In 1979, Dr. E. A. Kerr, who at that time was with the Ministry of Agriculture at Simcoe, Ontario, sent seed of Ont 7710. The fruit size of this tomato was reported to be about 64g. Dr. Kerr indicated it was I, og^c^, j^2^, u, sp, and segregating Ve. I had an interest in increasing fruit size with the ultimate goal to use Ont 7710 as the male parent to develop a hybrid tomato acceptable for chain store sales. A cross was made with the tomato variety "Starfire" strictly to select fruit from the F2. This was followed by eight generations of individual plant selections in which ease of fruit release, fruit size, crack resistance, firmness and eating quality were the characters of major interest. In 1988, 14 selections were made and for these the average fruit size for the last three years was recorded as follows: 1986 - 127.1g, 1987 - 149.8g and 1988 - 163.2g. In other words, the average fruit size by 1988 was increased by 270 percent. For the years 1982 through 1985, fruit size was not recorded.
It seems almost unbelievable, to this breeder, that fruit size could be increased this much within an inbred line. In fact, two of the 1988 selections have fruit sized of 199.8g and 204.3g, respectively. Out-crossing has been considered as a possibility but each year these particular lines were grown in close proximity so that, if crossing had occurred, it would likely be sibbing between the above sister lines. Also, since many other parent materials used within the breeding program had the J2 gene as well as other quite diverse characters, some of these characters would likely behave occurred in progeny had there been out-crossing. None of these non-parental characters appeared in segregations. In addition, if one assumes, as is reported in the literature, that no more than 4 percent out-crossing is likely, by only planting out 12 plants of each inbred parent each year, it seems unlikely that significant out-crossing would have occurred with only 12 plants.
It appears that selection pressure for fruit size within lines has accounted for this difference. In addition to fruit size, many of the other characteristics such as crack resistance, firmness, blotchy ripening, eating quality, etc. have also been subjected to this selection pressure. Although many of these characteristics have been subjectively evaluated and data, such as is available for fruit size, were no collected, significant improvements have been made in all these characteristics. For example, because close attention has been given to selecting inbred material blotchy ripening in both parental lines, hybrids are available which show little or no evidence of blotchy ripening.
The female parents used to made the hybrids are quite diverse in habit and origin, with fruit size varying in 86 lines from 177.1g to 336.0g. In conclusion, it may not be necessary to locate new genetic material when many of these quantitative characters were desired. These characteristics may very well be assembled within your tomato lines, if the correct selection pressure is applied.