Late-flowering Genotypes Research Articles

Delineation of loci governing an extra-earliness trait in lentil (Lens culinaris Medik.) using the QTL-Seq approach.

Developing early maturing lentil has the potential to minimize yield losses, mainly during terminal drought. Whole-genome resequencing (WGRS) based QTL-seq identified the loci governing earliness in lentil. The genetic analysis for maturity duration provided a good fit to 3:1 segregation (F2), indicating earliness as a recessive trait. WGRS of Globe Mutant (late parent), late-flowering, and early-flowering bulks (from RILs) has generated 1124.57, 1052.24 million raw and clean reads, respectively. The QTL-Seq identified three QTLs (LcqDTF3.1, LcqDTF3.2, and LcqDTF3.3) on chromosome 3 having 246244 SNPs and 15577 insertions/deletions (InDels) and 13 flowering pathway genes. Of these, 11 exhibited sequence variations between bulks and validation (qPCR) revealed a significant difference in the expression of nine candidate genes (LcGA20oxG, LcFRI, LcLFY, LcSPL13a, Lcu.2RBY.3g060720, Lcu.2RBY.3g062540, Lcu.2RBY.3g062760, LcELF3a, and LcEMF1). Interestingly, the LcELF3a gene showed significantly higher expression in late-flowering genotype and exhibited substantial involvement in promoting lateness. Subsequently, an InDel marker (I-SP-383.9; LcELF3a gene) developed from LcqDTF3.2 QTL region showed 82.35% PVE (phenotypic variation explained) for earliness. The cloning, sequencing, and comparative analysis of the LcELF3a gene from both parents revealed 23 SNPs and InDels. Interestingly, a 52 bp deletion was recorded in the LcELF3a gene of L4775, predicted to cause premature termination of protein synthesis after 4 missense amino acids beyond the 351st amino acid due to the frameshift during translation. The identified InDel marker holds significant potential for breeding early maturing lentil varieties.

Climate biogeography of Arabidopsis thaliana: linking distribution models and individual variation.

Patterns of individual variation are key to testing hypotheses about the mechanisms underlying biogeographic patterns. If species distributions are determined by environmental constraints, then populations near range margins may have reduced performance and be adapted to harsher environments. Model organisms are potentially important systems for biogeographical studies, given the available range-wide natural history collections, and the importance of providing biogeographical context to their genetic and phenotypic diversity. Global. Arabidopsis thaliana ("Arabidopsis"). We fit occurrence records to climate data, and then projected the distribution of Arabidopsis under last glacial maximum, current, and future climates. We confronted model predictions with individual performance measured on 2,194 herbarium specimens, and we asked whether predicted suitability was associated with life-history and genomic variation measured on ~900 natural accessions. The most important climate variables constraining the Arabidopsis distribution were winter cold in northern and high elevation regions and summer heat in southern regions. Herbarium specimens from regions with lower habitat suitability in both northern and southern regions were smaller, supporting the hypothesis that the distribution of Arabidopsis is constrained by climate-associated factors. Climate anomalies partly explained interannual variation in herbarium specimen size, but these did not closely correspond to local limiting factors identified in the distribution model. Late-flowering genotypes were absent from the lowest suitability regions, suggesting slower life histories are only viable closer to the center of the realized niche. We identified glacial refugia farther north than previously recognized, as well as refugia concordant with previous population genetic findings. Lower latitude populations, known to be genetically distinct, are most threatened by future climate change. The recently colonized range of Arabidopsis was well-predicted by our native-range model applied to certain regions but not others, suggesting it has colonized novel climates. Integration of distribution models with performance data from vast natural history collections is a route forward for testing biogeographical hypotheses about species distributions and their relationship with evolutionary fitness across large scales.

