Changes of tomato fruit firmness at different development stages were compared between hard
type accession‘ TS330’ and soft type accession‘ A57’．The results showed that the fruit firmness of‘ TS330’
was significantly higher than that of ‘A57’ at mature green stage，breaker stage and red ripening stage，of
which there were maximum differences during mature green stage．The cell wall thickness，cell density（cell
layers per unit thickness）and pectin content of ‘TS330’ fruit at mature green stage were significantly higher
than those of ‘A57’ fruit．The fruit firmness of ‘TS330’，F₁（‘TS330’בA57’）and ‘A57’ at mature
green stage were 26.86，21.09 kg · cm-2 and 19.11 kg · cm^-2，respectively．The tomato fruit firmness was
closely related to its cell density（ correlation coefficient 0.96） and pectin content（ correlation coefficient 0.99）．
The fruit firmness of‘ TS330’בA57’ F₂ population tended to a normal distribution，indicating that tomato
fruit firmness was controlled by multiple loci．