138 



The Journal of Heredity 



is to determine what characteristics in 

 wheat are dominant and what recessive. 

 Tschermak after an exhaustive and 

 critical study of the behavior of the 

 various contrasted unit characters in 

 wheat states that the following attri- 

 butes are respectively dominant and 

 recessive, in strict accordance with 

 Mendel's law: — 



WHEAT ALLELOMORPHS. 



Dominant. Recessive. 



Hairy leaves. Smooth leaves. 



Solid stem. Hollow stem. 

 Firm closing of glumes. Loose closing of glumes. 



Felted glumes. Smooth glumes. 



Black chaff. White chafT. 



Flinty grain. Floury grain. 



Winter form (late Spring form (early 



shooting). shooting). 



Lax ears. Dense ears. 



These have been confirmed in general 

 by Biflfen and Spillman, though in the 

 case of bearded and beardless wheats 

 the ratios are often very far from fol- 

 lowing Mendel's law, as Saunders," 

 Howard and others have pointed out. 



Biffen has obtained similar results at 

 Cambridge. In addition he has shown 

 that the following characters behave as 

 Mendelian units : — 



Recessive. 



White Grain. 



Soft opaque endo- 

 sperm. 



Immunity from yellow 

 rust. 



Dominant. 

 Red Grain. 

 Hard translucent 



endosperm. 

 Susceptibility to 



yellow rust. 



In the following characters there is 

 no dominance of either character, and 

 the progeny in the first generation are 

 intermediate : — 



Lax and dense ears. 

 Large and small glumes. 

 Long and short grains. 

 Early and late ripening. 



In the second generation two of the 

 intermediates occur to each ])ure char- 

 acter— D :2DR :R. 



The determination of the mode of 

 inheritance of these various unit char- 

 acters is of the greatest practical 

 imi)ortance, for it enables the breeder 

 to jjredict with tolerable certainty the 

 forms resulting from the mating of two 

 plants whose (jtialilies can be ex])resse.(l 

 in terms of one or more tmit characters. 



One of the most interesting of the 

 researches carried out in the production 

 of new varieties of wheat is that done by 

 Biflfen in the production of the appar- 

 enth' impossible combination in the 

 one \'ariety of prolificacy, resistance to 

 yellow rust, and high strength. 



The wheats grown in England are 

 very low in strength, and this defect is 

 reflected in the disjjarity in jirice at 

 Mark Lane between the Home-grown 

 wheat, and the strong foreign wheats 

 like Manitoba No. 1. It was formerly 

 thotight that this low strength of the 

 wheats grown in England was due to the 

 peculiarities of the climate. 



A trial of a large number of foreign 

 varieties of high strength tinder Englsh 

 conditions proved that while the greater 

 majority deteriorated immediately, there 

 were a few varieties which retained their 

 strength perfectly under the new cli- 

 matic conditions, and gave as good 

 results in the bakehouse as when grown 

 in their native lands. These varieties, 

 however, were of little use to English 

 farmers, for the>' lacked \-ielding power 

 of both grain and straw. Biffen, there- 

 fore, crossed these varieties of high 

 strength with the prolific English varie- 

 ties with the object of obtaining suitable 

 varieties of high strength. Strength is 

 defined as to the capacity of the flour 

 "to yield large well-i)iled loaves," and 

 while it is not an easy matter to give in 

 non-technical language the difference 

 between strong and weak wheat, it may 

 be said that in general strong wheats are 

 characterized by hard, more or less 

 transjjarent endosperm, whilst weak 

 wheats arc usually soft, starchy, and 

 opaque. In a certain cross between Red 

 Fife and Rough Chaff a statistical 

 examination of the |)rogen\' revealed the 

 fact that in the first generation all the 

 jilants possessed strong grain, and that 

 in the second generation the strength and 

 weakness behaved as Mendelian char- 

 acters giving the following ratio: — Nine 

 strong red. three strong white, thret' 

 weak red, one weak white. Biffen 

 showed that these characters of strength 

 and weakness in wheats could l)e handled 

 with the same definiteness as other 

 Mendelian characters. 



'•Saunders, Inheritance of Awns in Wheat, Conference on Genetics, VM). ]k M(). 