Flowering and fruit-set in cassava under extended red-light photoperiod supplemented with plant-growth regulators and pruning

BackgroundCassava (Manihot esculenta Crantz) is staple food and major source of calories for over 500 million people in sub-Saharan Africa. The crop is also a source of income for smallholder farmers, and has increasing potential for industrial utilization. However, breeding efforts to match the increasing demand of cassava are impeded by its inability to flower, delayed or unsynchronized flowering, low proportion of female flowers and high fruit abortions. To overcome these sexual reproductive bottlenecks, this study investigated the effectiveness of using red lights to extend the photoperiod (RLE), as a gateway to enhancing flowering and fruit set under field conditions.Materials and methodsPanels of cassava genotypes, with non- or late and early flowering response, 10 in each case, were subjected to RLE from dusk to dawn. RLE was further evaluated at low (LL), medium (ML) and high (HL) red light intensities, at ~ ≤ 0.5; 1.0 and 1.5PFD (Photon Flux Density) in µmol m−2 s−1 respectively. Additionally, the effect of a cytokinin and anti-ethylene as plant growth regulators (PGR) and pruning under RLE treatment were examined.ResultsRLE stimulated earlier flower initiation in all genotypes, by up to 2 months in the late-flowering genotypes. Height and number of nodes at first branching, particularly in the late-flowering genotypes were also reduced, by over 50%. Number and proportion of pistillate flowers more than doubled, while number of fruits and seeds also increased. Number of branching levels during the crop season also increased by about three. Earlier flowering in many genotypes was most elicited at LL to ML intensities. Additive effects on flower numbers were detected between RLE, PGR and pruning applications. PGR and pruning treatments further increased number and proportion of pistillate flowers and fruits. Plants subjected to PGR and pruning, developed bisexual flowers and exhibited feminization of staminate flowers. Pruning at first branching resulted in higher pistillate flower induction than at second branching.ConclusionsThese results indicate that RLE improves flowering in cassava, and its effectiveness is enhanced when PGR and pruning are applied. Thus, deployment of these technologies in breeding programs could significantly enhance cassava hybridizations and thus cassava breeding efficiency and impact.

Selection of superior late-blooming almond (Prunus dulcis [Mill.] D.A.Webb) genotypes using morphological characterizations.

Almond (Prunus dulcis [Mill.] D.A.Webb) is one of the earliest domesticated trees and the evidence dates back to 3000-2000 BC. In the present study, 198 almond seedling origin trees were studied to select late-flowering genotypes having high kernel quality. Significant variabilities were exhibited among the genotypes investigated based on the recorded traits. Full-blooming date ranged from mid-March to mid-April. The Ward dendrogram clustered the genotypes into two major clusters forming several subclusters. After clustering the genotypes based on the full-blooming dates, 68 late-blooming genotypes were recognized and reanalyzed based on the quantitative characters to select the superior ones. Nut-related characters were as follows: nut length: 22.34-43.05 mm, nut width: 14.07-24.34 mm, nut thickness: 9.21-18.00 mm, nut weight: 1.88-6.62 g, and shell thickness: 2.26-4.59 mm. Kernel-related characters were as follows: kernel length: 16.73-25.91 mm, kernel width: 8.50-13.64 mm, kernel thickness: 3.56-7.37 mm, and kernel weight: 0.35-1.41 g. Kernel weight was positively and significantly associated with nut weight, kernel thickness, kernel length, kernel width, nut length, and branch leaf width. Thus, these key variables are the main traits accounting for kernel weight, and they should be considered together in breeding with aiming at increasing the kernel weight. Based on ideal values of the important and commercial characters of almond, such as fruit yield, nut weight, shell hardness, kernel shape, kernel weight, and kernel taste, 19 late-blooming genotypes were promising and are recommended for cultivation in orchards.

Growth-defence trade-off in rice: fast-growing and acquisitive genotypes have lower expression of genes involved in immunity.

