Cytoplasmic male sterility in tomato


Tomato is a self-pollinating culture, but a low percentage (0 to 5 percent) of out-crossing may occur if two or more varieties are grown closely under certain conditions.
In the future, tomatoes with cytoplasmic male sterility could help farmers secure co-existence between conventional and GM tomato plantings. Co-Extra is looking to assess male-sterile tomatoes to see if they are truly free of viable pollen, and if so, if sufficient pollination can be obtained from neighbouring plants that are male-fertile.


Cytoplsmic male sterility in tomato is being investigated in field trials conducted in Bulgaria. Similarly to maize, tomato plants cannot set fruit without adequate pollination. Since male-sterile tomato plants should not self-pollinate, all seeds in male-sterile tomatoes should theoretically have been fertilised by a male-fertile plant.

To ensure that this is the case, seeds from male-sterile tomatoes undergo “paternity tests”. All seeds should contain genes from distantly situated, male-fertile tomato plants. If this is found to be true, it would prove that pollen donors are effective, as well as that male-sterile tomato plants truly do not produce viable pollen.

When the extent of pollen flow is better understood, and if the results turn out to be positive, researchers will suggest practices for using CMS to prevent unwanted out-crossing from transgenic tomatoes.


During the 2005 growing season, weather conditions in Bulgaria were unfavourable and atypical. This caused poor flowering on the male-fertile plants and, consequently, poor fruit setting on the male-sterile tomato plants.

Fruit-set on the male-fertile lines was also much lower than usual. However, robust fruit set was observed when the flowers on the male-sterile plants were pollinated by hand. Therefore, weather conditions, rather than biological factors, were to blame for poor fruit set - and also made it impossible to predict the efficiency of pollen donors under typical conditions. This experiment is being conducted again in 2006.

During the 2006 growing season, the field studies were carried out on the stability of two male-sterile tomato lines, with high practical application in tomato hybrid seed production in Bulgaria. These field trials were conducted under different climatic conditions.

An assessment of pollen flow in tomato fields has been carried out. 

More information:

Public Deliverables of the Co-Extra project


Atanas Atanassov / Mariana Radkova
AgroBioInstitute (ABI), Bulgaria