48 



iiilieritancc of smut resistance, using new specialized races of the 

 covered smut. Piotli ])arents are suscei)til)le to the Missouri race 

 of the covered smut, one ])arent, AFonarcli, l)ein,^' resistant to the 

 Missouri race of loose smut. The new s])ecialized race of covered 

 smut hehaves in exactly the oi)])()site fashion to the loose smut. 

 With the Missouri race of covered snuit, 100 per cent, of the 

 inoculated second j^eneration ])lants were infected. On the other 

 hand, of the sets of second t;-eneration ])lants inoculated with the 

 other two smuts, ap])roximately 25 pvr cent, were infected. 



Data were ohtained on new hyhrids involvinj^" Gothland and 

 Monarch, \'arieties which hchave in an o])i)osite fashion toward the 

 ^Missouri races of loose and covered smuts. With the present 

 hybrids, a somewhat hit^her percentage of infection of the second 

 generation ])lants inoculated with the loose smut was secured, while 

 with the co\-ered smut approximately 25 ])er cent, were infected. 



Interesting new hybrids involve the verv resistant variety Na- 

 varro, which has been crossed \vith Hull-less, !)lack Mesdag and 

 Gothland. Interesting data on the Ix'havior of the second genera- 

 tion ])lants inoculated with \arious races of smuts have been 

 secured. 



A large immber of lun'noculated second generation ])lants of all 

 these lu'brids have been grown, thus providing seed for a large 

 series of third generation progenies. These will he grown diuing 

 V)M) and, on the basis of their reaction, further light on the 

 inheritance of the smut-resistant (fuality may be obtained. 



PJiysioUxjic Races of flic Oaf Sum Is 



Additional ex])eriments were carried out with some of the 

 collections of both loose and covered smuts of oats in order to 

 determine the extent of their ])hysiologic s])ecialization. During 

 the ])ast tew years about 30 collections ol covered smut and about 

 60 collections ot loose smut, obtained 1 rom manv different regions, 

 have been irsed in ex])eriments in order to determine their s])eciali- 

 zation. Many races of both s])ecies of smuts ha\-e l)een clearly 

 delined. 