Plant ecologists and molecular biologists have long considered the hypothesis of a trade-off between plant growth and defence separately. In particular, how genes thought to control the growth-defence trade-off at the molecular level relate to trait-based frameworks in functional ecology, such as the slow-fast plant economics spectrum, is unknown. We grew 49 phenotypically diverse rice genotypes in pots under optimal conditions and measured growth-related functional traits and the constitutive expression of 11 genes involved in plant defence. We also quantified the concentration of silicon (Si) in leaves to estimate silica-based defences. Rice genotypes were aligned along a slow-fast continuum, with slow-growing, late-flowering genotypes versus fast-growing, early-flowering genotypes. Leaf dry matter content and leaf Si concentrations were not aligned with this axis and negatively correlated with each other. Live-fast genotypes exhibited greater expression of OsNPR1, a regulator of the salicylic acid pathway that promotes plant defence while suppressing plant growth. These genotypes also exhibited greater expression of SPL7 and GH3.2, which are also involved in both stress resistance and growth. Our results do not support the hypothesis of a growth-defence trade-off when leaf Si and leaf dry matter content are considered, but they do when hormonal pathway genes are considered. We demonstrate the benefits of combining ecological and molecular approaches to elucidate the growth-defence trade-off, opening new avenues for plant breeding and crop science.

Integrated analysis of miRNAome transcriptome and degradome reveals miRNA-target modules governing floral florescence development and senescence across early- and late-flowering genotypes in tree peony.

As a candidate national flower of China, tree peony has extremely high ornamental, medicinal and oil value. However, the short florescence and rarity of early-flowering and late-flowering varieties restrict further improvement of the economic value of tree peony. Specific miRNAs and their target genes engaged in tree peony floral florescence, development and senescence remain unknown. This report presents the integrated analysis of the miRNAome, transcriptome and degradome of tree peony petals collected from blooming, initial flowering, full blooming and decay stages in early-flowering variety Paeonia ostii 'Fengdan', an early-flowering mutant line of Paeonia ostii 'Fengdan' and late-flowering variety Paeonia suffruticosa 'Lianhe'. Transcriptome analysis revealed a transcript ('psu.G.00014095') which was annotated as a xyloglucan endotransglycosylase/hydrolase precursor XTH-25 and found to be differentially expressed across flower developmental stages in Paeonia ostii 'Fengdan' and Paeonia suffruticosa 'Lianhe'. The miRNA-mRNA modules were presented significant enrichment in various pathways such as plant hormone signal transduction, indole alkaloid biosynthesis, arachidonic acid metabolism, folate biosynthesis, fatty acid elongation, and the MAPK signaling pathway. Multiple miRNA-mRNA-TF modules demonstrated the potential functions of MYB-related, bHLH, Trihelix, NAC, GRAS and HD-ZIP TF families in floral florescence, development, and senescence of tree peony. Comparative spatio-temporal expression investigation of eight floral-favored miRNA-target modules suggested that transcript 'psu.T.00024044' and microRNA mtr-miR166g-5p are involved in the floral florescence, development and senescence associated agronomic traits of tree peony. The results might accelerate the understanding of the potential regulation mechanism in regards to floral florescence, development and abscission, and supply guidance for tree peony breeding of varieties with later and longer florescence characteristics.

The effect of spermidine and methionine application thorough two biosynthetic paths on flowering of early and late flowering genotypes of eggplant (Solanum melongena L.)

This research was carried out to investigate the effect of Spermidine (SPD) and its synthesis routes on flowering and fruit formation in two early and late flowering genotypes of eggplant in a completely randomized design. For this reason, the spermidine route was blocked with Cyclohexylamine (CHA) and Methylglyoxal-bis-guanilhydrazone (MGBG) separately to investigate each route effect. On the other hand, the route synthesis promotes with the precursor methionine (200 mg/L) and spermidine (0.5 and 1 mM), and distilled water was used as a control treatment. These treatments were applied in vegetative growth and ten days after flowering. Results showed that SPD increased the traits such as length of style, long-styled flowers, fruit number, and yield. The lowest amount of day to flowering was observed in SPD, 0.5 mM at early flowering genotypes. The highest fruit weight and yield were in SPD, 1 mM at late flowering genotype. SPD improved flowering and fruit characteristics in both genotypes. Conclusively, methionine precursor path's blocking had more inhibitory effects on reproductive and fruiting characteristics in the late flowering genotype, i.e., methionine was a more critical precursor in spermidine production induced flowering than spermidine application. The activity of synthetic pathways and their effects on different processes depends on the different cultivars and stages of the developmental stage of the eggplant.

