There have been frequent reports of more than one strain of the nitrogen-fixing symbiont, Frankia, in the same root nodule of plants in the genus Alnus, but quantitative assessments of their relative contributions have not been made to date. Neither has the diversity of other microbes, having potential functional roles in symbiosis, been systematically evaluated. Alnus rubra root nodule microbiota were studied using Illumina short read sequencing and kmer-based read classification. Single end 76 bp sequencing was done to a median depth of 96 million reads per sample. Reads were assigned to taxa using KrakenUniq, with taxon abundances being estimated using its companion program Bracken. This was the first high resolution study of Alnus root nodules using next generation sequencing (NGS), quantifying multiple Cluster 1 A Frankia strains in single nodules, and in some cases, a Cluster 4 strain. Root nodules were found to contain diverse bacteria, including several genera containing species known to have growth-promoting effects. Evidence was found for partitioning of some bacterial strains in older versus younger lobes.

A foundational study assessed effects of biochemical pathway introduction into poplar to produce eugenol, chavicol, p-anol, isoeugenol and their sequestered storage products, from potentially available substrates, coniferyl and p-coumaryl alcohols. At the onset, it was unknown whether significant carbon flux to monolignols vs. other phenylpropanoid (acetate) pathway metabolites would be kinetically favoured. Various transgenic poplar lines generated eugenol and chavicol glucosides in ca. 0.45% (~0.35 and ~0.1%, respectively) of dry weight foliage tissue in field trials, as well as their corresponding aglycones in trace amounts. There were only traces of any of these metabolites in branch tissues, even after ~4-year field trials. Levels of bioproduct accumulation in foliage plateaued, even at the lowest introduced gene expression levels, suggesting limited monolignol substrate availability. Nevertheless, this level still allows foliage collection for platform chemical production, with the remaining (stem) biomass available for wood, pulp/paper and bioenergy product purposes. Several transformed lines displayed unexpected precocious flowering after 4-year field trial growth. This necessitated terminating (felling) these particular plants, as USDA APHIS prohibits the possibility of their interacting (cross-pollination, etc.) with wild-type (native plant) lines. In future, additional biotechnological approaches can be employed (e.g. gene editing) to produce sterile plant lines, to avoid such complications. While increased gene expression did not increase target bioproduct accumulation, the exciting possibility now exists of significantly increasing their amounts (e.g. 10- to 40-fold plus) in foliage and stems via systematic deployment of numerous 'omics', systems biology, synthetic biology and metabolic flux modelling approaches.

A Gordonia species was cultured from soil of a red alder (Alnus rubra) plant. Here we present the assembled and annotated genome sequence to aid investigations into the potential of this organism as a symbiont and comparative studies of the genus Gordonia.

Fast growing hybrid poplar offers the means for sustainable production of specialty and commodity chemicals, in addition to rapid biomass production for lignocellulosic deconstruction. Herein we describe transformation of fast-growing transgenic hybrid poplar lines to produce 2-phenylethanol, this being an important fragrance, flavor, aroma, and commodity chemical. It is also readily converted into styrene or ethyl benzene, the latter being an important commodity aviation fuel component. Introducing this biochemical pathway into hybrid poplars marks the beginnings of developing a platform for a sustainable chemical delivery system to afford this and other valuable specialty/commodity chemicals at the scale and cost needed. These modified plant lines mainly sequester 2-phenylethanol via carbohydrate and other covalently linked derivatives, thereby providing an additional advantage of effective storage until needed. The future potential of this technology is discussed. MALDI metabolite tissue imaging also established localization of these metabolites in the leaf vasculature.

As South African demand for forest products increases and the land available for production diminishes, concerted efforts are needed to ensure sustainability of forest production. In this article we present some biotechnological approaches that are being investigated or are beginning to became integrated into forest breeding and production programmes in this country.

SYNOPSIS In this investigation, different approaches to the micropropagation of P. patula were attempted and assessed in order to identify the most promising one for commercial application. Of the regenerative routes investigated, viz. axillary bud proliferation (dwarf shoot formation) from juvenile shoots, adventitious bud production and somatic embryogenesis from young seedlings, the first appears to have the most potential in terms of yield, time in culture and availability of explant material.

SYNOPSIS Although genetic variation in wood properties of the three main pine species planted in southern Africa is high, there are important site relationships. Density. A study of density in Pinus patula on 147 sites in the main forestry region showed that wood formed during the early years was influenced mostly by soil properties, whereas wood formed later in the rotation was influenced more by climate. Density gradient was more closely related to site than was inner density, outer density or mean density. Spirality. The same study indicated that spirality decreased as site quality improved. Stem bumps. Nodal swellings in P. patula increase in size with age, affecting strength properties and veneers. Regression models contained site variables strongly related to stem stability and to exposure. It was concluded that bumps are a reaction by the tree to wind-induced stresses at the zones of greatest weakness, viz. at the nodes. Heart shake. Resin-infiltrated heart shakes cause severe losses in the recovery of sawn timber of P. elliottii. Research indicates a role of soil moisture in that the problem is more severe on wet sites. Abnormal wood. The incidence of this defect in P. taeda has resulted in the suspension of planting of this species by many growers. Abnormal wood is similar to compression wood except that it occurs concentrically and has properties which make the wood unutilisable. The problem appears to be strongly related to site quality and soil moisture conditions.

SYNOPSIS Culture conditions for the in vitro propagation of Eucalyptus grandis via somatic embryogenesis were investigated. Induction and maturation of somatic embryos, production of plantlets and hardening-off procedures are detailed.

ABSTRACT Abnormal wood found in mature P. taeda growing in the summer rainfall areas of South Africa can be induced in 15-month-old seedlings. NAA applied in lanolin at the base of the seedling at 1 × 10−5 M and GA3 as a soil drench at 50 mg/ℓ cause the formation of tracheids with distinct helical cavities and no S3 layer.

SYNOPSIS A preliminary anatomical study of abnormal wood formation in P. taeda is discussed. The abnormal wood is found in some trees growing on either level or sloping ground on a variety of soil types. The abnormal wood does not resemble compression wood found in P. taeda as it is found around the entire circumference of the trunk to a height of approximately three metres (although it can be found higher). It shows no early wood or late wood formation, no rudimentary S3 layer, less pitting and pronounced helical cavities. The formation of this abnormal wood seems to be induced by plant growth regulators as it can be found in an area of induced compression wood near a forming bud, where plant growth regulator levels would be higher.