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The heritability of agronomic characteristics in tall fescue (Festuca arundinacea Schreb.)

by Subhanij, Thiravira

Abstract (Summary)
Three genotypes of tall fescue (Festuca arundinacea Schreb.

cultivar Fawn and four genotypes from the cultivar Fortune were

used as parents to form 15 of a possible 21 single crosses to study

the heritability of certain agronomic characteristics. The Fawn

variety is considered to be tall in growth habit, vigorous and early

in anthesis. The Fortune variety represents germ plasm with a

shorter growth habit, less vigor and later anthesis. Crossing was

accomplished by mutual pollination in the greenhouse during

February 1972.

A greenhouse experiment was started in June 1972 using the

15 single crosses in a randomized block with three replications.

Plants were supplied with one half strength of a modified Hougland's

solution twice weekly until August 3 followed with an application of

the same nutrient solution every two weeks until they were taken to the field for establishment. Greenhouse data were collected on

July 7, August 4 and September 11.

These data indicated that the variation among single crosses

for tiller numbers and dry weight were greater as the plant grew

older. Nutrient stress affected dry matter yield by reducing the

variation and mean performance of the single crosses. Differences

among single crosses for shoot length, tiller number, and plant

spread were still quite evident under the stress conditions.

Shoot length showed significant general combining ability (GCA)

with non significant specific combining ability effects (SCA) on July 7

and September 11. GCA effects for tiller numbers were evident on

August 4 and September 11. Both GCA and SCA effects were significant

for plant spread on September ii. GCA for dry weight were

significant only on July 7. Based on the diallel analysis, additive

gene action was primarily responsible for shoot length, tiller numbers

and dry weight. Both additive and non additive gene action

influenced plant spread.

The field establishment included the 15 single crosses from

greenhouse experiments and the seven parent clones, established in

a randomized block design with three replications. From the diallel

analysis, it was observed that the GCA:SCA mean square for the

characters measured were: plant height (19:1), plant spread (2. 1:1),

anthesis date (3.2:1), panicle number (1.4:1), panicle length(l2:1), number of primary pedicels per panicle (7.4:1), five panicle seed

weight (0. 2:1), seed yield per plant (0. 4:1) and 100 seed weight

(15.1:1).

This indicated that additive gene action was of major importance

in the expression of plant height, number of primary pedicels and 100

seed weight. Non additive gene action was contributed substantially

more to the expression of five panicles seed weight and seed yield.

Both additive and non additive gene action contributed to plant spread

and anthesis. Inferences about gene action for panicle numbers and

panicle length were not as evident. This is because of the low

GCA:SCA ratio, a barely significant GCA for panicle number, and

no significant GCA or SCA for panicle length.

Single cross progeny were superior to mid parent for plant

height (9.27 percent), plant spread (20. 33 percent), anthesis (20.90

percent, which suggested earlier anthesis than mid parent), panicle

number (36. 69 percent), and panicle length (11. 44 percent). No

apparent superiority of single cross progeny over their corresponding

mid parent for number of primary pedicels and 100 seed weight

was observed.

Of all single crosses, only Fawn x Fortune crosses were

inferior to mid parents for five panicle seed weight (65.93 percent)

and seed yield (60. 22 percent). The Fawn x Fortune performance

for both of these characters (0.4062 and 1.23 g per plant,

respectively)was low, The diverse parentage of these crosses

may have resulted in irregular meiotic behavior in the F? which in

turn may have caused inviable gametes to be formed. This sterility

would result in the low seed yields observed. This is a problem that

should be cytologically investigated.

Crosses between diverse germ plasm (Fawn x Fortune crosses)

did result, however, in heterosis for all characteristics except number

of primary pedicels and 100 seed weight. But Fortune x Fortune

crosses, for certain characters such as plant height, plant spread,

panicle numbers, panicle length,exhibited even more heterosis. No

heterosis was observed in the Fawn x Fawn crosses.

Medium to high heritability estimates were observed for 100

seed weight, plant spread, anthesis date, panicle number and panicle

length, while medium to low heritability were observed for panicle

length. Low heritable value was evident for plant height, number of

primary pedicels, five panicle seed weight and seed yield. Heritability

estimates were based on parent progeny relationships involving

all single crosses and mid parents.

The relationships among various plant characteristics and

seed yield was studied. Five panicle seed weight and panicle

numbers were significantly correlated with seed yield. However

there was a non-significant association of panicle length with seed

yield and number of primary pedicels with seed yield.These relationships suggest that higher yielding genotypes

may be identified by observing only few panicles per plants. The

panicle characteristics examined in this study (other than seed weight)

were of little value in identifying high seed yield genotypes, but

panicle seed weight was positively related to plant yield.

Bibliographical Information:

Advisor:Frakes, R. V.; Chilcote, D. O.; Chilcote, W. W.; Crabtree, G. D.; Ullery, C. H.

School:Oregon State University

School Location:USA - Oregon

Source Type:Master's Thesis

Keywords:fescue

ISBN:

Date of Publication:02/27/1974

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