Genome-scale investigation and identification of variations associated with early flowering based on whole genome resequencing and transcriptome integrated analysis in tree peony

Tree peony, a traditional ornamental flower and candidate national flower of China, has thousands of varieties with different flower colors and types after a long history of natural selection and artificial breeding. However, the short and concentrated florescence period and a shortage of early- and late-flowering varieties limit the enhancement of ornamental values. Single nucleotide polymorphisms (SNPs) and insertion/deletion mutations (InDels) are important factors for mutant genotypes generation. Whole genome resequencing and transcriptome integrated analysis was conducted using early-flowering genotype Paeonia ostii ‘Fengdan’ (FD), early-flowering mutant of Paeonia ostii ‘Fengdan’ (MU), and late-flowering genotype Paeonia suffruticosa ‘Lianhe’ (LH) to identify variants related to the early-flowering phenotype. Comparison of FD vs LH, MU vs LH, and MU vs FD revealed 1,488 SNPs, 1,261 InDels, and 1,912 differential expressed genes (DEGs) specific to early-flowering genotype FD and MU, respectively. Additionally, 329 DEGs affected by SNPs and InDels variants were differentially expressed in three tree peony genotypes at the full-blooming stage. Furthermore, 37 DEGs affected by SNP variants and 44 DEGs affected by InDel variants were identified in the early-flowering genotype FD and its corresponding MU at the full-blooming stage. Most of these genes were related to phenylpropanoid biosynthesis, flavonoid biosynthesis, plant hormone signal transduction, RNA degradation, and MAPK signaling pathway. Additionally, four SNPs were validated in FD, MU, and LH by Sanger sequencing. Expression profiles of 25 DEGs containing SNP/Indels associated with the early-flowering trait were verified by RT-qPCR. The abundant genetic variations identified in this study offer valuable genomic resources for ongoing functional and molecular breeding research for the early-flowering breeding of tree peony.

Comparative Genomic and Expression Analysis Insight into Evolutionary Characteristics of PEBP Genes in Cultivated Peanuts and Their Roles in Floral Induction.

Phosphatidyl ethanolamine-binding proteins (PEBPs) are involved in regulating flowering time and various developmental processes. Functions and expression patterns in cultivated peanuts (Arachis hypogaea L.) remain unknown. In this study, 33 PEBP genes in cultivated peanuts were identified and divided into four subgroups: FT, TFL, MFT and FT-like. Gene structure analysis showed that orthologs from A and B genomes in cultivated peanuts had highly similar structures, but some orthologous genes have subgenomic dominance. Gene collinearity and phylogenetic analysis explain that some PEBP genes play key roles in evolution. Cis-element analysis revealed that PEBP genes are mainly regulated by hormones, light signals and stress-related pathways. Multiple PEPB genes had different expression patterns between early and late-flowering genotypes. Further detection of its response to temperature and photoperiod revealed that PEBPs ArahyM2THPA, ArahyEM6VH3, Arahy4GAQ4U, ArahyIZ8FG5, ArahyG6F3P2, ArahyLUT2QN, ArahyDYRS20 and ArahyBBG51B were the key genes controlling the flowering response to different flowering time genotypes, photoperiods and temperature. This study laid the foundation for the functional study of the PEBP gene in cultivated peanuts and the adaptation of peanuts to different environments.

