Genetic variation in stem growth components in white spruce seedlings and its implications to retrospective early selection
2003
Rweyongeza, D.M.,University of Alberta, Edmonton (Canada). Department of Agricultural, Food and Nutrition Science | Yeh, F.C.,University of Alberta, Edmonton (Canada). Department of Renewable Resources | Dhir, N.K.,Alberta Sustainable Resource Development, Edmonton (Canada). Forest Management Branch
We performed statistical and genetic analysis on stem growth components of white spruce greenhouse-grown seedlings to determine: (1) heritability of the second season branch increment (BI), the number of stem units (NSU) and mean stem unit length (MSUL), (2) the relative degree of determination of BI by NSU and MSUL, (3), the potential of BI, NSU and MSUL as early selection indicators for 11-year height. For data in original units, individual-tree heritability (hi**2) for NSU and MSUL was 0.232+/-0.097 and 0.264+/-0.101, respectively. The Corresponding values for heritability of family means (hf**2) were 0.457+/-0.101 and 0.492+/-0.106. Similar estimates were found with transformed data. Path coefficient analysis showed that BI was 58.29 % determined by NSU and 41.71 % by MSUL. We found that selection for MSUL in the greenhouse would yield 47.4 % and 85.1 % of genetic gain expected from direct selection for 11-year height at site A and B, respectively. The corresponding values due to selection for NSU were 19.1 % and -29.0 %. From this work, the following conclusions can be made: (1) variations in NSU and MSUL are equally but independently inherited, (2) although NSU contributed more to BI than MSUL did, both stem components are important if annual height growth is to be maximised, (3) for prediction of advanced-age field height, MSUL is a better indicator than NSU.
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