Sri Lankan Rice Varieties Research Articles

Variation in essential mineral element and toxic trace element concentrations in the seeds of Sri Lankan rice varieties as affected by milling and soil fertility

Concentration of mineral elements in rice seeds may vary depending on the soil fertility status and seed polishing (milling). In order to test this, 54 rice varieties were grown in the fields used to cultivate rice either with or without applying fertilizers for over 40 years. Part of the seeds collected from those varieties was polished before using for element analyses using ICP-MS while the rest considered as unpolished seeds. When comparing unpolished rice seeds produced at fertilized and unfertilized sites, the concentrations of Mg, Ca, K, Mn, Co, Cu, As and Cd were decreased, and the concentrations of Na, Al, Fe, Zn, and Mo were unchanged from fertilized to unfertilized sites. When comparing unpolished and polished rice seeds produced at fertilized and unfertilized sites, seed Mg, K, Mn, Fe, Co and Zn concentrations were higher in unpolished seeds than those in polished seeds, and the concentrations of Na, Al, Mo, Cd, As and Pb were similar between polished and unpolished seeds. Estimated values revealed that rice contributed 4–15% of the daily requirement of Fe, Cu, Zn, and 50–60% Mo irrespective of the soil fertility and polishing. Seed concentrations of As, Pb and Cd were lower than the maximum allowable levels. However, rice consumption contributed to the daily intake of 4–8 µg as, 2–6.5 µg Cd, and 19–25 µg Pb. Improving soil fertility is required to enrich rice seeds with most of the micronutrients and the milling should be done with much care to minimize nutrient loss in human diet.

Variation in amino acid profiles of selected Sri Lankan rice varieties induced by milling

AbstractStudy presents the variation in free amino acids (FAAs) and total AAs in rice at different milling degrees. Two rice cultivars; Pachchaperumal and Bg 406 were subjected to three (4%, 7%, 12%) degrees of milling, and the variations in AA composition of milled rice and resulting bran were studied. Milling caused significant (p < .05) reduction (5.7%–40.0%) of AAs in rice. Milling accounted for an increase in density of FAAs with sweet and sour taste in rice while reducing FAAs with bitter taste. Parboiling unequivocally aided the retention of AAs in rice upon milling. A variety‐specific distribution of AAs was observed inside the rice grain. Despite the reduction in AAs upon milling, the nutrient density, which is the ratio between the essential to nonessential AAs was not reduced in rice. Rice bran contained nutritional gamma amino butyric acid (GABA) (19.6%–29.1%) and essential AAs (35.7%–38.8%).Novelty impact statementMilling is a post harvesting technique used in the production of rice that improves the physical properties of rice, which are desired by the consumers that include whiteness, translucency and sensory properties as well as the storage stability. The amino acid content in rice is significantly reduced with the increase in milling degree. However, milling increases the ratio between the sum of FAAs with sweet and sour taste to, sum of free amino acids with bitter taste, which could be attributed to one of the factors leading to the enhanced sensory quality observed with the well‐milled rice. Parboiling enables the retention of nutritionally and functionally important amino acids that include essential amino acids and gamma amino butyric acid (GABA) during the milling process.

Sri Lankan traditional parboiled rice: A panacea for hyperglycaemia?

The research aimed to scientifically prove that parboiled Sri Lankan traditional rice elicits lower glycaemic responses comparative to raw unpolished or polished rice. Thus the proximate composition and glycaemic indices (GI) of raw, raw polished, and parboiled traditional Sri Lankan rice (Oryza sativa L.) varieties Godaheenati, Batapola el, Dik wee, Dahanala, Unakola samba, and Hangimuththan were studied as comparative data are not available. Cooked parboiled rice contained significantly high moisture (P<0.05) than raw or raw polished. Mineral content was low (<1.5%) regardless of processing. Crude protein was comparatively high (5.8-11.0% DM) with 2.1-5% (DM) fat with raw unpolished and parboiled having higher contents. Digestible starch of raw polished was highest compared to parboiled or raw unpolished (68.8-90.5% DM). Resistant starch was significantly (P<0.05) high in parboiled rice (1.1-7.2%) with the least total dietary fibre in raw polished rice. All varieties of parboiled and raw polished were found to elicit low GI and high GI respectively. High moisture, high resistant starch, and low starch in cooked parboiled rice contributed to low GI compared to raw unpolished or raw polished rice.

