Íslenskar landbúnaðarrannsóknir - 01.03.1979, Qupperneq 104

102 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
ÍSLENZKT YFIRLIT.
Rannsókn á eiginleikum íslengka hestsins.
ÞORVALDUR ÁRNASON,
II. Kynbótaeinkunn.
Á grundvelli niðurstaðna arfgengis og
fylgnisreikninga, sem lýst var í fyrri grein
þessa greinarflokks, var reiknuð kynbót-
aeinkunn fyrir einstaklingsúrval. Hlut-
fallslegt mikilvægi einstakra eiginleika var
fengið með því að nota margfeldisvægi
dómstiga kynbótahrossa. Kynbótaeink-
unLÍn er þá þannig:
I = 0.481X1 + 0.102X2 + 0.596X3 +
0.589X4 + O+6IX5 + 0.762X6 +
REFERENCES — HEIMILDARRIT:
Árnason, Þorvaldur, 1976: Studies on traits in the
Icelandic riding ponies. Unpublished M.Sc.
thesis, University of Edinburgh, Scotland.
Arnason, Þorvaldur, 1979: Studies on traits in the
Icelandic toelter horses. I. Estimation of some
environmental effects and genetic parameters.
J.Agr. Res. Icel. Vol. 11,1—2:81—92.
Becker, W.A., 1975: Manual of quantitative genet-
ics. Students Book Corporation, N.E. 700 That-
una, Pullman, Washington.
Cunningham, E.P., 1969: The relative eflficiencies of
selection indexes. Acta Agric. scand. 19: 45-48.
Falconer, D.S., 1960: Introduction to quantitative
genetics. Oliver and Boyd, Edinburgh.
Graybill, F.A., 1961: An introduction to linear stat-
istical models. Vol. 1, McGraw Hill Book Co.,
Inc., New York.
Harris, D.L., 1963: The influence of errors of par-
ameter estimation upon index selection. In Stat-
istical Genetics and Plant Breeding. (ed. W.D.
Hanson and H.F. Robinson) p. 491-500. Publ.
982, National Academy of Sciences - National
Research Council, Washington, D.C.
Harris, D.L., 1964: Expected and predicted progress
from index selection involving estimates of pop-
ulation parameters. Biometrics, 20: 46—72.
0.199X7 - 0.163X8 - 0.055X9 -
0.539X10
þar sem Xi ... Xio eru einkunnir fyrir
eiginleika dómstigans í réttri röð.
Leitast var við að reikna kynbótaeink-
unnir fyrir úrval byggt á afkvæmadómum
með misstórum afkvæmahópum, en
niðurstöður urðu sýnilega afar brenglað-
ar. Ástæða þess reyndist sú að erfða fer-
vika/samvika fylkið var ekki jákvætt af-
markað („positive definite“), sem leiddi af
sér tilraunir til andhverfunar á ,,singular“
fylkjum sem engar einstakar andhverfur
hafa. Stungið var upp á leið til lausnar
slíkra vandamála.
Hazel, L.N., 1943: The genetic basis for cunstruct-
ing selection indexes. Genetics, 28: 476-490.
Hazel, L.N. and Lush, J.L. 1942: The efficiency of
three methods of selection. J. Hered., 33:
393-399.
Henderson, C.R., 1963: Selection indexes and expec-
ted genetic advance. In Statistical Genetics and
Plant Breeding. (ed. W.D. Hanson and H.F.
Robinson), p. 141-163, Publ. 982, National Ac-
ademy ofSciences- National Research Council,
Washington, D.C.
Hill, W.G. and Thomþson, R., 1978: Probabilities of
non-positive definite between-group or genetic
covariance matrices. Biometrics, 34: 429-439.
Mao, I.L., 1971: The effect ofparameter estimation
errors on the efficiency of index selection and on
the accuracy of genetic gain prediction. Ph.D.
Thesis, Cornell University, Ithaca, New York.
Pig Industry Develoþment Authority, 1965: Combined
Tesing. Recommendations by the Statistics Sec-
tion for the Selection Index. (Mimeograph) DA
188. Pig Industry Development Authority,
London.
Smith, F.H., 1936: A discriminant function for plant
selection. Ann. of Eugenics. 7: 240-250.
IVilliams, J.S., 1962: The evaluation of a selection
index. Biometrics, 18: 375-393.