© 1994 Heron Publishing—Victoria, Canada
Somaclonal variation in growth, leaf phenotype and gas exchange characteristics of poplar: utilization of leaf morphotype
analysis as a basis for selection
N. Th. Saieed (1, 2), G. C. Douglas (3) and D. J. Fry (1, 4)
1. Department of Environmental Resource Management, University College, Dublin, Ireland / 2. On leave of absence from the Forestry Department, Mosul University, Iraq / 3. Agriculture and Food Development Authority, Kinsealy Research Centre, Malahide Road, Dublin 17, Ireland / 4. Author to whom correspondence should be addressed / Received December 20, 1991
Summary
Populus hybrid TT32 lines produced from 15 treatment tissue culture regimes exhibited somaclonal variation in morphological and gas
exchange parameters. Within four years of regeneration, discrete lines showing statistically validated superior, or inferior,
growth performance relative to the parental reference clone were identified. Significant differences in the ratio of leaf
length/width between treatment lines provided the earliest reliable indicator of the divergence in overall growth performance.
Despite discernible variation in leaf phenotype among primary regenerants and secondary propagules within individual lines,
the leaf length/width ratio was identified as a potential parameter for predicting growth performance. Its subsequent use
led to the recognition of four distinct leaf morphotypes; cordate, ovate, reniform and oval. Two or more of these morphotypes
were distributed within each of the original 15 treatment lines. Regrouping the data on the basis of leaf morphotype resulted
in a clear segregation of the morphological traits, and revealed differences that were not readily apparent by statistical
analysis based on treatment groups. The demonstration of similar relative performances by individual morphotypes with respect
to a range of growth and gas exchange parameters confirmed that variation in leaf morphology was indicative of differential
photosynthetic performance. Somaclonal variants with a leaf morphology was indicative of differential photosynthetic performance.
Somaclonal variants with a leaf morphotype closest to that of the parental line showed the highest overall potential for selection,
suggesting that the greatest benefits accrue from a minimal disturbance of the parental leaf phenotype.
Keywords:
leaf morphology, Populus, somaclones.