Assessment of Marker-trait Associations for Amylose Content, Gelatinization Temperature and Yield in Sri Lankan Rice Varieties

Rice provides a balanced diet, and regular rice consumption helps maintain a healthy life and prevents many common illnesses. Amylose content and gelatinization temperature are considered major physicochemical factors which significantly affect the nutrition and cooking quality of rice. The Waxy (Wx) gene controls the synthesis of amylose in the endosperm and the ALK gene controls the gelatinization temperature of rice. Both genes are present on chromosome 6. Improving the rice traits is crucially essential to the cultivators and the consumers to overcome the increasing demand for high-quality and nutritionally rich rice. Many studies have been successfully conducted to improve the agronomical traits of rice. However, the concern for improving nutrition and cooking quality-related traits of rice is less common among the breeders. Therefore, considering the current trends, introducing consumer-friendly novel varieties that can fulfill the nutritional requirements is essential to face the increasing domestic demand for high-quality rice. In the present study, we used frequently grown 54 local rice varieties and carried out a marker-based genetic analysis for three traits: amylose content, gelatinization temperature, and yield. Then statistical analysis was carried out using quantitative data of different agronomical and physicochemical traits to identify the correlation and potential to improve such essential traits. The level of amylose content is significantly associated with the gelatinization temperature indicating that AC and GT have a positive correlation. The DNA markers SSIIa and Seq1-2 markers showed monomorphic patterns indicating the narrow genetic basis of the rice varieties tested. This study revealed that existing high-yielding rice varieties could be successfully employed to increase the amylose content while decreasing the level of gelatinization temperature through breeding strategies to make nutritionally rich consumer-friendly novel varieties.

Fatty acid profiles of selected traditional and new improved rice varieties of Sri Lanka

This study evaluated fatty acid profiles (FAPs) of fifteen pigmented and non-pigmented traditional and new improved rice varieties (RVs) of Sri Lanka. Fat was extracted from rice flour, derivatized to methyl esters and analyzed by gas chromatography (n = 3 each). Results showed significant (P < 0.05) differences in FAPs among the tested RVs. Total fatty acids, saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA) and total unsaturated fatty acids of selected RVs varied from 22.00–32.29, 4.85–7.36, 9.44–14.55, 6.87–10.31 and 16.96–24.87 mg/g of rice respectively. Further, PUFA/SFA ratios varied from 1.22 to 1.63. The major fatty acids palmitic, oleic and linoleic acids together contributed nearly 90–96 % of total fatty acids present in rice. Interestingly, differences among RVs in terms of FAPs were due to differences in individual fatty acids in RVs irrespective of traditional or new improved and red or white RVs. In conclusion, nutritionally sound healthy RVs can be selected by studying its total FAP. This is the 1st study to report total FAP of a large set of Sri Lankan rice varieties and report differences among FAP of traditional and new improved rice varieties world over.

Comparative Evaluation of Nutritional Compositions of Different Sri Lankan Rice Varieties on Glycemic Regulation

The main nutrition of rice (Oryza sativa) is carbohydrates in starches, sugars and fibre. The amount and type of carbohydrates can be detrimental to health as they increase blood glucose levels, leading to the risk of diabetes. As intrinsic and extrinsic factors affect the glycaemic response of foods, understanding the influence of proximate composition and mineral content of rice on Glycaemic Index (GI) is useful. The nutritional composition and glycaemic potential of twelve rice varieties grown in Sri Lanka; Bg94-1, At405, Bw367, H.H.Z.36, Ld368, At362, Bg300, Bg352, Bg406, Madathawalu, Suduheenati and Pachchaperumal were studied. The GI was calculated using fourteen healthy subjects consisting of seven males and seven females fed with cooked rice containing 50 g carbohydrate and a reference food. The nutritional composition of the rice was compared with the GI of each variety. The GI of 12 rice varieties varied from 40-69. The proximate and mineral compositions were significantly different except for the moisture level. This study suggested a significant negative correlation between GI and calcium content. Among the studied rice varieties, "Sudu heenati" showed a high level of calcium, chromium, protein and fibre values with low GI, which would claims health benefits.

