Southern Forests: a Journal of Forest Science

Changes in anatomical characteristics of Falcataria moluccana wood due to Uromycladium tepperianum infection

2024-12-26T20:14:23+00:00

Serious problems have occurred on Falcataria moluccana plantations because of gall rust disease caused by Uromycladium tepperianum. The disease inhibits tree growth, reduces wood quality, and can cause tree mortality. The presence of galls is a notable symptom of this disease. The study aimed to investigate the anatomy of the galls and the changes in wood anatomical characteristics of F. moluccana due to the infection of U. tepperianum. Wood blocks containing outer bark, cambium and xylem with different levels of severity of gall rust attack were removed from the main stem of F. moluccana trees. Microscopic observations were conducted to observe the anatomical characteristics of the galls, affected wood and healthy wood. The results showed that the anatomy of galls was different from that of affected wood or healthy wood. The percentage of vessel area, diameter of vessel, percentage of ray parenchyma and the length of wood fibres were significantly different between normal wood and affected wood. The results could be useful in understanding gall formation and assessing its impact on wood quality.

Changes in protein expression in Acacia mearnsii De Wild (black wattle) as a result of exposure to frost-inducing temperatures

2024-12-26T20:32:21+00:00

Acacia mearnsii De Wild (black wattle) is one of the most important forestry crops in South Africa. The bark of this species contains high-quality tannins, while its wood is used for wood chips, charcoal and mining timber. One of the main problems faced by black wattle farmers is frost damage, thus there is an urgent need to develop frost-tolerant black wattle varieties. A quick method for the screening of frost tolerance variation would be beneficial for black wattle breeders and would result in the need for fewer families to undergo field trials. Frost tolerance in plants is directly related to their ability to undergo cold acclimation in response to changing weather conditions. During the cold acclimation process, many physiological changes occur, including modifications in protein expression. In this study, two-dimensional gel electrophoresis was used to investigate changes in protein expression among 40 black wattle families with varying levels of frost tolerance before and after a cold-stress treatment. The proteomic data generated from this was analysed using multivariate analysis. Six proteins were observed to be upregulated in frosttolerant black wattle families. The proteins were identified and have been previously shown to contribute to the protection of cellular membranes, maintenance of photosynthetic processes and the prevention of protein misfolding and aggregation.

Quantitative genetics and breeding strategies in hybrid populations of Pinus patula × Pinus tecunumanii

2024-12-26T20:40:21+00:00

Forestry companies SAFCOL and Sappi conducted a study in South Africa to examine genetic variation and select improved material in full-sib hybrid families of Pinus patula × Pinus tecunumanii. The results from the study on clonal and seedling hybrid populations of P. patula × P. tecunumanii low-elevation subpopulations (TECL) revealed a significantly larger impact of TECL compared to P. patula. The TECL parents exhibited higher general hybridising ability (GHA) variance for volume gain and modulus of elasticity (MOE). Consequently, future hybrid crosses should focus on increasing the number of TECL parents in the breeding programme to improve these traits. In the hybrid seedling population of P. patula × P. tecunumanii high-elevation subpopulation (TECH), P. patula exerted a substantial influence on volume gain and MOE. However, the TECH parents displayed zero estimates of GHA variance for volume and a low GHA variance for MOE, relative to GHA variance among P. patula parents for MOE. Thus, this study recommends testing more P. patula parents in new intercrosses of this variety to enhance volume and MOE gain.

Early selection for rust resistance in eucalypt progenies and implications for other traits of interest in tree breeding

2024-12-26T22:05:26+00:00

Planting of resistant clones is the main control strategy for rust caused by Austropuccinia psidii on eucalypts in Brazil. Phenotyping for resistance to rust is performed at the last stage of the breeding programme on genetic material preselected for growth and industrial traits, which therefore may include susceptible genotypes. An alternative way to increase the frequency of resistant individuals in the breeding population is to perform resistance phenotyping during the initial stages of the programme. However, the impact of this approach on other characteristics considered as priority in the selection of genetic material should be assessed. In this study, we evaluated whether early selection for resistance to rust influenced total diameter at breast height (DBH), height (TH), average annual increment (IMA) and basic wood density (BWD), which are important selection criteria in eucalypt breeding. For this, a total of 6 703 plants from 70 full-sib progenies of Eucalyptus grandis, E. urophylla and hybrids of these species were phenotyped for rust resistance before transplanting, under controlled conditions, and again at seven months after transplanting, under field conditions and natural infection. Subsequently, the breeding population was evaluated for BWD indirectly through pilodyn penetration at 24 months after planting, and for DBH, TH and MAI at 37 months. Considering the final phenotype, 25.3% individuals were classified as resistant and 74.7% were susceptible to rust. Comparative genetic analyses between resistant and susceptible individuals showed that selection for resistance, performed early, did not influence DBH, TH, MAI or BWD traits. Thus, the early selection of resistant genotypes speeds up the exclusion of susceptible genotypes, saving time and resources in the development of new commercial clones without interfering with other important traits for tree breeding.

