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Articles by Piyada Theerakulpisut
Total Records ( 4 ) for Piyada Theerakulpisut
  Piyada Theerakulpisut , Sumonthip Bunnag and Kanlaya Kong-ngern
  This study was designed to study genetic diversity and differences in pattern of physiological responses to salt stress among six rice cultivars differing in salt tolerance level. Six cultivars of rice were screened for salinity tolerance at seedling stage based on visual symptoms of salt injury index established at the International Rice Research Institute. The cultivar Pokkali was classified as tolerant, IR29 highly sensitive, three local Thai cultivars; Dang Dawk Kok, Luang Ta Moh and Supanburi 2 moderately tolerant and Khao Dawk Mali 105 sensitive. The genetic relationship between rice cultivars were analysed by using randomly amplified polymorphic DNA. Cluster analysis revealed that the three moderately tolerant Thai cultivars were closely related to one another and together with the tolerant Pokkali formed one group, the sensitive Khao Dawk Mali 105 and the highly sensitive IR29 were closely related to each other and placed in another group. The seedlings had been treated with NaCl at 6 and 12 dS m-1 for 7 days. Compared with the non-stressed plants, the magnitude of changes in some physiological parameters were different among different cultivars and were related to the level of salinity tolerance. The weight of shoots and roots and net photosynthesis rate showed high positive correlation with the level of salinity tolerance. The Na+:K+ ratio, proline content and electrolyte leakage of shoots were negatively correlated with the level of salinity tolerance. Cluster analysis of physiological responses revealed that salt responsiveness of Pokkali was distinct from all other cultivars. The pattern of responses of Khao Dawk Mali 105 to salinity was more similar to the moderately tolerant group than the highly sensitive IR29.
  Sumalee Chookhampaeng , Wattana Pattanagul and Piyada Theerakulpisut
  Hydroponically-grown seedlings of thirteen commercial tomato cultivars and breeding lines were exposed to 0 (control) and 200 mM NaCl (salt stress) for ten days. Salt tolerance was evaluated based on visual appearance of plant damage and the plants were assigned the scale from 1 (most tolerant) to 4 (most sensitive). The salinity scales ranged from 1.00-3.75. All genotypes responded to salt by an accumulation of Na+, reduction in K+, Ca2+, N and shoot/root dried weight and a small increase in P. Salinity tolerance scales, ion concentration and shoot/root dried weight differed greatly among tomato genotypes. Highest correlation was found between salinity tolerance scale classes and the reduction in root dried weight, followed by the reduction in shoot dried weight, Na+ concentration, Ca2+ /Na+ and K+/Na+ ratios. The amount of N and P content did not correlate with salinity scale classes. In general, Na+ concentration and the reduction in root/shoot dried weight were the most reliable parameters useful for screening salt tolerance of tomato at the vegetative stage.
  Sumitahnun Chunthaburee , Sujirat Sakuanrungsirikul , Teerawut Wongwarat , Jirawat Sanitchon , Wattana Pattanagul and Piyada Theerakulpisut
  Background and Objective: Anthocyanins have been implicated to offer some protective roles for vegetative and reproductive tissues under abiotic stresses. In this study, the effects of salt stress on physiological responses including anthocyanin accumulation and the expression of anthocyanin biosynthetic genes in seedlings of two cultivars of black glutinous rice (Oryza sativa L.) differing in the levels of salinity tolelance and leaf anthocyanin were investigated. Materials and Methods: Two rice cultivars namely Niewdam Gs. No. 00621 (salt-tolerant, deep purple leaf colour) and KKU-LLR-039 (salt-sensitive, greenish purple leaf color) were grown in a hydroponic culture until 21 days old. Thereafter, they were treated with 0, 75 and 150 mM NaCl for 0, 2, 4, 6 and 8 days. Leaf tissues were collected for physiological determination and expression analysis of anthocyanin biosynthesis genes. Results: The growth parameters, total chlorophyll and chlorophyll fluorescence ratio (Fv/Fm) were progressively reduced while the electrolyte leakage rate increased with increasing NaCl concentrations and the length of time of salinity treatments. For all physiological parameters, the cultivar Niewdam Gs. No. 00621 was less afftected under salt stress. The highest anthocyanin content was attained after 2 and 4 days of salt stress in KKU-LLR-039 and Niewdam Gs. No. 00621, respectively; followed by a reduction in both cultivars until 8 days of salt stress. Real-time PCR analysis showed that the patterns of expression of anthocyanin biosynthesis genes Phenylalanine Ammonia Lyase (PAL), chalcone synthase (CHS), dihydroflavonol 4-reductase (DFR) and anthocyanidin synthase (ANS) were related with variations in anthocyanin contents. The maximum expression levels of CHS, DFR and ANS compared to those of non-stressed controls were observed after 2 and 4 days of stress for KKU-LLR-039 and Niewdam Gs. No. 00621, respectively, thereafter the expression dramatically reduced after 6-8 days of stress. The anthocyanin content and relative expression of the four genes was higher in the leaves of Niewdam Gs. No. 00621 than in KKU-LLR-039. Conclusion: Higher accumulation of anthocyanins may be one of the protective physiological traits under salt stress. Therefore, the rice cultivar with deep purple leaf color suffered from less severe cellular damages and lower growth reduction under salt stress compared with the one with less intense anthocyanins.
  Kanlaya Kong-ngern , Sumontip Bunnag and Piyada Theerakulpisut
  In order to compare differential growth, physiological and biochemical responses of rice cultivars differing in salt tolerance, four rice cultivars; tolerant Pokkali (PK), moderately tolerant Luang Anan (LA) and two sensitive cultivars Khao Dawk Mali 105 (KDML 105) and Pathumthani 60 (PT 60) were grown in hydroponic culture for 2 weeks and then subjected to NaCl stress at 6 or 12 dS m-1 for thirteen days. The tolerant cultivar (PK) exhibited clearly different pattern of responses from the other cultivars in most of the examined aspects including lower growth inhibition, lower inhibition of net photosynthetic rate, lower Na+/K+ ratio in the shoots, less proline accumulation in the shoots, less membrane damage, lower hydrogen peroxide production, higher catalase and lower guaiacol peroxidase activities. Other parameters including Na+/K+ ratio in roots, proline accumulation in roots and osmotic potential in both roots and shoots did not show appropriate association with the level of salt tolerance. The reduction in growth resulted from drastic reduction in net photosynthetic rate which was observed as early as 24 h after exposure to stress and continued to decrease dramatically. Growth retardation was also related to salt-induced accumulation of hydrogen peroxide which caused lipid peroxidation and membrane leakage. Higher catalase activity in the tolerant cultivar played an important role in combating the hydrogen peroxide, leading to less damage and higher tolerance. The activity of peroxidase was lower in the tolerant cultivar than in the sensitive ones. The observed negative relationship between the amount of proline accumulation and the level of salt tolerance did not support the widely advocated role of proline as an osmoprotectant under salt stress. Further investigation needs to be done to determine the role of this compatible osmolyte in salinity stress response in rice. For practical purpose, those parameters which showed differential pattern of responses including lower Na+/K+ ratio in the shoots, less proline accumulation in the shoots, lower reduction in net photosynthesis rate, lower electrolyte leakage, lower hydrogen peroxide accumulation, higher catalase and lower guaiacol peroxidase activities may be regarded as potential biochemical indicators for selection of salt tolerant rice and targets for improvement through transgenic approaches.
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