Alleviating the inhibitory effect of salinity stress on nod gene expression in Rhizobium tibeticum – fenugreek (Trigonella foenum graecum) symbiosis by isoflavonoids treatment

Rhizobia-legume symbiosis depends on molecular dialog, which involves the production of specific plant flavonoid compounds as signal molecules. Rhizobium tibeticum was recovered from the root nodule of fenugreek and identified by sequencing the 16S rRNA gene. The effect of salinity stress on nod gene expression was measured in terms of β-galactosidase activity. R. tibeticum containing Escherichia coli lacZ gene fusions to specific nodulation (nod) genes were used to determine β-galactosidase activity. Combination of hesperetin (7.5 µM) and apigenin (7.5 µM) significantly increased β-galactosidase activity more than the single application of hesperetin or apigenin. Preincubation of R. tibeticum with hesperetin and apigenin combination significantly alleviates the adverse effect of salinity on nod gene expression and therefore, enhances nodulation and nitrogen fixation of fenugreek.     

多胞锈菌属（锈菌目，多胞锈菌科）3新种和两中国新记录

报道了多胞锈菌属Phragmidium(多胞锈菌科Phragmidiaceae)的3个新种和两中国新记录。新种是采自香莓Rubus pungens var. oldhamii上的多隔多胞锈菌P.multiseptatum、采自峨眉蔷薇Rosa omeiensis上的粗壮多胞锈菌P. robustum以及采自华中悬钩子Rubus cockburnianus上的西藏多胞锈菌P. tibeticum。中国新记录是二花悬钩子Rubus biflorus和掌叶悬钩子R. pentagonus上的八室多胞锈菌P. octoloculare以及秀丽悬钩子Rubus amabilis、香莓R.pungens var.oldhamii、柔毛针刺悬钩子R.pungens var. villosus和西藏悬钩子R. thibetanus上的香莓多胞锈菌P. rubi-oldhami。