Wx Gene Research Articles

A mutant allele of the Wx gene encoding granule-bound starch synthase I results in extremely low amylose content in rice.

An amino acid substitution (T506I) in the GT1 domain of granule-bound starch synthase I dramatically reduces amylose content in rice.

Revolutionizing Rice Grain Quality: A Holistic Review Integrating Conventional and Molecular Approaches

This review mainly focuses on the rice grain quality based on which rice varieties are distinguished into several quality classes like, physical quality, eating and cooking quality and nutritional quality. The rice breeding programme needs to focus on the development of nutrient-dense rice for value addition, helping in reducing malnutrition and Vitamin-A deficiency (VAD). There is enough scope to enhance the nutritional and cooking quality in small and medium grain rice germplasm by bringing them into the breeding programme through Fe and Zn and Vitamin-A biofortification, aided with molecular techniques. Many studies have been conducted to find out the quantitative trait locus (QTL) for enhancing the quality of grain. The QTL qBRR5 and qBRR3 are responsible for brown rice grain width and length found on chromosome 5 and on chromosome number 3, respectively and for head rice on chromosome number 1, 5, and 6. The QTLs present on chromosomes 3, 5, and 6 are responsible for head rice recovery, chalky appearance of rice grain as well as grain size and shape. The gene Wx, located on chromosome 6 linked with the QTL qAC6 regulate amylose content and gel consistency. The QTL SSIIa on chromosome 6, control both the amylopectin and gelatinization temperature. The QTLs for Fe and Zn content in rice grain are located on chromosome 2, 3, 8, 11 and 12. Development of “Golden rice” and innovations with Arabidopsis genes can significantly enhance β-carotene levels and address Vitamin-A deficiency, while RNAi techniques improve storage quality.

Adjusting the amylose content of semi-glutinous japonica rice by genome editing of uORF6 in the Wx gene

Amylose content, the key determinant of rice eating and cooking quality, is regulated primarily by the Waxy (Wx) gene. We adjusted the amylose content and transparency of semi-glutinous japonica rice carrying the Wxmp allele by genome editing of upstream open reading frame 6 (uORF6) of Wx.

IMPROVEMENT OF HIGH AMYLOSE CONTENT IN CH1 RICE VARIETY BY MARKER ASSISTED PSEUDO-BACKCROSS BREEDING

The objective of this research was to introgression of high amylose content into CH1 rice variety by using pseudo-backcrossing breeding. Crossing between CH1 and RD49 was performed to produce F1 progenies. After that, the progenies will backcross to CH1 to develop BC1F1 population. Then, the selected plants from the BC1F1 population were continuously selfed to develop BC1F2 and BC1F3 populations, respectively. For marker assisted selection, the OSR19 DNA marker that is specific to Wx gene was used for assisting the selection of plants with high amylose content in foreground selection to choose favorite genotype. Total 67 SSR markers used genetic background selection was done twice in BC1F1 and BC1F2 populations. The results showed that selection could be achieved for BC1F1 and BC1F2 plants having high amylose content and first highest ranking of genetic background similar to recurrent parent exhibited 91.04 and 97.76 percent, respectively. The marker assisted selection could accelerate 4 generations in backcross breeding program. The BC1F3 seeds of 6 selected lines were planted in paddy field for preliminary yield test. It was found that agronomic characters and yield of the selected lines were not statistically different from those of CH1 variety and high amylose content as donor parent.

