Eucalyptus Amplifolia and Corymbia Torelliana in the Southeastern USA: Genetic Improvement and Potential Uses

Eucalyptus amplifolia and Corymbia torelliana genetic improvement has been conducted in the lower southeastern USA by UF and collaborators since 1980. The collective accomplishments in genetic resources and potential commercial uses are summarized. For example, fast-growing, freeze-resilient E. amplifolia seeds are provided by 1st and 2nd generation seedling seed orchards (SSO) and a 2nd generation clonal seed orchard (CSO), while C. torelliana seed are available from 1st and 2nd generation SSOs. Breeding values (BV) have been developed for guiding the deployment of improved genotypes. Collaborative genetic improvement of these species is ongoing, including testing E. amplifolia in 11 countries and development of hybrid clones. Short Rotation Woody Crop (SRWC) systems may increase productivity and extend uses beyond conventional mulchwood to products such as medium density fiberboard (MDF), biochar, and energywood, while other possible applications include honey production, windbreaks, dendroremediation, and carbon sequestration. C. torelliana may be paired with E. grandis in two-row windbreaks to maximum windbreak effectiveness and may sequester as much carbon as E. grandis.

GENETIC SELECTION OF Pinus taeda L. THROUGH MULTI-ENVIRONMENT TRIAL

The aim of this study is to select progenies of Pinus taeda through multi-environmental trial to establish clonal seed orchards and advance breeding–program generations. Progeny test was carried out with 53 open-pollinated families planted in four different locations. The study followed a randomized block statistical design, with seven replications in linear plots planted with six plants each. DBH variable was measured in individuals at the age of nine years. All estimates were carried out in Selegen REML/BLUP® software. Genotype x environment interaction was detected; therefore, it required the definition of two breeding zones to minimize its effects. The genetic basis of the assessed population is restricted. Families were distributed into nine different groups, based on genetic divergence analysis, and grouping through the Tocher method, by using Mahalanobis distances. Based on the results, and by taking into consideration the balance between variability maintenance and genetic gains, it is recommended to establish a clonal seed orchard with 50 selected individuals in the experiment, based on a limited number of individuals per family. Intraspecific crossing between divergent families can also be used to increase heterosis and genetic variability in the assessed population.

Analysis of Growth and Physiological Variations Among Cyclocarya Species of Different Genotypes in a Clonal Seed Orchard

Background: Cyclocarya paliurus (C. paliurus) is a woody species that has many medical benefits to human health. Geographical species has been formed among different natural forests of C. paliurus, but gradually decrease or extinct by human’s excessively exploitation in recent years. So, it is worthy to conserve this native and valuable species in China. Environmental factors affected plant growth, and seed is the only way for breeding offspring among Cyclocarya species, herein, we assess plant growth of six genotypes (FJ, JX, TG, WF, JH, AJ) from 2017 to 2019 year and physiological variations from April to October in 2018 during the construction of a clonal seed orchard.Results: The survival rate of plant reached 100% in a C. paliurus seed orchard. Plant height and basal diameter varied in different genotypes. Plant of six genotypes had different changes in water content and total soluble sugar content from April to October, Ca content reached maximum among the four detected mineral content, four kinds of antioxidant enzyme activity was in order of SOD＞PPO＞POD＞CAT, and the highest content of phytochemical was total flavonoid. Plant growth and physiological changes during growth period was significantly correlated with environment factors by correlation analysis. Conclusions: Plants of ex situ conservation adapted changeable environmental factors by physiological changes and showed the differentiation of plant growth in a clonal seed orchard. This would provide a foundation for ex situ conservation management in Cyclocarya species and selection of suitable cultivation provenance.

