Arizona Agricultural Experiment Station 603 



the succeeding summer crop. In the wheat breeding work at 

 this Station, an early maturing wheat has, therefore, been con- 

 sidered as important as one which produces hard grains. For 

 these reasons the hard, late maturing wheats of the wheat belt 

 have been crossed with the local soft early maturing wheats, 

 with the idea of combining hardness of grain and early maturity 

 in a high yielding bread wheat. The inheritance of grain tex- 

 ture of these crosses was presented in the Thirty-First Annual 

 Report of this Station. The inheritance of earliness through 

 four generations is briefly stated as follows: 



INHERITANCE OF EARLINESS IN WHEAT 



The Sonora-Turkey cross illustrates the manner of inheri- 

 tance of earliness (or lateness) in crosses between the early and 

 the late maturing varieties. In comparing the earliness of 

 these wheats, the date of appearance of the first head on each 

 plant has been used. The mean heading date of 92 pure Sonora 

 plants in the spring of 1918 was April 7, while that of 90 pure 

 Turkey plants, which were planted at the same time, was May 

 1. The mean heading date of SOF^ plants of the cross between 

 these two varieties the same season was April 18, which is al- 

 most exactly intermediate between the two mean parental head- 

 ing dates. The standard deviations of the heading dates of the 

 pure Sonora, pure Turkey, and their F^ plants were 1.403t 

 0.070, 2.055$0.103, and 2.128$0.254, respectively. Fig. 

 5A. presents curves showing the range of heading dates for 

 the parents (Sonora and Turkey) and their F^ plants. Thirty 

 families, containing altogether 4892 plants, were grown in the 

 Fg generation, and the range of heading dates of these second 

 generation plants covered a period of 36 days, which is three 

 days greater than the period between the date of appearance of 

 the earliest head on the early parent (Sonora) and that of the 

 latest head on the late parent (Turkey). Fig. 5B. shows 

 the range of heading dates of family No. 2 consisting of 275 

 plants, and also the range of heading dates for the original par- 

 ents for the same season. Only 66 of the F, plants headed as 

 early as the latest head on the early parent (Sonora), while 

 1435 F2 plants headed as late as the earliest head of the late 

 parent, leaving 3391 F2 intermediate plants with heading dates 

 on days when neither parent was heading. In making selec- 

 tions for later plantings, a plant was classified as early if its 



^Signifies plus or minue. 