GWAS and Transcriptomic Analysis Identify OsRING315 as a New Candidate Gene Controlling Amylose Content and Gel Consistency in Rice

Cooking quality is the main factor determining the market value of rice. Although several major genes and a certain number of QTLs controlling cooking quality have been identified, the genetic complexity and environmental susceptibility limit the further improvement for cooking quality by molecular breeding. This research conducted a genome-wide association study to elucidate the QTLs related to cooking quality including amylose content (AC), gel consistency (GC) and alkali spreading value (ASV) by using 450 rice accessions consisting of 300 indica and 150 japonica accessions in two distinct environments. A total of 54 QTLs were identified, including 25 QTLs for AC, 12 QTLs for GC and 17 QTLs for ASV. Among them, 10 QTLs were consistently observed by the same population in both environments. Six QTLs were co-localized with the reported QTLs or cloned genes. The Wx gene for AC and GC, and the ALK gene for ASV were identified in every population across the two environments. The qAC9-2 for AC and the qGC9-2 for GC were defined to the same interval. The OsRING315 gene, encoding an E3 ubiquitin ligase, was considered as the candidate gene for both qAC9-2 and qGC9-2. The higher expression of OsRING315 corresponded to the lower AC and higher GC. Three haplotypes of OsRING315 were identified. The Hap 1 mainly existed in the japonica accessions and had lower AC. The Hap 2 and Hap 3 were predominantly present in the indica accessions, associated with higher AC. Meanwhile, the GC of accessions harboring Hap 1 was higher than that of accessions harboring Hap 3. In addition, the distribution of the three haplotypes in several rice-growing regions was unbalanced. The three traits of cooking quality are controlled by both major and minor genes and susceptible to environmental factors. The expression level of OsRING315 is related to both AC and GC, and this gene can be a promising target in quality improvement by using the gene editing method. Moreover, the haplotypes of OsRING315 differentiate between indica and japonica, and reveal the differences in GC and AC between indica and japonica rice.

CRISPR/Cas9-mediated enhancement of semi-dwarf glutinous traits in elite Xiangdaowan rice (Oryza sativa L.): targeting SD1 and Wx genes for yield and quality improvement.

In rice cultivation, the traits of semi-dwarfism and glutinous texture are pivotal for optimizing yield potential and grain quality, respectively. Xiangdaowan (XDW) rice, renowned for its exceptional aromatic properties, has faced challenges due to its tall stature and high amylose content, resulting in poor lodging resistance and suboptimal culinary attributes. To address these issues, we employed CRISPR/Cas9 technology to precisely edit the SD1 and Wx genes in XDW rice, leading to the development of stable genetically homozygous lines with desired semi-dwarf and glutinous characteristics. The sd1-wx mutant lines exhibited reduced gibberellin content, plant height, and amylose content, while maintaining hardly changed germination rate and other key agronomic traits. Importantly, our study demonstrated that exogenous GA3 application effectively promoted growth by compensating for the deficiency of endogenous gibberellin. Based on this, a semi-dwarf glutinous elite rice (Oryza sativa L.) Lines was developed without too much effect on most agronomic traits. Furthermore, a comparative transcriptome analysis unveiled that differentially expressed genes (DEGs) were primarily associated with the anchored component of the membrane, hydrogen peroxide catabolic process, peroxidase activity, terpene synthase activity, and apoplast. Additionally, terpene synthase genes involved in catalyzing the biosynthesis of diterpenoids to gibberellins were enriched and significantly down-regulated. This comprehensive study provides an efficient method for simultaneously enhancing rice plant height and quality, paving the way for the development of lodging-resistant and high-quality rice varieties.

Molecular and genetic basis for improving the quality of soft wheat grain

The increase in agricultural territories in Azerbaijan can no longer cover the problem of shortage of high-quality baking flour in the domestic market. Thus, there is a need to improve the quality of grain harvested from existing areas to obtain more grain products. The purpose of this study is to review and investigate the physico-chemical and genetic parameters of local and introduced soft wheat varieties to further identify promising areas of breeding. For this purpose, a PCR study of individual loci of the Wx genes responsible for amylose synthesis and electrophoresis of Glu genes encoding gluten quantity and quality were performed. In addition, for the varieties Shafaq 2 and Gonen, which were selected during the research for the test baking of bread, a PCR analysis was performed to compile the gliadin formula of the varieties using a sample of the Bezostaya 1 variety as a marker. The physico-chemical characteristics were determined according to quality standards, as well as baking bread sample. During the pilot sowing, one of the varieties – Girmizi Gul1, was sown on plots with various tillage methods – traditional, minimal, and zero. Thus, it was determined that the varieties Gonen and Ekinci 84 contain a zero allele of the Wx-B1 – Wx-B1b gene, which means that their endosperm contains higher-quality starch, and the varieties Askeran, Azemetli 95, Gonen, Kirmizigul, Nurlu 99, Tale 38, and Ugur, in turn, contain a zero allele of the gene GluA1 – GluA1d, which on the contrary worsens the gluten quality of these varieties. As for tillage, the traditional system showed itself to be the best, the minimal tillage was slightly worse, and the zero tillage system turned out to be the least suitable in these conditions. Thus, the obtained data outline further areas for conducting research and open up prospects for targeted selection for alleles of the considered genes

