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

Phenotypic Variation for Root Distribution of IR64, KDML105 and KDML105 Mutant Rice Varieties in Water Deficit and Well-Watered Conditions

ABSTRACT Phenotypic variation for root distribution is associated with the ability of plants to acquire water and nutrients available at different soil strata. Rice production is known to be susceptible to water deficit stress (WS) because rice requires much water for cultivation. In this study, we explored natural variation of root distribution among IR64, KDML105 and KDML105 mutant lines (MT1, MT2, MT3) derived from gamma irradiation combined with ethyl methane sulfonate treatment. Plants were grown in a root basket and a root box system. We found that KDML105 had lower root to shoot ratio (27.49%) and less rooting depth (27.25%) compared to IR64. In the root box system, we found that WS decreased an average shoot biomass by 32.9%. The mutant lines maintained their shoot mass under WS while that of KDML105 was significantly reduced. Physiological analysis revealed that MT2 had the lowest evapotranspiration rate of 76.6%. In addition, MT2 and MT3 increased photosynthetic pigments under WS. KDML105 increased its rooting depth while MT1 and MT2 reduced rooting depth by 17.5% and 15.2%,respectively, under WS. Root distribution was associated with crown root number per tiller but not necessary with water use efficiency in our system. Keywords: Rice, Root, Root distribution, Water deficit, Mutant ric

True-to-type micropropagated plants of para rubber (Hevea brasiliensis Müll. Arg.) via somatic embryogenesis

Plant micropropagation via somatic embryogenesis is a powerful technique for rapid mass propagation, especially in para rubber (Hevea brasiliensis Müll. Arg.). However, somaclonal variations are the major limitation of this process. To date, DNA fingerprinting, i.e., RAPD (Randomly Amplified Polymorphic DNA), Star Codon Targeted (SCoT), and SSRs (Simple Sequence Repeats), is one of the most successful technologies to detect the genetic fidelity in the somatic embryos. The aim of present study was to induce somatic embryos from inner integument explants of para rubber cv. ‘RRIM 600’ at different developmental stages and subsequent acclimatization and transplantation (under greenhouse and field conditions) of the propagated seedlings. The genetic stability of the plants derived from somatic embryos was also analysed in comparison to the mother plant using RAPD, SCoT and SSRs markers. Somatic embryos derived from inner integuments of 5-week-old immature seeds after pollination were more efficient than older and younger seeds. In addition, para rubber mother plants cv. ‘RRIM600’ and plants derived from somatic embryogenesis demonstrated the same pattern of DNA fragments, as confirmed by three PCR-based techniques, RAPD, SCoT and SSRs, whereas these in the pattern were different from ‘RRIT 226’, ‘PB 235’, ‘PB 251’, ‘PB 255’ and ‘BMP 24’. Interestingly, T2 plant was found to possess somaclonal variations when compared with mother plant. Based on the results, we confirm that the plants derived from somatic embryogenesis of para rubber cv. ‘RRIM 600’ were true-to-type to that of ‘RRIM 600’ master stock

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

Development of Arbuscular Mycorrhizal Fungi-Organic Fertilizer Pellets Encapsulated with Alginate Film

A novel formulation consisting of arbuscular mycorrhizal fungi (AMF) spores mixed with sterilized organic fertilizer (AMF-F) encapsulated by an insoluble calcium alginate film was developed to enhance AMF efficacy and stability. The hardness of the pellets increased from 7–8 N to approximately 80 N by increasing the alginate concentration of the coating film from 1 to 3%. The AMF spore germination rate for the AMF and AMF-F pellets coated with calcium alginate films depended on the alginate concentration. A 2% sodium alginate formulation for the coating films resulted in optimal AMF spore germination rates and mechanical properties for handling, transport, and stability. The inclusion of a sterilized organic fertilizer in the encapsulated AMF-F pellets considerably induced AMF mycelial growth and helped prolong the shelf life of the pellets. In soil, the AMF-F pellets encapsulated with alginate initially degraded faster than the alginate-encapsulated AMF pellets. However, both types of pellets were fully degraded within 30 days. It was demonstrated that AMF and AMF-F could promote colonization and provided resistance to drought stress in maize potted plants

Physiological, Morphological Changes and Storage Root Yield of Sweetpotato [Ipomoea batatas (L.) Lam.] under PEG-Induced Water Stress

