Sang-Urk Han

Genetic Gain and Diversity under Different Selection Methods in a Breeding Seed Orchard of Quercus serrata

Abstract Genetic gain and diversity were estimated in a 13- year old Quercus serrata breeding seed orchard under three selection (rouging) methods. The selections were based on individual selection, family selection, and family plus within family selection. Genetic gain was for stem volume and gene diversity was estimated by status number concept. Both estimated genetic gain and gene diversity were compared to those before selection and among selection scenarios. Estimated genetic gain for tree volume ranged from 4.0% to 9.1% for three selection methods under 50% selection intensity. Individual selection was better than family selection for retaining higher genetic gain and status number. Family plus within family selection was the best selection method, while individual selection was more efficient at the strong selection intensity. An optimal point, which maximized gain and diversity, was occurred at 50% selection intensity that would be applied for genetic thinning in the breeding seed orchard of Quercus serrata. The effect of genetic relatedness among families and possible pollen contamination on both genetic gain and gene diversity, although were not studied but their impact, are discussed. The selection method and intensity level applied should be chosen after careful consideration of the impacts on both genetic gain and diversity for seeds produced from the seed orchard.

Comparison in disease development and gas exchange rate of Pinus densiflora seedlings artificially inoculated with Bursaphelenchus xylophilus and B. mucronatus

Four‐year‐old seedlings of Pinus densiflora were inoculated with a suspension of B. xylophilus, or B. mucronatus adjusted to 3,000 nematodes per 50 μL sterilized distilled water in a greenhouse on July 21, 2008 to evaluate initial symptom development and the changes of gas exchange rate. B. xylophilus and B. mucronatus were distinguished by four restriction enzymes except Rsa I, and the result of ITS‐RFLP of B. xylophilus used in this experiment was completely matched to that of pine wood nematode reported previously. Needle dehydration and subsequent yellowing were observed in all seedlings inoculated with B. xylophilus isolate while the appearance of the seedlings was normal in all seedlings inoculated with B. mucronatus and control. Needle dehydration was observed in most seedlings inoculated with B. xylophilus between 2 and 3 weeks after inoculation. In seedlings inoculated with B. xylophilus, continuous decrease in photosynthetic rate was observed after 6 days of inoculation. Photosynthetic rate decreased more markedly after 12 days of inoculation when external symptoms appeared in most seedlings, and ceased almost completely 19 days after inoculation. Photosynthetic decline in seedlings inoculated with B. mucronatus was only observed at 19 days after inoculation but recovered above control level after 25 days of inoculation. We found that disease development and the changes of gas exchange rate in the seedlings of Pinus densiflora inoculated with B. xylophilus were not observed on those inoculated with B. mucronatus.

Assessment of Pathogenic Variation against Pitch Canker Pathogen, Fusarium circinatum in Pinus thunbergii and Responses of Natural Selection Pinus × rigitaeda to Branch Inoculation in a Seed Orchard

