Short communication Relationship between total nodulation and nodulation at the root crown of peanut, soybean and common bean plants Jusce ´ lio D. Cardoso a , Douglas F. Gomes a , Kelly C.G.P. Goes a , Nelson da S. Fonseca, Junior b , Orazilia F. Dorigo b , Mariangela Hungria c , Diva S. Andrade b, * a Department of Biochemistry and Biotechnology, University of Londrina, PR, Brazil b Instituto Agrono ˆmico do Parana ´, Cx Postal 481, CEP 86047-902, Londrina, PR, Brazil c Embrapa Soja, Biotecnologia do Solo, Cx Postal 231, CEP 86001-970, Londrina, PR, Brazil article info Article history: Received 21 February 2009 Received in revised form 21 April 2009 Accepted 16 May 2009 Available online 10 June 2009 Keywords: Arachis hypogaea Bradyrhizobium Glycine max Legume Phaseolus vulgaris Rhizobium Symbiosis abstract The objective of this study was to simplify the procedure for evaluation of legume nodulation, by exam- ining if there is a relationship between the nodulation of the whole root system and at the crown region. Roots of peanut, soybean and common bean plants growing in soils were split in two parts (crown and bottom) and assessed for nodulation (nodule number and dry weight). In general, most nodules were concentrated at the crown, and crown nodulation was generally positively correlated with total nodulation of all three legume crops. The results are highly applicable in studies such as strain selection for inoculants and assessment of inoculation technologies, among others, and is an important contribution to help reduce the time and labor required for the evaluation of nodulation parameters. Ó 2009 Elsevier Ltd. All rights reserved. Soybean (Glycine max L. Merr.), peanut (Arachis hypogaea L.) and common bean (Phaseolus vulgaris L.) are broadly grown in Brazil as protein sources and, in the case of the first and the second crops, also for oil production. These legume crops establish symbiotic associa- tions with soil bacteria which form spherical determinate nodules, where the process of N 2 fixation takes place. Rhizobial strain selec- tion programs and experiments aiming at evaluating the agronomic efficiency of different inoculants, strains, and inoculant technologies are based on the evaluation of several parameters related to the symbiosis, of which root nodulation represents a major component. However, despite its importance, the assessment of nodulation is very labor-intensive and time-consuming d especially when large numbers of samples are considered. Strategies have been searched, aiming at improving the procedure, one example being the deter- mination of nodulation on the roots of plants grown in pouches using an image analysis system (Vikman and Vessey, 1993; Lira and Smith, 2000). However, there is no information concerning the comparison of partial and whole root nodulation of soil-grown legumes. The aim of this study was thus to examine if there would be a relationship between nodulation evaluated in whole plant root system and at the crown region, what would allow a considerable reduction of the time and labor involved in the evaluation. Peanut and common bean plants were collected from green- house experiments, which were set up to evaluate the performance of rhizobial strains. Surface sterilized seeds were inoculated with 1.3–1.7  10 9 viable cells mL 1 of Bradyrhizobium spp. strains SEMIA 6144 (FEPAGRO collection, Porto Alegre, RS) and IPR-Ah-737 (Instituto Agrono ˆmico do Parana ´ - IAPAR collection) for the peanut (cultivar IAC Tatu ST) and Rhizobium spp. IPR-Pv- strains (IAPAR collection) for the common bean (cultivar IPR-Colibri). Further samplings were undertaken with soybean plants (cultivar BRS184) from an experiment of inoculant carriers in an acidic oxisol at the Experimental Station of IAPAR in Ponta Grossa (23  13 0 S and 50  03 0 W, altitude 880 m, climate Cfb, Ko ¨ ppen–Geiger classification) and common bean plants (28 cultivars) from two independent field experiments performed in an oxisol at the Experimental Station of IAPAR in Londrina (23  23 0 S and 50  11 0 W, altitude 610 m, climate Cfa). In these field experiments * Corresponding author at: Department of Soil Science, Rodovia Celso Garcia Cid, km 375, Cx. Postal 481, CEP 86047-902, Londrina, Parana ´, Brazil. Tel.: þ55 43 3376 2000; fax: þ55 4333762101. E-mail addresses: diva@iapar.br, andradeds@yahoo.com.br (D.S. Andrade). Contents lists available at ScienceDirect Soil Biology & Biochemistry journal homepage: www.elsevier.com/locate/soilbio 0038-0717/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.soilbio.2009.05.008 Soil Biology & Biochemistry 41 (2009) 1760–1763