Panicle-related Traits Research Articles

Identification of Newer Stable Genetic Sources for High Grain Number per Panicle and Understanding the Gene Action for Important Panicle Traits in Rice

Rice is an important food crop extensively cultivated worldwide, and rice's grain yield should be improved to meet future food demand. Grain number per panicle is the main trait that determines the grain yield in rice, and other panicle-related traits influence the grain number. To study the genetic diversity, 50 diverse Indian-origin germplasm were evaluated for grain number per panicle and other panicle traits for two consecutive seasons (Rabi 2019 and Kharif 2020). The maximum genotypic and phenotypic coefficient of variation was obtained for the number of spikelets and filled grains per panicle. The genotypes were grouped into eight clusters with Mahalanobis' D2 analysis and six groups using Principal component analysis. Based on, per se, performance for grain number per panicle and genetic distances, six parents were selected and subjected to full diallel mating. The genotypes CB12132, IET 28749, and BPT 5204 were the best general combiners for the number of filled grains per panicle and other panicle branching traits, viz., the number of primary and secondary branches per panicle. The hybrid BPT 5204 × CB 12132 identified as the best specific combination for most of the studied panicle traits. The additive gene effects were high for the number of filled grains per panicle, the number of primary branches, and secondary branches, whereas non-additive gene action was high for the number of productive tillers and grain yield per plant. The information obtained from this study will be useful in rice breeding programs to improve panicle traits, especially the grain number, which would result in higher grain yield.

The Integration of Genome-Wide Association Study and Homology Analysis to Explore the Genomic Regions and Candidate Genes for Panicle-Related Traits in Foxtail Millet

Panicle traits are important factors affecting yield, and their improvement has long been a critical goal in foxtail millet breeding. In order to understand the genetic basis of panicle formation, a large-scale genome-wide association study (GWAS) was performed in this study for six panicle-related traits based on 706,646 high-polymorphism SNP loci in 407 accessions. As a result, 87 quantitative trait loci (QTL) regions with a physical distance of less than 100 kb were detected to be associated with these traits in three environments. Among them, 27 core regions were stably detected in at least two environments. Based on rice-foxtail millet homologous comparison, expression, and haplotype analysis, 27 high-confidence candidate genes in the QTL regions, such as Si3g11200 (OsDER1), Si1g27910 (OsMADS6), Si7g27560 (GS5), etc., affected panicle-related traits by involving multiple plant growth regulator pathways, a photoperiod response, as well as panicle and grain development. Most of these genes showed multiple effects on different panicle-related traits, such as Si3g11200 affecting all six traits. In summary, this study clarified a strategy based on the integration of GWAS, a homologous comparison, and haplotype analysis to discover the genomic regions and candidate genes for important traits in foxtail millet. The detected QTL regions and candidate genes could be further used for gene clone and marker-assisted selection in foxtail millet breeding.

Detection of QTLs for panicle-related traits using an indica × japonica recombinant inbred line population in rice.

BackgroundThe panicle is the most important organ in rice, and all the panicle-related traits are correlated with rice grain yield. Understanding the underlying genetic mechanisms controlling panicle development is very important for improving rice production.MethodsNine panicle-related traits including heading date, panicle length, number of primary branches, number of secondary branches, number of grains per panicle, number of panicles per plant, number of filled grains per plant, seed-setting rate, and grain yield per plant were investigated. To map the quantitative trait loci (QTLs) for the nine panicle-related traits, a PCR-based genetic map with 208 markers (including 121 simple sequence repeats and 87 InDels) and a high-density linkage map with 18,194 single nucleotide polymorphism (SNP) markers were both used.ResultsUsing a recombinant inbred line population derived from an indica variety Huanghuazhan and a japonica line Jizi 1560, a total of 110 and 112 QTLs were detected for panicle-related traits by PCR-based genetic map and by high-density linkage map, respectively. Most of the QTLs were clustered on chromosomes 1, 2, 3, 6, and 7 while no QTLs were detected on chromosome 10. Almost all the QTLs with LOD values of more than 5.0 were repeatedly detected, indicating the accuracy of the two methods and the stability of the QTL effects. No genes for panicle-related traits have been previously reported in most of these regions. QTLs found in JD1006–JD1007 and RM1148–RM5556 with high LOD and additive values deserved further research. The results of this study are beneficial for marker-assisted breeding and provide research foundation for further fine-mapping and cloning of these QTLs for panicle-related traits.