Southern Forest Research Center, Korea Forest Research Institute, Jinju 660-300, Korea(Received on April 12, 2010; Accepted on September 18, 2010)A half-sib family of two 4-year-old seedlings of Pinus×rigitaeda was inoculated with each of 20 Pinus thunbergiiisolates of Fusarium circinatum (syn. Fusarium sub-glutinans f. sp. pini) from two pitch canker damagedsites in Jeju Island, South Korea. Initial symptoms ofneedle damages were visible on most of the seedlings at18 days after inoculation. The 20 tested isolates were notsignificantly different in virulence, based on lesionlengths at the site of inoculation (P = 0.217). The mostvirulent 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 inoculationexcept two seedlings inoculated with each of isolates FS-2 and FS-13, respectively. Using the FT-7, 38-year-old 11P. × rigitaeda trees, which were survived from a seedorchard severely damaged by pitch canker, were ino-culated on branches in the seed orchard in Jeju Islandto assess differences in susceptibility to pitch canker.The 11 trees differed significantly (P < 0.001) in suscep-tibility to F. circinatum based on average lesion lengthsmeasured 56 days after inoculation. It is possible thatinduced resistance contributed to their capacity to limitlesion development. The susceptibility of natural selec-tion P. × rigitaeda trees are more likely affected by inter-action with F. circinatum rather than environmentalconditions. Keywords : Fusarium circinatum, Natural selection, Pinusthunbergii, Pinus × rigitaeda, SusceptibilityPitch canker is a serious disease of pines, which is causedby the fungus Fusarium circinatum Nirenberg & O’Donnell(syn. Fusarium subglutinans f. sp. pini; telemorph: Giberellacircinatum Nirenberg & O’Donnell) distributed in differentparts of the world (Correll et al., 1991; Dwinell et al., 1985;Gordon et al., 2001; Nirenberg and O’Donnell, 1998).Advanced symptoms of the disease result in crown diebackand resinous cankers on branches and main stems (Storer etal. 2002). Pitch canker was first reported in 1946 on Pinusvirginiana in North Carolina, USA (Hepting and Roth,1946), and it later appeared on Pinus elliottii in Florida,Pinus taeda in Mississippi, and on Pinus radiata inCalifornia where it has caused a significant epidemic in itsnative range (Dwinell and Phelps, 1977; Gordon et al.,2001; Storer et al., 1997). The pathogen is also found inJapan (Kobayashi and Muramoto, 1989), South Africa(Viljoen et al., 1994), Mexico (Guerra-Santos, 1999), SouthKorea (Lee et al., 2000), Chile (Wingfield et al., 2002),Spain (Landeras et al., 2005), and was recently reportedfrom Italy (Carlucci et al., 2007). In South Korea, pitch canker was first noticed as a causeof branch dieback on the exotic species Pinus rigida Mill.in Incheon city in the mid-1990s. Pitch canker may bealleged to have introduced into South Korea through tworoutes: one from the USA to Incheon city and the otherfrom Japan to Jeju Island. The disease has caused a seriousdamage mostly on three-needle pines, P. rigida and P. ×rigitaeda in the southwestern part of the Korean peninsulaand Jeju Island. Most infections appear to result fromweather-related wounds from wind that serves as entrypoints of micro- or macro-conidia. The seed orchards of P. rigida and P. × rigitaeda in JejuIsland have been damaged by pitch canker for about tenyears perhaps because of warm temperature and geographiclocation near to Japan where the disease has been establish-ed since the late 1980s (Kobayashi and Muramoto, 1989;Woo et al., 2005). Recently, the disease occurred moreoften on sapling stands of a native two-needle pine P.thunbergii on the roadside and a golf course in Jeju Island.The isolates of F. circinatum obtained from different pinehosts, for example, P. nigra, P. pinaster, P. sylvestris, and P.radiata in Spain (Perez-Sierra et al., 2007) and P. taeda, andP. elliottii in USA (Hodge and Dvorak, 2007), were testedfor virulence. However, virulence to P. thunbergii isolatesof F. circinatum has not been reported previously.Phenotypes of relatively resistant pines are characterizedby a reduced rate of lesion development and thus less

Genetic Gain and Diversity of Orchard Crops Under Alternative Management Options in a Clonal Seed Orchard of Pinus thunbergii

Abstract Genetic gain and diversity, expressed by status number, of seed crops from a clonal seed orchard of Pinus thunbergii were estimated considering selection, fertility variation and pollen contamination, and compared for different management alternatives (selective harvest, genetic thinning and combination of both options). Management variables included the proportion of clones left after selective harvest and/or genetic thinning. The impact on genetic gain and diversity of seed crops was quantified as a function of the quantity and quality of gene flow from outside the seed orchard. Genetic gain varied with the proportion of selected or thinned clones. Genetic thinning by means of truncation selection of clones resulted in a large decrease in status number, which was accompanied by greater genetic gain than achieved by selective harvest alone. As expected, gene flow from outside the seed orchard greatly increased status number of the seed crop at higher rates of pollen contamination under all management options. The formulae and results of the present study could be used for identifying favorable selection intensity and alternatives for orchard management.

