Vegetable Improvement Newsletter
No. 6, February 1964
Compiled by H.M. Munger, Cornell University,
Ithaca, New York
1. Inbreeding and Heterosis in Asparagus
Philip Ito and T.M. Currence
Department of Horticulture, University of Minnesota, St.
Paul
Sib crosses were made to develop inbred lines. Ten female
plants from each of 9 inbred lines ranging four to eight
sib-crossed generations were chosen as maternal parents.
Parentage of these inbred lines was quite diverse including
the species brachyphyllus and two foreign varieties. Also
2 female and 2 male Washington plants that had proven outstanding
in progeny tests occur in the pedigrees. Ten female plants
from each of 6 varieties were also included as female parents.
These were from commercial seeds. One was designated by
the seed company as a commercial hybrid. The only male parent
was a plant of a perfect flowering line that came from Holland.
It had been selfed three generations.
A test of the 15 crosses and 16 parents in randomized blocks
has now been harvested one season. Yield of the nine inbred
lines was 55 percent of that of the 6 varieties. Inbred
lines ranged from 54 to 695 grams per twelve plant plots
and varieties from 588 to 1008. The loss in vigor was at
least to some extent recovered in the crosses. All crosses
ranged from 80 to 260 percent of their higher yielding parent
and 127 to 398% of the averages of both parents. These percentages
were definitely higher for inbred line crosses than they
were for variety by inbred crosses. Inbreds being low in
vigor is an apparent reason. The preliminary results based
on only one year's yield data do not show promise for hybrid
vigor to improve commercial asparagus. Two of the 9 inbred
crosses were approximately equal to the best of the 6 commercial
varieties for both average yield and average spear size;
but none of them can be considered as definitely superior
at this state of testing.
Uniformly large spears with high yielding ability is a
type hoped for. Uniformity was evaluated by diameter of
stalks taken during the first growing season. Coefficients
of variability based on single plant data are a measure
of uniformity. Coefficients of variability based on single
plant data are a measure of uniformity. Inbred lines should
be more uniform and should produce more uniformity in their
crosses due to a greater degree of homozygosity. The coefficients
of variability however, do not support of this expectation.
Some lines were more uniform than others but no relationship
to inbreeding is apparent. It seems probable therefore that
environment was responsible for much of the variation in
stalk diameter. Several other measurements of vigor give
approximately the same indications. Tentative conclusions
at this time are that inbreeding reduces vigor but vigor
is recovered in crosses. Hybrid vigor therefore occurs but
so far the tests give no indication that inbred crosses
will prove superior either in vigor or uniformity to good
open pollinated varieties.
2. Polyploidy in Cucumis sativus L.
J.L. Bowers
University of Arkansas, Fayetteville, Ark.
Seed of a gynoecious cucumber breeding line in the cracked
seed coat stage were soaked in 2 per cent colchicine solution
for a 4 1/2 hour period. In addition to this procedure for
including polyploidy, a group of seedlings growing in total
darkness were treated by placing one drop of the .2 per
cent colchicine solution on the growing point each day for
a period of ten days. Tetraploid plants have been obtained
by following both these procedures.
The tetraploid plants of the gynoecious line (Gy 34) have
been selfed out twice and the progeny have exhibited very
low fertility. The 4x plants were sprayed with gibrelate
"400" solution 1500 ppm, at weekly intervals.
The first spray was applied when the first true leaf was
half unfurled, and four spray applications were made. Excellent
male flower production was obtained, and most flowers produced
an abundance of pollen. The pollen grain from tetraploid
plants were about 6-8 microns larger in diameter than those
from diploid plants. Although we did not have the diploid
plants of line Gy 34 from comparison with the tetraploid
Gy 34 on the basis of male flower development, it appeared
that the gibrelate "400" treated tetraploids developed
more male flowers. The non-sprayed tetraploid plants did
not develop any male flowers and this has been typical for
the diploid form of Gy 34 when it is not sprayed.
