Early Seedling Growth Of Rice Research Articles

Genome Wide Association Analysis for Uniform Coleoptiles Emergence and Early Seedling Growth in Rice

Early seedling vigour (ESV) is a complex trait in rice. Detection of QTLs/genes controlling these traits can help us in enhancing the yield potential in rice varieties. Association mapping is a technique based on the principle of linkage disequilibrium that is used to find genes or quantitative trait loci (QTL) underlying the complex traits. In this study of haplotype breeding 281 rice genotypes were taken. ANOVA analysis showed P- value for traits and genotypes was found significant. Similarly, P-value for interaction between the traits and genotypes was also found to be highly significant (1.8663*10-208). Further, mean germination data positively correlated with mean shoot length, mean leaf number, mean culm diameter, mean shoot dry weight, and mean shoot area of 21st day among the 281 genotypes. Among the 281 number of genotypes, 111 genotypes are found to be in PCA1 and 170 genotypes are found to be in PCA2 based on the phenotypic analysis. PCA1 component constituted 29.93% and PCA2 constituted the 13.68% of total variation in the analysis. Besides, whole genome phylogenetic analysis showed three major groups of which Group 1 consists of 215 genotypes, group 2 consists of 38 genotypes and group 3 consists of 28 genotypes respectively. Especially, both the subgroups II and III comprised of the unique genotypes from the indica and aus subpopulations of rice. In this analysis, 16 significant associations (LOD Score >7) for different traits were identified using the three different models (MLM, farmCPU, and blink) for GWAS studies Especially, one major QTL was identified for the mean coleoptiles’ emergence for 10 DAS on 11th chromosome (18983591) which explained 49% of the phenotypic variance. Additionally, another major QTL contributing to the shoot length variation of 29.75% was identified in the Chr02 (32954393) for shoot length trait on 28 DAS. A candidate gene namely Os02g0778400 UMP/CMP kinase A/adenylate kinase (LOC_Os02g53790) was located in the significant SNP region of the GWAS analysis. Further characterization of this gene would assist in elucidation of the mechanism regulating the early seedling length in rice under direct seeded rice.

The Molecular Regulatory Pathways and Metabolic Adaptation in the Seed Germination and Early Seedling Growth of Rice in Response to Low O2 Stress

As sessile organisms, flooding/submergence is one of the major abiotic stresses for higher plants, with deleterious effects on their growth and survival. Therefore, flooding/submergence is a large challenge for agriculture in lowland areas worldwide. Long-term flooding/submergence can cause severe hypoxia stress to crop plants and can result in substantial yield loss. Rice has evolved distinct adaptive strategies in response to low oxygen (O2) stress caused by flooding/submergence circumstances. Recently, direct seeding practice has been increasing in popularity due to its advantages of reducing cultivation cost and labor. However, establishment and growth of the seedlings from seed germination under the submergence condition are large obstacles for rice in direct seeding practice. The physiological and molecular regulatory mechanisms underlying tolerant and sensitive phenotypes in rice have been extensively investigated. Here, this review focuses on the progress of recent advances in the studies of the molecular mechanisms and metabolic adaptions underlying anaerobic germination (AG) and coleoptile elongation. Further, we highlight the prospect of introducing quantitative trait loci (QTL) for AG into rice mega varieties to ensure the compatibility of flooding/submergence tolerance traits and yield stability, thereby advancing the direct seeding practice and facilitating future breeding improvement.

Quantitative Trait Locus Analysis of Seed Germination and Early Seedling Growth in Rice.

Seed germination and early seedling growth are important agricultural traits for developing populations of both irrigated and directly seeded rice (DSR). To investigate the genetic mechanisms underlying seed germination and early seedling growth in rice, 275 recombinant inbred lines (RILs) were genotyped in this study via the genotyping-by-sequencing (GBS) approach to construct a high-density linkage bin map based on the parent-independent genotyping method. Quantitative trait loci (QTLs) for 12 traits related to seed germination and early seedling growth were analyzed. Totally, 22 additive loci were detected, after analysis of the interaction between additive QTLs and environments, five stable additive loci were obtained. Among them, loci 4, 5, 12 and 14 exhibited clear pleiotropic effects that were associated with multiple traits. Analysis of the effects of the five additive stable loci showed that a single locus increased the corresponding phenotypic value. Ten of the 275 RILs pyramided the excellent alleles of the five stable genetic loci. Most phenotypic values of the ten RILs were greater than the average values. Four RILs (G260, G342, G371, and G401) with more excellent phenotypic values were subsequently selected; these RILs could serve as donor parents of favorable alleles in the breeding process. Due to the existence of pleiotropy, the use of these genetic loci for pyramid breeding can further increase the efficiency to reach breeding goals. In addition, these five stable loci have an average physical interval of only 170 kb, we also further identified five promising candidate genes by qRT-PCR, which provides us with a basis for future cloning of these genes. Overall, this work will help broaden our understanding of the genetic control of seed germination and early seedling growth, and this study provides both a good theoretical basis and a new genetic resource for the breeding of direct-seeded rice.

