Selection Of Superior Trees Research Articles

Needle functional features in contrasting yield phenotypes of slash pine at three locations in southern China

Pine resin, a valuable secondary metabolite, is derived from the products of photosynthesis. Pine needles, serving as the primary organ for photosynthesis and nutrient absorption, facilitate the continuous transport of nutrients to all plant organs through photosynthesis. The functional traits of pine needles exhibit a close association with the photosynthetic efficiency of pine trees, thereby affecting resin yield. The selection of superior trees with high-resin yield (RY) for slash pine (Pinus elliottii Engelm.) faces difficulties due to low selection efficiency and a high false selection rate caused by the absence of reliable indirect selection traits. The objective of this study was to systematically investigate the relationships between slash pine needle functional traits and RY in different regions. Understanding the relationship between functional traits of pine needles and RY is essential for addressing the challenges mentioned above. There were positive correlations between RY and most morphological traits, except for leaf dry matter content (LDMC), which showed a negative correlation. Moreover, low-resin yield trees exhibited lower values for most morphological variables, except for LDMC. High-yield trees exhibited higher stomata number per mm2 (STN), larger stomata diameter (STD) and size (STS), and stomata area per mm2 (STA) across all periods and sites when compared with low-yield individuals. Chloroplast pigment component analysis revealed that high yielders exhibited higher levels of chloroplast a (CHL a) and chloroplast a+b (CHL a+b) compared to low yielders, and positive correlations were found between resin yield and CHL a, chloroplast b (CHL b), and CHL a+b. Higher nutrient contents were observed in high resin yield individuals, and positive correlations were found between resin yield and most nutrients, except for potassium (K). Different needle functional traits exhibited varying periodic patterns of resin production. Most needle functional traits could be useful criteria for evaluating resin production in slash pine breeding programs, which could improve the efficiency of breeding, shorten the breeding cycle, and accelerate the breeding process.

Progeny performance and selection of superior trees within families in Larix olgensis

Larix olgensis is one of the most important timber species in Northeast China. Although L. olgensis seed orchards have been established for many years and some progeny tests have been conducted, studies of progeny performance and the selection of superior families are still lacking. These tests are important for upgrading and improvement of seed orchards. Here, we estimate the genetic variation for major economic traits between families to provide selection materials for the establishment of a second-generation seed orchard. This study examined 71 half-sib families and 2 control families of L. olgensis in the Xiyang forest seed orchard in Yongji County, Northeast China. We measured tree height, diameter at breast height, volume, branch angle, stem straightness degree and crown width of 4-year-old progeny. Genetic parameters for the studied traits were determined, and comprehensive analyses of multiple traits and breeding values were used for selection of superior families and individual trees within families. The results show that all these traits are significantly different (P < 0.01) among families where family variance was greater than environmental variance. The phenotypic and genotypic coefficients of variation ranged from 9.01% to 78.22% and from 1.81% to 39.20%, respectively. The heritability values of families and individual trees ranged from 0.663 to 0.959 and 0.034 to 0.983, respectively. There was a significant positive correlation between investigated traits. Using the multiple-traits comprehensive evaluation method, seven families and 56 superior individual trees were selected. Selection of superior parents using breeding values for timber yield, stem quality and crown width as a proxy for planting density again resulted in the selection of seven superior families. We determined that the comprehensive multiple-traits evaluation approach is effective for selecting superior families and individual trees for the establishment of advanced second generation seed orchards. Families selected based on breeding value may be used as preferred parents for future hybridization breeding.

Genetic diversity in populations of African mahogany (Khaya grandioliola C. DC.) introduced in Brazil.

Given its high-valued wood, the African mahogany (Khaya grandifoliola) has been envisaged as a renewable source of tropical hardwoods in Brazil. However, there are concerns about the hypothesized low diversity among the few K. grandifoliola germplasm sources introduced in the country. Using eight microsatellite markers, we evaluated the genetic diversity and divergence among 53 superior trees selected from three provenances of K. grandifoliola located in the state of Para. These populations are among the oldest plantations (>15 years) in Brazil and, therefore, the country's main seed sources. The average number of alleles per locus was 5.9, expected heterozygosity was moderate (^=0.56) and lower than the high observed heterozygosity (HO=0.74). Therefore, the intrapopulation fixation index was negative (f=-0.31) indicating the possibility that selection of superior trees might have favored heterozygous plants with heterosis. No genetic structure was observed between provenances. The genetic diversity observed within selected trees, with an effective population size (Ne) of 30.4, is comparable to that of natural populations of African and Brazilian mahoganies. Therefore, our results contradict the idea that the genetic diversity of K. grandifoliola introduced in Brazil is low and show that our germplasm can be exploited for breeding purposes.

