Diseases of Cereals : Rust and Take-all in Wheat. 717 



It is well known to many of you what good results have been 

 obtained by the scientific breeding of stock, but it is perhaps not so 

 well known what can be done by mating different varieties of wheat. 



The flowers of wheat are fertilized by their own pollen while they 

 are still closed, and it is questionable if crossing ever takes place 

 under natural conditions. This process of continuous self-fertilization 

 produces offspring which repeat the characters of the parent in almost 

 every detail, and striking variations which form the starting point for 

 selection to work upon are very rare. But it is well known that 

 crossing tends to produce variability, and by means of artificial 

 crossing these variations are produced. 



The principle of the process is comparatively simple. When two 

 varieties are chosen for a cross, the unfertilized flowers of one parent 

 are carefully castrated and the pollen or male element is taken from the 

 other and used to fertilize it. The seeds produced in this way are sown 

 by themselves, and the produce of the first generation is again sown 

 separately. There is a considerable amount of variation in this 

 second generation from the blending of the characters of the two 

 parents, and such plants are selected for seed as show the character- 

 istics it is desired to perpetuate. The third generation is again 

 treated similarly, and the process is continued until a race is 

 developed which possesses the characters aimed at in a high degree. 

 The "fixing" or permanently establishing these characters takes 

 several years, some coming true after three or four years, while others 

 continue to vary for a number of years. The great point gained by 

 crossing is that a relatively permanent race has been formed, and the 

 seed sown from it will reproduce the parent type. 



A very promising rust resisting cross named Bobs was received 

 from Mr. Farrer last season, and it is being tried on a large scale this 

 season. 



The bearing of all this on the prevention of rust is evident. By 

 creating a race of wheats thoroughly suited to our conditions, which 

 in addition to other desirable qualities have the property of 

 rust resistance^ lies the key to the solution of the rust problem. And 

 this opinion is borne out in a letter received some years ago from the 

 late Sir J. B. Lawes, the distinguished founder of the Rothamsted 

 Experimental Farm, which I have had the pleasure of visiting on 

 more than one occasion in his life-time. He writes : — " I have no 

 doubt that if I grew wheats which had previously been grown in a 

 hotter and drier climate than that of England, I should have the crop 

 destroyed by rust. I have no faith in specifics. You must try and 

 obtain wheats which will grow well in your climate. It will of 

 course take some years of experiment to obtain what you require, but 

 I feel sure that you are more likely to succeed if you direct your 

 attention to obtaining a rust resisting wheat than by trying specifics 

 or by manures." 



Take-all. 



The one-time mysterious disease known as Take-all has now been 

 proved by the investigations of this Branch to be due to a fungus. 



