Knowledgebase
Why are paste tomatoes oblong? #924316
Asked February 07, 2026, 11:40 AM EST
Wadena County Minnesota
Expert Response
Thanks for your interesting question.
Your question deals with the elongated shape found in paste tomato fruit. There are many reasons why this shape makes a tomato more susceptible to blossom end rot (BER). I don’t quite understand why you think that over time this enhanced susceptibility might eventually result in a change in the shape of paste tomatoes.
Essentially, most of the taste characteristics of paste tomatoes are intrinsically tied to an elongated fruit shape. If the fruit was not elongated, they would not be suitable as paste tomatoes. Instead of saying “…almost all paste tomatoes are ovoid/oblong/elongated…”, a better question might be to ask, “Why are ovoid/oblong/elongated tomatoes almost always paste tomatoes?”
Your question mentioned the ovate gene. This gene has two forms. One is a dominant form that is important in conferring roundness to the fruit. There is a recessive form that can under certain circumstances yield more shrunken fruit. However, it is one of many tomato genes affecting fruit development and shape. Because it is one of many, it is not by itself a significant player for the question you posed. The ovate gene does not directly influence moisture content of tomato fruit. I am not surprised that your searching for relevant research relating ovate to your question failed to yield suitable information.
To give you a better understanding of what is going on, the following points regarding BER are important:
1). As you probably know, BER is associated with a calcium deficiency in tomatoes. This deficiency is not attributable to low calcium levels in the soil but to low calcium levels within the plant.
2) BER occurs when a plant is unable to take up sufficient calcium via its root system. This is why BER tends to occur more often in the fruit of young tomato plants, where the root system is just developing, than in the fruit of older plants that have an established root system. Perhaps you have noticed this among your plants?
3). When calcium is taken up by tomato roots, it is in a water soluble form. This dissolved calcium is transported throughout the plant via conducting tubes known as xylem. Xylem tubes enter the developing fruit at the stem site where the fruit is attached. Once calcium enters the developing fruit, it slowly diffuses through the fruit. The part of the fruit that receives the smallest amounts of calcium is the farthest from the stem attachment of the fruit. This is why BER typically is most severe at the very end of the fruit.
4). In plants, calcium is a very important constituent of cell walls. When calcium is deficient, strong cell walls are not formed. The cells then collapse and begin to decompose. This is outwardly seen by the discolored, “mushy” tissue at the bottom of tomato fruit experiencing BER.
5). The process of fruit development begins at the stem attachment of the fruit and moves outward. This means that the ends of tomato fruits are the most active regions of cell division. This cell division involves a high level of cell wall formation. This heightens the need for calcium at these ends.
6). Elongated tomato fruit are primarily growing in length rather than in an outward direction that would increase fruit width. This means that in a developing Roma tomato, the ends of the tomato are far more likely to experience a calcium deficiency than in, say, a Beefsteak tomato where cell growth is occurring both in fruit elongation and in fruit expansion. This is why BER is more common in paste tomatoes than in non-paste tomatoes.
The other piece of the puzzle posed in your question involves features of paste tomatoes. The following are relevant:
1). Our domestic tomatoes originated thousands of years ago in regions of South America as a vine having very small, round fruit. Domestication of them led to their being grown in cultivated gardens. Their fruit had a high moisture content and contained large numbers of seeds.
2). To develop tomatoes more suitable for use in the making of sauces, in the mid-1950’s the United States Department of Agriculture embarked upon an extensive breeding program involving the creation of many different types of hybrid tomatoes. The objectives of this program were to produce plants with six primary characteristics: 1). resistance to verticillium wilt (V) and fusarium wilt (F); 2). fruit having a low moisture content so that their contents would be dense and not watery; 3). fruit possessing a thick outer wall that would prolong their storage times; 4). fruit whose shapes (usually elongated) facilitated easy packaging and shipping; 5). fruit having low numbers of small seeds; and 6). fruit with few locules. Locules are the cavities within the fruit containing the seeds. By reducing their number, very dense fruit are produced. They were termed paste tomatoes
3). Roma tomatoes were one of the paste tomatoes developed. If you have purchased Roma seeds, you will have seen “VF” on the seed packet indicating their wilt resistance. If you have ever harvested seeds from Roma fruit, you have encountered their small sizes and low numbers.
Bottom line: Elongated fruits are an absolute characteristic of paste tomatoes. This shape prolongs their storage times and enables compact packaging. Granted this shape increases their susceptibility to BER, but in the development of paste tomatoes it was felt that this susceptibility was more than offset by the many positive characteristics of elongated paste tomatoes.
See the following for further information on these and other related points:
https://leereich.com/2024/07/and-the-best-paste-tomato-is.html
https://askthefoodgeek.com/best-tomatoes-for-paste/
https://aihd.ku.edu/foods/tomatoes.html - :~:text=Origins,associate with the word tomato.
https://www.canr.msu.edu/resources/blossom_end_rot_tip_sheet
https://www.smartgardener.com/plants/3770-tomato-roma-tomatoes/diseases/784-verticillium-wilt
https://spice.alibaba.com/spice-basics/oblong-tomato?utm_source=chatgpt.com
Good luck. I apologize for the length of my answer. Over the years in having answered thousands of questions, your answer is the most detailed one that I’ve ever written. I did this due to your interest in tomato breeding and my perception that you had sufficient background knowledge to understand a more in-depth response. Please get back to me with any additional questions you might have. Thanks for consulting our forum.
With respect to your question and my recent response, I would like to clarify a possible point of confusion. In my response of 2/11/26, I made the following statement:
"Xylem tubes enter the developing fruit at the stem site where the fruit is attached. Once calcium enters the developing fruit, it slowly diffuses through the fruit. The part of the fruit that receives the smallest amounts of calcium is the farthest from the stem attachment of the fruit. This is why BER typically is most severe at the very end of the fruit."
I want to stress that I was NOT implying that the developing fruit lacked xylem tubes. Such tubes are found within the entire fruit and can provide, among other dissolved nutrients, calcium to the entire fruit. As these xylem tubes reach the end of the developing tomato fruit however, their dissolved calcium content is much reduced because of what was lost to the rest of the fruit in transport to its end.
Hopefully, this will clarify any misconception that I might have previously created.
Thanks again for using our forum.