Assessment of Variability for Nutritional Traits of Burr Medic (Medicago polymorpha L.) Genotypes with Different Phenology

The objective of this study was to determine compatible genotypes for both grazing and ley farming systems concerning nutritional traits among burr medic (Medicago polymorpha L.) genotypes with different flowering times. Therefore, the variability for nutritional traits of early- (n=13), medium- (n=12) and late-flowering (n=19) genotypes from a breeding study carried out during the 2016-2018 years was assessed using one-way ANOVA and chemometric techniques such as principal component (PCA) and cluster (CA) analyses. Except for the acid detergent protein, calcium and magnesium contents, there were significant differences in the nutritional traits among the genotypes with different flowering times. The medium-flowering genotype had a significant advantage over especially early-flowering genotype in crude protein, acid detergent fiber, metabolizable energy, and relative feed value. There were significantly mutual correlations between most of the studied traits. Consequently, considerable amounts of variability were determined among the genotypes for all the traits under consideration. The 44 genotypes formed three clusters, in which cluster sizes ranged from 3 to 29 accessions per cluster. The PCA 1 and 2 had the highest eigenvalues of 6.44 and 1.35, describing 63.27% and 15.91% of the total variance, respectively. The PCA and CA results indicate that medium- and late-flowering genotypes had the best nutritional traits due to probably high photosynthetic capacity in the conditions of the present study.

Adaptive significance of flowering time variation across natural seasonal environments in Arabidopsis thaliana.

The relevance of flowering time variation and plasticity to climate adaptation requires a comprehensive empirical assessment. We investigated natural selection and the genetic architecture of flowering time in Arabidopsis through field experiments in Europe across multiple sites and seasons. We estimated selection for flowering time, plasticity and canalization. Loci associated with flowering time, plasticity and canalization by genome-wide association studies were tested for a geographic signature of climate adaptation. Selection favored early flowering and increased canalization, except at the northernmost site, but was rarely detected for plasticity. Genome-wide association studies revealed significant associations with flowering traits and supported a substantial polygenic inheritance. Alleles associated with late flowering, including functional FRIGIDA variants, were more common in regions experiencing high annual temperature variation. Flowering time plasticity to fall vs spring and summer environments was associated with GIGANTEA SUPPRESSOR 5, which promotes early flowering under decreasing day length and temperature. The finding that late flowering genotypes and alleles are associated with climate is evidence for past adaptation. Real-time phenotypic selection analysis, however, reveals pervasive contemporary selection for rapid flowering in agricultural settings across most of the species range. The response to this selection may involve genetic shifts in environmental cuing compared to the ancestral state.

Effect of flowering stage and storage conditions on pollen quality of six male date palm genotypes

Availability of efficient male genotypes is critical for successful artificial pollination and regular bearing of female date palms. The effect of flowering stage and storage conditions on pollen quality of six male date palm genotypes encoded ‘ABD1′, ‘P4′, ‘P3′, ‘P8′, ‘P7′ and ‘P13′were evaluated. Pollen collected from spathes developed at the middle of flowering stage exhibited the best viability (90%) and germinability (85%) compared to other stages. Pollen viability was greater than 90%, except for ‘P8′ that exhibited 80%, while, germinability greatly varied among the genotypes. Pollen quality decreased during 4 months of storage upon genotype and temperature, with a minimum reduction at −30 °C followed by 4 °C. Heat shock exposure (33 ± 2 °C) following storage revealed that pollen stored at −30 °C or 4 °C should be used for pollination on the same day of take out to avoid dramatic quality loss. The ‘ABD1′, an early flowering genotype, proved highest pollen quality both at fresh stage and after storage. While, the ‘P3′, a late flowering genotype, retained its pollen quality during storage. However, the ‘P13′ genotype exhibited excellent pollen quality when fresh, but greatly loses germinability during storage.

Post-anthesis thermal stress induces differential accumulation of bioactive compounds in field-grown barley.

