Tomatoville® Gardening Forums - View Single Post - Roma type and beefsteak type on same plant.

Stan Marzano · April 8, 2015

I sent pics to my local agriculture extension (Penn State) and they replied with this:
Hi,

I talked to a few folks and contacted our tomato breeder. He looked at the pictures and provided me with the following:

"Most likely the noted gardener has crossed two hybrid varieties and the progeny are heterozygous for many major genes and modifiers affecting fruit shape and size. Now depending on the physiological stage of the fruiting branch, weather conditions at the time of fruit pollination and fruit set (e.g. pollination intensity), etc. you may have variation in gene expression leading to development of different fruit shape/size. You normally do not see such phenomenon in pure lines or hybrid varieties developed from crosses between inbred lines (though once in a while you may also see a few fruit that are atypical in size or shape; I have seen that as well quite a few times). However, the frequency of abnormal (unexpected) fruit shape/size increases with the level of heterozygosity in tomato plants. AND not all heterozygous plants show the same level of variation. Note that you normally see more variation in fruit size/shape in heirloom OP varieties than commercial hybrid cultivars/inbred lines. I do not expect the variation this gardener sees is heritable. I expect that if from the same plant he collects seed separately from Roma type and round tomatoes, he will see the same pattern of fruit shape/size in the next generation (i.e., when comparing the two groups). In other words, I do not expect that the progeny of Roma type fruit to be Roma type only and the progeny of round fruit to be round. The progeny would be more or less the same."

This is very interesting. Thank you for sharing it.

Take care,

Elsa

However I did not cross 2 hybrids, I crossed 1 hybrid (BTD) and one heirloom (opalka) Please correct me if I'm wrong.

April 8, 2015	#14
Stan Marzano Tomatovillian™ Join Date: Jul 2014 Location: Nj Posts: 34	I sent pics to my local agriculture extension (Penn State) and they replied with this: Hi, I talked to a few folks and contacted our tomato breeder. He looked at the pictures and provided me with the following: "Most likely the noted gardener has crossed two hybrid varieties and the progeny are heterozygous for many major genes and modifiers affecting fruit shape and size. Now depending on the physiological stage of the fruiting branch, weather conditions at the time of fruit pollination and fruit set (e.g. pollination intensity), etc. you may have variation in gene expression leading to development of different fruit shape/size. You normally do not see such phenomenon in pure lines or hybrid varieties developed from crosses between inbred lines (though once in a while you may also see a few fruit that are atypical in size or shape; I have seen that as well quite a few times). However, the frequency of abnormal (unexpected) fruit shape/size increases with the level of heterozygosity in tomato plants. AND not all heterozygous plants show the same level of variation. Note that you normally see more variation in fruit size/shape in heirloom OP varieties than commercial hybrid cultivars/inbred lines. I do not expect the variation this gardener sees is heritable. I expect that if from the same plant he collects seed separately from Roma type and round tomatoes, he will see the same pattern of fruit shape/size in the next generation (i.e., when comparing the two groups). In other words, I do not expect that the progeny of Roma type fruit to be Roma type only and the progeny of round fruit to be round. The progeny would be more or less the same." This is very interesting. Thank you for sharing it. Take care, Elsa However I did not cross 2 hybrids, I crossed 1 hybrid (BTD) and one heirloom (opalka) Please correct me if I'm wrong.