Additional information on on the inheritance of ry, a modifier gene for red color in yellow tomato fruits.

Thompson, A. E.

In 1951, Dr. J. P. McCollum made a selection of a reddish-orange fruited tomato from PI 125831 growing in the North Central Region tomato collection at Wooster, Ohio. A description of this material and the explanation for its inheritance was published by Dr. P. A. Young in TGC 6:33. Crosses had been made with this material at Illinois in 1954 and the F2 populations analyzed in 1955. Results of these crosses confirm Dr. Young's findings and give evidence of the allelic nature of ry and r.

Four crosses were made with the following types: Webb Special, a high pigment red variety (r^+^r^+^t^+^t^+); Garden State, a normal red variety (r^+^r^+^t^+^t^+); U. of I. Acc. 34, apricot (r^+^r^+^t^+^t^+ at at) and U. of I. Acc. 36, yellow-tangerine (rrtt). The latter two accessions were obtained from Dr. J. A. Jenkins in 1953. The following table presents the essential data derived f from these crosses.

It did not prove possible to visually separate the various genotypes within the yellow and tangerine classifications with any degree of accuracy. No F3 or backcross progenies have been analyzed. The cross involving Acc. 36 (yellow-tangerine) provides the evidence that r and rz are allelic. Further information will be needed to establish this point with certainty. The symbol ry as proposed by Dr. Young should be retained until this situation is clarified.

The cross involving Webb Special gave high pigment segregates in both the red and yellow classifications, but did not give a good fit to either a 3:1 or 15:1 ratio. The normal and high pigment classes were combined in the table.

Parents and Genotype          Fl Phenotype      F2 Phenotype  
                                            Red Yellow Tangerine     

UI Acc. 29 x Webb Special        red        174    60      
ry ry           r^+^r^+

Garden State x UI Acc. 29        red        168    56      
r^+^r^+          ry ry 

UI Acc. 34 x UI Acc. 29          red        116   109      
at at r^+^r^+    at^+^at^+ ry ry

UI Acc. 29 x UI Acc. 36          yellow     ---   169   57 
ry ry t^+^t^+    rrtt     

Parents and Genotype          Expected          X^2       

UI Acc. 29 x Webb Special        3:1           .0513
ry ry           r^+^r^+

Garden State x UI Acc. 29        3:1           Exact fit
r^+^r^+          ry ry 

UI Acc. 34 x UI Acc. 29          9:7           1.9948
at at r^+^r^+    at^+^at^+ ry ry

UI Acc. 29 x UI Acc. 36         12:4            .0059 
ry ry t^+^t^+    rrtt    

The second table presents the relative carotenoid pigment content of the parents involved in the above reported crosses with some additional strains for comparison.

Strain                 Genotype                

Acc.   29             ry ry t^+^t^+                  
Acc.   34             r^+^r^+^t^+^t^+ at at            
Acc.   36             rr tt                         
Garden State          r^+^r^+^t^+^t^+                  
Webb Special          r^+^r^+^t^+^t^+ hp1 hp1 hp2 hp2  
Golden Queen          rr t^+^t^+                     
1002-hp               rr t^+^t^+ hp1 hp1 hp2 hp2     
Snowball              rr t^+^t^+                      
1005-hp               rr t^+^t^+ hp1 hp1 hp2 hp2     

                      Carotenoid      Content
Strain            Total Pipment    Beta Carotene

Acc.   29              9.7            1.56
Acc.   34             14.6            3.20
Acc.   36             12.3            ---
Garden State         117.6            1.68
Webb Special         146.4            3.82
Golden Queen           2.0            0.24
1002-hp                4.6            0.36
Snowball               2.0             *
1005-hp                2.6            0.16
            *  none     detected

1002-hp is a yellow, high pigment selection from a cross involving Webb Special and Golden Queen, 1005-hp is a yellow, high pigment selection from Webb Special x Snowball. It should be noted that Acc. 29 has a significantly higher production of both total pigments and beta carotene than any other yellow strain tested. The beta carotene content appears to be in the same range as normal red tomatoes. It does, however, have the characteristic reduction in total pigment production of the r allele when compared to r^+.