Genetic parameter estimates for growth and form traits in common ash (Fraxinus excelsior, L.) in a breeding seedling orchard at Little Wittenham in England期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

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Genetic parameter estimates for growth and form traits in common ash (Fraxinus excelsior, L.) in a breeding seedling orchard at Little Wittenham in England

Authors:	Weston F Mwase Peter S Savill Gabriel Hemery

Institution:	(1) Department of Forestry and Horticulture, Bunda College of Agriculture, University of Malawi, P.O. Box 219, Lilongwe, Malawi;(2) Oxford Forestry Institute, Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, England, UK;(3) Northmoor Trust, Little Wittenham, Abingdon, Oxford, OX14 4RA, England, UK

Abstract:	Data from a trial of 36 families at Little Wittenham, North Oxford was used to assess growth traits and stem form in common ash (Fraxinus excelsior, L.). The trial followed a design described by Barnes (Silv Genet 44(2–3):81–88, 1995) as the Breeding Seedling Orchard (BSO). The objectives of the study were to determine variation in growth and form traits and estimate genetic parameters of families. Assessments conducted at 3–8 years for height, diameter at breast height (dbh), straightness and forking showed significant differences (P < 0.05) among families with Guys (19), Settrington (34), Overbury (23) and Grimthorpe (36) being the best performers while Coleford (3 and 5) Gwynedd (27) and Bacheiddon (32) were the least performers. At the overall level, the additive genetic coefficient of variation (CV_A) ranged between 10.2 and 12.7% for height and 1.5 and 2.1% for dbh. Height had a high genetic correlation (r_g = 0.85) with dbh whilst forking had low correlation (r_g = 0.25) with height. Estimates of heritability decreased with age from ${\text{h}}^{2}_{{\text{i}}}$ = 0.62 at 3 years to ${\text{h}}^{2}_{{\text{i}}}$ = 0.30 at 8 years for height while values for dbh decreased from ${\text{h}}^{2}_{{\text{i}}}$ = 0.48 at 4 years to ${\text{h}}^{2}_{{\text{i}}}$ = 0.27 at 8 years. Some genetic gains are possible despite the low genetic variation among families; height had the greatest potential of genetic gain (12.5% at 8 years). Results suggest that early selection of superior families of Fraxinus excelsior appears to be feasible and it could be possible to achieve simultaneous improvement in both growth and form.

Keywords:	CV_A Correlations Dbh Forking Genetic gain Height Heritability
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