Seed production records have been kept for individual plants
of the tetraploid group. There does appear to be some variation
in seed production between different plants and an effort
will be made to select for higher fertility.
3. A Radiation-Induced Seedling Marker Gene for Cucumbers
R.W. Robinson and W. Mishanec
New York State Agricultural Experiment Station, Geneva
A mutant cucumber plant in the R2 generation
following seed treatment with thermal neutrons was first
noticed because of the glossy appearance of its foliage.
The mutant lacked epidermal hairs on its foliage and spines
on its fruit. It appears useful as a seedling marker, since
mutant plants are easily classified in the first true leaf
stage and have been good vigor and fertility. It is inherited
as a monogenic recessive, designated glabrous (gl)
and its linked with the yellow cotyledon (yc) gene.
4. Bush Cucurbita moschata
E.M. Meader and Lib Hung
Department of Horticulture, University of New Hampshire,
Durham, N.H.
Spring of 1959, seeds of Cucurbita moschata labeled:
F3 bush BX60, and with notes on the packet "Short
internodes - very small plant- many pistillate flowers but
few corollas open normally - have failed to correct this
fault. Bred here. M. Hardin were received from the late
Mr. Hardin, Geary, Oklahoma. When some of these seeds were
grown in the field at Durham, only normal vines were observed.
The last three seeds of Hardin's F3 bush BX60
were planted in the greenhouse in the spring of 1962 and
selfed seeds were saved from one plant after a cooking test
had been made of the mature fruits. This plant was not
bush and the fruit was not oblate, thick-walled pumpkin
rated of good quality.
The selfed seeds of F3 bush BX60 - 1 in 1963
gave in the filed 31 light-green colored, viney plants and
15 dark-green bush plants. segregation was in a 2:1 ratio.
As noted b Hardin, the bush plants produced abnormal flowers.
Unusually large ovaries developed below the closed corollas,
some being 6 inches long and 2 inches in diameter. When
the closed corollas were torn open (they never opened normally)
and self-pollinations were made, some large fruits resulted.
All proved to be void of seeds. Pollen from the bush plants
seemed normal. Some pollen was used to pollinated C.
mixta (P. I. 165558). Ample amounts of plump seeds
were obtained from this cross.
It is of interest that O.H. Pearson, S.R.S., Hollister,
California, who saw the bush plants of C. moschatain
the filed at Durham in August, said that he had somewhat
similar material at one time but failed to maintain the
character. Hardin's bush character in C. moschata
has not been lost yet, as it is being carried as a recessive
in the remnant (50 seeds) of NH #F3 bush BX60-1
and in the hybrid with C. mixta. It is doubtful
if the parents that gave Hardin's bush character in C.
moschata can ever be ascertained. Similar to the bush
character in C. maxima late in the growing season
the bush C. moschata tends to make longer internodes
so that a short vine ( 5 to 6 feet) results.
5. Short Internodes and Raceme Type Baby Lima Beans
R. E Wester and E M. Rahn
U.S. Department of Agriculture, Beltsville, Maryland
A cooperative project between the Delaware Agricultural
Experiment Station and the U.S.D.A. was started in 1963
to develop a baby lima bean variety with short internodes
and racemes to replace Thaxter with long internodes and
racemes. One hundred lines were tested in 1963. Field selections
were made from one line that had the above characters. These
were grown at Beltsville during 1963-64 winter and will
be further tested at Georgetown, Delaware, with other lines
that have never been tested. These lines are resistant to
downy mildew strains A and B.
Downy mildew strains A a B in 1963 by R. E Wester,
John MacLeod, and J.W. Heuberger. Downy mildew strain A
was recovered from a number of locations a in Mary land,
Delaware, and New Jersey, but strain B was not
during the 1963 season.
