Senegalia Senegal response to inoculation with rhizobial strains vary in relation to seed provenance and soil type Niokhor Bakhoum, David W. Odee, Dioumacor Fall, Fatou Ndoye, Aboubacry Kane, Jacinta M. Kimiti, Alzouma M. Zoubeirou, et al. Plant and Soil An International Journal on Plant-Soil Relationships ISSN 0032-079X Volume 398 Combined 1-2 Plant Soil (2016) 398:181-193 DOI 10.1007/s11104-015-2655-6 1 23 Your article is protected by copyright and all rights are held exclusively by Springer International Publishing Switzerland. This e- offprint is for personal use only and shall not be self-archived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com”. 1 23 Author's personal copy Plant Soil (2016) 398:181–193 DOI 10.1007/s11104-015-2655-6 REGULAR ARTICLE Senegalia Senegal response to inoculation with rhizobial strains vary in relation to seed provenance and soil type Niokhor Bakhoum & David W. Odee & Dioumacor Fall & Fatou Ndoye & Aboubacry Kane & Jacinta M. Kimiti & Alzouma M. Zoubeirou & Samba Nd. Sylla & Kandioura Noba & Diégane Diouf Received: 22 April 2015 /Accepted: 25 August 2015 /Published online: 2 September 2015 # Springer International Publishing Switzerland 2015 Abstract Results Nodulation and growth of S. Senegal var- Aims The focus of the study was to determine the sym- iedinrelationtorhizobialstrain,provenance,soil biotic and growth response of three Senegalia Senegal type, and their interactions. Generally, nodulation (Syn. Acacia Senegal, gum arabic tree) provenances, was higher in Dahra than Goudiry soils, while namely Dahra (Senegal), Tera (Niger) and Makueni Makueni provenance was the most compatible (Kenya) to inoculation with selected S. Senegal- host. Inoculation had a significant effect on all nodulating rhizobia in soils from Dahra and Goudiry parameters measured in Dahra field soil. By con- regions of Senegal, representing typical soil and trast, inoculation had a significant effect on height enviromental conditions for establishing gum arabic (shoot length), and shoot, root and total dry matter production plantations. but not on nodulation. In the two field soils, seed Methods A greenhouse experiment was performed to provenance effect was significant for all parame- evaluate the effect of 11 rhizobial strains on nodulation ters measured. The interaction between inoculation and growth of three S. Senegal provenances in two field and provenance showed a significant effect on all soils, differing in nutrient status and indigenous parameters measured except nodule number in rhizobia. After 4 months, plants were harvested for Dahra field soil while in Goudiry, the interaction determination of nodulation, shoot and root dryweight. had a significant effect on seedling height and Responsible Editor: Henk Schat. N. Bakhoum (*) : F. Ndoye : A. Kane : S. N. Sylla : D. W. Odee K. Noba : D. Diouf Centre for Ecology and Hydrology, Bush Estate, Penicuik, Département de Biologie Végétale, Faculté des Sciences et Midlothian EH26 0QB, UK Techniques, Université Cheikh Anta Diop, BP 5005 Dakar, Senegal D. Fall e-mail: [email protected] Institut Sénégalais de Recherches Agricoles/Centre National de Recherches Forestières, Route des Pères Maristes, BP 2312 Dakar, N. Bakhoum : D. Fall : F. Ndoye : A. Kane : S. N. Sylla : Senegal D. Diouf LCM-Laboratoire Commun de Microbiologie IRD/ISRA/UCAD, J. M. Kimiti Centre de recherche de Bel-Air, BP 1386, CP 18524 Dakar, South Eastern Kenya University, P.O. Box 170-90200, Kitui, Senegal Kenya D. W. Odee A. M. Zoubeirou Kenya Forestry Research Institute, P.O. Box 20412-00200, Faculté des Sciences, Université Abdou Moumouni, BP Nairobi, Kenya 10662 Niamey, Niger Author's personal copy 182 Plant Soil (2016) 398:181–193 shoot, root, and total dry matter but this effect was species is believed to have reduced over the past years. not significant with nodulation parameters. The species remains under pressure as a result of its Conclusions S. Senegal is variable in its response to overexploitation by human population, shortage of rain- inoculation, it is therefore advantageous to select and fall in the Sahel, overgrazing. In addition, it is due to match effective rhizobia-provenance symbionts for each inappropriate agricultural practices, leading to the deg- site. radation and/or lack of regeneration of S. Senegal park- lands. Therefore, there is a need to conserve and sus- Keywords S. Senegal . Provenance variation . tainably manage the species if they are to meet the Environmental conditions . Inoculation . Acacia . increased demand for fuelwood, fodder, soil improve- Mesorhizobium . Senegal . Rhizobia ment through N2 fixation, protection of the environment and to cater for gum production, which is an important source of cash (Fagg and Allison 2004). The N2-fixing Introduction capacity of a legume tree is often used to explain its ability to grow better on and