System. zyxwvutsrqpon Appl . Microbiol. zyxwvutsrqpo 22, 11 9- 132 (1999) SYSTEWTIC AND ht t p: / / www. urbanf i scher. de/ j ournal s/ sam APPLIED MICROBIOLOGY O Urban & Fischer Verlag zyxwvutsrqp Agrobacterium zyxwv bv. 1 Strains Isolated from Nodules of Tropical Legumes zyxwv PHILIPPE DE/LAJUDIE’3273, ANNE wILLEMS2, GISELLE NICK4, SALAH HASSAN MOHAMED’, URBAIN TORCK~, RENATA COOPI$AN2, ABDELKARIM FILALI-MALTOUF’, ICAREL I<ERSTERS2, BERNARDkDREYFUS3, ICRISTINA LINDSTROM4 and MoNIQUE/GILLIS~ ILaboratoire de Microbiologie des Sols, Dakar, Senegal, West-Africa ’Laboratorium voor Microbiologie, Universiteit Gent, Ghent, Belgium 3Laboratoire des Symbioses Tropicales et Méditerranéennes, ORSTOM-CIRAD, Campus de Baillarguet, Montpellier Ctdex, France 4Department of Applied Chemistry and Microbiology, University of Helsinlti, Helsinki, Finland 5Laboratoire de Microbiologie et de Biologie Moléculaire, Faculté des Sciences, Université Mohammed V, Rabat, Morocco Received December 3,1998 zyxwvutsr Summary Bacterial strains were isolated from root nodules of various legumes, mainly trees, from different places in Africa. Polyphasic taxonomy, including numerical analysis of comparative whole-cell protein patterns obtained by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), 16s rRNA gene se- quencing, auxanographic tests (API 50), and DNA:DNA hybridizations indicated that these strains be- longed to zyxwvutsrqpo Agrobacterium biovar l. These strains were not capable of inducing any nodule or tumor for- mation on plants. No PCR amplification was observed using nifH primers, suggesting that they do not carry symbiotic genes. Biological implications of the presence of Agrobacteriunz in nodules are dis- cussed. Key words: Agrobacteriunz bv. 1 - Taxonomy - Legume - Symbiosis - Acacia - Africa - Rhizobium - Tropical tree Introduction In arid regions of Africa, deforestation has become a major problem and many countries develop reforestation programs for soil fertility maintenance, in which legume trees are generally included among planted species. Usu- ally native species are preferred, such as Acacia senegal in Senegal and Sudan, but sometimes introduced species give better results than native ones. This is the case for Prosopis juliflora, a tree native of America which ap- peared to grow better than other native species tested in Senegal (DEANS et al., 1995). In Morocco Acacia cyaizo- phylla and Acacia cyclops, two tree species native of Sa- harian to sub-humid zones of West Australia, are used for dune stabilization; Acacia mollissima, a tree native of semi-arid regions of Australia is used for wood produc- tion and soil regeneration; Acacia horrida, native of East Africa, is used for fences. Leguminous plants can establish nitrogen-fixing sym- biosis with a variety of bacteria belonging to several -_ genera including Rhizobium, Sinorhizobium, Mesorhi- zobiuin, Azod2zÕbhm, (YOUNG and ‘i . -- -’_ I HAUKKA, 1996) ‘and Allorhizobiuin (DE LAJUDIE et al., 1998a). Several reports have been published concerning tropical tree rhizobia in Mexico and South America (MARTINEZ-ROMERO et al., 1991), Brazil (MOREIRA et al., 1993; DE LAJUDIE et al., 1998b), Sudan (ZHANG et al., 1991; DE LAJUDIE et al., 199813; NICK, 1998) and Senegal (DREYFUS and DOMMERGUES, 1981; DUPUY et al., 1994; DE LAJUDIE et al., 1994; DE LAJUDIE et al., 1998a,b), which in each case demonstrated their large genetic diversity, lead- ing to the descriptions of several new bacterial species. Natural nodulation of trees is often reported to be poorly efficient in terms of fixed nitrogen, although high nitrogen fixation can be observed with certain strains in laboratory conditions (DANSO et al., 1992; NDOYE et al., 1995). This suggests that the most competitive strains for nodule occu- pancy in nature are generally not the most efficient nitro- gen fixers. Therefore it is crucial to obtain data on nodula- tion of leguminous trees, especially when dealing with in- troduced plant species. It is questionable whether appro- priate native rhizobia, able to establish an efficient nitro- 0723-2020/99/22/01-119 $ 12.0010 Fonds Documenure QRSTW