252 



Rust in Wheat. 



[JULY,. 



not break readily. These differences in the straw are of con- 

 siderable importance for there can be little donbt that the 

 weakening of the straw by the attacks of rust is largely 

 associated with its lodging under unfavourable weather con 

 ditions. For instance, in the fen country it may often be 

 noted that the first parts of a field to lodge are those where the 

 rust is thickest. Further, in the numerous variety trials made 

 in the course of these experiments, the most susceptible wheats 

 have always been the first to be beaten down in stormy weather. 

 This fact probably explains the survival of Little's Anti-mildew 

 in the fen country. There, where all the conditions are in 

 favour of the crop becoming laid, there is a great demand for 

 a stiff-strawed wheat which will give the farmer more oppor- 

 tunity to cut the crop with a binder. The property of rust- 

 resistance means that the strength of the straw is unimpaired, 

 and in spite of other defects this feature has proved so valuable 

 that it has probably been the deciding factor in retaining this 

 variety. 



The experiment just described offers some hope of more 

 rational methods of coping with plant diseases coming into 

 use. At present the use of fungicides is practically the only 

 method the cultivator has at his disposal. This is costly, 

 particularly when the operation has to be repeated time after 

 time owing to the fungicides being washed off by rain. 

 Further, it often happens that spraying does not prove 

 altogether efficacious. If, then, it can be shown that other 

 diseases besides yellow rust can be brought under the control 

 of the plant breeder, in the course of time we may expect to 

 see disease-resisting varieties of most of our staple crops 

 raised. There is already evidence in existence indicating that 

 this is the case, for a similar series of trials on the inheritance 

 of immunity ' to the well-known white mildew of barley has 

 given almost identical results. 



The immune varieties of wheat which have been raised in 

 the course of these preliminary experiments have no particular 

 value beyond their immunity. Numbers of crosses have, 

 however, been made from which varieties suitable for general 

 cultivation will be produced, and now that the main outlines 

 of the story are clear there should be no difficulty in raising 

 these in sufficient quantity for distribution in the course of 

 a few seasons. 