Effect of alkalinity on germination efficiency index, seedling growth, free proline and sugar during early seedling growth of rice

Effect of varying level of alkalinity (pH 8.5, 8.8 and 9.2) induced by sodium carbonate on germination efficiency index, seedling growth, free proline and sugar content were recorded in embryo-axis of three rice genotype NDR-501, USAR-1, and IR-24 after 72, 96, 120 h of soaking. Germination efficiency index (GEI), seedling growth and sugar (reducing and non-reducing) decreased with increasing alkalinity levels as compared to control at all the stages of seedling growth. Free proline content of embryo-axis increased with increasing alkalinity levels at all stages of seedling growth. Since tolerant genotypes accumulated relatively more free proline, high sugar content and GEI than susceptible hence these parameter can be used as one of the indices for rapid screening of salt tolerant genotypes. Key words: Alkalinity, genotype, free proline, sugar, germination.

국내 식물자원 및 약용식물 추출물이 벼 유묘 생장에 미치는 영향

국내 식물자원 및 약용식물 추출물이 벼 유묘 생장에 미치는 영향

Phytotoxicity of Arsenate and Salinity on Early Seedling Growth of Rice (Oryza sativa L.): A Threat to Sustainable Rice Cultivation in South and South-East Asia

Arsenic (As) contamination is an important environmental consequence in some parts of salinity-affected South (S) and South-East (SE) Asia. In this study, we investigated the individual and combined phytotoxicity of arsenic (As) [arsenate; As(V)] and salinity (NaCl) on early seedling growth (ESG) of saline-tolerant and non-tolerant rice varieties. Germination percentage (GP), germination speed (GS) and vigor index (VI) of both saline-tolerant and non-tolerant rice varieties decreased significantly (p > 0.01) with increasing As(V) and NaCl concentrations. The highest GP (91%) was observed for saline non-tolerant BRRI dhan28 and BRRI dhan49, while the lowest (62%) was for saline-tolerant BRRI dhan47. The ESG parameters, such as weights and relative lengths of plumule and radicle, also decreased significantly (p < 0.01) with increasing As(V) and NaCl concentrations. Relative radicle length was more affected than plumule length by As(V) and NaCl. Although VI of saline-tolerant and non-tolerant rice seedlings showed significant variation (p < 0.05), weights and lengths of plumule and radicle of different rice varieties did not show significant variation for As(V) and NaCl treatments. Results reveal that the combined phytotoxicity of As(V) and NaCl on rice seed germination and ESG are greater than their individual toxicities, and some saline-tolerant rice varieties are more resistant to the combined phytotoxicity of As(V) and NaCl than the saline non-tolerant varieties.

Effect of Sodium Chloride Salinity on Seed Germination and Early Seedling Growth of Rice (Oryza sativa L.)

Effect of Sodium Chloride Salinity on Seed Germination and Early Seedling Growth of Rice (Oryza sativa L.)

Putrescine Reduces NaCl-Induced Inhibition of Germination and Early Seedling Growth of Rice (Oryza sativa L.)

Changes induced by NaCl and putrescine during germination and early seedling growth of rice were examined for 120 h. Rates of germination and growth of embryo axis decreased when seeds were subjected to salt stress (100, 150 and 200 mM NaCl). NaCl at 150 mM concentration significantly reduced the water uptake of seeds and the rate of mobilisation of reserves. All concentrations of putrescine (0.001, 0.01, 0.1 and 1.0mM) applied exogenously to seeds increased the rate of germination and seedling growth when NaCl(150 mM) was also present and 0.01 mM putrescine gave maximum response. Addition of putrescine (0.01 mM) to NaCl solution (150 mM) reduced the net accumulation of sodium and chloride ions in seeds and increased their water uptake. Thus, putrescine can alleviate the adverse effects of NaCl during germination and early seedling growth of rice.