Calycophyllum spruceanum (Benth.) Hook. f. ex Shum. is an important timber tree species in the Peruvian Amazon Basin. Farmers and industry use wood from young trees of this species, so tree breeders should investigate genetic variation in juvenile wood properties to verify whether they can be improved. A previous study using the same provenance/progeny test showed that there was significant genetic variation in tree growth and wood density, that heritability was higher for density than for growth, and that density and growth were positively correlated at 39 months. This paper presents results for wood shrinkage at 39 months and their correlations with tree growth and wood density. Data were collected on thinned trees. Shrinkage values were relatively low when considering wood density of this species. There was significant genetic variation in wood shrinkage due to families within provenances and, in some cases, due to provenances. Heritability estimates were moderately high for linear and volumetric shrinkage (0.37-0.50) and lower for the tangential/radial shrinkage ratio (0.21-0.29) across zones. The genetic correlations that were considered significant ranged from 0.30 to 0.80. In general, genetic correlations suggest that selection of faster-growing trees with higher wood density would result in wood with greater shrinkage and a larger tangential/radial shrinkage ratio.
Tag: genetic variation
Operationalizing an innovative systems approach for breeding agroforestry trees
Key messages
- ‘Systems approach’ plant breeding is about considering multiple global challenges together within the breeding process, to make sustainable progress in addressing those challenges.
- For a systems approach to tree breeding to be successful, the starting point is a broad set of measures that define breeding success. The values applied should extend beyond the traditional ones of productivity and profitability, and embrace resilience, sustainability, nutritional security, local cultures and conservation.
- Policy interventions that encourage a systems approach to tree breeding should provide incentives for tree researchers and breeders to embrace these broader values during tree characterization and genetic improvement. There should also be specific incentives for tree breeders to bring together existing breeding methods in novel ways to ensure that multiple values are addressed.
Evidence of early genetic variation in survival and growth traits of baobab (Adansonia digitata L.)—the way forward for domestication and breeding
The results of a Adansonia digitata provenance and clone trials situated in Sadore (Niger) and Samanko (Mali) indicate genetic variation at both provenance level and among clones. There were significant differences among provenances at Sadore in both survival and height by age 10. Differences in survival were very marked, and suggest that provenances ranged from very poorly- to well-adapted to the Samanko site. However, height was weakly and negatively correlated to survival; possibly the trees may have grown slightly taller because of less competition. West African provenances have a tendency towards faster growth than those of East African origin, and the provenances from drier locations tend to be better adapted. While early variation among 4 year-old clones of leaf development, an important production trait, was indicated, future observations at later ages on fruit traits will be required to make valid selection decisions. The reported 10 year-old provenance variation in tree survival and growth suggest valuable gains could be made by selection of the best provenances. Further trials across a wider range of sites, representative of target planting sites are recommended. Both genebanks contain valuable genetic plant materials worth maintaining for further research and development.
Policy Support for Home Gardens in Vietnam Can Link to Sustainable Development Goals
Despite research evidence on the diverse benefits of home gardens and their potential contributions to multiple sustainable development goals (SDGs), the role of policy towards supporting these contributions remains unclear in developing countries like Vietnam. In this study, we found that 25 out of Vietnam’s 86 key rural development and agricultural policies enacted over the last decade (2010–2021) set specific targets for home gardens. The targets, however, focus strongly on income generation with indicators stipulating e.g., 50–80% of total income from home gardens should be generated by the main product. The policies set no specific target for other potential roles of home gardens beyond the economy of rural households and can exacerbate the widespread transformation of home gardens in Vietnam into farming practices with low crop diversity. The latter potentially limits contributions of home gardens to two (SDG 1, 10) of at least 11 (SDG 1–3, 5, 6, 8, 10–13, 15) of Vietnam’s 17 SDGs. To narrow the gap between research and policy in home garden contributions to Vietnam’s SDGs, we need to better mainstream integrated home garden systems and their diverse benefits, enrich policy targets beyond the income generation, and strengthen coordination among state departments for policy implementation.
Diversity, chemical composition, and domestication potential of allanblackia parviflora a. Chev. in West Africa
Allanblackia parviflora A. Chev. is an indigenous tree species which is found in West African rainforest zones. It is an underutilized fruit tree species that has been targeted for improvement as part of efforts to domesticate high-value indigenous multi-purpose trees for fruit and seed production in Africa. Allanblackia has several benefits, such as providing shade, timber, and medicine; however, the production of edible oil from its seeds is the economically most important use. There is evidence that the Allanblackia seed oil, which is used for cooking, the production of margarine and the manufacturing of ointments and soap, is being developed as a new agri-business in Ghana, Nigeria, Cameroon, and Tanzania. Despite the nutritional and socio-economic importance of A. parviflora, it is still at the early stages of its domestication process. Even though several researchers have explored the biology of this species, there is very limited scientific information available on its morphological and genetic diversity and silvicultural management in West Africa. Therefore, this systematic review presents an up-to-date overview on the uses, seed chemical composition, and morphological and genetic diversity of this fruit tree species, and proposes a way forward for future research towards improvement and domestication. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
‘Systems approach’ plant breeding illustrated by trees
A ‘systems approach’ to plant breeding is increasingly recognised as required to address broad global challenges including the transgression of multiple planetary boundaries. In this opinion piece we describe a systems approach to plant breeding that is based on advancing novel and creative linkages between existing breeding methods that are oriented to multiple global trends and values. We illustrate our concept for how biodiversity can be mobilised strategically to address pressing global needs by considering the case study of tree genetic improvement. We choose ‘tree diversity breeding’ as our example based on the increasingly crucial roles of trees in supporting continued human development and the environment, and because of trees’ enormous diversity that provides significant opportunities for a systems approach to genetic improvement.