Impact of seasonal, geographical and varietal variations on amino acid profile of Sri Lankan rice varieties (Oryza sativa L.)

With the aim of assessing the feasibility of utilization of amino acid (AA) profiles in characterization of rice varieties grown under distinct influential conditions, the impact of seasonal, geographical and varietal variations on AA and organic acid profiles in rice was investigated. Seven traditional rice varieties with diverse grain and agronomic characteristics were cultivated in two major distinct agro ecological regions of Sri Lanka across the two major cultivation seasons. The AA and organic acid compositions were determined using liquid chromatographic technique. Rice grains contained twenty AAs (41.2–75.1 mg/100 g) including Gamma Amino Butyric Acid (GABA) in free form and sixteen AAs in bound form (70.0–105.4 g/kg). Rice grains contained low levels (4.3–103.3 mg/kg) of fumaric, succinic and malic acids while citric acid (314.6–534.5 mg/kg) being the major organic acid present. Wet agro-ecological conditions favored total AA formation in rice. The impact caused from the season was found pronounced over the impact arising from the geographical location on the AAs in free form in rice. Principal Component Analysis (PCA) indicated that AA profile could be used for differentiation of rice based on the season and the variety.

Influence of canopy architecture on the light interception, photosynthetic and biomass productivity in irrigated elite Sri Lankan rice varieties

Purpose: Canopy light interception and extinction play a crucial role in determining crop yield. Developing new rice varieties with improved canopy architecture along with modified intrinsic photosynthetic mechanisms will ensure the global food security. However, a comprehensive understanding of local rice varieties addressing on such avenues have not been reported. Hence, our pioneering experiments were carried out to elucidate such underlying properties among locally developed two elite rice varieties viz; At-362 and Bg 94-1 grown in the Ampara district of Sri Lanka. Research Method: The field experiment was carried out at the Agro Tech Park, Malwatta (7°20'N and 81°44'E altitude 16.0 m above sea level) between October 2019 to January 2020 implemented with Randomized Complete Block Design with four replicates. The Photosynthetically Active Radiation (PAR) distribution on the above and below canopy level was measured during the pre and post-anthesis stages. Then leaf stomatal conductance, chlorophyll fluorescence parameters and the chlorophyll content were also measured. At harvest, the final biomass produced were compared. Findings: The result revealed that variety At-362 had a higher Leaf Area Index (LAI) of 2.64 at pre anthesis and tend to decline at the latter part of their growth cycle. The striking feature was the extinction coefficient (k) seems to be much lower (0.47) in the At-362 variety than the Bg 94-1 (0.60) depicting that the former has produced vertical leaves (erect-leaf type) while the latter tends to produce horizontal leaf plans in the canopy. Hence, light attenuation was high and eventually, the bottom canopy layer received much lower PAR. Furthermore, LAI had a strong negative correlation with understory PAR indicating that the canopy architecture with an improved light interception will lead to permit more light penetration and utilization through the improved quantum yield efficiencies than the horizontal canopies. Hence significantly (p&lt;0.05) improved above-ground biomass and panicle weight were observed in At-362. Originality/value: This experiment depicts that rice yield could be further improved through introgression of canopy architectural features along with improved photosynthetic traits.

Effect of near canopy thermal changes on growth, yield and grain sterility of three ultra-short age rice varieties under aerobic and flooded conditions

