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ŠUMARSKI LIST 3-4/2019 str. 29     <-- 29 -->        PDF

In this study we wanted to investigate different parameters providing informations about the efficassy of orchards in producing genetically diverse progeny. We used available inventory data from the company „Croatian Forest” ltd. about the numbers and the age of ramets, as well as evidented crops in two clonal seed orchards (CSOs) of pedunculate oak : CSO „Plešćice” and CSO „Petkovac”.
For CSO „Plešćice” we used inventory data on ramets and crops for the years 2003, 2006, 2007, 2008, 2009 and 2010. and for CSO „Petkovac” for the years 2003, 2004, 2005, 2006, 2008, 2009 and 2010. After 2010 the collection of crops per clone was abandoned in both orchards and we only have data for overall crops in the orchards, until the year 2017.
We calculated the amounts and variability of acorn crops in different years, as well as projections of crops for years 2018 and 2019 based on polynomial regression curves, for all years of evidented crops between years 2003 and 2017. Results are shown in Table 1 and Figures 1 and 2. All other analysis were possible only for years in which crops were collected separately by clones.
We used Pearson’s product-moment and Spearman’s rank correlations to compare distributions of crops per clones between pairs of investigated years, ie. rank of clones in crops production between investigated years. Both correlations were mostly statistically significant with some exceptions (Table 2)
Clone fructification balance described by cummulative curves of acorn production in different years, per percentage of fructifying clones is shown in Figures 3 and 4. Clone balance curves in both orchards show irregular distribution of crops per clones, meaning that in investigated years minority of clones contributed to majority of crops. In conditions of equal clone fertility and maximal sinchronicity of clones, clone’s contribution to crops would be in concordance with the number of its ramets (clone size). Table 3 shows that in CSO Plešćice this correlation was weaker then in CSO Petkovac and, unlike in CSO Petkovac, not significant in all years.
Estimations of effective population sizes and genetic diversity of crops in different years is shown for female clone fertility in Table 4. For calculations of biparental contribution of clones, we used three scenarios encompassing various versions of potential male contribution in effective population sizes. Results are shown in Table 5. The values of effective (status) number of parents (Np) for the first scenario, where male contribution is proportionate to the percentage of clone’s ramets in the overall number of ramets of all clones, is intermediate between the other two scenarios. Lowest effective (status) number of parents (Np) and highest values of group ancestry coefficients (Θ) result from the second scenario where male contribution is equal to female. The highest effective numbers are gained for third scenario where equal male contribution of all clones is presumed.
In both CSOs, Spearman rank correlation between female effective numbers (Nf) and overall crops in different investigated years is statistically significant at p < 0,05 level.
These two CSOs are still filled with new ramets and are still relatively young. With increasing age and ramets’ tree sizes better results in crops and its genetic diversity are expected. For implementation of measures of crops genetic diversity estimations, it is necessary to monitor successively flowering and fructification in the CSOs through the years. The monitoring can then be combined with knowledge on genetic gain and clones’ breeding values obtained through recently established CSOs progeny trials. Therefore, we recommend collection of CSOs’ crops separately by clones, because without expensive molecular analysis it is the only way to get relevant information of individual clones contribution to genetic diversity of crops produced in the CSOs.
Key words: Pedunculate oak, clonal seed orchards, variability of the amounts of crops in different years, genetic diversity of crops, clone fructification balance