Regulation of tomato fruit size by plant density and truss thinning

The market prefers Class 1 fruit in the D size grade (i.e. 47 - 57 mm in diameter, 50-90g fresh weight).  When a long-season tomato crop is grown at one planting density throughout its life it is likely to produce too many small fruit in the early part of the season and too many large fruit in the summer. these projects set out to determine whether it was possible to get a better match between assimilate production and fruit number by using truss thinning, altering initial plant density and taking side shoots. Planting at higher plant densities increased the overall yield of marketable and Class 1 fruit but reduced mean fruit size. Taking side shoots tended to depress yields in the first 12 weeks of production, especially at the higher plant density, but treatment increased marketable and class 1 yield once the side shoots came into fruit production. Truss thinning reduced the yield of small fruit produced by the treated trusses but also reduced their overall production of class 1 fruit. The study concluded that all three techniques could be used by growers to improve the uniformity of fruit size but cautioned that further work needed to be conducted which lead to the follow on piece of work, PC065a                                                                    

AIM:

To establish whether it is possible to achieve improved uniformity of fruit size throughout the year.

 OBJECTIVES:

 * Use truss thinning, changes in initial planting density and manipulation of side shoots to alter fruit number to test whether fruit size is regulated by the availability of assimilate from photosynthesis and the numbers of fruit competing for this assimilate

* determine whether any of these techniques can be used in commerce to improve fruit size uniformity throughout the year