Characterization of Yield and Panicle-related Traits of Early Maturing Rice Varieties by Cultivation Times in the Honam Plain Area of Korea

Characterization of Yield and Panicle-related Traits of Early Maturing Rice Varieties by Cultivation Times in the Honam Plain Area of Korea

Construction of chromosome segment substitution lines of Dongxiang common wild rice (Oryza rufipogon Griff.) in the background of the japonica rice cultivar Nipponbare (Oryza sativa L.)

Dongxiang common wild rice (Oryza rufipogon Griff.) is believed to have the northernmost distribution of any wild rice species. Many favorable genes were lost during rice domestication, and Dongxiang common wild rice is a potential source of many genes related to biological and abiotic stress resistance and high grain yield. Despite its importance, japonica rice has not yet been used as a background material for the construction of introgression lines carrying Dongxiang common wild rice chromosome segments. In this study, we used Dongxiang common wild rice as the donor parent and Nipponbare (Oryza sativa L), a reference-sequence japonica cultivar, as the recurrent parent to develop a set of 104 chromosome segment substitution lines (CSSLs) through crossing and backcrossing with marker-assisted selection based on 203 polymorphic molecular markers evenly distributed across 12 chromosomes. The 104 CSSLs covered 87.94% of the genome of Dongxiang common wild rice. Each CSSL contained an average of four introgressed segments, and the average segment length was 3.3 Mb. Quantitative trait locus (QTL) analysis of the panicle-related traits of the CSSLs at two sites (Beijing and Nanchang, Jiangxi Province) revealed 18 QTLs for eight traits. Among these 18 QTLs were two known grain length- and width-related genes and four novel QTLs. In addition, two QTLs were verified, and two novel QTLs were identified, for panicle neck length, a domestication-related trait. The developed CSSLs potentially represent a valuable population for detecting favorable genes in common wild rice and creating germplasm resources for japonica rice breeding.

Identification and fine mapping of qGN1c, a QTL for grain number per panicle, in rice (Oryza sativa)

Grain number per panicle (GN) is one of the most important determinants of grain yield potential in rice. However, the underlying genetic and molecular mechanisms that regulate GN remain largely unknown. In this study, quantitative trait loci (QTLs) for grain yield–related traits were detected using a set of chromosomal segment substitution lines (CSSLs) that were generated from a cross between the indica cultivar 9311 as the trait donor, and the japonica cultivar ‘Nipponbare’ as the recipient. In total, 25 QTLs for panicle-related traits, including GN, panicle length, primary branch number, and secondary branch number, were identified on eight chromosomes. Among the QTLs, qGN1c for GN was found to be located near Gn1a, a previously reported major QTL for GN on chromosome 1. Fine mapping placed qGN1c within a region of ~ 379 kb in a chromosomal interval flanking Gn1a, indicating that qGN1c is an uncloned gene. Evaluation of agronomic traits in a near isogenic line (NIL-qGN1c9311) suggested that qGN1c does not have additional impacts on agronomic traits except GN and thousand grain weight. More importantly, the grain yields per plant for the NIL-qGN1c9311 were significantly increased by 13.34% and 14.46% in two planting locations. Therefore, we conclude that the identification of qGN1c provides a useful genetic tool for the improvement of grain yield in rice breeding, and our findings will be helpful in cloning qGN1c.

Genetic dissection of wheat panicle traits using linkage analysis and a genome-wide association study.

Coincident regions on chromosome 4B for GW, on 5A for SD and TSS, and on 3A for SL and GNS were detected through an integration of a linkage analysis and a genome-wide association study (GWAS). In addition, six stable QTL clusters on chromosomes 2D, 3A, 4B, 5A and 6A were identified with high PVE% on a composite map. The panicle traits of wheat, such as grain number per spike and 1000-grain weight, are closely correlated with grain yield. Superior and effective alleles at loci related to panicles developments play a crucial role in the progress of molecular improvement in wheat yield breeding. Here, we revealed several notable allelic variations of seven panicle-related traits through an integration of genome-wide association mapping and a linkage analysis. The linkage analysis was performed using a recombinant inbred line (RIL) population (173 lines of F8:9) with a high-density genetic map constructed with 90K SNP arrays, Diversity Arrays Technology (DArT) and simple sequence repeat (SSR) markers in five environments. Thirty-five additive quantitative trait loci (QTL) were discovered, including eleven stable QTLs on chromosomes 1A, 2D, 4B, 5B, 6B, and 6D. The marker interval between EX_C101685 and RAC875_C27536 on chromosome 4B exhibited pleiotropic effects for GW, SL, GNS, FSN, SSN, and TSS, with the phenotypic variation explained (PVE) ranging from 5.40 to 37.70%. In addition, an association analysis was conducted using a diverse panel of 205 elite wheat lines with a composite map (24,355 SNPs) based on the Illumina Infinium assay in four environments. A total of 73 significant marker-trait associations (MTAs) were detected for panicle traits, which were distributed across all wheat chromosomes except for 4D, 5D, and 6D. Consensus regions between RAC875_C27536_611 and Tdurum_contig4974_355 on chromosome 4B for GW in multiple environments, between QTSS5A.7-43 and BS00021805_51 on 5A for SD and TSS, and between QSD3A.2-164 and RAC875_c17479_359 on 3A for SL and GNS in multiple environments were detected through linkage analysis and a genome-wide association study (GWAS). In addition, six stable QTL clusters on chromosomes 2D, 3A, 4B, 5A, and 6A were identified with high PVE% on a composite map. This study provides potentially valuable information on the dissection of yield-component traits and valuable genetic alleles for molecular-design breeding or functional gene exploration.