Wide variation in aggressiveness and growth in South African Fusarium circinatum isolates with geographical origin as the primary determinant

2024-12-26T22:16:28+00:00

Fusarium circinatum is a globally important fungal pathogen that causes pitch canker on a wide range of Pinus species. In this study, we considered mycelial growth in culture and aggressiveness of a South African population of F. circinatum isolates. The specific aim was to determine how these phenotypes are correlated with one another and other isolate characteristics, including mating type, host species and geographic origin of the isolates. The study involved the selection of 102 isolates of F. circinatum from five provinces of South Africa based on genotype, mating type and original host from which they were isolated, after which pathogenicity tests were carried out on Pinus patula seedlings. Mycelial growth in culture was also determined for all the isolates at three different temperatures. In the pathogenicity tests, most of the isolates produced significant lesions. While seven had low levels of aggressiveness, other isolates tested were as or more aggressive than a standard set of isolates routinely used for resistance/ tolerance screening. Most F. circinatum isolates grew best at 25 °C, followed by growth at 20 °C and 30 °C. A notable correlation between aggressiveness and the geographical origin was identified. Moreover, the study highlighted a moderately positive relationship between the growth rate of F. circinatum isolates and their reported aggressiveness. The extensive data gathered on the aggressiveness of F. circinatum will offer a broad range of isolates for future comparative studies using other genotypes of F. circinatum and will also aid in the consideration of F. circinatum isolates used for tolerance screening studies.

Genetic control of Fusarium circinatum tolerance in Pinus patula × P. tecunumanii hybrid families

2024-12-26T22:34:54+00:00

The pine pitch canker fungus, Fusarium circinatum, has caused large-scale mortality of Pinus patula crops in South African nurseries and high in-field post-planting mortality. Tree breeders have identified selection and breeding of tolerant material as the likely long-term solution to this disease. In this study, the greenhouse artificial inoculation screening method was employed to investigate the genetic control of F. circinatum tolerance in a factorial mating design of Pinus patula × P. tecunumanii low elevation (PPTL) and high elevation (PPTH) hybrid families and their parental species. Results indicated that F. circinatum tolerance is under moderate genetic control (h² between 0.13 and 0.36) as assessed in a hybrid factorial mating design with a large number of PPTL and PPTH families. The PPTL hybrid displayed the highest level of tolerance, followed by pure P. tecunumanii LE, then the PPTH hybrid, pure P. tecunumanii HE and lastly pure P. patula. A general hybridising ability (GHA) and specific hybridising ability (SHA) analysis was also conducted to rank parent families as well as hybrid families. These breeding values can be used to identify superior families for commercial production and further breeding. A poor correlation between frost tolerance and F. circinatum tolerance was also found when compared to a previous frost tolerance study utilising the same hybrid families. The results from this study indicated that it is possible for breeders to cross selected P. patula seed parents with selected P. tecunumanii pollen parents to develop F. circinatum tolerant hybrid families for commercial production.

Strong soil–vegetation relationship in riparian forests of the middle Rio Doce watershed, south-eastern Brazil

2024-12-26T22:46:53+00:00

Phytosociological surveys and soil quality studies are relevant tools for the implementation of restoration programmes. This study aimed to characterise the vegetation of the tree and sapling strata in preserved riparian forests of the middle portion of the Rio Doce watershed in the Atlantic Rain Forest, Brazil. In addition, we tested the association between edaphic factors and the vegetation community. We sampled three sites of the middle sector of the Rio Doce watershed in Itueta (two sites) and Santa Rita do Itueto (one site) municipalities in Minas Gerais, south-eastern Brazil. At each sampling site, we inventoried 15 plots of 100 m² (10 × 10 m) for the tree stratum. Within each plot of the tree stratum we delimited a 25 m² (5 × 5 m) plot, totalling 4 500 m² and 1 125 m² respectively for the tree and sapling strata. We employed co-inertia analysis to test the relationship between soil factors and the plant community and to highlight the taxon– environment relationship. We recorded 157 species belonging to 31 families, with 105 species from 24 families in the tree stratum, and 85 species from 22 families in the sapling stratum. Edaphic factors were highly heterogeneous among plots, although most of the plots presented soils with neutral pH and high fertility (base saturation > 50%). Co-inertia analyses showed highly significant associations between edaphic factors and the plant community, both for the tree (RV = 0.486, p < 0.001) and the sapling strata (RV = 0.692, p < 0.001). We highlighted the existence of a clear edaphic– floristic gradient, with a significant association of certain species with contrasting soil conditions. Knowledge about the association between environmental characteristics and floristic composition can assist in the selection of species with greater chances to establish in specific environmental conditions.

Evidence-based global yield benchmarks in unthinned industrial plantation eucalypts

2024-12-26T20:08:54+00:00

There is increasing global demand for wood and wood products for a growing diversity of applications. Even-aged plantation forests are efficient in providing goods and services from relatively small areas of land. Eucalypt plantations have been an important component of wood supply worldwide and planted area expansion and productivity improvements have increased significantly over three decades, yet the opportunity may still exist for yield improvements per unit of land area. Increases in eucalypt productivity have resulted largely from an extensive network of field trials and studies published by researchers across the world and particularly in Brazil. This study collates eucalypt yield data primarily from studies of planting density and site factors, both as trials and as plantation sample plots. Studies selected for inclusion are those planted with successful genotypes and under conditions of standard silvicultural practice at the time. The final dataset comprises 309 records of eucalypt mean annual increment (MAI) at rotation age from 61 published sources across 129 locations in 18 countries worldwide. The MAI data are used to derive a benchmark eucalypt yield for high, moderate and low site quality in Kӧppen–Geiger climate zones across a stand density gradient from 200 to 2 500 trees ha−1.The benchmark provides a comparison for plantation eucalypt growers to gauge their own productivity. A gap between benchmark and yield flags the opportunity for improvement and provides a focus for strategies to improve yield. Gap analysis can help foster co-operation, shared solutions and technology transfer across geographically separated growers sharing similar climatic conditions. Of particular significance is support for small-scale and medium-scale tree farmers who are becoming increasingly important in the supply chain. In places where expansion of a eucalypt plantation area is contemplated, it is envisaged that the yield benchmark will provide input to the cost benefit, risk analysis and sustainability planning considerations that are essential before planting starts.