Barley (Hordeum vulgare L.) is a healthy grain because of its high content of dietary fibre and phenolic compounds. It faces periods of high temperature during grain filling, frequently reducing grain weight. Heat stress may also affect some of the bioactive compounds present in the grain. To produce quality grains that provide nutritional and health benefits, it is important to understand the effect of environmental stresses on the quantity and quality of bioactive compounds. We have studied the effect of post-anthesis thermal stress on barley bioactive compounds and antioxidant capacity under Mediterranean field conditions during two consecutive growing seasons in four barley genotypes. Thermal stress affected grain weight and size and changed the relative composition of bioactive compounds. The relationship between heat stress and grain β-glucans and arabinoxylans content was indirect, as the resulting increases in concentrations were due to the lower grain weight under stress. Conversely, heat stress had a significant direct impact on some phenolic compounds, increasing their concentrations differentially across genotypes, which contributed to an improvement in antioxidant capacity of up to 30%. Post-anthesis thermal stress had a significant effect on β-glucans, arabinoxylans, phenolic compound concentration and antioxidant capacity of barley grains. Final grain quality could, at least partially, be controlled in order to increase the bioactive concentrations in the barley grain, by cultivation in growing areas prone to heat stress. Late sowings or late flowering genotypes could also be considered, should a premium be implemented to compensate for lower yields. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Phenological development of subterranean clover cultivars under contrasting environments

AbstractSix subterranean clover cultivars (representing early and late flowering genotypes from three subspecies) were used to describe and quantify their phenological development. The vegetative (V) and reproductive (R) development phases, in response to different environments created by eight sowing dates were quantified. The period from sowing to emergence was constant in thermal time at 110°Cd and the first trifoliate appeared at ~300°Cd. Crops sown in autumn had the longest period from runner initiation until floral bud initiation (R1), which would allow an extended period of grazing, particularly for later flowering cultivars like ‘Denmark’. To maximise seed set (particularly in year 1) a maximum period between R3 and R11 is required (seed set window). This ranged from 319 ± 42.3°Cd for ‘Leura’ to 661 ± 73.1°Cd for ‘Narrikup’. The complete crop life cycle from sowing (V0) to maturity (R11) ranged from 1269 ± 31°Cd (equivalent of 123 ± 6.3 days) for ‘Antas’ sown in July to 2799 ± 47°Cd (300 ± 3.9 days) for ‘Woogenellup’. When sowing occurred in an increasing photoperiod (June–November) the life cycle of all cultivars was 59% shorter than when sown in a decreasing photoperiod. The numeric scale was able to describe all the variation in the phenological phases and could be used to quantify thermal time requirements for specific phenophases. This would allow subterranean clover management to be optimised (husbandry, grazing and seed harvest) at a local level, and provides the basic parameters for inclusion in annual pasture simulation models.

Genetics of lodging resistance in chickpea (Cicer arietinum L)

Lodging (stem bending) is a serious problem causing severe yield reduction, poor grain filling, lower harvest index and deterioration in grain quality of chickpea in environments characterized by favorable temperatures and soil moisture conditions. Breeding for lodging resistance is also required to improving adaptation to better agronomy for achieving a breakthrough in its productivity and stability of production. However, no information is available on genetics of lodging resistance in chickpea. The objectives were to (i) characterize the newly identified lodging resistant germplasm FLIP07-183C for important plant characteristics and (ii) study the inheritance of lodging resistance in an inter-varietal cross between lodging susceptible high yielding desi cultivar Pusa 362 and the newly identified lodging resistant kabuli germplasm FLIP07-183C. FLIP07-183C was a tall, erect, late flowering genotype with semi-determinate stem growth habit and large seeds. It contained higher lignin content than the lodging susceptible cultivar, Pusa 362. Lodging resistance was found to be dominant over susceptibility. The segregation patterns in F2 and F3 of the cross Pusa 362 × FLIP07-183C showed that two dominant non-allelic genes with duplicate gene action controlled lodging resistance in FLIP07-183C. The two non-allelic duplicate dominant genes for lodging resistance in FLIP07-183C are designated as Sb1/sb1 and Sb2/sb2. The homozygous recessive for both alleles (sb1sb1sb2sb2) produced a lodging susceptible phenotype. The utilization of genes identified for lodging resistance has the major impact on chickpea breeding for better adaptation to cool climate, high fertility and irrigated environments.

