Considering the detrimental effects of salt stress on the physiological mechanisms of plants in terms of growth, development and productivity, intensive efforts are underway to improve plant tolerance to salinity. Hence, an experiment was conducted to assess the impact of the foliar application of salicylic acid (SA; 0.5 mM) on the physiological traits of fenugreek (Trigonellafoenum-graecum L.) plants grown under three salt concentrations (0, 75, and 150 mM NaCl). An increase in salt concentration generated a decrease in the chlorophyll content index (CCI); however, the foliar application of SA boosted the CCI. The malondialdehyde content increased in salt-stressed fenugreek plants, while a reduction in content was observed with SA. Likewise, SA application induced an accumulation of proline, total phenolics, and flavonoids. Moreover, further increases in total free amino acids and shikimic acid were observed with the foliar application of SA, in either control or salt-treated plants. Similar results were obtained for ascorbate peroxidase, peroxidase, polyphenol oxidase, and catalase with SA application. Hence, we concluded that the foliar application of SA ameliorates salinity, and it is a growth regulator that improves the tolerance of fenugreek plants under salt stress.

The genus Cassia and Senna have been classified under subfamily Caesalpinioideae of family Fabaceae (Leguminosae) of order Fabales. There is a scarce taxonomical studies of the genus Cassia and Senna inhabiting Egyptian environments, thus, the main objective of the current was to revise and authenticate the phylogenetic relationship between studied taxa of the species of the genera Cassia and Senna in Egypt using the recent tools of ITS barcoding, RAPD analysis and metabolic profiling, in comparing to the traditional taxonomical features. From the cluster analysis of the traditional 27 morphological characters, the studied taxa were categorized into two major clades with an average taxonomic distance of 4.3. The clade I include Cassia fistula, C. renigera, C. javanica L subsp. nodosa and C. roughiia that belongs to series Obolospermae, and C. grandis that belongs to series Grandes. The clade (II) includes Senna surattensis and S. alata at taxonomic level 3.6. The taxonomical description of the studied taxa was confirmed from the molecular analysis of ITS sequences and RAPD analysis. The ITS sequences of the tested plants species C. fistula L, C. grandis MD4, C. javanica subsp. nodosa MD7, C. roxburghii MD5, C. renigera MD5 were deposited at genbank with accession numbers MW367973, MZ960447, MW386305, MW326753 and MW32685, respectively. While, the ITS sequences of the S. surrattensis and S. alata were deposited into genbank accession # MD14 MW367670 and MD20 MW412635, respectively. Thus, from the molecular analysis, two clades were clearly separated into Clade I of Cassia and Clade II of Senna. The cluster I represented by C. fistula, C. renigera, C. roxburghii, and C. javanica sub nodosa, and the cluster II represented by S. alata and S. surattensis. From the PCA of RAPD, a clearly discrimination between the two Taxa was observed revealing the characteristic grouping of Cassia and Senna. The species Senna alata and Senna surattensis were grouped together, but the species of C. renigera, C. javanica, C. roxburghii and C. grandis was grouped on a distinct group. The separation of Cassia and Senna species into two clusters verify the segregation of the genus Cassia L. senso lato into two distinct genera namely Senna P. and Cassia L. The morphological, molecular traits of the studied plants were authenticated from the metabolic profiling by GC-MS analysis. Among the 23 identified metabolites, four compounds namely hexadecanoic acid, methyl ester, 9-Octadecenoic acid (Z)-ethyl ester and Vitamin E were detected with fluctuated concentrations, among C. fistula, C. grandis, C. javanica subsp. nodosa and C. roxburghii. Conclusively, the traditional morphological features, molecular barcoding using ITS sequences, RAPD analysis and metabolic traits by GC-MS analysis, authenticates the taxonomical diversity of the genus Cassia and Senna.

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