i8o 



The Journal of Heredity 



of course suggested that white is dom- 

 inant to yellow and yellow to green. 

 This conclusion was fully borne out 

 by the results of crossing. In Table I 

 are presented the data for parents, 

 Fi and Fo in nine pedigrees from crosses 

 involving differences in fruit color. 



The dominance of white over yellow 

 and of yellow over green is evident. 

 In pedigrees 17 and 6 there is an ap- 

 proximation to a 3:1 ratio of white to 

 yellow in the F2; and in 3 and 4, an 

 approximation to a 3:1 ratio of yellow 

 to green. Dominance of yellow over 

 green is not quite complete. The Fi in 

 pedigrees 3 and 4 and a majority of the 

 yellow segregates in the F2 (presum- 

 ably the heterozygous ones) are some- 

 what washed or tinged with green. 



Pedigrees 1, 14, and 15, however, 

 differ from the first four in the fact 

 that a few green plants made their 

 appearance in the F2. The total number 

 of plants in these three pedigrees is 

 205, of which 155, or almost exactly 

 3/4, are white. Of the 50 non-white 

 plants, 40, or a little over 3/4, are yel- 

 low, the other 10 being green. This 

 count (155:40:10) is very close to a 

 12:3:1 ratio, according to which we 

 should expect in the population under 

 discussion 154 white, 38 yellow and 13 

 green. It is evident that in pedigrees 

 6 and 17, the white parents contain 

 hypostatic yellow factors and have a 

 genotype which may be represented by 

 the formula WWYY. Such plants 

 when crossed with yellows could never 

 throw any greens. In pedigrees 1, 

 14, and 15, however, the white parents 

 evidently do not contain hypostatic 

 yellow and apparently have the geno- 



type WWyy. Such a plant when 

 crossed with pure yellow (wwYY) 

 would give WwYy in Fi and 12/16 

 white, 3/16 yellow and 1/16 green in 

 F2, the result which we observed. 



In pedigrees 5 and 7, however, there 

 is a great preponderance of white in 

 the F2, a total of 64 white to 2 yellow. 

 In several cases, also, the yellows which 

 have appeared in white fruited lines 

 during inbreeding have constituted 

 considerably less than a quarter of a 

 given group of offspring. We evidently 

 have here two independent factors for 

 white, Wi and W2. A white homozy- 

 gous for both these would of course 

 give, when crossed with a yellow, 15 

 white to 1 yellow in F2, a ratio which is 

 close to that which we found in these 

 two pedigrees. 



As responsible for the \-arious body 

 colors in the fruits of these squashes we 

 may therefore assume two separate, 

 dominant factors for white; a factor for 

 yellow recessive to white and dominant 

 over green, and a fundamental recessive 

 factor for green. 



In each of these main color types 

 there is much variation. There are 

 buff, cream, and plain whites, deep 

 and light yellows, and greens. These 

 are definitely inherited but the mode of 

 inheritance is hard to trace. Evidently 

 a number of modifying factors are here 

 at work. 



STRIPING OF FRUIT 



In several of the lines fruit color is 

 not uniform, but stripes differing in 

 color from the body appear in the 

 furrows (Fig. 18). Yellow and green 

 stripes have appeared in lines normally 



Table L Inheritance of Body Color in Fruit of Summer Squash 