Association between sequence variants in panicle development genes and the number of spikelets per panicle in rice

BackgroundBalancing panicle-related traits such as panicle length and the numbers of primary and secondary branches per panicle, is key to improving the number of spikelets per panicle in rice. Identifying genetic information contributes to a broader understanding of the roles of gene and provides candidate alleles for use as DNA markers. Discovering relations between panicle-related traits and sequence variants allows opportunity for molecular application in rice breeding to improve the number of spikelets per panicle.ResultsIn total, 142 polymorphic sites, which constructed 58 haplotypes, were detected in coding regions of ten panicle development gene and 35 sequence variants in six genes were significantly associated with panicle-related traits. Rice cultivars were clustered according to their sequence variant profiles. One of the four resultant clusters, which contained only indica and tong-il varieties, exhibited the largest average number of favorable alleles and highest average number of spikelets per panicle, suggesting that the favorable allele combination found in this cluster was beneficial in increasing the number of spikelets per panicle.ConclusionsFavorable alleles identified in this study can be used to develop functional markers for rice breeding programs. Furthermore, stacking several favorable alleles has the potential to substantially improve the number of spikelets per panicle in rice.

Quantitative trait loci identification and meta-analysis for rice panicle-related traits.

Rice yield is a complex trait controlled by quantitative trait loci (QTLs). In the past three decades, thousands of QTLs for rice yield traits have been detected, but only a very small percentage has been cloned to date, as identifying the QTL genes requires a substantial investment of time and money. Meta-analysis provides a simple, reliable, and economical method for integrating information from multiple QTL studies across various environmental and genetic backgrounds, detecting consistent QTLs powerfully and estimating their genetic positions precisely. In this study, we aimed to locate consistent QTL regions associated with rice panicle traits by applying a genome-wide QTL meta-analysis approach. We first conducted a QTL analysis of 5 rice panicle traits using 172 plants in 2011 and 138 plants in 2012 from an F2 population derived from a cross between Nipponbare and H71D rice cultivators. A total of 54 QTLs were detected, and these were combined with 1085 QTLs collected from 82 previous studies to perform a meta-analysis using BioMercator v4.2. The integration of 82 maps resulted in a consensus map with 6970 markers and a total map length of 1823.1 centimorgan (cM), on which 837 QTLs were projected. These QTLs were then integrated into 87 meta-quantitative trait loci (MQTLs) by meta-analysis, and the 95% confidence intervals (CI) of them were smaller than the mean value of the original QTLs. Also, 30 MQTLs covered 47 of the 54 QTLs detected from the cross between Nipponbare and H71D in this study. Among them, the two major and stable QTLs, spp10.1 and sd10.1, were found to be included in MQTL10.4. The three other major QTLs, pl3.1, sb2.1, and sb10.1, were included in MQTL3.3, MQTL2.2, and MQTL10.3, respectively. A total of 21 of the 87 MQTLs' phenotypic variation were>20%. In total, 24 candidate genes were found in 15 MQTLs that spanned physical intervals<0.2Mb, including genes that have been cloned previously, e.g., EP3, LP, MIP1, HTD1, DSH1, and OsPNH1. However, it would be beneficial to identify a greater number of candidate genes from these MQTLs. Mining new genes that modulate yield and its related traits would assist researchers to better understand the relevant molecular mechanisms. The MQTLs found in this study that have small physical and genetic intervals are useful not only for marker-assisted selection and pyramiding, but they also provide important information of rice yield and related gene mining for future research.

