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Common vetch (Vicia sativa L.) is an important annual diploid leguminous forage. In the present study, transcriptomic profiling in common vetch in response to salt stress was conducted using a salt-tolerant line (460) and a salt-sensitive line (429). The common responses in common vetch and the specific responses associated with salt tolerance in 460 were analyzed. Several KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways, including plant hormone and MAPK (mitogen-activated protein kinase) signaling, galactose metabolism, and phenylpropanoid phenylpropane biosynthesis, were enriched in both lines, though some differentially expressed genes (DEGs) showed distinct expression patterns. The roots in 460 showed higher levels of lignin than in 429. α-linolenic acid metabolism, carotenoid biosynthesis, the photosynthesis-antenna pathway, and starch and sucrose metabolism pathways were specifically enriched in salt-tolerant line 460, with higher levels of accumulated soluble sugars in the leaves. In addition, higher transcript levels of genes involved in ion homeostasis and reactive oxygen species (ROS) scavenging were observed in 460 than in 429 in response to salt stress. The transcriptomic analysis in common vetch in response to salt stress provides useful clues for further investigations on salt tolerance mechanism in the future. [ABSTRACT FROM AUTHOR]

Alfalfa is the most important forage legume with symbiotic nitrogen-fixing nodule in roots, but it is sensitive to aluminum (Al), which limits its plantation in acidic soils. One rhizobia clone of Sinorhizobium meliloti with Al tolerance (AT1) was isolated from the nodule in AlCl3-treated alfalfa roots. AT1 showed a higher growth rate than the standard rhizobia strain Sm1021 under Al-stressed conditions. Alfalfa growth was improved by inoculation with AT1 under Al-stressed conditions, with increased length and fresh weight in shoots and roots. High nitrogenase activity and pink effective nodules were obtained in AT1-inoculated plant roots under Al stress, with increased total nitrogen compared with the non-inoculated control. The application of exogenous NH4+-nitrogen increased the Al resistance in alfalfa. It is suggested that rhizobia's increase of the Al resistance in alfalfa is associated with its improved nitrogen status. Inoculation with Al-tolerant rhizobia is worth testing in an acidic field for improved alfalfa productivity. [ABSTRACT FROM AUTHOR]

Chinese milk vetch (Astragalus sinicus L.) is an important leguminous green manure that frequently suffers from seasonal drought. To improve its drought tolerance, the effects of rhizobia inoculation on drought tolerance and the underlying physiological mechanism were investigated. Drought tolerance in combination with nitrogen assimilation, free amino acids, and polyamines was investigated in milk vetch with active nodules (AN), with inactive nodules (LN), or without nodules (NN). AN plants had increased drought tolerance compared to LN and NN plants. Glutamine synthetase (GS), glutamine 2-oxoglutarate amino transferase (GOGAT), and glutamate dehydrogenase (GDH) activities were decreased after drought, with higher levels in AN plants than in LN and NN plants under both control and drought stress conditions. Higher levels of proline (Pro), arginine (Ala), alanine (Ala), and glutamate (Glu) were observed in AN plants compared with LN and NN plants. Putrescine (Put), spermidine (Spd), and spermine (Spm) levels were increased in response to drought, and higher levels of Put and Spd were maintained in AN plants. It is suggested that active nodulation leads to increased drought tolerance in milk vetch, which is associated with improved nitrogen fixation and ammonium assimilation, which in turn lead to the promotion of free amino-acid and polyamine synthesis. [ABSTRACT FROM AUTHOR]