De novo transcriptome analysis revealed genes involved in flavonoid biosynthesis, transport and regulation in Ginkgo biloba

Ginkgo biloba breeding commonly concentrates on the selection of superior trees that have high flavonoid contents. The flavonoids present in Ginkgo leaves have strong medicinal implications, including anti-dengue, anti-HIV, anticancer, antioxidant and anti-inflammatory properties. Flavonoids play important roles in plant immune responses; however, the molecular mechanisms underlying these interesting responses remain unclear. To obtain a comprehensive understanding, we performed the transcriptome sequencing of Ginkgo with different flavonoid contents. Using an Illumina sequencing platform, we obtained approximately 533,952,528 clean reads. After the sequences were filtered and assembled, the transcriptome data generated 37,625 unigenes, of which 21,472 (57.07%) were successfully annotated in five public databases. Among those genes, many candidates were involved in flavonoid biosynthesis, transport and regulation. Expression profiles were generated, and 457 genes were found to be significantly differentially expressed between the Sample_GB_FH1/2/3 (FH) and Sample_GB_FL1/2/3 (FL) libraries; 246 (53.83%) genes were up-regulated, and 211 (46.17%) were down-regulated. These genes included 14 genes that were enriched in flavonoid transport, 1 MYB gene that encoded a putative transcription factor (TF), and 1 dihydroflavonol reductase (DFR) gene that was involved in the flavonoid pathway. Our results provide comprehensive gene expression information about the Ginkgo transcriptome and can facilitate our understanding of the molecular mechanisms of flavonoid development in Ginkgo. Furthermore, our results markedly expand both the available Ginkgo genetic library and analyses of the species and provide valuable information to the Ginkgo-related pharmaceutical industry.

GENETIC CHARACTERIZATION OF SELECTED MACADAMIA GERMPLASM AND THE IMPLICATIONS ON BREEDING AND CONSERVATION IN KENYA

Macadamia is the most important nut crop in Kenya with an estimated annual production of about 13,510 metric tones with an estimated value of $ 4.8M. The cultivated macadamia is derived from two species; the rough-shelled M. tetraphylla and the smooth shelled M. integrifolia. The Kenyan macadamia industry relies on selection of superior trees from germplasm derived from open-pollinated seeds of the two species planted between 1946 and 1968. Twenty six macadamia accessions sampled from five populations; Bob Harries, Thika, Kirinyaga, Embu and Meru in central and eastern Kenya were analyzed using 110 polymorphic markers of six AFLP primer combinations. The highest percentage of polymorphic loci of 80.0% was observed in the Bob Harries population and the least, 67.3%, from Thika population. Expected heterozygosity was also highest in the Bob Harries population. Phylogenetic analysis based on UPGMA of genetic distances of the five populations revealed the Bob Harries population, the source of macadamia germplasm in Kenya to be closely related only to the Kirinyaga population and distantly related to the Thika population, a preservation block of selected superior germplasm. Cluster analysis based on the 26 accessions did not distinctly separate the species indicating a high level of heterozygosity and genetic mixture of the original gene pool used in Kenya. Analysis of molecular variance further indicated higher genetic variation within the populations, 96%, than among the populations, 4%, and high genetic differentiation among the accessions (theta=0.1909). The results of this study indicate high genetic diversity within the Kenyan macadamia germplasm. This information can immediately be used for enhanced breeding and more effective sampling of populations for conservation.

Variability of Baobab (Adansonia digitata L.) fruits’ physical characteristics and nutrient content in the West African Sahel

