First Micro-Tomato Crosses

The micro tomato project is off and running!  Last year I made a number of crosses between “micro” tomatoes and full size tomatoes.  I’m growing several F1 plants (plants grown from seed of the cross) over the winter to generate F2 seed for next summer.

The first cross is Chibikko x Green Zebra.  The female is listed first in a cross. Because both parents are stable, open pollinated, varieties all the F1 plants should be identical.  Thus, I need only one plant to produce F2 seeds.

Chibikko is a very compact plant reaching maybe 18 inches tall and produces small red cherry tomatoes about 0.5-1 oz in size.  It’s a decent winter tomato in a 6 inch pot on a sunny windowsill.

Chibikko was picked as the female for a particular reason.  It is a dwarf plant and the genes responsible for the dwarfism are recessive.  This provides a way to ensure that the cross was successful.  If the Chibikko flower had self pollinated all the resulting plants would be completely recessive and dwarf.  If the cross is successful with the Green Zebra pollen, all the resulting plants will have one copy of the recessive dwarf genes (from Chibikko) and one copy of the dominant non-dwarf genes (from GZ) and all plants will be full size.  The F1 plants I am growing are most definitely not dwarf, so I am confident that the cross was successful.

Chibikko fruit. Image used by permission of Tatiana Kouchnareva.

Green Zebra is a famous tomato released in the early 1980’s by tomato breeder Tom Wagner.  It was selected and featured by Alice Waters for her restaurant Chez Panisse.  It is a large plant with vines reaching 8-9 feet that produce tangy, green-when-ripe, green and yellow striped fruits in the 4-6 oz range.  The interior of the fruit stays green.


Green Zebra fruit. Image used by permission of Heritage Tomato Seeds.


The goal for this cross is a striped cherry tomato on a very compact plant. The green stripes are conferred by the gs gene.  Cleverly, “gs” is short for Green Stripe!  gs is another recessive allele so will likely not be readily apparent in the F1 generation this winter for the same reason as the dwarf characteristics not being apparent in this generation.

This will be a fun cross to sort out over the future generations!  I expect to see ranges of plant size, fruit colors, striping and, of course, taste.  The key will be growing many of the F2 generation to select very compact plants since this trait is controlled by several genes.

The second cross I’m currently growing is more complex.  The female is still Chibikko but the male is a fantastic hybrid called Sungold.  The fact that Sungold is a hybrid adds complexity because all the plants grown from seed of the cross (the F1 generation) will be different from each other (unlike the cross of Chibikko and GZ).  The more plants I grow, the more genetic variability I will capture!

Sungold is an incredibly vigorous and productive plant. I’ve had vines reach 12-15 feet or more by the end of the season.  The orange cherry tomatoes are amazingly sweet with tropical flavors.  It is on the “must grow” lists of almost everyone who tries one!  If you grow one cherry tomato, grow this one and give it your best garden spot.  You won’t be disappointed.


Sungold F1 fruit. Image used by permission of Tatiana Kouchnareva.


The goal of this cross is to transfer as much of that sweet Sungold tomatoey goodness into a compact plant.  This will be a difficult task given the assumed complexity of the parentage of Sungold (parents of commercial hybrids are a closely guarded secret).  I might have to employ a lot of back crossing to sungold in future generations to get even more of the Sungold genetics integrated into my lines.

The F1 plants are just starting to flower so no pictures yet of the fruit.  Stay tuned.


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