Optimization of Germinated Conditions for Somatic Embryos in Liriodendron Hybrids

The development of somatic embryos is a key technology in plant breeding. To gain the best cultural conditions,the factors influencing on germination and transplanting survival rate of the somatic embryos in Liriodendron hybrids were optimized,including the development period of somatic embryos,macro-element,Vitamin C,genotypes,plant hormones and transplant medium in this study. The results showed that the optimal development phase of germination was torpedo-shaped embryo,and the base cultural medium of 3/4 MS with vitamin C can keep normal form from somatic embryos. The germination rate of somatic embryo had obvious genotype difference,among which the hybrid 1 × 5002 was the most sensitive( 82. 46%),and the hybrid 1 × 4088 was the most insensitive( 13. 24%). The medium with 0. 1 mg/L of KT + 0. 1 mg/L of IBA can help promote the germination of somatic embryogenesis. In addition,the yellow soil was more suitable than mixed peat soil for transplanting Liriodendron hybrids seedlings. Therefore,the obtainment of the optimal conditions has important guidance for production practices of Liriodendron hybrids.

Mating patterns and pollen dispersal in a Japanese larch(Larix kaempferi) clonal seed orchard： a case study

Pollination dynamics highly determines the genetic quality of seed orchard crops. However, there is less research about the effect of mating patterns on seed productivity of orchard crops. So far, clonal seed orchards have been producing genetically improved seedlings used for most Japanese larch(Larix kaempferi(Lamb.) Carr.) plantations in China. In the present study, a total of 17 highly variable simple sequence repeat(SSR) markers were used for genotyping a progeny trial population consisting of 647 open-pollinated progenies germinated from seeds which were collected from 63 maternal clones with 140 potential paternal clones in a Japanese larch clonal seed orchard in China. Paternity analysis was used in the present case study in order to evaluate the level of paternal gametic contribution, estimate pollen contamination and selfing rates, and investigate pollination patterns,pollen dispersal patterns and the impact of mating patterns on seed productivity of orchard crops. We observed 93.7% of the success rate of the parental assignment, unequal paternal gametic contribution(0–12.4%) with 6.3% of the progenies derived from pollen contamination or unsampled pollen donors, and absence of evidence for selfing. We also found that pollination rate highly depended on the distance between pollen donors and maternal parents, the majority of the identified crossing(65.7%)occurred between clones within a 150-m radius, and large variations in growth performance existed among the paternal halfsiblings. Progeny growth performance(diameter at breast(DBH) and height(HGT)) was measured at Age-20 in order to investigate the impact of mating patterns on timber production of orchard crops. As either the paternal or maternal, two clones(i.e., clones Z38 and Z62) were identified to have produced progenies with higher average stem volume breeding values than that of all of the progenies. Specifically, the genetic gains for volume were 3.53% for the two clones as paternal parents, and 8.26% as the maternal parents at Age-20. Thus, both elite clones were ideal candidates for the construction of next-generation clonal seed orchards due to their synchronous reproductive phenology with greater crossing rate and higher genetic gain. These results improved the pedigree information to provide solid evidence of mating patterns for future design and effective management of seed orchards and for the development of viable long-term breeding strategies for other coniferous species.