_B and
_W) were calculated. Broad-sense heritability was calculated as (
_B +
_W)/(
_B +
_W +
_R).Within and between-cultivar genetic variation for alfalfa digestibility
Bernadette Julier, Christian Huyghe and Christian Ecalle
INRA, Station d’Amélioration des Plantes Fourragères,
F - 86 600 Lusignan, France
The genetic structure (synthetic) of alfalfa varieties and the tetraploidy of the species can generate a large within-variety variation. We compared within-variety and between-variety variation for digestibility and fiber contents on 11 varieties. From 7 to 20 plants per variety were cloned in 15 cuttings, and planted in 1995 in 5-plant-plots in a 3 block design. Space between plants was 10 cm in both directions. Three harvests were made in 1996: 30 May, 04 July, 10 October. Each plot was cut, and forage was dried, weighed, and analyzed for enzymatic digestibility and fiber contents (NDF, ADF, ADL), by prediction with NIRS.
In each cut, analysis of variance was performed with block effect (fixed), variety and plant within variety effects (random). Variety effect represents between-variety variation, and plant within variety effect represents within-variety variation. Variances of random effects (
_B and
_W) were calculated. Broad-sense heritability was calculated as (
_B +
_W)/(
_B +
_W +
_R).
All effects were highly significant for all traits. Within and between-variety variances are presented in table 1. Large within-variety variances existed for digestibility and fiber contents in each cut, similar or larger than between-variety variances. Within-variety variance for forage yield was much larger than between-variety variance.
Breeding for a higher digestibility in alfalfa should take into account within-variety variation, in addition to between-variety variation. Breeding schemes must be accordingly adapted.
Table 1. Within and between-variety variances and heritabilities for digestibility (Dig), fiber contents (NDF and ADL) and forage yield, in three cuts on alfalfa.
|
Cut of 30-05-1996 |
Cut of 04-07-1996 |
Cut of 10-10-1996 |
||||||||||||
|
Dig |
NDF |
ADL |
Yield |
Dig |
NDF |
ADL |
Yield |
Dig |
NDF |
ADL |
Yield |
|||
|
|
0.93 |
1.30 |
0.05 |
2 |
0.88 |
0.86 |
0.04 |
0.02 |
1.35 |
1.59 |
0.10 |
2.0 |
||
|
|
1.78 |
2.55 |
0.12 |
291 |
1.46 |
2.24 |
0.07 |
5.79 |
1.08 |
1.39 |
0.07 |
67.9 |
||
|
h_ |
0.50 |
0.55 |
0.60 |
0.74 |
0.33 |
0.33 |
0.27 |
0.68 |
0.51 |
0.50 |
0.54 |
0.54 |
||