Characterisation of nodulation capacity with native rhizobia in germplasm of the under-utilised forage species Macroptilium

Abstract

Context. The Gran Chaco is a livestock producing region of Argentina with several under-utilisedlegume forage genetic resources, including species from the genus Macroptilium. Aims. We aimedto generate reliable characterisation and selection schemes in germplasm of Macroptilium forbiological nitrogen fixation with native rhizobia, and evaluate the germplasm variability for initialgrowth and nodulation capacity with native soil of subtropical environment. Methods. The trialevaluated 20 accessions of four Macroptilium species with or without added nitrogen. Thevariables were analysed through a nested ANOVA with the factor species, accessions nested withinspecies, nitrogen level, and the corresponding interactions. Relationships between variables andaccessions were examined using principal component analysis. Key results. There was variability inthe symbiotic response and initial growth, and most of the variance was explained by differencesbetween species. Nodulation capacity was related with biological nitrogen fixation, since theaccessions with higher nodule number and nodule weight showed higher initial growth and highercrude protein content in shoot. Conclusions. We found variability for nodulation capacityassociated with biological nitrogen fixation within the evaluated germplasm of Macroptilium. Inrelation to effectiveness, five of 20 accessions evaluated were classified as effective. Implications. Our breeding approach could contribute to develop native legume forage cultivars with better symbiosis with native rhizobia, which would reduce implantation costs and reduce the use of chemical nitrogen fertilisers.