On the hybridization and DNA polymorphism in hickory (Carya cathayensis Sarg.)
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Hickory, a nut-producing and wind-pollinated non-timber species narrowly distributed in the region between Zhejiang and Anhui provinces of China, has grown in wild or semi-wild condition for a long time. For no cultivar developed so far under the species, propagation through seeding is mainly adopted in the production. Reciprocal hybridization between hickory and pecan (<i>C. illinoensis</i>) has been conducted since the 1960s and heterosis and a seedling phenotype resembling to the maternal parent have been observed. But analyses of hickory samples from natural forest with such molecular markers as RAPD, ISSR, SRAP, AFLP and SSR have revealed a low DNA polymorphism. What is more, apomixis in hickory has been embryologically confirmed, but found to be distributed unevenly on the chromosomal regions. With ten pairs of SSR primers applicable to both species, we analyzed two populations of the progeny resulting from reciprocal hybridization between hickory and pecan (47 individuals each population) and amplified heterozygous loci were identified, which indicates that hickory and pecan can be reciprocally crossed. Both progeny populations had no significant difference in such parameters as the number of effective alleles (<i>N<sub>e</sub></i>), Shannon information index (<i>I</i>), observed heterozygosity (<i>H<sub>o</sub></i>), expected heterozygosity (<i>He</i>) and unbiased expected heterozygosity (<i>uH<sub>e</sub></i>) (<i>P</i>＞0.05) and the average <i>I</i> of each progeny population was not low (0.511 and 0.496, respectively) although the mean<i> H<sub>e</sub></i> of both populations was similar (0.371 and 0.317, respectively). The analysis of molecular variance showed that 71% of the variation occurred between individuals within the population. Analysis with the Structure software also found each individual of both progeny populations had a relatively low proportion of genome originating from the paternal parent, potentially indicating phenotypic resemblance to its maternal parent. It has been reported that pecan is highly heterozygous, so is hickory from our work.
Keyword: Biodiversity conservation
ID: 3485343