Journal article
Identifying abnormalities in symbiotic development between Trifolium spp. and Rhizobium leguminosarum bv. trifolii leading to sub-optimal and ineffective nodule phenotypes
Annals of Botany, Vol.110(8), pp.1559-1572
2012
Abstract
Background and Aims: Legumes overcome nitrogen limitations by entering into a mutualistic symbiosis with N 2-fixing bacteria (rhizobia). Fully compatible associations (effective) between Trifolium spp. and Rhizobium leguminosarum bv. trifolii result from successful recognition of symbiotic partners in the rhizosphere, root hair infection and the formation of nodules where N 2-fixing bacteroids reside. Poorly compatible associations can result in root nodule formation with minimal (sub-optimal) or no (ineffective) N 2-fixation. Despite the abundance and persistence of strains in agricultural soils which are poorly compatible with the commercially grown clover species, little is known of how and why they fail symbiotically. The aims of this research were to determine the morphological aberrations occurring in sub-optimal and ineffective clover nodules and to determine whether reduced bacteroid numbers or reduced N 2-fixing activity is the main cause for the Sub-optimal phenotype. Methods:Symbiotic effectiveness of four Trifolium hosts with each of four R. leguminosarum bv. trifolii strains was assessed by analysis of plant yields and nitrogen content; nodule yields, abundance, morphology and internal structure; and bacteroid cytology, quantity and activity.Key ResultsEffective nodules (Nodule Function 83-100 ) contained four developmental zones and N 2-fixing bacteroids. In contrast, Sub-optimal nodules of the same age (Nodule Function 24-57 ) carried prematurely senescing bacteroids and a small bacteroid pool resulting in reduced shoot N. Ineffective-differentiated nodules carried bacteroids aborted at stage 2 or 3 in differentiation. In contrast, bacteroids were not observed in Ineffective-vegetative nodules despite the presence of bacteria within infection threads.ConclusionsThree major responses to N 2-fixation incompatibility between Trifolium spp. and R. l. trifolii strains were found: failed bacterial endocytosis from infection threads into plant cortical cells, bacteroid differentiation aborted prematurely, and a reduced pool of functional bacteroids which underwent premature senescence. We discuss possible underlying genetic causes of these developmental abnormalities and consider impacts on N 2-fixation of clovers.
Details
- Title
- Identifying abnormalities in symbiotic development between Trifolium spp. and Rhizobium leguminosarum bv. trifolii leading to sub-optimal and ineffective nodule phenotypes
- Authors/Creators
- V.J. Melino (Author/Creator) - Murdoch UniversityE.A. Drew (Author/Creator) - South Australian Research and Development InstituteR.A. Ballard (Author/Creator) - South Australian Research and Development InstituteW.G. Reeve (Author/Creator) - Murdoch UniversityG. Thomson (Author/Creator) - Murdoch UniversityR.G. White (Author/Creator) - Commonwealth Scientific and Industrial Research OrganisationG.W. O'Hara (Author/Creator)
- Publication Details
- Annals of Botany, Vol.110(8), pp.1559-1572
- Publisher
- Oxford University Press
- Identifiers
- 991005541340407891
- Copyright
- © 2012 The Author.
- Murdoch Affiliation
- Centre for Rhizobium Studies
- Language
- English
- Resource Type
- Journal article
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- Collaboration types
- Domestic collaboration
- Citation topics
- 3 Agriculture, Environment & Ecology
- 3.97 Plant Pathology
- 3.97.892 Rhizobium-Legume Symbiosis
- Web Of Science research areas
- Plant Sciences
- ESI research areas
- Plant & Animal Science