Identification of QTLs for yield-related traits in RILs derived from the cross between pLIA-1 carrying &lt;i&gt;Oryza longistaminata&lt;/i&gt; chromosome segments and Norin 18 in rice

To improve rice yield, a wide genetic pool is necessary. It is therefore important to explore wild rice relatives. Oryza longistaminata is a distantly related wild rice relative that carries the AA genome. Its potential for improving agronomic traits is not well studied. Introgression line (pLIA-1) that carries Oryza longistaminata’s chromosome segments, showed high performance in yield-related traits under non-fertilized conditions. Therefore, to illustrate Oryza longistaminata’s potential for improving yield-related traits, RILs from the F1 of a cross between pLIA-1 and Norin 18 were developed and QTL analysis was done using the RAD-Seq method. In total, 36 QTLs for yield-related traits were identified on chromosomes 1, 2, 3, 5, 6, 7, 8, 10, and 11. Clusters of QTLs for strongly correlated traits were also identified on chromosomes 1, 3, 6, and 8. Phenotypic data from recombinant plants for chromosomes 1 and 8 QTL clusters revealed that the pLIA-1 genotype on chromosome 1 region was more important for panicle-related traits and a combination of pLIA-1 genotypes on chromosomes 1 and 8 showed a favorable phenotype under non-fertilized conditions. These results suggest that Oryza longistaminata’s chromosome segments carry important alleles that can be used to improve yield-related traits of rice.

Different effects of DEP1 on vascular bundle- and panicle-related traits under indica and japonica genetic backgrounds

Rice (Oryza sativa L.) is a major food for more than half of the world’s population and serves as a model monocot plant. DEP1 (dense and erect panicle 1), corresponding to an erect-panicle architecture, may bring the third breakthrough in rice breeding after the introduction of the semi-dwarf trait and the application of heterosis in hybrid rice. The aim of this study was to determine the effects of DEP1 on yield components and vascular bundle-related traits under indica and japonica genetic backgrounds. We analyzed a series of recombinant inbred lines, which were derived from a cross between the japonica variety SN265 with an erect panicle and the indica variety R99 with a curved panicle. The results showed that effects of the DEP1/dep1 allele were much stronger than the effects of the indica/japonica genetic background on vascular bundle-related traits and yield components. As the frequency of indica alleles increased, the grain yield per plant and the harvest index significantly increased in lines with the dep1 allele. Among the indica-type lines, those with the dep1 allele showed superior values for almost all of the vascular bundle-related traits and yield components. Our results provide new insights into the use of a high-yield-related gene derived from japonica in the indica genetic background.

Variation in inflorescence architecture associated with yield components in a sorghum germplasm

This study was undertaken to analyse the variation in panicle-related traits of 206 sorghum accessions collected from 27 Asian and African countries. Significant differences among the accessions were observed for 18 measured traits. First, we found that the patterns of the observed panicle-related traits reflected the distribution of the accessions of different origins. Second, the distribution of several components of inflorescence architecture in sorghum accessions influenced their yield components. Principal component analysis of the data showed a wide range of variations across the 206 sorghum accessions. Despite their geographical isolation, no distinct separation between the Asian and African accessions was observed. Correlation coefficient and path coefficient analysis indicated that panicle length (PanL), the total number of branches, rachis length (Rac) and panicle width had a positive direct effect on grain yield. Finally, we showed that the variation in the inflorescence architecture of sorghum accessions was dependent not only on the PanL, but also on the total number of branches, the maximum length of primary branches, Rac, panicle diameter and panicle width. Thus, there are major panicle determinants that are strongly associated with grain yield which should be considered in breeding programmes. These results will serve as a starting point for further evaluation of sorghum germplasm via quantitative trait loci analysis and may be useful for improving yield based on careful consideration of trait selection and inflorescence morphology.

Genetics of panicle-related traits of agronomic importance in rice through triple test cross analysis

A triple test cross analysis was carried out to study the genetics of some panicle related traits of agronomic importance in "Basmati" rice. Partitioning of total epistasis into i type and j + l type of epistasis revealed that j + l types of interactions were significant for number of panicle per plant and yield per plant. Additive and dominance gene effects were important for panicle length, number of secondary branches per panicle, number of filled grains per panicle, number of sterile grains per panicle and panicle density. However, additive effects were the only source of variation for number of primaryv branches per plant and fertility percentage. The magnitude of additive variance was higher for all the traits and the degree of dominance was less than unity indicating partial dominance. The non-significant correlation between sums and differences did not show any evidence of directional dominance. Epistatic interactions j + l type can be manipulated to improve number of panicles per plant and yield per plant through recurrent selection. The predominance of additive gene effect suggests the occurrence of selection in late segregating populations however, early selection is proposed for number of primary branches per panicle and fertility percentage to improve rice yield.