The present study was carried out to evaluate variability in fruit characteristics and nutritional quality of Baobab fruits with the aim of providing the background to select trees bearing fruit with desirable characteristics for further utilisation. Vitamin C, total sugar and ash contents were assessed in 178 Baobab fruit samples from 11 sites in Burkina Faso, Mali and Niger. Furthermore the following tree and fruit physical characteristics were recorded: tree height, bark colour, fruit size, pulp weight, seed weight, seed size and pulp colour. The content (mean ± SD) of vitamin C was 4.78 ± 1.02 g kg−1, sugar 514 ± 72 g kg−1 and fruit weight 293 ± 96 g. There was a significant correlation between annual precipitation of the tree population site and vitamin C content but not with sugar content. For sugar, there were significant positive correlations with latitude and longitude. Negative correlations were found between fruit size and both longitude and latitude with smaller fruits generally being found to the north/east. No relation was found between pulp or bark colour and the sugar or vitamin C content. The contents of protein, lipid, carbohydrates, ash and moisture in the seeds ranged from 156 to 159, 143 to 150, 641 to 652, 44 to 49 and 50 to 55.7 g kg−1 respectively. The variation for vitamin C and sugar found within populations is a first indication that valuable gains could be made by selection of superior trees.

THE ‘IDEOTYPE CONCEPT’ AND ITS APPLICATION TO THE SELECTION OF CULTIVARS OF TREES PROVIDING AGROFORESTRY TREE PRODUCTS

ABSTRACT The ideotype concept has been developed and modified for a number of different crops, including forest trees, over the last 35 years. In recent years it has been used in the domestication of agroforestry trees producing Agroforestry Tree Products (AFTPs), as an aid to the multiple-trait selection of superior trees for cultivar development. For example in west and central Africa, ‘fruit’ and ‘kernel’ ideotypes have been identified in lrvingia gabonensis (Bush Mango), based on quantitative characterisation of a number of fruit, nut and kernel traits. Subsequently, recognising the opportunity to develop different markets for the commercially important kernels, the ‘kernel ideotype’ has been subdivided into ‘oil’ and ‘food-thickening’ ideotypes, with options for further subdivision of the latter into ideotypes with either high viscosity or high drawability characteristics. Similar opportunities for the development of single-purpose cultivars from multi-purpose species have been identified in Sclerocarya birrea (Marula), indicating that with increasing information about the variability of AFTP's it is possible to develop a hierarchy of different ideotypes to meet different market opportunities. In S. birrea and Dacryodes edulis, future options exist to extend ideotypes with recognition of the variability in both nutritional and organoleptic qualities. In Australia, a very broad-based ideotype has been developed for the indigenous shrub Kunzea pomifera (Muntries) established on both morphological and physiological traits. Similar approaches are identified for timber trees (e.g. Triplochiton scleroxylon) and those like Santalum austrocaledonicum producing essential oils. It is concluded that ideotypes are a useful tool for visualising and conceptualising how to combine specific rare combinations of visible and invisible traits, aimed at the maximisation of Harvest Index, even when the traits are only weakly related.

DOMESTICATION OF DACRYODES EDULIS: STATE-OF-THE-ART

ABSTRACT Dacryodes edulis is one of the important local fruit tree species of West and Central Africa. This paper reviews the activities of a regional programme to domesticate high-value indigenous fruit trees in the region. This programme is coordinated by the International Centre for Research in Agroforestry (ICRAF) and implemented in Cameroon in collaboration with the Institute of Agricultural Research for Development (IRAD), National Agricultural Extension and Research Programme (PNVRA) agents and NGOs and universities of the region. It is based on a participatory approach to domestication that is in marked contrast to that of food crop domestication under the Green Revolution. The participatory process with farmers started with priority setting between species, progressed to germplasm collection and the establishment of village nurseries for clonal propagation of superior trees, and is currently involved in the selection of superior trees for cultivar development. Work is also in progress on post-harvest processing, market development and the integration of cultivars into agroforestry systems.

Clonal production of tea tree oil high in terpinen-4-ol for use in formulations for the treatment of thrush.

A programme of evaluation and selection of superior trees has led to the vegetative propagation of highly productive clones which produce tea tree oil high in terpinen-4-ol. These will soon provide commercial quantities of a particularly active oil of consistent quality for use in formulations for therapeutic use and in particular for vaginal thrush.

Site-fitness and growth-rate selection of Eucalyptus for biomass production

Abstract Calorespirometric investigation of the metabolism and temperature responses of tissues from Eucalyptus trees can be used to identify plants with superior growth characteristics. Measurements of the metabolic heat rate, rate of CO 2 evolution and O 2 uptake over a range of temperatures are analyzed with a mechanistic model of plant growth to allow early selection of superior trees. This analysis provides information about indexes of genetic characteristics to use in breeding programs and guidelines for matching trees to appropriate climatic conditions. These procedures can enhance the rate of production of biomass by shortening the time to harvest and can increase total economic returns.