Canopy temperature (CT) represents the temperature experienced by the uppermost portion of the vegetative canopy of a crop. CT may better explain the high temperature-induced grain sterility and yield losses than air temperature does. However, less scientific attention was paid on CT related investigations on rice under Sri Lankan context. Therefore, Sri Lankan rice varieties were evaluated at the Rice Research and Development Institute, Bathalagoda under two soil moisture conditions to study the canopy thermal dynamics and its impact on growth, grain sterility and yield. This Experiment was arranged in a two-factor factorial Completely Randomized Design with eight replicates. Factor one was soil moisture condition (aerobic and flooded) and factor two was rice variety (Bg 250, Bg 252 and Ld 253). CT was continuously monitored at 10 minutes intervals. Growth and yield parameters were recorded once a week. Number of tillers was negatively correlated with maximum CT while plant height was positively correlated with minimum CT in both conditions. CT at spikelet opening had a negative impact on pollen fertility and positive impact on grain sterility irrespective of moisture condition. Under flooded condition, grain yield was negatively correlated with maximum CT at 13:00 h. Moreover, growth and yield performances were superior under flooded conditions compared to aerobic conditions. Interactive effect of soil moisture × variety was significant for 1000-grain weight and % pollen fertility where the highest values were recorded by Bg 250 (29.33 g) and Bg 252 (96.4%) in flooded conditions, respectively. In conclusion, monitoring CT dynamics can be considered as a useful tool to assess growth and yield performances of rice under varying soil moisture conditions. Field investigations are suggested to confirm the results.

Intrusion of heavy metals/metalloids into rice (Oryza sativa L.) in relation to their status in two different agricultural management systems in Sri Lanka

The contentious results of elevated As and Cd levels, in both Sri Lankan rice and in agrochemicals have recently raised tremendous attention. These claims could not standalone due to the study's poorly designed sampling and analytical methodologies. In this work, selected traditional Sri Lankan rice and hybrid rice varieties were cultivated (under fertilized and organic conditions) using a split-plot design during Yala (May to August) and Maha (September to March) seasons in two regions: Anuradhapura and Kurunegala. As, Cd, Cr, Hg, Pb, and Se contents were determined in harvested rice grain and straws for Chronic Kidney Disease of unknown etiology (CKDu) risk assessment. In addition, analysis of these elements in water, soil, and agrochemicals was used to estimate their geochemical behavior. The majority of agrochemicals and fertilizers had Cd, Cr, and Pb. Grain Cd contents in rice varieties were ranged from not detectable to 158.9 μg kg−1 in both cultivation seasons, and soil was sought to be the primary Cd source. As, Se, Hg, and Pb were also not detectable in both rice grain and straws. Native variety Pachcha Perumal rice grain showed a low Cd accumulation in both seasons at both regions. Kuruluthuda and Madathawalu showed a moderate accumulation versus other varieties. Cultivating and consuming these native traditional rice varieties practicing organic farming could be a possible way to combat CKDu risks. The correlations (between the rice grain Cd content and farming condition, location, or season of cultivation) were tested linear regression to fit data on to Freundlich model, and no distinct statistical correlations were observed (p > 0.05). Mean chromium contents (38.5–112.1 μg kg−1) detected in the rice grain were not alarming. Soil, irrigation water, and agrochemicals were free from As and Hg. However, rice straws contained substantial amounts of Cd. Therefore, use of it as organic manure should be limited.

A STRATEGY FOR DETERMINING THE CHEMICAL COMPOSITION OF RICE STRAW

As rice is the staple food of most Asian countries, rice straw has become one of the largest agricultural wastes in Asia. It has not been subjected to adequate value additions yet. However, it has excellent potential to be converted to valuable materials, as it contains a significant amount of cellulose. Therefore, it would be beneficial in many ways to identify the cellulose yields of straws of different rice varieties. In general, the cellulose content of biomass is determined by wet chemical methods. Though these methods are accurate, they are not convenient to use under industrial conditions. This research work focuses on investigating the potential of thermal analysis as an alternative way to predict cellulose yields. For the study, rice straws of most frequently cultivated traditional Sri Lankan rice varieties: Suwandel and Raththal, as well as technically modified Sri Lankan rice varieties: BG300 and BG352, were selected. The results obtained by the proposed method were validated by an established three-step chemical extraction process.

