Increased Tiller Number Research Articles

EFFECT OF SALINITY AND POTASSIUM FERTILIZER APPLICATION ON YIELD CONTRIBUTING CHARACTERISTICS OF RICE

Salt tolerant variety BR 41 was grown in kharif 2 season by pot experiment to study the effects of salinity and potassium fertilizer on agronomic characteristics of rice (Oryza sativa L.). The agronomic parameters increased with increasing salinity up to 12 dSm-1 level but with plant height. The increase in tiller number, panicle number, shoot dry matter and total grain yield was statistically significant at 5% (LSD0.05) level, whereas the increase in 1000 grain weight was significant at 1% (LSD0.01) level. Application of potassium fertilizer at different salinity levels did not produce significant change in agronomic parameters with an exception in shoot dry matter.

Dwarf and High Tillering1 represses rice tillering through mediating the splicing of D14 pre-mRNA.

Strigolactones (SLs) constitute a class of plant hormones that regulate many aspects of plant development, including repressing tillering in rice (Oryza sativa). However, how SL pathways are regulated is still poorly understood. Here, we describe a rice mutant dwarf and high tillering1 (dht1), which exhibits pleiotropic phenotypes (such as dwarfism and increased tiller numbers) similar to those of mutants defective in SL signaling. We show that DHT1 encodes a monocotyledon-specific hnRNP-like protein that acts as a previously unrecognized intron splicing factor for many precursor mRNAs (pre-mRNAs), including for the SL receptor gene D14. We find that the dht1 (DHT1I232F) mutant protein is impaired in its stability and RNA binding activity, causing defective splicing of D14 pre-mRNA and reduced D14 expression, and consequently leading to the SL signaling-defective phenotypes. Overall, our findings deepen our understanding of the functional diversification of hnRNP-like proteins and establish a connection between posttranscriptional splicing and SL signaling in the regulation of plant development.

Effects of pre-sowing seed treatments on rice yield, grain quality and soil chemical properties in salt-affected soils

This study aimed to evaluate the effects of sowing density and iron (Fe) coated seeds on rice grain yield, grain quality, and soil properties in saline soils in Phuoc Long district, Bac Lieu province, Vietnam. Experimental treatments include: (T1) Intact dry seed (50 kg seed/ha); (T2) Hydro-primed seed (120 kg seed/ha); (T3) Hydro-primed seed (50 kg seed/ha); (T4) Hydro-primed then sprouted seed (50 kg seed/ha); (T5) Fe-coated dry seed (50 kg seed/ha); (T6) Fe-coated hydro-primed seed (120 kg seed/ha); (T7) Fe-coated hydro-primed seed (50 kg seed/ha); (T8) Fe-coated hydro-primed seed which was sprouted before sowing (50 kg seed/ha); (T9) Hydro-primed then sprouted seed (120 kg seed/ha); (T10) Transplanting (50 kg seed/ha). The results indicated that applying Fe-coated seeds significantly increased tiller number at 45 and 60 DAS compared to free-Fe-coated seeds and transplanting treatments. There was no significant difference in tiller number among treatments at harvest stage. The plant height, yield, amylose, protein contents, gel consistency, soil pH, Eh, and Fe content in soil solution among the treatments did not differ significantly. This study demonstrated that reducing seed rate, broadcasting dry seeds, and coating seeds with Fe could reduce production cost while plant growth, yield and grain quality are maintained.

High-resolution bin-based linkage mapping uncovers the genetic architecture and heterosis-related loci of plant height in indica-japonica derived populations.

Plant height (PH) is an important trait affecting the plant architecture, seed yield, and harvest index. However, the molecular mechanisms underlying PH heterosis remain unclear. In addition, useful PH-related genes must be urgently identified to facilitate ideal plant architecture breeding in rice (Oryza sativa L.). In the present study, to explore rice quantitative trait loci (QTLs) and heterosis-related loci of PH in rice, we developed a high-generation (>F15 ) population of 272 recombinant inbred lines (RIL) from a cross of two elite varieties, Luohui 9 (indica/xian) × RPY geng (japonica/geng), and two testcross hybrid populations derived from the crosses of RILs and two cytoplasmic male sterile lines (YTA [indica] and Z7A [japonica]). Using deep resequencing data, a high-density genetic map containing 4758 bin markers was constructed, with a total map distance of 2356.41 cM. Finally, 31 PH-related QTLs for different PH component lengths or tiller numbers across five seasons were identified. Two major environment-specific PH QTLs were stably detected in Hainan (qPH-3.1) or Hubei (qPH-5.1), which have undergone significant functional alterations in rice with changes in geographical environment. Based on comparative genomics, gene function annotation, homolog identification, and existing literature (pioneering studies), candidate genes for multiple QTLs were fine-mapped, and the candidate genes qPH-3.1 and qPH-5.1 for PH were further validated using CRISPR-Cas9 gene editing. Specifically, qPH-3.1 was characterized as a pleiotropic gene, and the qPH-3.1 knockout line showed reduced PH, delayed heading, a decreased seed setting rate, and increased tiller numbers. Importantly, 10 PH heterosis-related QTLs were identified in the testcross populations, and a better-parent heterosis locus (qBPH-5.2) completely covered qPH-5.1. Furthermore, the cross results of fixed-genotype RILs verified the dominant effects of qPH-3.1 and qPH-5.1. Together, these findings further our understanding of the genetic mechanisms of PH and offer multiple highly reliable gene targets for breeding rice varieties with ideal architecture and high yield potential in the immediate future.

