TOBACCO RESISTANT TO BLACK SHANK a 
accomplished by the soil adhering to implements and tools used in 
cultivation and to the feet of work stock and men. Other means of 
spread include the use of diseased plants for transplanting, applica- 
tion of contaminated manure or diseased tobacco scrap and stems to 
the soil, and the use of contaminated water on plant beds or in the 
operation of transplanting in the field. 
Spread to new centers of infection has probably been brought about — 
by contaminated drainage water, the use of diseased plants from 
infested seedbeds, movement of contaminated soil on road machinery 
and on other heavy equipment going from one section to another, or 
the use of diseased tobacco scrap or stems. 
TESTING FOR DISEASE-RESISTANT PARENTS 
Prior to 1930 no attempt had been made to develop resistance to 
black shank in flue-cured tobaccos. At that time, seeds of 66 flue- 
cured varieties, strains, and selections were collected at the Tobacco 
Experiment Station, Oxford, N. C., and seeds also were obtained of 
varieties representing the dark fire-cured, Burley, and Turkish types 
and the species Nicotiana rustica L. Tests conducted during 1931 
in the vicinity of Walkertown, N. C., on heavily contaminated soil 
showed that there was little or no resistance to the black shank 
organism in fiue-cured tobaccos. Two varieties of N. tabacum L. 
(ordinary tobacco), three varieties of N. rustica L., from Russia, and 
a variety of the Cuban type known as Cuban High Nicotine were 
highly resistant. Two dark fire-cured hybrids developed for black 
root rot resistance were fairly resistant to black shank. All these 
resistant types had leaf, stalk, or other characteristics very different 
from flue-cured tobaceos, and none was considered suitable for use 
in making crosses on flue-cured varieties. 
Of four strains of cigar-wrapper tobacco developed by the North 
Florida Experiment Station and tested during 1932, three showed 
a high degree of resistance under the local conditions. One of these 
(301) has proved very useful in developing resistant varieties suit- 
able for flue curing. | 
DESCRIPTION OF PARENT STOCKS 
While a number of crosses were made, only those hybrids were 
continued that showed most promise for resistance and possessed 
desirable characteristics of the flue-cured type. The parents of only 
those strains that have shown most promise are here described. The 
flue-cured parentage includes four varieties: Virginia Bright Leaf, 
White Stem Orinoco, Warne, and 400. 
Virginia Bright Leaf.—This variety has a rather wide range of 
adaptability and is grown with good success over most of the flue- 
cured area. ‘The leaves are fairly broad and taper to a moderately 
sharp point. They are about three-fifths as broad as long, and the 
broadest region is about one-third the distance from the stem end 
to the tip. The leaves grow semiupright and are moderately spaced 
on the stalk. The date of maturity is about average for flue-cured 
varieties, and the yield is satisfactory. It is a medium-bodied tobacco. 
White Stem Orinoco.—This variety before reaching the topping 
stage somewhat resembles a cedar tree in shape. The leaves are 
