Remediation of salt-affected soil by the addition of organic matter: an investigation into improving glutinous rice productivity

Soil salinity may limit plant growth and development, and cause yield loss in crop species. This study aimed at remediating saline soil using organic matter (OM) treatment, before the cultivation of RD6 rice (Oryza sativa L. spp. indica). Physiological and morphological characters of rice plants, as well as crop yield, were evaluated from salt-affected soil with varying levels of salinity. The chlorophyll a and total chlorophyll pigments of rice plants grown in salt-affected soil (2% salt level) with the application of OM were maintained better than in plants grown without OM treatment. The degree of reduced photosynthetic pigments in rice plants was dependent on the level of salt contamination. Pigment content was positively related to maximum quantum yield of PSII (Fv/Fm) and quantum efficiency of PSII (ΦPSII), leading to reduced net photosynthetic rate (Pn) and reduced total grain weight (TGW). Photosynthetic abilities, including chlorophyll a and total chlorophyll pigments and ΦPSII, in rice plants grown with OM treatment were greater than in those cultivated in soil without the OM treatment, especially in high salt levels (1-2% salt). The remediation of salt-affected soil in paddy fields using OM should be applied further, as an effective way of enhancing food crop productivity

Gamma Irradiation Causes Variation and Stability of Artemisinin Content in <em>Artemisia annua</em> Plants

Artemisinin is an anti-malarial sesquiterpene lactone isolated from Artemisia annua L., a traditional Chinese herb of the family Asteraceae. The plant contains relatively low artemisinin content, ranging from 0.01 to 0.8% of the plant dry weight, depending on the geographical origin, seasonal, and somatic variations. Ionizing radiation has been recognized as a powerful technique for plant improvement, especially in crop plants. This technique creates genetic variability in plants, which can be screened for desirable characteristics. Very little is known about the effect of gamma irradiation on the potential increase of artemisinin production in A. annua. In this study, 130 shoot tips excised from the population of in vitro A. annua plantlets (with an average leaf artemisinin content of 0.18 ± 0.09%) were exposed to 5 Gy 60Co gamma irradiation and subsequently transferred to a suitable medium for in vitro development of plantlets. The resulting 90 stable survived after four passages appeared to have a wide variation of artemisinin content, ranging from 0.02 to 0.68% of dry weight. All the viable plantlets were then transferred from the in vitro cultures to ex vitro conditions both in a greenhouse and an open field. A significant correlation was observed between artemisinin content among individual pairs of the vitro plantlets and ex vitro mature plants, with the correlation coefficient (R2) values of 0.915 for the greenhouse plants and 0.797 for the open field plants. Among these, the highest artemisinin-containing plant appeared to accumulate 0.84% artemisinin of dry weight in the open field, which is almost five times higher than the original plants. These results suggest that gamma irradiation with 5-Gy dose can produce viable variants of A. annua that can maintain the biosynthetic capability of artemisinin throughout the in vitro-ex vitro transfer and development of the first generation of mature plants

A highly efficient method for Agrobacterium mediated transformation in elite rice varieties (Oryza sativa L. spp. indica)

An Agrobacterium mediated transformation method was developed for the Thai rice variety,  Pathumthani 1 (PT1), and the Indian rice variety, Pokkali (PKL). Various aspects of the transformation method, including callus induction, callus age, Agrobacterium concentration and co-cultivation period were examined, in order to improve transformation efficiency. Optimized transformation conditions were established using Agrobacterium strain EHA105, which carries a virulent plasmid, pCAMBIA1301.  A modified Murashige and Skoog (MS) medium supplemented with 1 mg/l 2, 4-D and 0.5 mg/l picloram was optimized for callus induction. Three week old calli were used to co-cultivate with 0.8 -1 OD600  Agrobacterium for 30 min and the culture was continued on agar medium without antibiotics for 2 days. This method can be used to induce high quality calli within three weeks. Based on GUS determination, it was demonstrated that the transformation method was improved significantly, with a high level of transformation efficiency.Keywords: Agrobacterium tumefaciens, indica rice, mature seed-derived callus, rice transformation, transgenic riceAfrican Journal of Biotechnology Vol. 9(34), pp. 5488-5495, 23 August, 201

Field Screening of Sugarcane (Saccharum spp.) Mutant and Commercial Genotypes for Salt Tolerance