Identification and characterization of regulatory pathways involved in early flowering in the new leaves of alfalfa (Medicago sativa L.) by transcriptome analysis

BackgroundAlfalfa (Medicago sativa L.) is a perennial legume extensively planted throughout the world as a high nutritive value livestock forage. Flowering time is an important agronomic trait that contributes to the production of alfalfa hay and seeds. However, the underlying molecular mechanisms of flowering time regulation in alfalfa are not well understood.ResultsIn this study, an early-flowering alfalfa genotype 80 and a late-flowering alfalfa genotype 195 were characterized for the flowering phenotype. Our analysis revealed that the lower jasmonate (JA) content in new leaves and the downregulation of JA biosynthetic genes (i.e. lipoxygenase, the 12-oxophytodienoate reductase-like protein, and salicylic acid carboxyl methyltransferase) may play essential roles in the early-flowering phenotype of genotype 80. Further research indicated that genes encode pathogenesis-related proteins [e.g. leucine rich repeat (LRR) family proteins, receptor-like proteins, and toll-interleukin-like receptor (TIR)-nucleotide-binding site (NBS)-LRR class proteins] and members of the signaling receptor kinase family [LRR proteins, kinases domain of unknown function 26 (DUF26) and wheat leucine-rich repeat receptor-like kinase10 (LRK10)-like kinases] are related to early flowering in alfalfa. Additionally, those involved in secondary metabolism (2-oxoglutarate/Fe (II)-dependent dioxygenases and UDP-glycosyltransferase) and the proteasome degradation pathway [really interesting new gene (RING)/U-box superfamily proteins and F-box family proteins] are also related to early flowering in alfalfa.ConclusionsIntegrated phenotypical, physiological, and transcriptomic analyses demonstrate that hormone biosynthesis and signaling pathways, pathogenesis-related genes, signaling receptor kinase family genes, secondary metabolism genes, and proteasome degradation pathway genes are responsible for the early flowering phenotype in alfalfa. This will provide new insights into future studies of flowering time in alfalfa and inform genetic improvement strategies for optimizing this important trait.

Development of EST-SSR Markers Linked to Flowering Candidate Genes in Elymus sibiricus L. Based on RNA Sequencing.

Elymus sibiricus L. is an important cold-season grass with excellent cold and drought tolerance, good palatability, and nutrition. Flowering time is a key trait that affects forage and seed yield. Development of EST-SSR (expressed sequence tag simple sequence repeat) markers based on flowering genes contributes to the improvement of flowering traits. In the study, we detected 155 candidate genes related to flowering traits from 10,591 unigenes via transcriptome sequencing in early- and late-flowering genotypes. These candidate genes were mainly involved in the photoperiodic pathway, vernalization pathway, central integrator, and gibberellin pathway. A total of 125 candidate gene-based EST-SSRs were developed. Further, 15 polymorphic EST-SSRs closely associated to 13 candidate genes were used for genetic diversity and population structure analysis among 20 E. sibiricus accessions, including two contrasting panels (early-flowering and late-flowering). Among them, primer 28366, designed from heading date 3a (HD3a), effectively distinguished early- and late-flowering genotypes using a specifically amplified band of 175 bp. The polymorphic information content (PIC) value ranged from 0.12 to 0.48, with an average of 0.25. The unweighted pair group method analysis (UPGMA) cluster and structure analysis showed that the 20 E. sibiricus genotypes with similar flowering times tended to group together. These newly developed EST-SSR markers have the potential to be used for molecular markers assisted selection and germplasm evaluation of flowering traits in E. sibiricus.

