Hayes and Garber - Cucurbit Breeding

FLAX AND TOBACCO 167
state experiment stations. The Howards, in India, likewise
urged the use of self-fertilized seed. Garner (1912) states that
several types have been inbred by growing the seed under bag
from six to eight years without any observable change in vigor
or habits of growth. These facts, together with the studies
of inheritance of quantitative characters, show that the pureline
theory and Mendel's law furnish a reliable guide to tobacco
breeding operations.
As quality of cured leaf is of such great importance in tobacco,
it is necessary that the breeder have a thorough knowledge of the
sort of leaf desired. Practical breeding operations must then be
carried on under the soil and climatic conditions in which the crop
is to be grown. An added complication
is the necessity of basing
the final judgment of a particular selection upon the comparative
value of the cured leaf after fermentation. The difficulties of
comparing numerous strains, while not insurmountable, are
naturally much greater than for an equal number of small grain
selections.
Mutations in Tobacco. The sudden appearance of giant
plants with abnormally high leaf number has been recorded in
the Sumatra, Maryland, Cuban, and Connecticut Havana varieties
of N. tabacum (Allard, 1916). These new forms under field
conditions have a much longer period of vegetative vigor than
the normal varieties.
Consequently blossoming does not take
place under ordinary field conditions. Otherwise the general
habit of each of these new types is not very different from the
normal variety from which it was obtained.
Two of these new varieties of giant habit are of some commercial
importance. A short account of their first recorded appearance
together with their cultivation as commercial varieties will
be given. Giant plants were noted in 1912 in the Cuban variety
which is grown under shade in the Connecticut Valley. (Hayes
and Beinhart, 1914). The history of the normal Cuban variety
from which the giant type was obtained is of interest (Hayes,
1915). Seed of the normal variety was saved under bag, which
insures self-fertilization, from 1904 to 1909 inclusive. In 1910
and 1911 seed was saved in bulk from plants which were grown
under the cheese-cloth cover used in producing shade-grown
tobacco, but individual plants were not bagged. During the
period from 1904 to 1910 no abnormal types were observed.
Studies of leaf inheritance in the Cuban variety were made from