Growth and physiological attributes and sugar quality parameters are considered key criteria for screening sugarcane cultivars for salt tolerance. Maximum cane growth and yield were found in a positive check (‘K88-92’) as well as in cv. ‘(A3)AE1-18’ when subjected to salt affected soil. Percent reduction in Fv/Fm, quantum efficiency of PSII (ΦPSII) and water use efficiency (WUE) due to salt stress was considerably low in ‘K88-92’, ‘(A3)AE1-18’ and ‘KK3’ which was associated with very low salt-induced reduction in net photosynthetic rate and growth characters such as shoot length, number of internodes, and internodal length as well as yield traits. In addition, brix, polarlization, fiber, purity and commercial cane sugar (CCS) in ‘(A18)AE2-15’ and ‘(A3)AE1-18’ were well maintained under saline stress. By subjecting the data for various physiological, growth, yield and sugar quality parameters to the Ward’s cluster analysis ‘K88-92’ (positive check), ‘(A3)AE1-18’ and ‘KK3’ were identified as salt tolerant, whereas ‘(A11)AE1-114’ and ‘K97-32’ as salt sensitive

Physio-Biochemical Responses of Oil Palm (Elaeis guineensis Jacq.) Seedlings to Mannitol- and Polyethylene Glycol-Induced Iso-Osmotic Stresses

The aim of this investigation was to comparatively examine the physio-biochemical responses of oil palm seedlings to mannitol- and PEG-induced iso-osmotic stresses. The water content of osmotically stressed oil palm seedlings decreased, but the proline content and the electrolyte leakage of the seedlings increased with decreasing water potential (Ψw). However, the responses varied with the strength of osmotic stress and type of osmotic agent. Relative electrolyte leakage (REL) was negatively correlated to chlorophyll content in the osmotically stressed leaves. Chlorophyll a (Chla), chlorophyll b (Chlb), total carotenoids (Cx+c) and total chlorophyll (TC) in the seedlings were significantly reduced by osmotic stress, subsequently reducing maximum quantum yield of PSII (Fv/Fm) and photon yield of PSII (Φpsii), thereby lowering net-photosynthetic rate (Pn) and inhibiting growth. Physio-biochemical parameters, including REL, Fv/Fm, and Φpsii in oil palm seedlings were reduced more greatly by PEG-induced osmotic stress than by mannitol-induced stress. A deterioration in morphological characters, including leaf chlorosis, leaf burn, and green leaf area reduction were demonstrated in oil palm seedlings under osmotic stress induced by either mannitol or PEG. However, the toxic symptoms in oil palm seedlings under PEG-induced stress were severer than in those under mannitol-induced iso-osmotic stress, especially under severe osmotic stress

Calcium-alleviated salt tolerance in indica rice (Oryza sativa L. spp. indica): Physiological and morphological changes

Abstract Calcium (Ca) is a signaling molecule that plays an active role in regulating various mechanisms involved in recognition and response to abiotic stresses in plants. However, not much has been done to evaluate its role in regulating physiological and biochemical process in response to salt-induced stress. Two rice genotypes, Pokkali salt tolerant and IR29 salt susceptible, grown on liquid Murashige and Skoog medium (MS) supplied by 1.98 mM CaCl 2 (control) were compared to 2 (3.96 mM), 4 (7.92 mM) and 8 (15.84 mM) folds exogenous CaCl 2 pretreatment subsequently exposed to 200 mM NaCl salt stress. Thus, the present investigation evaluated the potential of exogenous calcium chloride (CaCl 2 ) supply in improving the growth performance and photosynthetic ability in salt stressed rice. In IR29 salt susceptible rice, leaf area of salt-stressed seedling was significantly recovered by exogenous application of 7.92 mM CaCl 2 , which was greater by 1.38-folds over that in 1.98 mM CaCl 2 application. Exogenous CaCl 2 (7.92 mM) enhanced proline accumulation in both Pokkali (3.26 mol g -1 FW) and IR29 (4.37 mol g -1 FW) genotypes, and reduced relative electrolyte leakage thereby indicating its positive role in membrane stability. Treatment of 7.92 mM CaCl 2 significantly enhanced the photosynthetic abilities, including maximum quantum yield of PSII (F v /F m ), photon yield of PSII ( PSII ), photochemical quenching (qP) and net photosynthetic rate (P n ), in two genotypes of salt-stressed rice seedlings, especially in salt susceptible IR29 genotypes. The study concludes that an exogenous application of 7.92mM CaCl 2 significantly enhanced the photosynthetic abilities and overall growth performances in the photoautotrophic growth of salt-stressed rice seedlings. Exogenous calcium in the culture media may absorb by root tissues, transfer to whole plant and function as salt defense mechanisms including calcium signaling in the abscisic acid (ABA) regulation system and calcium sensing in stomatal closure when plant subjected to salt stress. Keywords: calcium, salinity alleviation, leaf area, photosynthetic abilities, salt stress. Abbreviations：CaCl 2 _calcium chloride; Chl a _chlorophyll a; Chl b _chlorophyll b; F v /F m _maximum quantum yield of PSII; MS_Murashige and Skoog; P n _net photosynthetic rate; qP_photochemical quenching; PSII _photon yield of PSII; PPFD_photosynthetic photon flux density; REL_relative electrolyte leakage; C x+c _total carotenoid