Affiliation:
1. Laboratoire de Biologie Moléculaire des Relations Plantes-Microorganismes, Centre National de la Recherche Scientifique-Institut National de la Recherche Agronomique, BP 27, Auzeville, 31326 Castanet-Tolosan cedex, France
Abstract
Abstract
The availability of a wide range of independent lines for the annual medic Medicago truncatula led us to search for natural variants in the symbiotic association with Sinorhizobium meliloti. Two homozygous lines, Jemalong 6 and DZA315.16, originating from an Australian cultivar and a natural Algerian population, respectively, were inoculated with two wild-type strains ofS. meliloti, RCR2011 and A145. Both plant lines formed nitrogen-fixing (effective) nodules with the RCR2011 strain. However, the A145 strain revealed a nitrogen fixation polymorphism, establishing an effective symbiosis (Nod+Fix+) with DZA315.16, whereas only small, white, non-nitrogen fixing nodules (Nod+Fix−) were elicited on Jemalong 6. Cytological studies demonstrated that these non-fixing nodules are encircled by an endodermis at late stages of development, with no visible meristem, and contain hypertrophied and autofluorescent infection threads, suggesting the induction of plant defense reactions. The non-fixing phenotype is independent of growth conditions and determined by a single recessive allele (Mtsym6), which is located on linkage group 8.
Publisher
Oxford University Press (OUP)
Subject
Plant Science,Genetics,Physiology
Cited by
52 articles.
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