Biological responses of Sri Lankan rice (Oryza sativa L.) varieties to rhythmic sound patterns (music and religious chants)

Abstract. Munasinghe DSP, Weerakoon SR, Somaratne S. 2020. Biological responses of Sri Lankan rice (Oryza sativa L.) varieties to rhythmic sound patterns (music and religious chants). Nusantara Bioscience 12: 154-161. Influences of music cause either promoting or restricting the growth of plants. The effects of Pirith chanting and rhythmic sound patterns (Western classical music, Eastern classical music, Rock music) were focused in the present study. Seeds of Two (02) rice varieties (Bg 300 and Kuruluthuda) in f0 and f1 generations were subjected to dormancy break treatment, kept in a soundproof confined chamber, and arranged in Randomized Complete Block Design (RCBD) with two (02) replicates and 10 seeds per replicate. Seeds were germinated under the three sound rhythms, Pirith chanting, and silence. Plants kept under silence served as the control. Sound rhythms and Pirith were played separately for an hour, at 30 cm distance away from the seeds with an intensity of 55-60 dB for seven (07) days continuously, maintaining equal environmental conditions. Following seven (07) days, the percentile germination rate was recorded. Germinated seeds were planted in plastic pots filled with paddy soil, up to ¾ of the total depth, and pots were arranged in Randomized Complete Block Design (RCBD) with five (05) replicates and three (03) plants per replicate. Following one week, plants were subjected to sound rhythm treatments and silence for three (03) months continuously. Measurement of growth and yield performance were recorded every fortnight. Significantly different (p &lt; 0.05) growth and yield performances in both generations were observed under Pirith, Eastern Classical and Western Classical music. Higher rates of growth were observed for rice varieties exposed to Pirith, Eastern and Western classical music. Similarly, yield was also higher compared to rice varieties exposed to rock music. The findings suggest that soft rhythmic sounds are the most appropriate type of music which improved growth and yield performance of rice varieties, Bg 300, and Kuruluthuda. However, further studies are needed to confirm present results and to elucidate the mechanism of responses to Pirith chanting and other rhythmic sound patterns using phytochemical and biochemical analyses.

Single nucleotide polymorphisms in GBBSI and SSIIa genes in relation to starch physicochemical properties in selected rice (Oryza sativa L.) varieties

Single nucleotide polymorphisms in GBBSI and SSIIa genes in relation to starch physicochemical properties in selected rice (Oryza sativa L.) varieties

Identification of phosphorus efficient rice cultivars under low P nutrition through hydroponic based screening

Phosphorus (P) is one of the major nutrients required by plants. A higher portion of P in lowland rice soils is found in unavailable forms due to fixation. Therefore, continuous application of P fertilizer to rice (Oryza sativa L.) is needed to obtain a satisfactory yield. Identification and subsequent cultivation of high yielding rice varieties which can withstand low level of P is a better alternative to the continuous P application. The objective of this study was to categorize Sri Lankan rice varieties according to their response to P deficient conditions. Forty eight rice varieties including three old improved varieties and 45 new improved varieties were evaluated at deprived (10 μM P) and sufficient (50 μM P) P levels in a nutrient solution culture. Multiple plant traits; number of tillers, root and shoot dry weights and P content in shoot tissues were assessed at 52 days after planting. Rice variety Bg 94-1 gained higher biomass and P uptake (i.e. shoot P content- mg/plant). Simultaneously, At402 had lower biomass gain and shoot P content. Rice varieties were grouped into two distinct clusters based on their responses to P deficiency such as biomass gain, P uptake and number of tillers per plant. This study showed that At 405, Bg 94-1, At 307, Bg 304, Bg 300 and At 354 are promising rice varieties with higher response to low level of P supply.

Mineral contents of Sri Lankan rice varieties as affected by inorganic fertilization

Application of inorganic fertilizers may incorporate minerals into rice grains. Distribution of minerals in rice grains vary in bran and kernel. The aim of the present study was to compare mineral contents (MCs) of bran and kernels of selected newly improved rice varieties in Sri Lanka with and without fertilizers. Twenty rice varieties were tested. Rice bran and rice kernels were analyzed for Ca, Mg, Mn and Zn using Atomic Absorption Spectrophotometer. Calcium contents of brans and kernels ranged from 952 to 1605 mg/kg and 613 to 1107 mg/kg dry matter in fertilized varieties, respectively. High MCs were observed in fertilizer applied varieties. Higher MCs were found in the bran of rice grains. The MCs of rice grains were significantly different among the varieties and affected by fertilizer application and processing. Applications of inorganic fertilizers strengthened the MCs of rice kernels and bran.