Phylogeographic distribution of rhizobia nodulating common bean (Phaseolus vulgaris L.) in Ethiopia
Rhizobia are soilborne bacteria that form symbiotic relations with legumes and fix atmospheric nitrogen. The nitrogen fixation potential depends on several factors such as the type of host and symbionts and on environmental factors that affect the distribution of rhizobia. We isolated bacteria nodulating common bean in Southern Ethiopia to evaluate their genetic diversity and phylogeography at nucleotide, locus (gene/haplotype) and species levels of genetic hierarchy. Phylogenetically, eight rhizobial genospecies (including previous collections) were determined that had less genetic diversity than found among reference strains. The limited genetic diversity of the Ethiopian collections was due to absence of many of the Rhizobium lineages known to nodulate beans. Rhizobium etli and Rhizobiumphaseoli were predominant strains of bean-nodulating rhizobia in Ethiopia. We found no evidence for a phylogeographic pattern in strain distribution. However, joint analysis of the current and previous collections revealed differences between the two collections at nucleotide level of genetic hierarchy. The differences were due to genospecies Rhizobium aethiopicum that was only isolated in the earlier collection.
Trees and their seed networks: The social dynamics of urban fruit trees and implications for genetic diversity
Trees are a traditional component of urban spaces where they provide ecosystem services critical to urban wellbeing. In the Tropics, urban trees’ seed origins have rarely been characterized. Yet, understanding the social dynamics linked to tree planting is critical given their influence on the distribution of associated genetic diversity. This study examines elements of these dynamics (seed exchange networks) in an emblematic indigenous fruit tree species from Central Africa, the African plum tree (Dacryodes edulis, Burseraceae), within the urban context of Yaoundé. We further evaluate the consequences of these social dynamics on the distribution of the genetic diversity of the species in the city. Urban trees were planted predominantly using seeds sourced from outside the city, resulting in a level of genetic diversity as high in Yaoundé as in a whole region of production of the species. Debating the different drivers that foster the genetic diversity in planted urban trees, the study argues that cities and urban dwellers can unconsciously act as effective guardians of indigenous tree genetic diversity.
Nutritional composition of baobab (Adansonia digitata L.) fruit pulp sampled at different geographical locations in Kenya
Baobab (Adansonia digitata L.) is a multipurpose tree indigenous to the semi-arid and sub-humid zones of sub-Saharan Africa. Despite it’s multiple uses and valuable properties, information on its nutritional and phenotypic characteristics is rare, particularly in Eastern Africa. For the present study 64 baobab trees were sampled at six different locations of inland and coastal Kenya and the nutritional composition of 59 samples of fruit pulp was determined, including water, minerals, vitamin C and total acidity. The pulp of the studied baobab fruits is a valuable source of minerals and vitamins, particularly of vitamin C (mean 175 ± 62 mg/100 g edible portion on fresh weight basis (EP)), potassium (mean 1006 ± 280 mg/100 g (EP)) and calcium (mean 375 ± 93 mg/100 g EP). However, we found high tree-to-tree differences for all analyzed parameters with highest coefficients of variation detected for iron (47%), zinc (41%) and vitamin C (36%). Additionally we observed nutritional variations regarding iron, potassium, total acidity and pH value among the six locations. The results of this study will contribute to select superior baobab mother trees for future domestication programs and nutrition interventions and to promote the cultivation and use of baobab in Kenya.
Phylogeography and Symbiotic Effectiveness of Rhizobia Nodulating Chickpea (Cicer arietinum L.) in Ethiopia
Chickpea (Cicer arietinum L.) used to be considered a restrictive host that nodulated and fixed nitrogen only with Mesorhizobium ciceri and M. mediterraneum. Recent analysis revealed that chickpea can also establish effective symbioses with strains of several other Mesorhizobium species such as M. loti, M. haukuii, M. amorphae, M. muleiense, etc. These strains vary in their nitrogen fixation potential inviting further exploration. We characterized newly collected mesorhizobial strains isolated from various locations in Ethiopia to evaluate genetic diversity, biogeographic structure and symbiotic effectiveness. Symbiotic effectiveness was evaluated in Leonard Jars using a locally released chickpea cultivar “Nattoli”. Most of the new isolates belonged to a clade related to M. plurifarium, with very few sequence differences, while the total collection of strains contained three additional mesorhizobial genospecies associated with M. ciceri, M. abyssinicae and an unidentified Mesorhizobium species isolated from a wild host in Eritrea. The four genospecies identified represented a subset of the eight major Mesorhizobium clades recently reported for Ethiopia based on metagenomic data. All Ethiopian strains had nearly identical symbiotic genes that grouped them in a single cluster with M. ciceri, M. mediterraneum and M. muleiense, but not with M. plurifarium. Some phylogeographic structure was observed, with elevation and geography explaining some of the genetic differences among strains, but the relation between genetic identity and symbiotic effectiveness was observed to be weak.