Evaluation of some biochemical and biomolecular indicators in rice (Oryza sativa L.) during the seedling stage under NaCl stress.

Approximately 900 million hectares of farmland are destroyed by soil salinization, reducing global grain crop yield and quality. Although some current rice cultivars exhibit salt tolerance and high production yields, the exact mechanisms of their salt stress responses remain unclear. Hence, this study aims to elucidate the biochemical and biomolecular responses in different rice varieties, namely OM 9577 (salt-tolerant), OC 10 (moderately salt-tolerant), and Dai Thom 8 (salt-sensitive). The research findings indicate that increasing NaCl concentration leads to a decline in the fresh, dry mass of shoots and roots of all examined varieties (from 7.5 to 27% in OM 9577, OC 10; and from 16 to 54% in Dai Thom 8), as well as an increase in Na⁺ accumulation. OM 9577 and OC 10 accumulated higher levels of Ca²⁺, protein, proline, glycine betaine, sugars, and some monosaccharides (d-lyxofuranose, D-arabinose, ß-D-glucopyranose, ß-D-mannopyranose, D-galactofuranose) compared to Dai Thom 8. Transcript levels of some genes related to salt-tolerant mechanisms also have determined, including OsSOS1, OsNHX1, OsHKT1;4, OsHKT1;5, OsCaM, OsMAPKKK, OsCDPK, OsWAK, OsCML31, OsSOD, OsAOX1b, Os79, OsDUF26, OsWRKY26, OsWRKY62, OsAP2/ERF–58. The data demonstrated that transcript levels of some target genes were higher in OM 9577 and OC 10 than those in Dai Thom 8. Specifically, transcript levels of OsWRKY62, OsCML31, Os79, OsSOS1, OsHKT1:5, and OsCDPK were highest in OM 9577, while OsDUF26 and OsNHX1 transcript levels were highest in OC 10. These results offer potential biochemical and biomolecular markers for screening salt-tolerant rice cultivars and improving existing cultivars by transgenic or conventional breeding. [ABSTRACT FROM AUTHOR]