Hayes and Garber - Cucurbit Breeding

238 BREEDING CROP PLANTS
Le = long internodes
Length of internodes. .
{
{ ,
(Lei
= very long internodes
.
Number of internodes.
= 20-40 internodes
=
1 40-60 internodes
=
2 20-30 internodes
Absences
le = short internodes
t = 10-20 internodes
Le is the height factor isolated by Mendel, while T is Keeble and
Pellew's factor for thickness of stems which White has interpreted
On the
as a factor for internode number and internode length.
factorial basis given, the phenotypic condition of the tails of
which there are three classes would be:
1. LeT = 20-40 long internodes.
2. Le Ti = 40-60 long internodes.
3. LeiT 2 = 20-30 very long internodes.
The phenotypic nature of the half dwarfs would be :
4. Le t
= 10-20 long internodes.
5. le T = 20-40 short internodes.
True dwarfs would represent the absence of both dominant
factors Le and T or let. With the same material that Mendel
used, the same results for height have been obtained.
The inheritance of time of flowering involves several factors as
is shown by complicated F 2 ratios (Tschermak, 1916) (Keeble
and Pellew, 1910). Keeble and Pellew found linkage between
the factors for thick stems and late maturity and likewise between
the opposite condition, thin stems and early maturity.
Vilmorin (1910) made a large series of crosses with edible
pod races. In some cases both FI and F z produced only plants
with edible pods. In other crosses hard inedible pods were produced
in FI and ratios of 9 hard to 7 edible were obtained in F 2 .
Results may be explained by the supposition that hard pod
varieties (development of parchment-like tissue) may be due to the
presence of two factors (White, 1917) PPVV. Non-parchment
varieties may have either the formulae PPvv, ppVV or ppvv. White
cites earlier workers who have always found parchmented pods
to be inflated and non-parchmented to be constricted. Nohara
(1918), in a cross between a Japanese pea and a French variety,
both of which produced soft edible pods, obtained a ratio of 9
parchmented to 7 non-parchmented in FI. Results were also
explained by a two-factor hypothesis.