WHEAT. 257 



certain method, of obtaining the desirable biotypes, and is 

 generally confined to experimental stations. However, some 

 valuable varieties have been obtained by farmers selecting out- 

 standing plants. 



(3) Cross-Breeding or Hybridisation. — Besides the im- 

 portant factor of hybrid vigour, the object is to combine the 

 desirable characteristics of the two or more wheats in the 

 one. The following dominants and recessives have been 

 noted : — 



DoMiNAKTS. Recessives. 



Hairy Leaves. Smooth Leaves. 



Solid stem. Hollow stem. 



Firm closing of glumes. Loose closing of glumes. 



Felted glumes. Smooth glumes. 



Susceptibility to rust. Immunity to rust. 



Black chaff. White chalf. 



Fhnty grain. Floury grain. 



Winter form {late shooting). Spring form (early shooting). 



Lax ears. Dense ears. 



Red grain. White grain. 



Bald J Bearded. 



Unless reciprocal crosses are wanted, always cross so as to 

 have the mother plant the recessive. 



Some of the most valuable wheats to-day have been 

 obtained by hybridisation — e.g.. Marquis, Prelude. Federa- 

 tion, the most commonly grown variety in Australia, is a 

 cross between Yandilla King and Purple St»-aw. 



Whea.t crosses with barley — e.g., Nepaul Barley x Early 

 Lambrigg Wheat gave Bob's Rustproof. 



Common wheat crosses readily with Emmer, Speltz and 

 Einkorn ; wheat-rye hybrids have also been obtained, and in a 

 few cases these hybrids have been induced to produce seeds; 

 however, on the whole, they are sterile. 



Diseases and Pests. 



Rust (Puccina spp.) — The chief menace to wheat-grow- 

 ing in South Africa ; in fact, wheat-growing is really restricted 

 to rust-evading areas — i.e., those areas where the early 

 summer is not hot and moist. Under irrigation, early 

 varieties are fairly safe in the Orange Free State and Trans- 

 vaal, and as a class the durums are very resistant, so is 

 emmer. Occasionally varieties are found more resistant ohaa 

 others; some will remain immune for several seasons, but wij! 

 suddenly become susceptible. No remedy, but resistant 