restore the fertility of N- In the arid and semi-arid lands of Africa, low and erratic depleted soil (Dommergues 1995). rainfall, high temperatures and poor soil water and nu- S. Senegal is a promiscuous species that could be trient availability limit agricultural productivity (Mertz nodulated with various rhizobial taxa and strains et al. 2012). Thus, multipurpose trees such as Senegalia (Bakhoum et al. 2014; de Lajudie et al. 1998;Fall (Acacia) species that provide a means to maximise et al. 2008;Nicketal.1999; Njiti and Galiana 1996; agricultural potential and stabilise yields under stressful, Odee et al. 1995;Odeeetal.1997;Sarretal.2005b). unpredictable growing conditions are important for re- Nevertheless, previous studies have shown that forestation and reclamation of marginal lands, for fuel S. Senegal is mainly nodulated in Senegal by rhizobial wood, timber, shelterbelts and soil improvement strains phylogeneticaly close to Mesorhizobium (Midgley and Bond 2001; Raddad and Luukkanen plurifarium (Bakhoum et al. 2014; Fall et al. 2008; 2007). Previous phylogenetic studies indicated that Sarr et al. 2005b). Recent studies showed that inocula- Acacia Miller s.l. is polyphyletic. Recently, tion with Mesorhizobium strains significantly improved Kyalangalilwa et al. (2013) segregated genera for nodulation and S. Senegal plant growth under water- Acacia s.l. and proposed new combinations for the limited conditions (Fall et al. 2011), and enhanced plant African species in Senegalia and Vachellia. The nutrient content and rhizospheric soil fertility of Senegalia clade is represented in Africa, Central and S. Senegal plants (Bakhoum et al. 2012). While in South America, and Asia with more than 60 species. another study, inoculation improved plant nodule num- S. Senegal (L.) Britton & P. Wilson [Syn. Acacia ber but not shoot N content (Ndoye et al. 2012). Like Senegal (L.) Willd.] is a complex group formed by several other African acacias, S. Senegal has the poten- closely related species widely distributed through the tial to fix N2 under a range of soil and environmental arid and semi-arid lands of sub-Saharan Africa (Odee conditions if nodulated by effective rhizobia (Gray et al. et al. 2015). This tree is adapted to survive under harsh 2013; Ndoye et al. 1995; Raddad et al. 2005). S. Senegal environmental conditions such as low and erratic rain- is morphologically variable. It has four distinct varieties, fall, intense solar radiation, and high wind velocity namely vars. Senegal, kerensis, leiorhachis and rostrata (Cossalter 1991). (Fagg and Allison 2004), of which three (Senegal, S. Senegal is a N2-fixing shrub or tree with consid- leiorhachis and kerensis) are found in East Africa and erable economic and ecological importance, producing one (Senegal) in West Africa. Rangewide genetic stud- a natural gum (gum arabic) widely used in the food and ies of the species also show differentiations among beverage industry, pharmaceuticals, other technical ap- varities and provenances across its native range, with plications and provisioning of several ecosystem ser- clear genotypic distinction between west African and vices in the drylands of tropical Africa (Ballal et al. east and southern Africa (Chevallier and Borgel 1998; 2005;Gaafaretal.2006;Grayetal.2013;Odeeetal. Odee et al. 2012;Odeeetal.2015). Therefore, there is 2011; Omondi et al. 2010) and a well-established tradi- an important need to select appropriate plant tional agroforestry tree component (Raddad et al. 2005). phenotypes/genotypes and rhizobia that are the most However, in Senegal the number of Senegalia (Acacia) compatible to each other. The essential requirement to Author's personal copy Plant Soil (2016) 398:181–193 183 realize this objective is to increase understanding of the medium (Vincent 1970). S. Senegal seeds of the Dahra effect of abiotic factors such as soil characteristics and provenance were inoculated with soil samples and climatic conditions on nodulation and growth of differ- grown in a controlled environment (Easy-lighting, ent plant provenances. 200 W 8 U 8500LM 6400 K° blue – 2700 K° red, Cis As part of an international consortium aimed at im- products, Paris, France) for three months with a photo- proving growth and sustainable production of gum ara- period of 16 h (under daylight) and eight hours (night), bic, we evaluated the symbiotic and growth response of temperature of 30 ± 1 °C (night), relative humidity of S. Senegal provenances (Dahra, Senegal; Tera, Niger 70 ± 5 % and a photosynthetically active radiation and Makueni, Kenya) inoculated with 11 (PAR) of 120 μmol m2-1 s−1. Mesorhizobium (rhizobial) strains and grown in two Senegalese (Dahra, arid and Goudiry, semiarid) soils Rhizobial strains used under greenhouse conditions. Table 1 shows the 11 rhizobial strains strains used in this study. They were all isolated from S.