Molecular Breeding of Zheyou810, an Indica–Japonica Hybrid Rice Variety with Superior Quality and High Yield

Rice heterosis has played a significant role in improving rice yields in China since the 1970s. The utilization of heterosis between the indica and japonica subspecies of rice is especially important in this regard. However, inter-subspecies hybridization between indica and japonica rice is hampered by the inadequate seed-setting rate and inferior rice quality of hybrid offspring, which has limited its development. The discovery and cloning of wide-compatibility gene S5-n and the granular starch synthase gene Wx have provided a solution to this problem, paving the way for the breeding of inter-subspecies hybrid rice. Here we demonstrated the breeding process of Zheyou810 and its performances in regional trials. Employing marker-assisted selection through the utilization of KASP (Kompetitive Allele-Specific PCR), a high-yielding and superior-quality indica–japonica hybrid rice variety named Zheyou810 was developed. Zheyou810 achieved an average yield of 10,737.75 kg/ha (12.58% higher than control Jiayou5) in the national regional trials across 2019 and 2020, and 11,777.25 kg/ha (13.36% higher than Jiayou5) in the production trial in 2020, respectively. The quality of rice has also been improved, reaching the standards set by the Ministry of Agriculture of the People’s Republic of China for Grade 3 premium rice (NY/T593). In 2021, Zheyou810 was approved by the national examination showing broad application prospects.

RNA-Seq Revealed the Molecular Mechanism of Nutritional Quality Improvement in o16-wx Double-Mutation Maize

The enhancement of the nutritional composition of maize grains could be achieved by the introduction of a mutation with a heightened lysine content. To obtain double-recessive mutant lines for the o16 and wx genes, a molecular-marker-assisted selection technique was used to backcross them into conventional maize lines. The resultant maize was subsequently utilized to explore the molecular mechanism responsible for the maize’s nutritional quality. Based on this, an RNA-seq investigation was conducted using the employing kernels during the development period of maize kernel (18, 28, and 38 DAP) to examine the gene expression involved in amino metabolism. The results revealed that a total of 27 and 34 differentially expressed genes (DEGs) were identified in tryptophan metabolism and lysine metabolism, respectively, across three time periods. In the lysine synthesis pathway, the genes encoding AK, ASD, and DapF were found to be up-regulated at various stages, encouraging lysine synthesis. Conversely, in the lysine degradation pathway, the genes encoding ALDH7A1 and LKR/SDH were down-regulated, suggesting an increase in lysine content. In the process of tryptophan metabolism, the down-regulation of genes encoding TAA and ALDH led to an increase in tryptophan content. In addition, the down-regulation of genes encoding α-zein resulted in a decrease in zein content, thereby enhancing the nutritional quality of maize. These findings hold substantial significance for elucidating the transcriptional-level molecular mechanism, underlying the accumulation of o16 and wx genes to improve maize grain quality, as well as offering valuable insight for the development of biomarkers and gene editing.

