- Response to heterosis for plant height, anthesis date, panicle
number, seed yield, and fall vigor rating was determined in a tall.
fescue group selected for diverse morphology, origin, and anthesis
date. Parents, single-cross progeny (SX), and first generation
selfed progeny (S₁) were included in the study.
Each experimental plot consisted of 14 plants spaced three feet
apart in a row with four feet between rows. Plants were established
in the field in September, 1969, in a randomized block design with
four replications. Data were collected during the summer and fall of
Single-cross progeny were superior to parents with the
exception of seed yield, with parents above S₁ progeny except in plant
Single-crosses averaged 15. 36, 2. 60, 28.21, 24. 79, and 23. 04 percent above the mid-parent for plant height, early anthesis date,
panicle number, seed yield, and fall vigor rating respectively.
Single-crosses averaged 5.85 and 10.27 percent above the high-parent
for panicle number and fall vigor rating respectively.
Crosses between maturity groups resulted in the greatest
heterosis above the mid-parent for all characteristics and above the
high-parent for panicle number (117.50 percent of the high-parent).
Early x early single-crosses were tallest (106. 49 percent of the high-parent)
and had the most vegetative vigor (115. 36 percent of the high-parent).
Indications are that crosses between parents of diverse
morphology and origin result in a greater expression of heterosis than
crosses among similar parents. Diverse anthesis date appears to
increase response to heterosis.
Vigor and associations among vigor characteristics were
determined from single-cross and S₁ seed and seedlings. Respiration,
germination, root and shoot growth, rate of growth, and unit growth
characteristics were measured using a Gilson differential respirometer
and a seed germinator.
For most seed and seedling vigor characteristics S₁ 's and SX's
were very similar. Early S₁ and early x early SX groups were
consistently more vigorous than late S₁ and late x late SX groups with
the early x late SX group intermediate between early x early and late x late SX groups for all seedling vigor characteristics.
Root length and vigor index were two of the better indicators of
early seedling vigor, with vigor index favored because it takes less
time to measure and requires less space. Selection on the basis of
vigor index should be an effective laboratory method of screening for
higher seedling vigor in tall fescue.
There was a significant association between most seed and seedling
vigor characteristics in SX's and S₁'s, and most seed and seedling
vigor characteristics were associated with from one to three mature
plant characteristics, most often fall vigor rating.
Three methods of selection for high and low seedling vigor (seed
weight, head selection on shoot length, and emergence from deep
seeding) resulted in small changes in seed weight and vigor index of
Clones from a population with low seed weight and seedling vigor
were self-pollinated and topcrossed to a source with high seed weight
and seedling vigor. Positive associations between topcrosses and S₁'s
for seed weight and vigor index suggests a lack of appreciable
heterosis for these characteristics.
The association of forage and seed yield was studied in duplicate
populations of parents and five progeny groups. These were: first
generation selfed (S₁), open-pollinated OP), polycross (PX), single-cross
(SX), and selfed single-cross (F ). Nurseries were planted in a randomized block design with four replications, with harvests made
during the spring and summer of 1969.
There were significant associations of forage and seed yield in
four progeny groups with no association in parents and polycross
progeny. The highest correlation occurred in the S₁ progeny (r
High forage and seed yields in certain OP, PX, and SX
progenies indicate the possibility of breeding for both characteristics