Hayes and Garber - Cucurbit Breeding

FLAX AND TOBACCO 161
from selfing these self-sterile species are spoken
of as cases of
pseudo-fertility.
Results of crosses between self sterile and self fertile varieties
are given
in Table XXXVI:
TABLE XXXVI. INHERITANCE OF STERILITY IN CROSSES BETWEEN SELF-
FERTILE AND SELF STERILE TOBACCO SPECIES
PARENTS Fi Ft
Forgetiana X Langsdorffii Self-fertile 144 self-: 37 selfvigorous
fertile sterile
Alata X Langsdorffii Self-fertile 162 self-: 38 selfvigorous
fertile sterile
The self-fertile condition proved dominant in FI and a ratio of
approximately 4 self-fertile to 1 self-sterile plant was obtained
in F 2 . The self-sterile plants of F 2 proved self-sterile in later
East explained these results by a dominant factor,
generations.
F, for fertility and a subsidiary factor, D, for pseudo-fertility
which exhibits itself only in the presence of the factors for sterility,
ff.
This pseudo-fertility factor produces some fertility under
certain conditions, thus tending to lower the number of self-sterile
forms.
East has suggested that differences in the rate of pollen
germination are largely responsible for the differences in the
length of pollen tubes from compatible and incompatible pollinations.
When self-sterile plants are self-pollinated the pollen
grains germinate but the pollen tubes grow so slowly that abscission
of the flower occurs before the pollen tube reaches the ovary.
Color Characters. Color of corolla has been studied for Nicotiana
crosses. East (19166) found that in crosses between N.
Langsdorffii and N. alata there was a dominance in F\ of yellow
over white in the color of the corolla. The Langsdorffii parent
produces blue pollen and the alata yellow. Reciprocal crosses
gave blue pollen in FI, although the color was somewhat lighter
than in the blue-pollen parent. Results in F 2 showed 342
plants with blue pollen and 100 plants with yellow pollen. Yellow-pollen
plants bred true in F 3 . Here we have a cross between
species which exhibits a monohybrid ratio.
According to Allard (1919a) N. tabacum exhibits three distinct
flower colors carmine, pink, and white. In crosses between carmine
and pink theFi was carmine. The Fi pollinated with the carmine
parent gave all carmine colored progeny while the Fi crossed
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