Grain quality characteristics analysis and application on breeding of Yuenongsimiao, a high-yielding and disease-resistant rice variety

Rice quality is one of the main targets of rice breeding and is a complex trait that involves grain appearance, milling, cooking, eating and nutritional quality. For many years, rice breeding has contended with imbalances in rice yield, quality, and disease and lodging resistance. Here, the milling and appearance quality, cooking quality, starch rapid viscosity analyzer (RVA) profile, and nutritional quality of grains of Yuenongsimiao (YNSM), an indica rice variety with high yield, high quality and disease resistance, were determined. YNSM had excellent appearance and quality, with low amylose contents and high gel consistency, and these characteristics exhibited significant correlations with the RVA profile such as hot paste viscosity, cool paste viscosity, setback viscosity, and consistency. Moreover, 5 genes related to length-to-width ratio (LWR) as well as the Wx gene were used to detect the main quality genotype of YNSM. The results showed that YNSM is a semilong-grain rice with a relatively high brown rice rate, milled rice rate and head rice yield and low chalkiness. The results indicated that the LWR and food quality of YNSM might be related to gs3, gw7 and Wxb. This study also reports the quality characteristics of hybrid rice developed using YNSM as a restorer line. The quality characteristics and the genotype for grain quality determined through gene analysis in YNSM may facilitate the breeding of new rice varieties that achieve a balance of grain yield, resistance and quality.

Combined effects of SSII-2RNAi and different Wx alleles on rice grain transparency and physicochemical properties

Near-isogenic lines Nip(Wxb/SSII-2), Nip(Wxb/ss2-2), Nip(Wxmw/SSII-2), Nip(Wxmw/ss2-2), Nip(Wxmp/SSII-2) and Nip(Wxmp/ss2-2) in the Nipponbare (Nip) background containing the SSII-2RNAi cassette combined with different Waxy (Wx) alleles were investigated in terms of rice grain transparency and quality profiles. Rice lines carrying the SSII-2RNAi cassette displayed downregulation of SSII-2, SSII-3 and Wx genes. Introduction of the SSII-2RNAi cassette decreased apparent amylose content (AAC) in all transgenic lines, but grain transparency differed between low AAC rice lines. Grains from Nip(Wxb/SSII-2) and Nip(Wxb/ss2-2) were transparent, while those of rice were increasingly translucent with decreasing moisture due to cavities within starch granules. Rice grain transparency was positively correlated with grain moisture and AAC, but negatively correlated with cavity area within starch granules. Starch fine structure analysis revealed a marked increase in short amylopectin chains with DP 6–12, but a decrease in intermediate chains with DP 13–24, resulting in decreased gelatinisation temperature. Starch crystalline structure analysis showed that the transgenic rice starches have lower crystallinity and lamellar repeat distance than controls due to differences in starch fine structure. The results highlight the molecular basis underpinning rice grain transparency, and provide strategies for improving rice grain transparency.

Generating waxy rice starch with target type of amylopectin fine structure and gelatinization temperature by waxy gene editing

Waxy rice, which lacks amylose, is an important variant in rice, and its starches have been widely used. New waxy rice varieties generated via the CRISPR/Cas9 gene-editing system is described. Herein, four waxy rice starches with different physicochemical properties were successfully obtained by the CRISPR/Cas9 editing Waxy (Wx) gene. The results showed that the amylose content (AC) of wx mutant starches ranged from 0.26 to 1.78 %, and CZBwx1 starches had the best gel consistency and highest water solubility among all wx mutants. Mutations of Wxb allele produced more short-chains (degree of chain polymerization (DP) 6–11), and less medium- and long-chains (DP12–70) than that of Wxa, while the AC of Wxa allele mutants was higher than the mutations of Wxb allele. The gelatinization temperature (GT) of wxa mutant starches was higher than that of wxb mutant starches. Moreover, we found that the GT and amylopectin fine structure type of waxy rice starch did not change after Wx gene editing. Based on these findings, it is possible to produce waxy rice starch with different physicochemical properties, containing target GT and chain length distributions of amylopectin.

