18 BULLETIN 1015, U. S. DEPARTMENT OF AGEICULTUEE. 
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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