Levels of pigment intensity of immature fruits.

Reynard, George B.

Continued work with derivatives of the Webb Special tomato and with other varieties and strains has resulted in at least four levels of intensity of the green or greenish-yellow color in the immature fruit. We have established true breeding strains on unifom ripening u u and green base + + fruit types, giving eight distinguishable phenotypes. A third series is in preparation with the ug ug unifom (gray) ripening type; two levels have been established in this, resulting in a total of ten different phenotypes.

Separate strains with only hp/1 or hp/2 were not isolated by Dr. Thompson (Science 121:896-897, 1953) so that assignment of a complete series of symbols, correlating it with his assignments, must await progeny tests. The three lightest green phenotypes do not produce high pigmented ripe fruit, so that use of the "hp" symbol is not indicated. The symbols "gp" for green pigment are suggested for all but the highest level in the series described here, the highest level having the same genes, hp\1 hp\2 as described by Thompson and by Kerr (TGC 5). Upon identificition of one or more of the "gp" genes with the "hp" genes, a unified series will be proposed.

Experience is of course necessary to become familiar with the different phenotypes, and separation of single plants within segregating populations is difficult but extremely interesting. Epistatic and hypostatic relationships are under study.

At present, our interpretation of the different fruit types is as follows:

fruit     Fruit
pigment-  ripening
ation     genotype  Phenotype name   Strain or variety

gp\1         uu     Whitish green    Niihau              sp Sm I
gp\2         uu     Yellowish green  Ace                 sp
gp\2, gp\3   uu     Apple            Ontario
hp\1, hp\2   uu     Dark apple       Campbell #1043 and  sp
                                     Illinois 32-19-55
gp\1         ++     Light green base Waltham Mold
                                     Proof Forcing
gp\2         ++     Green base       Impr. Garden State  sp
                                     Rutgers and Marglobe
gp\2, gp\3   ++     Apple green base Kings
hp\1, hp\2   ++     Dark apple green baae  Webb Special
gp\2         ug     Grayish-green    Campbell #146       Sm I
gp\2, gp\3   ug     Apple gray-green Campbell Kc57       I

The ten phenotypes are dintinguishable in the field. The dark apple and dark apple green base types invariably have dark foliage. In addition to the Kings variety, the variety Early Pak has darker pigment than Improved Garden State, and other strains in our trials have similar pigmentation. Within these, some are accompanied by dark foliage and some are not; this distinction may help in separation of perhaps another gene in the series.

The presence of several levels of green and ripe fruit pigment intensity has been noted by many doing tomato variety breeding and evaluation. The reasons for this variation are apparent as shown above. Simple segregation was found in the cross Waltham Mold Proof Forcing x Niihau, 3:1 light green base : whitish green. An example of complex segregation was found in the cross Waltham Mold Proof Forcing x Ontario. The two parental phenotypes were recovered but in addition, four more, resembling Niihau, Ace, Improved Garden State and Kings. Thus, six phenotypes arose from the cross.

It is believed that comparison of other varieties, having fruit different from Marglobe, Rutgers or Improved Garden State, with the above series would help fit them in the proper place.