Molecular characterization and phylogenetic analysis of novel Wx genes from Psathyrostachys juncea and Eremopyrum bonaepartis

The ratio of amylose/amylopectin can greatly influence the end-use quality of wheat products, and amylose synthesis only needs the granule-bound starch synthase I that is encoded by the Waxy (Wx) gene. Hence, the Wx allele variability is a vital determinant of amylose synthesis. In this study, four novel Wx genes were isolated from two diploid Triticeae species. Their sequence variations were analyzed, which showed that the polymorphism among the Wx-F1 alleles was low; only seven single nucleotide polymorphisms (SNPs) and one amino acid (AA) residue change (Arg541 ? Cys) were detected in the exon regions, and this change in Wx-F1b was predicted to have deleterious effects on protein function. The two Wx-Ns1 alleles in this study were different from two published alleles obtained using three overlapping primer sets. The polymorphism among the four Wx-Ns1 alleles was high, and 37 SNPs and ten AA residue changes were found, while all of those substitutions were neutral. However, one substitution (Leu237 ? Pro) between Wx-H1 and Wx-Ns1 was predicted that would probably affect the protein function. Divergence time analysis showed that Wx-Ns1a diverged from Wx-Ns1b about 1.06 MYAs. Phylogenetic analysis indicated that Wx-F1 were more closely related to Wx-O1 from Henrardia persica, Wx-R1 from Secale cereale ssp. cereale, and Wx-Xe1 from Eremopyrum triticeum, while Wx-Ns1 were more closely related to Wx-H1 from Hordeum vulgare ssp. vulgare and Wx-Hch1 from Hordeum chilense. These genes may be important candidates for wheat quality improvement.

Development of Soft Rice Lines by Regulating Amylose Content via Editing the 5′UTR of the Wx Gene

The type of soft rice with low amylose content (AC) is more and more favored by consumers for its better eating and cooking quality, as people’s quality of life continuously improves in China. The Wx gene regulates the AC of rice grains, thus affecting the degree of softness of the rice. Mei Meng B (MMB), Tian Kang B (TKB), and DR462 are three indica rice maintained lines with good morphological characters, but also with undesirably high AC. Therefore, CRISPR/Cas9 technology was used to edit the Wx gene of these lines to create a batch of soft rice breeding materials. New gene-edited lines MMB-10-2, TKB-21-12, and DR462-9-9, derived from the above parental lines, respectively, were selected in the T2 generations, with an AC of 17.2%, 16.8%, and 17.8%, and gel consistency (GC) of 78.6 mm, 77.4 mm, and 79.6 mm, respectively. The rapid viscosity analysis (RVA) spectrum showed that the three edited lines had a better eating quality as compared to the corresponding wild type, and showing new characteristics, different from the high-quality soft rice popular in the market. There was no significant difference in the main agronomic traits in the three edited lines compared to the corresponding wild types. Moreover, the chalkiness of DR462-9-9 was reduced, resulting in an improved appearance of its polished rice. The present study created soft rice germplasms for breeding improved quality hybrid rice, without changing the excellent traits of their corresponding wild type varieties.

Genetic analysis of palmytic acid content in the oil of maize based on Waxy mutation

Aim. Determination of the effect of wx mutation on the palmitate content and genetic analysis of this trait in waxy maize. Methods. In two-year experiments, 10 unrelated maize inbreds of the common type and 10 inbreds – carriers of the wx mutation were analyzed. Genetic analysis of palmitate content was carried out in the diallel crosses of 6 indreds – carriers of the wx mutation by the second Griffing method. The palmitate content was determined by Peysker’s gas chromatographic method. Results. Carriers of the wx mutation of maize exceeded the maize of common type in the content of glycerides of palmitic acid in oils. The content of palmitate in unrelated inbreds – carriers of the wx mutation was subjected to quantitative variability and ranged from 13.3 % to 16.4 %. Inheritance of palmitate content in the waxy corn was carrired out by the type of incomplete dominance with a predominant contribution of additive effects to the variation. A higher level of trait was controlled by recessive alleles of polygens. Conclusions. The obtained results suggest the presence in chromosome 9 of spatial linkage of the mutant wx gene with palmitate - coding locus, the effect of which is modified by a polygenic complex.

