Early Nodulin Genes are Not Markers of the Capacity of Woody Legumes to Nodulate

Abstract

Knowing whether trees can develop nodules in which nitrogen is fixed is important for managing inputs during culture. Early nodulin genes, such as ENOD2 and ENOD12, could function as molecular markers for the capacity to nodulate if they are conserved only in species that nodulate. Several nodulating species are known to possess these genes; but, their occurrence has not been studied among non-nodulating taxa, including Cercis canadensis L. (redbud), Gleditsia triacanthos L. var. inermis Willd. (honey locust), and Gymnocladus dioica (L.) C. Koch (Kentucky coffee tree). Our objective was to determine the relationship between the capacity to nodulate and the occurrence of putative ENOD2 or ENOD12 genes by probing the genomes of these non-nodulating species and the genomes of two legumes that nodulate, Albizia julibrissin Durazz. (silk tree) and Laburnum alpinum (Mill.) Bercht. & J. Presl (Scotch laburnum). ENOD2 and ENOD12 cDNA clones from Glycine max (L.) Merill (soybean) and Pisum sativum L. (pea), respectively, and cloned ENOD2 PCR fragments from Maackia amurensis Rupr. & Maxim. (Amur maackia) and Styphnolobium japonicum (L.) Schott (Japanese pagodatree) were used as probes for Southern hybridizations. Sequences from genomes of silk tree, Scotch laburnum, honey locust, and Kentucky coffee tree hybridized to ENOD2 probes on Southern blots. Putative ENOD12 sequences were detected in the genomes of Scotch laburnum, redbud, and honey locust. Thus, we conclude that ENOD2 and ENOD12 can not be used as markers for the capacity to nodulate.