18 BULLETIN 1015, TJ. S. DEPARTMENT OF AGRICULTURE. 



them to be well adapted to all parts of the United States in which 

 tomato wilt is present. 



Very few commercial varieties possess appreciable resistance to 

 wilt. The Duke of York and the Buckeye State, apparently one va- 

 riety under two names, are highly resistant, but they produce poor 

 fruit. Livingston's Globe is somewhat resistant, but its purple fruit 

 is objectionable to canners and is not in universal favor in other 

 markets. Moreover, it is very susceptible to nail-head rust, a de- 

 structive disease prevalent in the South, where this variety is most 

 commonly grown. 



Varieties that normally produce a heavy crop of excellent fruit 

 and vary considerably in the degree of wilt resistance possessed by 

 their individual plants afford the best material for the development 

 of superior wilt-resistant varieties by selection. Although such va- 

 rieties may be very susceptible to wilt, they are nevertheless val- 

 uable if they produce occasional resistant plants, as such plants are 

 usually much better material than selections from more resistant va- 

 rieties that produce a poorer crop of fruit. Most varieties transmit 

 approximately the same degree of wilt resistance to all their plants 

 and consequently offer little opportunity for improvement by selec- 

 tion. 



Tomato plants selected for wilt resistance usually transmit to their 

 immediate offspring as much resistance as can be developed from 

 them by subsequent selection. In a few instances increased resist- 

 ance has been obtained in the second selection, but not in later se- 

 lections. This may be due either to a limited response of the ma- 

 terial to selection or to an obscuration of real differences by fluc- 

 tuations. 



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