Mass production of seed by controlled crossing of selected individuals is an increasingly important method of capturing genetic gain from tree breeding. In Eucalyptus the conventional controlled pollination (CP) method requires at least three separate visits to a flower, and seed is correspondingly costly. This paper reports development of a cost-efficient pollination technique referred to as one-stop pollination (OSP) for application in seed orchards of Eucalyptus globulus Labill. in Chile. Emasculation of the flower at anthesis is followed by slicing the stigma and top of the style to provide a site for pollen adherence. Pollen is applied immediately, followed by isolation of the style from contaminating pollen by covering with a section of tubing. It is then not necessary to revisit until capsule harvest. Seed yield per capsule after OSP treatment was equivalent to that achieved by treating flowers with supplementary pollination at the time of natural stigma receptivity. Only 5% of those flowers pollinated at anthesis without style wounding set a capsule, compared with 69% with OSP. Seed yield for OSP averaged 26 seeds per capsule compared with 12 for open-pollinated samples from the same trees. The effect of orchard location on OSP harvest percentage and seed yield was demonstrated. With application of OSP in the environment of the Chilean orchard, we estimate a sevenfold reduction in seed production cost in comparison to conventional pollination techniques.
& Context Tree orientation is controlled by asymmetric mechanical stresses set during wood maturation. The magnitude of maturation stress differs between longitudinal and tangential directions, and between normal and tension woods. & Aims We aimed at evaluating patterns of maturation stress on eucalypt plantation trees and their relation with growth, with a focus on tangential stress evaluation. & Methods Released maturation strains along longitudinal and tangential directions were measured around the circumference of 29 Eucalyptus nitens trees, including both straight and leaning trees. & Results Most trees produced asymmetric patterns of longitudinal maturation strain, but more than half of the maturation strain variability occurred between trees. Many trees produced high longitudinal tensile stress all around their circumference. High longitudinal tensile stress was not systematically associated with the presence of gelatinous layer. The average magnitude of released longitudinal maturation strain was found negatively correlated to the growth rate. A methodology is proposed to ensure reliable evaluation of released maturation strain in both longitudinal and tangential directions. Tangential strain evaluated with this method was lower than previously reported. & Conclusion The stress was always tensile along the longitudinal direction and compressive along the tangential direction, and their respective magnitude was positively correlated. This correlation does not result from a Poisson effect but may be related to the mechanism of maturation stress generation.
Sophora toromiro is an endemic tree of Rapa Nui with religious and cultural relevance that despite being extinct in the wild, still persists in botanical gardens and private collections around the world. The authenticity of some toromiro trees has been questioned because the similarities among hybrid lines leads to misclassification of the species. The conservation program of toromiro has the objective of its reinsertion into Rapa Nui, but it requires the exact genotyping and certification of the selected plants in order to efficiently reintroduce the species. In this study, we present for the first time the complete chloroplast genome of S. toromiro and four other Sophora specimens, which were sequenced de-novo and assembled after mapping the raw reads to a chloroplast database. The length of the chloroplast genomes ranges from 154,239 to 154,473 bp. A total of 130–143 simple sequence repeats (SSR) loci and 577 single nucleotide polymorphisms (SNPs) were identified.
Sophora toromiro (Phil) Skottsb. is a species that has been extinct in its natural habitat Easter Island (Rapa Nui) for over 50 years. However, seed collections carried out before its extinction have allowed its persistence ex-situ in different botanical gardens and private collections around the world. The progenies of these diverse collections have been classified in different lines, most of them exhibiting high similarity as corroborated by molecular markers. In spite of this resemblance observed between the different lines, one of them (Titze) has dissimilar floral elements, thus generating doubts regarding its species classification. The floral elements (wing, standard and keel) belonging to three different S. toromiro lines and two related species were analyzed using geometric morphometrics. This method was applied in order to quantify the floral shape variation of the standard, wing, and keel between the different lines and control species. Geometric morphometrics analyses were able to distinguish the floral elements at both intra (lines) and inter-specific levels. The present results are on line with the cumulative evidence that supports the Titze line as not being a proper member of the S. toromiro species, but probably a hybridization product or even another species of the Edwardsia section. The reintroduction programs of S. toromiro should consider this information when assessing the authenticity and origin of the lines that will be used to repopulate the island.
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