Genetic diversity is important for developing salt‐tolerant rice ( Oryza sativa L.) cultivars. Certain Thai rice accessions display salt tolerance at the adult or reproductive stage, but their response to salinity at the seedling stage is unknown. In this study, a total of 10 rice cultivars/line, including eight Thai cultivars and standard salt‐tolerant cultivar and susceptible line, were screened using a hydroponic system to identify salt‐tolerant genotypes at the seedling stage. Different morphophysiological indicators were used to classify tolerant and susceptible genotypes. Phylogenetic analyses were performed to determine the evolutionary relationships between the cultivars. Results showed that ‘Lai Mahk’, ‘Jao Khao’, ‘Luang Pratahn’, and ‘Ma Gawk’ exhibited salt stress tolerance comparable with the standard salt‐tolerance check ‘Pokkali’. Whole‐exome single‐nucleotide polymorphism (SNP)‐based phylogenetic analysis showed that the Thai rice cultivars were monophyletic and distantly related to Pokkali and IR29. Lai Mahk and Luang Pratahn were found closely related when using the whole‐exome SNPs for the analysis. This is also the case for the analysis of SNPs from 164 salt‐tolerance genes and transcription regulatory genes. The tolerant cultivars shared the same haplotype for 16 genes. Overall, the findings of this study identified four salt‐stress‐tolerant Thai rice cultivars, which could be used in rice breeding programs for salinity tolerance.

Here, we investigated physiological responses, yield components, starch properties, and starch biosynthesis genes in five Thai rice (Oryza sativa L.) cultivars (SPR1, Hawm Daeng, RD43, RD69, and PTT1) with distinct starch characteristics under salt stress. Salt stress decreased flag leaf greenness (SPAD), normalized difference vegetation index (NDVI) levels, and carotenoid reflectance index 1 (CRI1) levels in all cultivars, resulting in reduced net photosynthesis, transpiration rates, and yield components across all cultivars, with Hawm Daeng and PTT1 being most susceptible. In contrast, RD69 and SPR1 were more tolerant, exhibiting recovered chlorophyll fluorescence levels and total performance index values after 3 days. Salt stress reduced apparent amylose content (AAC) and increased rapidly available glucose (RAG) levels in all cultivars. Granule-bound starch synthase I (GBSSI) expression declined the most in PTT1 and Hawm Daeng. SPAD, NDVI, CRI1, and photosynthetic parameters were correlated with GBSSI expression at the milky and dough stages of grain development. GBSSI expression levels showed little to no correlation with slowly available glucose but correlated with resistant starch levels at the booting stage of grain development. Salt stress affected yield components and rice starch quality, with variations depending on salt susceptibility, which in turn affected GBSSI expression levels during the milky and dough stages of grain development.

Rice ( Oryza sativa L. ) is a staple food for half of the world's population, and increasing attention has been given to its starch properties in relation to health concerns such as diabetes. Drought stress can limit rice production, particularly in key producing countries including China, India, and Thailand. This study examined the effects of drought on physiological traits and starch properties in five Thai rice varieties that differ in apparent amylose content (AAC): “RD43” (intermediate AAC), “RD69” (low AAC), “Suphanburi 1 (SPR1)” (high AAC), “Hawm Daeng (HD; photoperiod insensitive)” (high AAC), and “Pathumthani 1 (PTT1)” (low AAC). Plants were subjected to 6 days of drought stress at the booting stage, followed by recovery. Drought stress negatively affects physiological responses, such as Soil–Plant Analysis Development (SPAD) values and vegetation indices. Principal component analysis revealed distinct variety‐specific responses and recovery capacities, indicating clear genotype‐dependent differences in drought tolerance. Yield components, including grain weight, total grain weight per plant, and the number of filled grains, were also negatively affected. In addition, drought altered starch properties, particularly AAC. RD43 showed the greatest tolerance to drought stress based on physiological responses, but exhibited the largest change in AAC, suggesting strong drought sensitivity of starch traits. By contrast, SPR1 was more sensitive in physiological responses but maintained relatively stable AAC. We also found a significant correlation between physiological parameters (SPAD, NDVI, SR, G, and SRPI) and AAC. Among these, SRPI showed the strongest relationship with AAC, and a significant correlation coefficient was detected in all cultivars tested ( r = 0.496–0.685, depending on genotype). Lower SPAD values and reflectance indices (NDVI, SR, G, and SRPI) measured during the booting stage were consistently associated with reduced AAC in the final grain, indicating that declines in these parameters correspond to reductions in grain quality. These findings demonstrate how Thai rice varieties differ in their physiological and starch responses to drought and highlight the potential of measuring SPAD and reflectance indices at the booting stage as indicators associated with AAC under drought stress.

Sonchus arvensissubsp.arvensisis a perennial plant that serves both as a traditional medicinal herb and a prolific invasive weed. Its recent introduction to Southeast Asia, including Java, Indonesia, poses a potential threat to native biodiversity, yet its genetic provenance and invasion history in the region are uncharacterized. To provide a reliable species-level identification, we employed DNA barcoding of the chloroplast genesrbcLandmatK. Phylogenetic analysis revealed that samples from the four geographically distinct areas were genetically uniform based on these markers and were placed within a clade containing EurasianS. arvensisaccessions. The invader was distinct from the native AustralasianSonchusspecies. This work represents the first molecular confirmation ofS. arvensisin Java using DNA barcodes. While it establishes species identity, further genomic studies are required to resolve the population history, introduction pathway, and ecological impact of this invasive species.

Accurate species identification is fundamental to biodiversity studies, conservation, and the utilization of medicinal plants. The genusSonchus(Asteraceae) presents significant taxonomic challenges due to morphological plasticity and potential hybridization. DNA barcoding using the chloroplastrbcLand nuclear ribosomal ITS2 regions was used to delimit threeSonchusspecies (S. arvensis,S. oleraceus, andS. malayanus) collected from Bromo Mountain, Indonesia. To complement molecular data and explore chemotaxonomic markers, leaf metabolite profiles were analyzed using gas chromatography-mass spectrometry (GC-MS). TherbcLmarker showed high sequence conservation (99.58-100% identity) across species, confirming genus-level identification but failing to resolve species boundaries. The ITS2 region exhibited moderate variation (98.03-100% identity), with substantial overlap amongS. asper,S. oleraceus, andS. malayanus, suggesting recent divergence or possible conspecificity. Neighbor-joining phylogenetic analysis of both markers clustered accessions into broad clades corresponding to continental and island lineages, though low intraspecific divergence obscured taxonomic resolution. In contrast, GC-MS profiling revealed distinct species-specific chemotypes.Sonchus arvensiswas characterized by high abundances of neophytadiene (27.46%) and phytol (13.22%).Sonchus oleraceuscontained phytol (23.28%) as the major compound, with lower levels of neophytadiene (6.59%) and several methylated fatty acid esters.Sonchus malayanusdisplayed a distinct profile dominated by compounds with lower identification confidence, including (E)-4-trimethylsilyl-3-buten-2-ol (19.21%), alongside confidently identified guaiacol and trimethylamine. The discordance between molecular and chemical data underscores the limitations of single-locus barcoding in closely relatedSonchusspecies. This study demonstrates that integrative taxonomy, combining molecular, phytochemical, and morphological evidence, provides a more robust framework for species delimitation in this genus. The identified volatile compounds, particularly neophytadiene and phytol, represent promising chemotaxonomic markers and warrant further investigation for their ecological and pharmacological significance.