REPORT OF THE DEPARTMENT OF 

 HORTICULTURE. 



INFLUENCE OF CROSSING IN INCREASING THE 

 YIELD OF THE TOMATO * 



RICHARD WELLINGTON. 

 SUMMARY. 



The infusion of new blood obtained by crossing somewhat 

 closely related varieties has been found, in many plants, to in- 

 crease the vigor and yield of fruits to a very marked degree. 

 Among the common commercial crops, corn, bean and tomato 

 have been proven experimentally to be greatly benefited by such 

 crossing. 



The increase in vigor and size produced by crossing is undoubt- 

 edly due either to the heterozygous condition, w^hich stimulates 

 the growth of either the size or the number of cells ; or to a com- 

 bination of two or more size-increasing characters, such as thick 

 internodes and long internodes, which dominate over characters 

 of decreasing dimensions. 



All the experiments on tomato crosses conducted at this Sta- 

 tion during the years 1907-1910 have given consistent gains in 

 favor of the yield of the F^ (the first filial) generation ; and the F2 

 (second) and F3 (third) generations have fallen off in yield in 

 direct ratio to the decrease in the number of heterozygous plants. 

 When a homozygous condition for all the plants in a strain has 

 been obtained, the average yield of the plants should remain con- 

 stant from year to year, varying only with the external factors, — 

 food, moisture, and temperature. Thus, if the F,( plants, which 

 were used for the production of the F^ generation grown in the 

 summer 19 10 were mostly homozygous, the non-drop in yield 

 can be understood. 



The results obtained in these experiments warrant the produc- 

 tion of F^ generation tomato seed not only by the grower but by 

 all seedsmen who wish to furnish the best grade of seed to their 

 buyers. The production of such seed requires time and care, and 

 consequently, it must be sold at higher prices. 



*A reprint of Bulletin No. 346, March, 1912; for "Popular Edition," 



see p. 823.-. 



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