Penetration experiments with a plunger (6mmφ) were carried out on processing tomato in order to serch for appropriate indicators of fruit hardness which is an important character in the breeding of a variety adapted to mechanical harvesting.
The observations were summarized as follows :
1 ) The resisting force of fruit to penetration was large in the varieties of Kagome 70, AT 70/24, VF 145, and TE-30, and the smallest in Super Roma VF among the varieties examined.
2 ) The resisting force tended to be large in such varieties whose average fruit weight was from 65 to 100g. However, no definite relation was found between the other morphological characters and the resisting force.
3 ) The resisting force of fruit decreased with the progress of maturity in each variety.
4 ) The degree of defornration accompanied by the penetration was high in San Marzano, Super Roma VF, and Chico, and the lowest in ES-58.
5 ) The degree of deformation tended to become higher in varieties bearing pear-shaped fruits than in those bearing round-shaped fruits. However, there was an exceptional variety, AT 70/24 in which the degree of deformation was not so high regardless of its the smallest F. S value. The degree of deformation in a variety tended to be reciprocal to its fruit size.
6 ) The penetrating energy was relatively high in Kagome 70, Chico, VF 145, and San Marzano and the lowest in H-1409. The penetrating energy was influenced not only by the resisting force but also by the degree of deformation.
7 ) The penetrating energy decreased with the progress of maturity in each variety.
The energy in a mature fruit was approximately half as compared to that in an immature fruit.