Seed productivity and variability of Scots pine (Pinus sylvestris L.) clones of Finnish origin in seed orchard in the central part of Ukraine

Global climate change has mainly impacted the forest ecosystems in Europe. Today, it is not fully understood how these changes will affect the reproductive process of trees on seed orchards. The main aim of the study is to evaluate the growth, condition and reproductive function of Scots pine clones of Finnish origin after moving them to the southern direction of natural distribution area. Variability and seed productivity of 25-year-old clones of Scots pine of Finnish origin in the clonal seed orchard under climatic conditions of the central part of Ukraine (Vinnitsa region) was investigated. Grafted seedlings of Scots pine of Finnish origin were moved southward at a distance of over 1,500 km. Climatic conditions of Vinnytsia region, where the clones were displaced, differed by an increase in the mean and maximum temperatures by 3.3–3.6ºC, as well as an increase in the mean temperatures during the cold period and a rise in the minimum by 2.1–2.3ºC. The climate in the seed orchard location was characterized by the most significant increase in the mean temperatures in April and May (5.3–5.8ºC), which greatly influenced the intensity of the formation of microstrobili and macrostrobili. The ratio of precipitation to the amount of temperatures decreased more than twice. Analysis of the grafted trees’ vitality of Finnish origin and seed progeny of the local population, estimation of their intensity (height, diameter), state (category of the state) and reproductive processes (intensity of formation of microstrobili and cones) was carried out on the clonal seed orchard. In conditions of climate change, most of the clones of Finnish origin were characterized by a higher intensity of flowering compared to the local population. Some clones of Finnish origin (E80 and E729) dominated the local population by the seed yield. According to a comprehensive analysis of vitality, the intensity of growth and reproductive capacity, the best clones of Finnish origin were E80, E1883 and E2254. Low adaptive ability was noted in the clones E2312, K634 and K801. According to the research results, it was found that changes in climatic conditions did not significantly affect the vitality, development and condition of the clones. There was observed intensification of the formation of microstrobili and cones. Seed viability and quality of Scots pine of Finnish origin obtained on seed orchards located in the southern conditions requires further research.

Identification of Pinus sylvestris clones with highest and lowest allelopathic potential

Allelopathy is a kind of interaction between plants in which the inhibitory effect on growth and germination can play an important role during the struggle for existence in interspecific competition. The species (or clone of one species) with a higher allelopathic potential might win the competition and place themselves in a better biosocial position for growth. Also, the clones with a lower allopathic potential might be useful in agroforestry, e.g. as trees useful for shading the crops. The allelopathic potential of Scots pine (Pinus sylvestris L.), the tree species with a wide range of distribution in Europe and of great economic importance, was estimated in this study. To this end, needles from trees growing in a clonal seed orchard were collected and used as a material to obtain water leachates. The leachates were diluted to 25 and 50% and used in allelopathy tests. The differences between potentials of leachates from Scots pine clones to inhibit germination and growth of the test plant (Sinapis alba L. cv. Borowska) were assessed. The clones 1702 and 1703 were characterized as highly allelopathic, with the potential confirmed in two independent allelopathic tests. The clones 355 and 2209 were characterized as clones with a moderate allopathic potential. The possibility of selecting clones with the known allelopathic potential for the successful use in forestry was discussed.

Seed Germination Variation among Crop Years from a Pinus sylvestris Clonal Seed Orchard

Maternal effects were assessed by germinating seeds sourced over multiple years from the same cloned mother trees, comparing germination capacity and rate between crop years. The relationships between climatic variables, seed characteristics and germination capacity were determined, and thermal time parameters were used to predict seed dormancy release and germination under the climatic conditions in the year after seed collection. There were significant differences in seed weight (P < 0.05), seed length and embryo occupancy (both P < 0.001) among crop years. Temperature during the seed development period explained 70% of the variation in seed weight and 63% of the variation in embryo occupancy. Germination capacity was significantly (P <0.001) different among crop years, among temperatures and among chilling durations, and thermal time requirements for germination increased from older (2007) to younger (2012) seeds. The mean base temperature without chilling was 7.1°C, while after chilling it was 4.6°C and 3.6°C for four and eight weeks chilling respectively. The mean thermal time to 50% germination without chilling was 135.1°Cd, while after chilling it was 118.3°Cd and 154.0°Cd for four and eight weeks chilling respectively. This experiment demonstrates that year-to-year differences in the environment experienced by mother trees during seed maturation can affect seed germination characteristics.