Inheritance of Digestibility and Fiber Content in Alfalfa.

F. Guines, B. Julier, and C. Huyghe

INRA, UGAPF, Lusignan, France

A 7x7 factorial design was used to asses the inheritance of digestibility and fiber content of alfalfa. 7 male and 7 female plants randomly taken from the Flamande population were crossed. The F1 progenies were studied in three locations in France in a randomized block design with three replicates and a total of eight cuts. The enzymatic digestibility, fiber content (NDF: neutral detergent fiber, ADF: acid detergent fiber and ADL: acid detergent lignin) and leaf to stem ratio were predicted by NIRS (Near Infra Red Spectroscopy).The statistical models used for testing the F1 progeny effect and the factorial analysis were respectively: Yijk=µ+Ci+r(C)ij+Gk+GCki+Eijk and Yijkl=µ+Ck+Mi+Fj+MFij+MCik+FCjk+FMCijk+r(c)kl+Eijkl, with µ mean, C: condition effect (one year, one cut, one location), r: replicate effect, G: F1 genotype effect, E: error, M: male effect, F: female effect. G, M and F effects were declared as random effects. Additive and dominance variance based on an autotetraploid model were calculated according to Wricke and Weber (1986): s 2A=2(s 2M+s 2F)-2/3s 2MF and s 2D=6s 2MF. For each character, broad-sense() and narrow-sense () heritabilities were calculated as: h2B=s 2G/(s 2G+s 2GC+s 2E) and h2N=(s 2A+1/3s 2D)/(s 2A+s 2D+s 2E).

Table 1. Estimates of variance components, broad sense heritability () and narrow sense heritability () of quality traits of alfalfa in 8 conditions.

Genotype effect and broad sense heritability

Factorial analysis and narrow sense heritability
 

L/S ratio

0.002*

0.001*

0.013

0.12

0.001*

0.001*

0

0.004

0

0.01

0.29

NDF

0.90*

0.55*

4.02

0.16

0.25*

0.70*

0.07

1.85

0.42

4.52

0.29

ADF

0.67*

0.40*

3.00

0.16

0.21*

0.50*

0.05

1.38

0.3

3.37

0.29

ADL

0.02*

0.02*

0.18

0.10

0.006*

0.019*

0.001

0.05

0.003

0.20

0.20

Enzymatic

solubility

0.58*

0.51*

3.33

0.13

0.19*

0.44*

0.03

1.23

0.20

3.380

0.25

L/S ratio: leaf to stem ratio, NDF: cellulose + hemicellulose + lignin, ADF: cellulose + lignin, ADL: lignin,s 2G: genotype variance, s 2GC: genotype x condition interaction, s 2E: error variance, s 2F: female variance, s 2M: male variance, s 2FM: male x female interaction, s 2A: additive genetic variance, s 2D: dominance genetic variance.

The analysis showed significant F1 genotype effect, condition (location x year x cut) and interaction genotype x condition effects for all quality traits. The error variances were high explaining the relatively low broad-sense heritabilities. The genetic variance for NDF and ADF was high and higher than the interaction genotype x condition variance. The factorial analysis showed significant female and male effects with an higher male effect. The narrow-sense heritability was higher for NDF and ADF than for ADL and enzymatic solubility. The additive variance was higher than the dominance variance for all quality traits meaning that a genetic progress is possible for quality traits.

Reference

Wricke, G. and Weber, W.E. 1986. Quantitative genetics and selection in plant breeding. Walter de Gruyter Publ., Berlin.

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