Exploring Flowering Genes in Isabgol (Plantago ovata Forsk.) Through Transcriptome Analysis

Flowering is one of the major developmental processes that govern the economic yield of crop plants. However, little is known about the molecular mechanisms underlying flowering in Isabgol, an important high-value medicinal crop. Here, we analyzed the leaf transcriptome of early and late flowering genotypes by high throughput next-generation sequencing to uncover the genes and pathways involved in flowering time and flower development. Illumina paired-end sequencing of Isabgol leaves at the stem elongation stage, generated 8,976,119 and 4,282,684 reads respectively in DPO-14 (early flowering) and DPO-185 (late flowering) genotypes. The sequence assembly resulted in 40,175 and 39,533 transcripts respectively in early and late genotypes. A total of 17,768 (95.50) in DPO-14 and 21,255 (94.10) in DPO-185 CDS were annotated. There were 8981CDS were differentially expressed of which 1220 (13.58%) were significantly upregulated while 1485 (16.53%) CDS were significantly downregulated in DPO-185 compared with DPO-14. In total, 229 genes were identified belongs to distinct flowering pathways in Isabgol. A putative schematic network of flowering pathway regulation in Isabgol was proposed. Significant DEGs (60 genes) related to flowering time and flower development were detected between the early and late flowering genotypes. Significant differences in fold change expression of 17 genes were observed in early and late flowering genotypes. Many differentially expressed genes (DEGs) involved in flowering time and flower development were identified. The expression data will serve as a resource for unraveling the functions of specific genes involved in flower development in Isabgol and other plants. These findings are significant for further understanding of the molecular basis for flowering time regulation, breeding, and molecular biology in Isabgol as well as other crop plants.

Induction of Earlier Flowering in Cassava through Extended Photoperiod

Erect plant architecture is preferred by farmers but results in late and scarce flowering, which slows down breeding considerably. Inducing earlier and abundant flowering in crossing nurseries (involving erect genotypes) is a key objective for cassava and was the subject of this study. Five genotypes with contrasting flowering behavior were grown under dark night (DN) and extended photoperiod (EP) conditions for three seasons. EP was achieved with different red light emitting diodes (LEDs) with 625–635 nm wavelength all night long or through night-breaks. EP reduced height and number of days to first branching, particularly in non- or late-flowering genotypes. A minimum of 0.02 μmol m−2 s−1 was required to elicit earlier flowering in plants illuminated all night. Early results using five genotypes were validated across 116 genotypes planted in a crossing nursery. EP promoted earlier flowering in erect-plant genotypes but reduced the number of branching events in early flowering genotypes to some extent. 50W LED lamps, fixed at 3 m above ground in a 4.5 m grid, proved to be a practical approach to extend photoperiod in breeding nurseries. Night breaks also proved effective, thus opening the possibility of using solar panels where electricity is not available.

Flowering problems and their possible solution in cassava breeding

Six elite cassava clones were chosen from cassava breeding program at the National Crops Resource Research Institute (NaCRRI) based on their flowering characteristics and seed set. The clones were planted in randomized complete block experimental design with 3 replications. The floral biology of these cassava clones were studied, focusing on morphological traits and developmental timing. Since cassava develops branches in levels, data was sourced from the 1st level of branching through the 4th level of branching. The result indicated that days to branching generally varied among all the genotypes studied, indicating the need to use different planting dates for different genotypes to ensure synchronization of flowering. The time difference among genotypes from branching to visible inflorescence was not larger than one and a half days and this difference did not seem to be a factor for synchronization. The general number of female flowers was low in all genotypes across branching levels. This suggests there is a need to apply techniques that could enhance flowering in cassava. Conversely, the number of male flowers outnumbered the female flowers, suggesting that male flower production may not be a limiting factor to hybrid seed production. The male flower opened 20 to 30 days later after the opening of the female flowers. This calls for delayed planting of the early flowering genotypes when used as female parent. It was recommended that in order to synchronize flowering, the late flowering genotypes have to be planted ahead of the early flowering genotypes. In addition, applying techniques such as growth regulators, red light and finding the most optimal locations for flowering is recommended for further study as a way of enhancing flowering among cassava genotypes.