No abstract

Acorn production varies considerably among individual trees, years, and locations, which directly affect oak regeneration and populations of wildlife species. This study was conducted to estimate the acorn production capacities of trees in a clonal seed orchard (CSO) of Quercus acutissima by analyzing the relationship among morphological characteristics of acorns, growth characteristics of trees, and the number of acorns per tree in 9-year-old and 15-year-old trees, respectively. The age of the tree did not affect individual acorn morphological characteristics (weight, length, and width), but increased the mean acorn yield per tree from 1.26 kg at 9-year-old to 2.71 kg at 15-year-old. The number of acorns per tree showed strong positive correlations (P < 0.0001) with both crown width and crown volume of the tree. According to our equation, it was estimated that the management of tree density (to 180 trees per ha) and crown volume (to 78 m 3) may have the maximum acorn production per ha. Therefore, our results suggested that optimal management of tree density and crown volume may be very effective in increasing the acorn production in CSO of Q. acutissima, which further provides an important initial step in establishing a governmental policy for seedling supply plans.

A half-sib family of two 4-year-old seedlings of Pinus × rigitaeda was inoculated with each of 20 Pinus thunbergii isolates of Fusarium circinatum (syn. Fusarium subglutinans f. sp. pini) from two pitch canker damaged sites in Jeju Island, South Korea. Initial symptoms of needle damages were visible on most of the seedlings at 18 days after inoculation. The 20 tested isolates were not significantly different in virulence, based on lesion lengths at the site of inoculation (P = 0.217). The most virulent isolate FT-7 showed the longest lesion length. Some seedlings began to die 46 days after inoculation. All seedlings were dead by 68 days after inoculation except two seedlings inoculated with each of isolates FS-2 and FS-13, respectively. Using the FT-7, 38-year-old 11 P. × rigitaeda trees, which were survived from a seed orchard severely damaged by pitch canker, were inoculated on branches in the seed orchard in Jeju Island to assess differences in susceptibility to pitch canker. The 11 trees differed significantly (P < 0.001) in susceptibility to F. circinatum based on average lesion lengths measured 56 days after inoculation. It is possible that induced resistance contributed to their capacity to limit lesion development. The susceptibility of natural selection P. × rigitaeda trees are more likely affected by interaction with F. circinatum rather than environmental conditions.

Nutritional composition, including total phenolics, tannins and nutrient components, of acorns of Q. actissima, Q. serrata, Q. variabilis and Q. mongolica were analyzed. Acorns were collected from each tree species, which were grown in a seed orchard. Contents of both total phenolics and tannins in acorns of Q. serrata were higher than those of Q. actissima (p < 0.05). Interestingly, Q. serrata contained the highest amount of water soluble tannins (71 ㎎/g dw) and the lowest levels of water insoluble tannins (8.1 ㎎/g dw) among 4 oak species, resulting that acorns of Q. serrata had the lowest proportion of insoluble tannins. Among 4 oak species tested, Q. mongolicav acorns contained the highest levels of both total dietary fiber (TDF) and ascorbic acid, while the content of beta-carotene in Q. mongolicav was 52-fold lower than that in Q. variabilis (520 ㎍/100 g). Our result showed that nutritional composition of acoms was significantly different between oak species, indicating that tastes or nutritional values might be different as well among major oak species in Korea.

In order to identify major metabolic components involved in the regulation of superior clonal seedling's growth of Populus davidiana, we compared various clonal growth parameters (total dry weight, stem dry weight, and leaf dry weight) with the levels of metabolites in either leaf or stem of the corresponding rooted cutting seedlings. In leaf tissues, the contents of sugars, including glucose, sucrose, and inositol were significantly correlated with stem dry weight. In contrast, the levels of amino acids in stems, glutamic acid, alanine, and threonine, were correlated with leaf dry weight. Leaf tissues of superior clones contained sugars at least 1.3-fold higher than regular clones, while stem tissues accumulated 1.2-fold higher levels of amino acids compared to regular clones. In addition, superior clones accumulated higher amount of metabolites in tissue-dependent manner; i.e. rythronic acid, malic acid, and petanedioic acid in leaves, and succinic and maleic acid in stems. In conclusion, our results showed that clonal growth performance of P. davidiana was correlated with different types of metabolites in tissue-dependent manner, suggesting that tissue-dependent metabolic profiling might be a prerequisite process for identifying metabolic markers for growth traits of P. davidiana.