Genome wide association study on development and evolution of glutinous rice

BackgroundGlutinous rice as a special endosperm type is consumed as a staple food in East Asian countries by consumers’ preference. Genetic studies on glutinous rice could be conducive to improve rice quality and understand its development and evolution. Therefor, we sought to explore more genes related to glutinous by genome wide association study and research the formation history for glutinous.ResultsHere, genome-wide association study was performed to explore the associated loci/genes underlying glutinous rice by using 2108 rice accessions. Combining the expression patterns analysis, 127, 81, and 48 candidate genes were identified to be associated with endosperm type in whole rice panel, indica, and japonica sub-populations. There were 32 genes, including three starch synthesis-related genes Wx, SSG6, and OsSSIIa, detected simultaneously in the whole rice panel and subpopulations, playing important role in determining glutinous rice. The combined haplotype analyses revealed that the waxy haplotypes combination of three genes mainly distributed in Southeast Asia (SEA), SEA islands (SER) and East Asia islands (EAR). Through population structure and genetic differentiation, we suggest that waxy haplotypes of the three genes firstly evolved or were directly inherited from wild rice in japonica, and then introgressed into indica in SER, SEA and EAR.ConclusionsThe cloning and natural variation analysis of waxy-related genes are of great significance for the genetic improvement of quality breeding and comprehend the history in glutinous rice. This work provides valuable information for further gene discovery and understanding the evolution and formation for glutinous rice in SEA, SER and EAR.

Type‐2 Diabetes and Identification of Major Genetic Determinants of Glycemic Index in Rice – A Review

AbstractRice consumers of different parts of the world always face the risk of diabetes and related health complications. Dietary intervention is the best adapted measure to maintain blood glucose levels and manage the diseases in rice consuming populations. The glycemic index of rice varieties is negatively correlated to the amylose content. Research studies have proven that the consumption of rice varieties with low glycemic index has beneficial effects in controlling diabetes. The genetic basis for the diversity observed for amylose content in different rice varieties is well elucidated. Waxy gene (Wx) is known to encode Granule–Bound Starch Synthase I (GBSS I) enzyme, which determines the amylose content in rice. Different allelic variations of Wx gene exist, which can be correlated to varying amylose content in rice. The PCR‐based markers for detecting single nucleotide polymorphism mutation at Wx locus provides a cost‐effective alternative to genotype rice varieties. This review outlines the anti‐diabetic properties of rice and strategies to identify rice varieties with a low glycemic index at the molecular level. The molecular basis of the glycemic index allows breeders to successfully identify rice germplasms with low glycemic index and engineer rice varieties with high grain yield and low glycemic index.

Effect of chemical fertilizer reduction on the quality of hybrid rice of different amylose contents.

To promote the reduction and efficiency of chemical fertilizers in rice production, two hybrid rice varieties with different amylose contents (16.43% and 27.58%) were selected to study the yield and quality performance of different quality rice varieties under reduced nitrogen/phosphorus conditions. Thus, the specific mechanism of the long-term nitrogen/phosphorus reduction effect on the quality of low- and high-amylose content (16.43% and 27.58%) rice was investigated by comparative analyses of the rapid visco analyzer and X-ray diffraction patterns, amylose contents, and starch structures of the samples. The results revealed that the effect of nitrogen fertilizer on the quality and yield of the hybrid rice was greater than that of phosphorus fertilizer. Indeed, reducing the former increased the Wx gene expression and amylose content of the rice varieties. Moreover, it reduced the starch crystallinity of Yixiangyou 1108 (2.16%), increasing the space between the starch grains and thus, chalkiness. Reducing nitrogen/phosphorus application did not significantly affect the yield and quality of the high-amylose rice but affected that of the high-quality rice with lower amylose contents. Thus, for high-amylose rice created for processing, appropriate chemical fertilizer reduction will not affect their yield and processing demand. PRACTICAL APPLICATIONS: Fertilization with different nitrogen and phosphorus fertilizers will seriously affect rice quality. The rice varieties with low amylose content (AC) could produce high taste quality rice by increasing nitrogen fertilizer and decreasing phosphorus fertilizer. The rice varieties with relatively high ACs should reduce the application of nitrogen/phosphorus fertilizer to appropriately increase AC, which can be used to produce healthy food with high resistant starch.