6. Dark Red Surface Color Character in Tomato
Paul G. Smith
Department of Vegetable Crops, University of California,
Davis
A dark red surface color character for ripe fruit has been
found in small-fruited cherry type tomato. F1
plants had essentially the same color as the dark parent,
suggesting a single dominant tree. The inheritance will
be studied more completely in the summer of 1964.
This character may have value for breeders of market type
tomatoes because of the more attractive appearance as compared
with normal fruit. The deep red color extends only through
the fruit wall and not throughout the fruit.
7. Effect of Hot Weather on Flesh Color of Tomatoes
P.A. Young
Ordinary varieties of tomatoes ripen with prettiest flesh
color at temperatures near 60 to 80° F. Temperatures
near 90 to 95° F. often result in lighter red and more
yellow color. Gulf State Market tomatoes in hot weather
commonly showed soft purple-red blossom-ends before the
hard green tops turned red, making the fruits unmarketable.
Weather often is hot, part of the time in the ripening season
of tomatoes, so we need varieties that develop satisfactory
red color in hot weather. Flesh color was studied in the
tomato variety test in the summer of 1963. The plants were
set in a field on June 3rd and ripened fruits in July and
August when temperatures often were 90 to 95° F. Rutgers
set few fruits in hot weather.
Alpha 88FR tomato produced abundant dark red fruits in
the spring crop but the fruits in the summer crop had pale
pink and white flesh color; it set abundant fruits in hot
weather. In contrast to Alpha 88FR, the new Red Bobs variety
from Canada set abundant fruits with bright red flesh color
in summer weather. Satisfactory red flesh color also developed
in Pinkdeal, Hotset and Early Alberta in hot weather. Thus,
resistance to heat sterility is combined with development
of bright red flesh color in some varieties already. The
problem remains to develop varieties with these virtues
plus the large plants and fruits needed for commercial canning
purposes.
Common varieties of tomatoes less than entirely ripe usually
have white locule walls in the fruits. The sliced tomatoes
are attractive with their contrasting red and white colors.
We should like them that way. However, better color of canned
tomatoes can be attained with fruits that have pink to red
cores and locule walls. This can be improved by crosses
and selections. High Crimson tomatoes need to become very
ripe to develop their superior color, thus being like cannery
varieties.
8. Solving Some Problems for Greenhouse Tomatoes
P.A. Young
Experience with greenhouse tomatoes in 1948 to 1964 indicates
emphasis on some methods for increasing profits and decreasing
losses. Varieties are to be chosen for each area of production.
For example, Tuckcross "O" was unsatisfactory
for winter production at Jacksonville, Texas because the
stems were spindly and the fruits were small. In contrast
at Arlington, Texas where there is more sunlight in winter,
Tuckcross "O" developed thick stems and large
fruits in winter. At Jacksonville, Tuckcross V bore best
in winter.
Flower development and fruit setting are apt to be poor
when light intensities are less than 1000 foot-candles in
daytimes for a week or longer. Such dim light is common
in foggy or stormy weather in November to January at Jacksonville,
Texas so the tomato plants often stopped blooming then.
The Weston Exposure Meter is useful in determining the light
intensity (illuminance) in the tomato greenhouse, as the
meter reading X4 gives foot-candles. Illuminance of 2000
to 5000 foot-candles facilitates fine growth of the plants.
Plans for fertilizing the tomatoes vary with the light available
from week to week. Common tomato varieties presumably are
influenced little by length of day but are greatly influenced
by the total amount of light per day.
Tomato plants for the greenhouse were grown in a mixture
of perlite-peat-sand with abundant commercial fertilizer
in 5 inch flower pots. The fall weather was hot, dry and
windy so the plants were watered abundantly with a garden
hose. Soon the plants began to grow poorly and showed leaf
symptoms indicating either fertilizer excess or deficiency.
A test showed that the mixture in the pots was nearly lacking
in fertilizer so it was necessary to fertilize the plants
through their leaves to save them. The fertilizer had been
leached from the soil in the pots.