Sweetpotato is an important tuberous root crop rich in nutrients such as vitamins and carbohydrates, and can grow well in arid regions with less water consuming crop. The aim of this research was to evaluate the storage root yields, physiological, biochemical and morphological traits in sweetpotato cv. ‘Japanese Yellow’ subjected to polyethylene glycol (PEG)-induced water deficit. At harvest (4 months after planting) the number of storage roots per plant and storage root fresh weight in sweetpotato treated with 5% PEG (-0.54 MPa) in nutrient solution of hydroponic culture declined by 20.0% and 47.4% compared to the control without PEG, respectively. Leaf area and leaf dry weight significantly decreased by 85.6% and 95.3%, respectively when exposed to water deficit stress. Sucrose content (114.7 mg g-1 dry weight; DW) in storage roots of sweetpotato grown under PEG-induced water deficit conditions was enriched by 2.2 fold of control (52.5 mg g-1 DW) and was greater than in storage roots derived from soil culture (70.3 mg g-1 DW). Total soluble sugar in the root and storage root tissues was enriched and may play a key role as osmotic adjustment (OA) in PEG-induced water stressed plants. Free proline and sucrose contents were also dominated in the leaf tissues to maintain the leaf osmotic potential in water stressed plants. In addition, chlorophyll degradation, chlorophyll fluorescence diminution and stomatal closure were found in plants grown under PEG-induced water deficit conditions, leading to reduction in net photosynthetic rate (Pn) and subsequently lesser amounts of glucose and fructose contents in the leaf tissues. Sucrose and free proline in the roots of sweetpotato play a key role as major osmotic adjustment when subjected to PEG-induced water deficit condition. Basic knowledge gained from this research will further be investigated the drought defense mechanism in sweetpotato via osmoregulation system

Regulation of curcuminoids, photosynthetic abilities, total soluble sugar, and rhizome yield traits in two cultivars of turmeric (Curcuma longa) using exogenous foliar paclobutrazol

Paclobutrazol (PBZ) is a member of plant growth retardants, commonly applied for growth regulation, yield improvement, and biotic and abiotic stress alleviation. However, the effects of PBZ on turmeric (Curcuma longa L.; Zingiberaceae), a rhizomatous herb, have not been well established. The objective of this investigation was to gain a better understanding of the effect of PBZ on two different varieties of turmeric plants, ‘Surat Thani’ (‘URT’; high curcuminoids >5% w/w) and ‘Pichit’ (‘PJT’; low curcuminoids <3% w/w). Pseudostem height of cv. ‘PJT’ treated by 340 µM PBZ was significantly decreased by 14.82% over control, whereas it was unchanged in cv. ‘URT’. Interestingly, leaf greenness (SPAD value), maximum quantum yield of PSII (Fv/Fm) and photon yield of PSII (ΦPSII) in cv. ‘PJT’ treated by 340 µM PBZ were significantly elevated by 1.47, 1.28 and 1.23 folds, over control respectively. Net photosynthetic rate (Pn) in cv. ‘PJT’ declined by 38.58% (340 µM PBZ) over control, as a result of low levels of total soluble sugars (TSS; 127.8 mg g-1 DW) in turmeric rhizome. A positive relation between photosynthetic abilities and aerial fresh weight was demonstrated. In addition, a negative relationship between TSS and total curcuminoids was evidently found (R2 = 0.4524). Curcuminoids yield in turmeric rhizomes significantly dropped, depending on the degree of exogenous foliar PBZ applications. In summary, cv. PJT was found to be very sensitive to PBZ application, whereas rhizome yield and growth traits and high amount of curcuminoids were retained in cv. ‘URT’. Plant growth retention in turmeric cv. ‘URT’ using 170 mM PBZ foliar spray without negative effects on rhizome biomass and total curcuminoids content was demonstrated

Regulation on Antioxidant Defense System in Rice Seedlings (Oryza sativa L. ssp. indica cv. ‘Pathumthani 1’) Under Salt Stress by Paclobutrazol Foliar Application

The present study investigated the effect of paclobutrazol (PBZ) foliar application on oxidative metabolism in salt-stressed rice (Oryza sativa L. cv. ‘Pathumthani 1’; PTT1) seedlings. Fourteen-days-old rice seedlings, grown in the pots were pretreated with 15 mg L-1 paclobutrazol supplied as foliar spray. One week after pretreatment, the rice seedlings were exposed to salt stress (150 mM NaCl) for 12 days. It was observed that salinity enhanced the production of reactive oxygen species (ROS), including superoxide radical (O2•−), hydrogen peroxide (H2O2) and hydroxyl radical (OH·). It also increased reactive oxygen species-associated oxidative damage, measured in terms of lipoxygenase activity, conjugated dienes, malondialdehyde content and relative electrolyte leakage. Increase in these parameters was associated with the decrease in the activity of enzymatic antioxidants [superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT)] and the levels of non-enzymatic antioxidants [ascorbic acid (AsA), total glutathione and α-tocopherol contents). Pretreatment of seedlings with paclobutrazol significantly lowered reactive oxygen species accumulation and membrane damage (p < 0.05), which can be correlated with the increased antioxidant activity (both enzymatic and non-enzymatic traits) under salt stress. The study concluded that paclobutrazol-treatment up-regulates the antioxidant defense system and recuperates the salt-induced oxidative damage in ‘Pathumthani 1’ rice seedlings under salt stress