Molecular characterization and expression of α-gliadin genes from wheat cultivar Dacke in Bg 250 rice variety

ABSTRACTThe main seed storage protein in wheat is gluten. It consists of gliadin and glutenins. Gluten gives high elasticity and extensibility during bread making, facilitating the formation of the dough. Rice is the staple food of Sri Lankans but, it has poor dough making ability compared to wheat. The aim of the present work was to characterize, clone and express α-gliadin in the T0 generation of Bg 250 rice variety as a preliminary step in improving the dough making ability of rice flour. Five α-gliadin recombinant pCR™2.1-TOPO® clones were selected for sequence analysis. Of the five clones, two functional genes and three pseudogenes were identified. Phylogenetic analysis revealed the two functional genes, (accession numbers KC660359 and KC660358) to be closely related to the α-gliadin genes of Triticum monococcum. The α-gliadin gene (KC660359) contained five cysteine residues, one less than the normal occurrence of cysteine residues in α-gliadin genes. To date there are no reports on expression of gliadin gene in transgenic rice. This novel gene was successfully expressed in the Sri Lankan rice variety Bg 250 under the control of the rice GluB-1 endosperm specific promoter.

Natural and Induced Glufosinate-resistance in selected Rice (&lt;em&gt;Oryza sativa L&lt;/em&gt;.) Varieties in Sri Lanka

Purpose: Herbicide-resistant rice varieties in combination with post-emergent broad-spectrum herbicides improve the effectiveness of weed management in rice fields. Herbicide-resistance can be acquired naturally or induced by classical or modern breeding techniques. In the present study, screening of Sri Lankan rice varieties to glufosinate was examined and attempts were made to develop glufosinate-resistant rice varieties with the help of the breeding technique, mutagenesis.Research Method: Natural glufosinate-resistance was studied in seven (7) traditional and eighteen (18) inbred rice varieties under 0.27, 0.30 and 0.33 kg ha -1 glufosinate concentrations. Induced glufosinate-resistance in seed-derived calli of four glufosinate-susceptible rice varieties using Ethyl Methane Sulfonate was also observed and these were then treated with 0.2% (v/v) glufosinateto to determine induced glufosinate-resistance in seed-derived calli. Findings: Two traditional varieties (Pachchaperumal, Ma Wee) and fifteen inbred varieties (At362, Bg250, Bg300, Bg352, Bg357, Bg358, Bg359, Bg360, Bg366, Bg369, Bg379/2, Bg403, Bg450, Bg454, and Bg94-1) were resistant to glufosinate. Hardly any distinct yield penalty in Bg94-1, Bg403, Bg454, Bg379-2 and Ma Wee was observed under all glufosinate concentrations. Visual symptoms and chlorophyll damages caused by glufosinate for all varieties recovered within 14 days of treatment. Higher glufosinate-resistance was observed in EMS-mutated calli derived from seeds of naturally glufosinate-susceptible varieties. Molecular (AFLP) analysis confirmed in vitromutation and theM31E10 primer combination was a potential AFLP marker to identify glufosinate-resistance in rice varieties.Research Limitation: The study reports the results of screening natural and induced glufosinate-resistance in Sri Lankan rice. Inheritance of glufosinate-resistance is to be tested through several generations in Sri Lankan rice varieties.Original Value: Study provides a screening method applicable to Sri Lankan Rice varieties in identification of herbicide-resistance to permitted concentrations of glufosinate.

