HYBRIDISATION AND WHEAT HYBRIDS 387 



first accomplished by A. S. Wilson, who recorded in 1875 the production 

 of a sterile hybrid from the pollination of wheat with rye. Since that 

 date similar successful crosses have been described or figured by Carman, 

 Bernard, Rimpau, Signa, Schliephacke, Miczynski, Tschermak, McFadden, 

 Ito, Jesenko, Leichty, and Backhouse. Nilsson-Ehle has twice observed 

 natural hybrids between winter wheat and winter rye. 



With the exception of Jesenko's hybrids with the wild Triticum 

 dicoccoides and Emmer (Triticum dicoccum) all the work has been carried 

 out with Bread Wheat (T. vulgare) and rye. 



The cross only succeeds when wheat is made the mother plant, and 

 then only with difficulty. 



Jesenko pollinated more than 3500 flowers of rye with wheat pollen 

 without the production of a single fertile grain ; the reverse cross, how- 

 ever, he found effective on an average of about six times per 1000 pollina- 

 tions as indicated in the following results of trials in 1909-1912. 



In 1909, 580 flowers on 18 care yielded i hybrid grain. 

 In 1910, 339 flowers on 12 ears yielded o hybrid grain. 

 In 1911, 3060 flowers on 102 ears yielded 29 hybrid grains. 



(i ear yielded 12.) 

 In 1912, 2150 flowers on 70 ears yielded 5 hybrid grains. 



Similarly, Leighty obtained no result after 80 pollinations of rye with 

 wheat, and only 3 grains from 172 pollinations of wheat with rye pollen. 

 Backhouse also found the crossing of wheat and rye difficult except in tin- 

 case of a Chinese beardless variety of T. vulgart^ which he states set 32 

 out of 40 flowers pollinated with rye. 



Jesenko discovered that the rye pollen germinates on the stigma and 

 penetrates the style of the wheat gynaccium, probably reaching the 

 micropyle of the ovum in the majority of cases, but the union of the sperm 

 with the ovum is prevented, or the cross - fertilised ovum ceases to 

 develop. 



In some instances grains containing a small amount of endosperm 

 were obtained apparently as the result of fertilisation, but these refused 

 to germinate, the embryo being missing or imperfectly formed. 



The hybrid plant exhibits the blended inheritance of both parents, 

 with the rye-like characters perhaps more conspicuous than those of 

 wheat. 



When young, the F, plants resemble wheat in having a green coleop- 

 tile and well-developed auricles on the leaves, but the culms and leaves 

 of the fully developed plants are greyish green, or dark green like those of 

 rye, and the upper internode, especially ot the first and second straws, are 

 more or less pubescent like those ot most forms of the latter plant. The 

 hybrids tiller extensively, and continue to produce shoots late in the season 



