Improvement of Seed Orchard Management Based on Mating System of Cajuputi Trees

Breeding plan of cajuputi in Indonesia is aimed to increase plantation productivity of oil yield and 1.8 cineole content. Seed orchard of cajuputi at Paliyan, Gunungkidul, established using selected and genetically improved materials, has been producing seeds for operational plantation. This seed orchard would perform optimally if the mating systems of all individuals contribute to the inheritance of all genetic potential of the offsprings. Therefore, investigation of the mating systems of cajuputi was indispensible. The study has been carried out on 10 selected mother trees and the 24 offsprings of each mother trees using 8 microsatellite markers of nuclear DNA, namely Hin-2 (100-132 bp), Hin-4 (79-114 bp), Hin-5 (128-148 bp), Hin-7 (136-224 bp), Sal-1 (93-99 bp), Sal-3 (118-219 bp), Xho-1 (96-111 bp) and Xho-4 (150-216 bp), respectively. The result showed relatively high genetic variation of the offspring (HE=0.602, HO=0.594) originated from parent trees in the seed orchard. Parent trees tend to outcross(tm=0.951, ts=0.806), although seeds originated from biparental inbred (tm – ts = 0.145) and correlated paternity(rp=0.098) have also been observed. This genetically viable population could maintain its reproduction fi tness forshort term and adapt to the dynamic environmental changes for long term. Key words: mating system, cajuputi, seed orchard, microsatellite

Low levels of outcrossing in Pinus leucodermis: further evidence in artificial stands

Outcrossing rates were estimated in two artificial stands of Pinus leucodermis, a wind pollinated conifer characterized by a relatively high level of selfing. Multilocus outcrossing rates, estimated by assaying five enzyme loci, were lower than 86% in the two stands, using both dormant and germinating seeds, and not different from those observed in two natural populations located in the same area. The lack of relevant differences between single-locus minimum variance means and the multilocus outcrossing rate estimates observed in both the artificial stands indicates that most of the apparent selfing is probably caused by actual self-fertilization. The presence of a high level of self-fertilization in this species seems confirmed also in artificial stands, where the density is higher and neighbourhood structure should be less pronounced. The high level of self-fertilization found in P. leucodermis, which is probably due to the presence of a reduced number of recessive embryonic lethals as a consequence of genetic drift, could represent a selective advantage for this pioneering and precocius species. Key words: mating system, outcrossing rates, artificial stands, Pinus leucodermis.

Effects of stand density on outcrossing rate in two Norway spruce (Picea abies) populations

The mating system was investigated in two neighbouring Norway spruce (Picea abies (L.) Karst.) populations with markedly different stand densities. The amount of outcrossing was estimated using open-pollinated array data at four enzyme loci. Multilocus estimates of the proportion of viable progeny owing to outcrossing were 0.956 and 0.955 for the low- and high-density stand, respectively, indicating that the large reduction in stand density had no impact on outcrossing rates. The multilocus estimate was higher than the mean single-locus estimate only for the low-density stand. The lowering of the mean estimate in the low-density stand is probably a consequence of the clustering of related individuals. The regression of pollen allele frequencies on ovule genotype, which is a direct measure of the effective selfing caused by consanguineous matings, had a significant coefficient for the low-density stand and a nonsignificant one for the high-density stand. This obvservation confirms that the major effect of low-stand density in Norway spruce is the occurrence of consanguineous matings. Key words: mating system, outcrossing rate, inbreeding, Norway spruce, stand density.