volunteer taste testers!). We will repeat the exact same process the next year (F3 generation), choosing one plant among 20-30 to self-polinate and save seed from, and we will continue doing this until there is little to no variation among the 20-30 plants we grow (meaning they have become homozygous and seeds saved from “selfing” the plant will all be the same). In the end, we will have something completely different from what we started with, our own variety selected to grow well here in Seattle and selected for the tastes we like! This process will take many generations before we get there, and we may not have our own consistent variety for a handful of years.

To make the cross between two different varieties, we bring the pollen of one variety to the stigma of another variety. We have to be very careful to make sure that it is only the pollen of the variety that we want to cross that makes it to the female part of the variety we are crossing it with, otherwise we won’t know for sure which the male parent was. This is done differently depending what we are crossing.

In crossing winter squash, we tape up both the male and female flowers in the afternoon before they open up (we know the timing because flowers will turn yellow before they open up the next day). The following morning, we cut the male flower from one variety, go to the female of another variety, cut the tape on both, open up the flowers, and dab the anther (which contains the pollen) of the male flower on the pistils (which has the stigma) of the female flower. Then we tape up the female flower right away so no bees can bring more pollen from a different variety.

Tomatoes are a little trickier; they have both male and female parts on same flower (called perfect flowers), and are buzz pollinated, meaning when a bumble bee comes to a tomato flower, it buzzes at a certain frequency causing the anthers to shed a puff of its pollen which gets on the flower’s own stigma and results in self pollination. So in crossing varieties of tomatoes, we pull off all of the anthers of the first variety using tweezers so that the anthers won’t pollenate the flower’s own pistil. Next we get pollen from a flower of the second variety we want in our cross by mimicking a bumble bee’s buzz with a tuning fork that is of the same frequency. When we tap the tuning fork to the flower, a puff of pollen is released and we use a pipe cleaner to catch the pollen and bring it to the stigma of the first variety. We dab the pollen on the stigma, and then cover up the flower to avoid letting other pollen in.

We are making a number of different crosses this year and we’ll decide which ones to actually grow the F1 generation from based on a taste testing of the different varieties we are crossing. The varieties of Winter Squash we are working on crossing include Discus Bush Buttercup, Sweet Meat, Potimarron (a red Kuri), Triamble, and Honeynut (a mini-butternut). The varieties of Tomatoes that we are working on crossing include Jaunne Flamme, Black Krim, Ananas Noire, Opalka, Thessalonika, and Hungarian Heart.