&lt;i&gt;In silico&lt;/i&gt; promoter analysis reveals rice &lt;i&gt;Wx&lt;/i&gt; promoter could be a TATA-less promoter with a putative pyrimidine rich region

Rice waxy gene is one of the major genes, which determines the amylose content of a rice grain. The expression of this gene is regulated by various stimuli such as temperature, light, drought and diseases. Promoter region of a gene is responsible for changing the level of expression with the help of transcription factors and their binding sites, cis-acting regulatory elements found in the promoter region ranging from 2000 bp upstream and 500 bp downstream relative to the transcription start site. Present study investigated the putative transcription factor binding sites in the promoter region and possible expression regulation stimuli using five Sri Lankan rice varieties, two glutinous rice varieties, Arabidopsis thaliana and potato. The promoter regions of the plants were extracted either after mapping selected varieties from rice 3000 genome project or from promoter databases. Signal scan was carried out to capture putative signal sequences, and kappa incidence of coincidence vs guanine cytosine content, guanine cytosine skew, and multiple sequence alignment were also performed. The results revealed that rice Wx promoter could be a TATA-less promoter with a putative pyrimidine patch, and categorized under ATCG middle class of promoters. The possible transcription regulation stimuli of waxy gene include dehydration, light, temperature, and hormones. There were signal sequences related to mesophyll, root nodule, seed and root specific regulation of expression.

Development of a Sri Lankan rice variety Bg 94-1 harbouring cry2A gene of Bacillus thuringiensis resistant to rice leaffolder [Cnaphalocrocis medinalis (Guenée)

The rice leaffolder (RLF) [ Cnaphalocrocis medinalis (Guenee)] is a major lepidopteran insect pest of rice in Sri Lanka and the larvae cause significant yield losses annually. Insecticidal crystal protein gene, cry2A driven by the 35S cauliflower mosaic virus (CaMV) promoter with a double enhancer sequence was transformed into scutellum derived embryogenic calli of Bg 94-1 via Agrobacterium tumefaciens mediated transformation procedure. Transformation vector pCAMBIA 1305.1 containing the transgene construct CaMV 35S d-cry2A-NOS, hygromycin phosphotransferase and β-glucuronidase (GUS)-Plus was employed in this study. Transformed calli were subjected to 4 ‒ 5 rounds of hygromycin selection. Molecular analysis of the generated plants together with an insect bioassay using RLF larvae confirmed successful transformation and expression of this transgene in T0 generation of rice plants. A total of 19 putative transgenic plants could be confirmed from a total of 60 T0 generation plants examined. Insect feeding bioassay demonstrated that T0 transgenic rice plants are effective against RLF larvae, and showed approximately 89 % larval mortality after 3 days and 100 % mortality after 5 days of feeding. Further molecular analysis of T1 generation of the transgenic lines confirmed the stable integration of cry2A transgene into the Bg 94-1 genome. Findings of this study demonstrated that the cry2A gene of Bacillus thuringiensis ( Bt ) was successfully transformed into Bg 94-1 via Agrobacterium mediated transformation and have developed resistance against the RLF larvae. Thus, this study highlights the importance of developing transgenic rice, which can provide insect resistance against a major lepidopteran insect pest of rice in Sri Lanka.

Evaluation of genetic diversity of cis-acting elements of Abscisic acid responsive element binding protein (ABRE-BP) in selected Sri Lankan rice varieties

Salinity is a major abiotic stress that affects rice cultivation. Osmotic stress caused by salinity activates tolerance mechanisms in rice. The Abscisic Acid Responsive Element Binding Protein (ABRE-BP), transcribes for a bZIP family transcription factor that binds to the cis-regulatory element Abscisic Acid Responsive Element (ABRE) at the promoter of downstream salinity responsive genes and regulates their expression. Hence, the study was focused on analyzing the nucleotide diversity of a region in ABRE-BP promoter. Analysis of the ABRE-BP sequences of 47 Sri Lankan rice varieties and two reference varieties retrieved from a public database revealed many insertions and deletions (INDELs) and single nucleotide polymorphisms (SNPs) in the promoter. Eleven, abiotic stress related cis-elements were identified, but none of the INDELs spanned over them. However, SNPs either deleted existing cis-elements or created new cis-elements. The salinity stress responsive elements, MYBCORE and GT1GMSCAM4 were detected in few varieties, and were not associated with salinity tolerance based on current available salinity ratings. The presence of SNPs in cis-elements clustered them to nine groups at 68% similarity. The DNA polymorphisms on stress responsive cis-acting elements did not show a strong association with the known salinity ratings of many varieties. Nevertheless, the presence of INDELs affects the relative distance between elements, and thus may alter the expression of the ABRE-BP that regulates downstream stress responsive genes.