Generation of a New Glutinous Photothermosensitive Genic-Male-Sterile (PTGMS) Line by CRISPR/Cas9-Directed Mutagenesis of Wx in Rice (Oryza sativa L.)

The Photothermosensitive Genic-Male-Sterile (PTGMS) line, Y58S, an indica rice variety, combines high-quality and high-light-efficiency use, disease and stress resistance, and excellent plant type and mating force. Y58S is widely used to assemble two-line hybrid rice varieties, especially super hybrids. The Wx gene is the main effector gene for controlling amylose synthesis, which determines the amylose content (AC) of rice grains. By editing this gene, a glutinous line with a low AC can be obtained. In this study, the CRISPR/Cas9 system was used to mediate the editing of the Wx gene, which caused ultra-low AC mutations that produced a PTGMS glutinous rice strain with excellent waxiness. The results showed that 18 positively transformed plants were obtained from the T0 generation, with a mutation rate of 64.29%, of which six were homozygous mutant plants, indicating that the gene-editing target had a higher targeting efficiency and a higher homozygosity mutation rate. Compared to the wild type, the AC of the mutants was significantly lower. Through molecular marker detection and screening of T1 and T2 generations, five homozygous T-DNA-free mutant strains were identified that were consistent with Y58S in fertility and other agronomic traits except for AC. Among these, the AC of the W-1-B-5 homozygous mutant, the glutinous PTGMS line wx-Y58S, was as low as 0.6%. Our research revealed that the Wx gene of excellent PTGMS rice can be edited to generate a new waxy PTGMS line using the CRISPR/Cas9 system. This study provided a simple and effective strategy for breeding high-yield, high-quality, and glutinous two-line hybrid rice, and provided excellent sterile lines for their large-scale application. Once put into use, waxy hybrid rice will greatly improve the yield of glutinous rice and increase social benefits.

Physical and nutrient characterization of the grains from traditional rice varieties of Kerala and validation of the trait linked molecular markers

Kerala is rich with traditional rice varieties that could grow in various agro- climatic conditions of the state. However many of these traditional varieties are not cultivated and have become extinct due to low yield, promotion of high breed variety seeds and high-cost in continuing the cultivation with traditional seeds. The lack of knowledge about the nutraceutical values of traditional rice varieties among farmers leads to the non-participation in cultivation. Present study was aimed at to characterization of thirty traditional rice varieties in terms of physico-chemical, cooking quality as well as molecular screening with markers specific to quality traits. All the varieties used is unique in their quality parameters, among them Njavara Veluthath (13.57%) and Orumundakan (13.35%) were rich in protein content whereas, Karimbalan (311.54 mg/Kg and 102.41 mg/kg) and Veliyan (218.25 mg/Kg and 56.88mg/kg) were superior in Iron and Zinc content. The carotene content ranged from 0.14 mg/100g (Mullan kayama) to 0.56 mg/100g (Njavara veluthath) and amylose content was maximum in Cheruviripp (29.52%). Thus, these varieties need to be conserved and promote them by commercialize and through general public awareness about their medicinal benefits. Correlation analysis showed positive significant relationship between Iron and Zinc content, while amylose content had positive correlation with volume expansion and optimum cooking quality. The SSR marker RM535 linked to Quantitative Trait Loci for Iron and Zinc content was detected in thirteen varieties, RM190 linked with Wx gene locus associated with amylose content in seventeen varieties and the marker RM520 linked to QTL for protein content was detected in all the varieties.