Study of quantitative genetics of gum arabic production complicated by variability in ploidy level of Acacia senegal (L.) Willd

Abstract

Gum arabic is an important international commodity produced by trees of Acacia senegal across Sahelian Africa, but documented results of breeding activities are limited. The objective of this study was to provide reliable estimates of quantitative genetic parameters in order to shed light on the breeding potential for improvement of gum yield and quality. For this purpose, we measured growth on 617 offspring from 60 open-pollinated trees after 18 years, and gum yield and quality based on two seasons, 18 and 19 years after establishment. Genotyping with eight microsatellite markers revealed that progenies consisted of both diploid and polyploid trees, and growth, gum yield, and gum quality varied substantially among ploidy level, populations, and progenies. Analysis of molecular variance and estimates of outcrossing rate supported that trees within open-pollinated families of diploids were half sibs, while the open-pollinated families of polyploids showed low variation within families. The difference in sibling relationship observed between ploidy levels complicated estimation of genetic parameters. However, based on the diploid trees, we conclude that heritability in gum arabic production is low to high with presence of high levels of additive genetic variation, although the genetic parameters could only be estimated with fairly high standard error. The findings suggest that improvement through breeding can increase the productivity of A. senegal substantially. However, the results also stress the importance of testing ploidy levels of selected material and use of genetic markers to qualify the assumptions in the quantitative genetic analysis.

Polyploidy can Confer Superiority to West African Acacia senegal (L.) Willd. Trees

“…All 634 living trees in the field trial were genotyped with 8 polymorphic microsatellite markers (SSR) as described in Diallo et al (2015) . By comparing the flow cytometry results with the SSR markers for the 59 mature trees, we concluded that polyploids could always be separated from diploids by the presence of more than two alleles per locus in at least 1 of the 8 loci (Appendix 1).…”

“…Investigating a progeny trial with mature A. senegal , we discovered that the trees had mixed ploidy levels ( Diallo et al, 2015 ). As the trial was established with the purpose of breeding for increased gum production, the trees were planted in an experimental design and thus represent a unique possibility for studying the long-term performance of di- and polyploid trees.…”

Senegalia senegal (synonym: Acacia senegal), its importance to sub-Saharan Africa, and its relationship with a wide range of symbiotic soil microorganisms

“…Gum arabic fractionated by hydrophobic affinity chromatography detects a broad spectrum of arabinogalactans, arabinogalactan-proteins, and/or glycoproteins (Osman et al, 1993;Renard et al, 2006). Diallo et al (2015) reported that provenances as well as certain families of polyploids had a different nitrogen content in their gum arabic. However, provenances, families, or plant ploidy levels appeared to have only a minor effect on carbon content.…”

“…Thus, like nitrogen content, protein quantity in S. senegal gum arabic changes with environmental conditions, but it may also be affected by ploidy level. Research by Diallo et al (2015) showed that for both diploid and polyploidy trees, plant growth and gum yield/quality differed among ploidy levels, and in populations and progenies.…”

Characterization of Phenotypic Variability of Sudanese Gum Arabic Tree <i>Acacia Senegal</i> var. <i>senegal</i> Using Multiprimer Random Amplificatıon of Polymorphic DNA (RAPD)

“…The current study stresses the importance of using DNA markers in assessing the mating system and the relationship within and among families as part of the estimation of quantitative genetic parameters to support breeding activities in A. senegal. [2]. In genetic improvement, it is essential to estimate heritability and phenotypic variability for different traits to make successful decisions in breeding strategies.…”