Above-ground vegetation indices and yield attributes of rice crop using unmanned aerial vehicle combined with ground truth measurements

Rice is an important economic and staple crop in several developing countries. Indica rice cultivars, ‘KDML105’ and ‘RD6’ are clear favourites, popular throughout world for their cooking quality, aroma, flavour, long grain, and soft texture, thus consequently dominate major plantation area in Northeastern region of Thailand. The objective of present study was to validate UAV (unmanned aerial vehicle)-derived information of rice crop traits with ground truthing non-destructive measurements in these rice varieties throughout whole life span under field environment. Plant height of cv. ‘KDML105’ was more than cv. ‘RD6’ for each respective stage. Whereas, number of tillers per clump in ‘KDML105’ exhibited stability at each developmental stage, which was in contrast to ‘RD6’ (increased continuously). Moreover, 1,000 grain weight, total grain weight and aboveground biomass were higher in ‘KDML105’ than in ‘RD6’ by 1.20, 1.82 and 3.82 folds. Four vegetative indices, ExG, EVI2, NDVI and NDRE derived from UAV platform proved out to be excellent parameters to compare KDML105 and RD6, especially in the late vegetative and reproductive developmental stages. Positive relationships between NDVI and NDRE, NDRE and total yield traits, as well as NDVI and aboveground biomass were demonstrated. In contrast, total chlorophyll pigment in cv. ‘RD6’ was higher than in cv. ‘KDML105’ leading to negative correlation with NDVI. ‘KDML105’ reflected rapid adaptation to Northeastern environments, leading to maintenance of plant height and yield components. Vegetation indices derived from UAV platform and ground truth non-destructive data exhibited high correlation. ‘KDML105’ was rapidly adapted to NE environments when compared with ‘RD6’, leading to maintenance of physiological parameters (detecting by UAV), the overall growth performances and yield traits (measuring by ground truth method). This study advocates harnessing and adopting the approach of UAV platform along with ground truthing non-destructive measurements of assessing a species/cultivars performance at broad land-use scale

Evaluation of water deficit tolerance in maize genotypes using biochemical, physio-morphological changes and yield traits as multivariate cluster analysis

Drought is an abiotic stress that inhibits plant growth and development and, therefore, declines crop productivity, as seen in maize plant. The aim of this investigation was to identify the candidate maize varieties that can be grown under water limited conditions using physio-morphological and yield attributes. Eight genotypes of maize including ‘Suwan4452’ (drought tolerant) as a positive check, ‘CP301’, ‘CP-DK888’, ‘DK7979’, ‘DK9901’, ‘Pac339’, ‘S7328’, and ‘Suwan5’ were selected as test plants. Physiological, biochemical and morphological characteristics at seedling (24 day after sowing; DAS) and reproductive (80 DAS) developmental stages of plants under 20-day water withholding (WD), and yield traits at harvesting period were analysed. Leaf temperature in each genotype increased with the degree of water deficit stress, leading to leaf chlorosis, and reduction in maximum quantum yield of PSII (Fv/Fm), photon yield of PSII (ΦPSII), net photosynthetic rate (Pn), overall growth and yield. Pn and stomatal conductance (gs) in drought tolerant genotype, ‘Suwan4452’, were decreased by 19.1% and 18.6%, respectively, whereas these in drought sensitive, ‘Pac339’, were significantly declined by 53.9% and 61.8%, respectively. Physio-morphological parameters, growth performance and yield-related traits of maize genotypes grown under water deficit conditions and well-watered conditions were subjected to Ward’s cluster method for identification of water deficit tolerant cultivars. Maintaining photosynthetic abilities, osmotic adjustment and CWSI in drought tolerant genotypes of maize were evidently demonstrated to keep overall growth performance and yield attributes. Based on multivariate cluster analysis and PCA (principal component analysis), ‘Suwan4452’, ‘CP-DK888’ and ‘S7328’ were categorized as drought tolerant genotypes whereas ‘Suwan5’, ‘Pac339’, ‘DK7979’, ‘CP301’ and ‘DK9901’ were identified as drought susceptible cultivars. Hybrid maize cvs. ‘CP-DK888’ and ‘S7328’ may further be suggested to be grown in the rainfed area without irrigation