Estimation of genetic gain and diversity under various genetic thinning scenarios in a breeding seed orchard of Quercus acutissima

Genetic gain and diversity were estimated based on three simulated thinning scenarios at various thinning intensities in a breeding seed orchard of Quercus acutissima. The seed orchard was composed of 32 families with 744 individual trees with volume at age 15. The three thinning scenarios were individual thinning (IT) which thinning was based on the individual performance, family thinning (FT) with the removal of inferior families regardless of individual performance, and family + within family thinning (FWF) with family first and then individual from inferior families. The genetic gain was estimated based on stem volume. Expected genetic gain (volume at age 15) under IT was higher than FT and FWF at all thinning intensities. The FWF provided higher genetic gain than FT but lower than IT. The FT gave the lowest genetic gain compared to the other thinning scenarios at all thinning intensities. The loss of gene diversity (GD), estimated by coancestry and family size, was higher under FWF and lower under FT at moderate thinning intensities. The study showed that genetic gain estimation and GD loss were inversely coupled. The IT gave highest genetic gain but lowest GD at the highest thinning intensity.

A Comparison in Growth and Water Use Efficiency between Superior and Inferior Families from Open-Pollinated Progenies of Pinus densiflora under Different Environmental Conditions

To understand the relationship of growth and water use efficiency (WUE) between superior and inferior families from open-pollinated progenies of P. densiflora, two families (one superior and one inferior families) in two open-pollinated progeny test sites were selected using volume growth at 26 years. And we compared environmental factors and WUE which was calculated from measured δ 13 C in the wood. The δ 13 C change during the last 20 years showed steady decrease and same pattern as WUE in the fertile site, while there was an inverse relationship between δ 13 C and WUE in poor site, indicating an interaction between gene and environment. The superior family showed higher WUE than inferior family in poor site, indicating efficient stomatal control of the former under water stress. Water use efficiency calculated by carbon isotope composition can be used as a selection criterion for drought tolerance families in openpollinated progenies of P. densiflora.

Component Analysis of Acorns of Quercus mongolica and Quercus Variabilis

To compare seed components of plus trees, seed powder ground after seedcoat removal was analyzed for two oak species, i. e., Quercus monglica (white oak) and Quercus variabilis (red oak), which are typical oak trees in Korea but have different fruiting characteristics. Thus we aimed at analyzing and comparing many ingredients including minerals, sugars, etc. Two species were similar to each other in the content of water, crude ash, crude protein and carbohydrates, but crude lipid content in Q. variabilis was 2.5 times higher than that in Q. mongolica. Crude proteins of Clone 124 was 1.5 times higher than that of Clone 75 in Q. mongolica. Crude lipid content showed the highest value in Clone 0511 of Q. variabilis, and more phosphate and iron was found in Q. monglica than in Q. variabilis. Glucose showed 85.4% and 88.3% on average of the total monosacchrides in two species, and galactose and arabinose were also found. In the content of phosphate, iron, and crude lipid, differences were found between two species and among clones of two species.

Effects of Fusarium circinatum on Disease Development and Gas Exchange in the Seedlings of Pinus spp.

Department of Environmental Horticulture, University of Seoul, Seoul 130-743, Korea (Received on June 6, 2011; Revised on August 23, 2011; Accepted on August 23, 2011)Four-year-old seedlings of Pinus thunbergii, Pinus densiflora and Pinus rigida were inoculated with Fusariumcircinatum isolate (FT-7), the pitch canker fungus, from P. thunbergii, to evaluate the effects of the pathogenon disease development and gas exchange rate. Needle dehydration was evident on 2 of 10 seedlings of P.thunbergii and P. rigida at 18 and 21 days after inoculation, respectively, while no symptoms were observed inP. densiflora seedlings throughout the experiment. Gas exchange stopped completely in 4 of 5 measuredseedlings of P. thunbergii and 2 of 5 measured seedlings of P. rigida at 25 days after inoculation, and in theremaining 3 seedlings of P. rigida at 39 days after inoculation. Disease development in P. thunbergii seedlingswas faster than that in P. rigida seedlings. By the time, the experiment was ended at 78 days after inoculation,9 of 10 seedlings of P. rigida and 8 of 10 seedlings of P. thunbergii seedlings treated with FT-7 was almost dead,but all seedlings of P. densiflora were still healthy. We suggest that P. densiflora is resistant to F. circinatum inthe current study, and gas exchange rate of the species after inoculation does not differ significantly comparedto that of untreated control. Keywords : Fusarium circinatum, Gas exchange, Inoculation, Pitch canker