Identification and Evaluation of Wheat-Aegilops bicornis Lines with Resistance to Powdery Mildew and Stripe Rust.

Wheat pathogens, especially those causing powdery mildew and stripe rust, seriously threaten yield worldwide. Utilizing newly identified disease resistance genes from wheat relatives is an effective strategy to minimize disease damage. In this study, chromosome-specific molecular markers for the 3Sb and 7Sb chromosomes of Aegilops bicornis were developed using PCR-based landmark unique gene primers for screening wheat-A. bicornis progenies. Fluorescence in situ hybridization (FISH) was performed to further identify wheat-A. bicornis progenies using oligonucleotides probes Oligo-pSc119.2-1, Oligo-pTa535-1, and Oligo-(GAA)8. After establishing A. bicornis 3Sb and 7Sb chromosome-specific FISH markers, Holdfast (common wheat)-A. bicornis 3Sb addition, 7Sb addition, 3Sb(3A) substitution, 3Sb(3B) substitution, 3Sb(3D) substitution, 7Sb(7A) substitution, and 7Sb(7B) substitution lines were identified by the molecular and cytological markers. Stripe rust and powdery mildew resistance, along with agronomic traits, were investigated to evaluate the breeding potential of these lines. Holdfast and Holdfast-A. bicornis progenies were all highly resistant to stripe rust, indicating that the stripe rust resistance might derive from Holdfast. However, Holdfast-A. bicornis 3Sb addition, 3Sb(3A) substitution, 3Sb(3B) substitution, and 3Sb(3D) substitution lines showed high resistance to powdery mildew while Holdfast was highly susceptible, indicating that chromosome 3Sb of A. bicornis carries previously unknown powdery mildew resistance gene(s). Additionally, the transfer of the 3Sb chromosome from A. bicornis to wheat significantly increased tiller number, but chromosome 7Sb has a negative effect on agronomic traits. Therefore, wheat germplasm containing A. bicornis chromosome 3Sb has potential to contribute to improving powdery mildew resistance and tiller number during wheat breeding.

Impact of Sclerospora graminicola infection on physiological mechanisms and hormonal regulation of floral reversion in pearl millet [Pennisetum glaucum (L.) R. Br

The present study was undertaken to assess the impact of Sclerospora graminicola infection on the physiological and developmental changes in pearl millet. Disease progression of biotrophic pathogen Sclerospora graminicola causing downy mildew was determined to alter the anatomical, biochemical and photosynthetic characteristics of the flag leaf. The defense mechanism was initiated by the host plant in response to S. graminicola infection. The plugging of stomatal pores and vascular bundles with an increase in trichome density was observed post infection. The infection caused an increase in internal CO2 concentration, decrease in net photosynthetic rate, stomatal conductance and transpiration rate of the flag leaf. The disease infection reduced the total soluble sugar content of the host plant, whereas increased the starch and the total phenolic content. The increase in starch content in the downy mildew infected leaves might have imparted feedback inhibition leading to reduced photosynthetic activity. The leaf malondialdehyde (MDA) content and enzymatic antioxidants viz. peroxidase, polyphenol oxidase and indole-3-acetic acid (IAA) oxidase increased post infection. Hence, this imbalance in flag leaf metabolic activity affected the developing panicle and induced developmental alterations which redirected floral development and fate of the meristem. An increase in tiller number was possibly due to the release of apical dominance caused by fungal infection which regulated the endogenous auxin content to a three fold increase. Floral reversion due to the pathogen infection suggests that there was transport of auxin from the developing axillary buds that might have led to malformed ear proliferation. The information on carbon assimilation and hormone imbalance causing floral reversion in pearl millet by downy mildew pathogen can aid in management practices aimed at reducing the disease impact on the crop.

Soil water repellence increased early wheat growth and nutrient uptake

PurposeSoil water repellence causes uneven soil wetting which can constrain dryland crop and pasture establishment and yield. The same processes are likely to affect nutrient availability from soil and fertiliser, but the effects of repellence on crop growth and nutrition per se have seldom been reported. Here, we investigated early wheat (Triticum aestivum cv. Mace) growth and nutrient uptake responses to repellence.MethodsWheat was furrow-sown in severely repellent sandy loam soil (with a wettable furrow base to allow for germination) or completely wettable soil, under uniform plant density and variable topsoil thickness (20 or 100 mm) and fertiliser band placement (below or away from the seed). Tiller number, shoot dry matter, shoot N concentration, total nutrient uptake, and root length density (RLD) were determined.ResultsContrary to expectations, repellence significantly increased tiller number (by up to 2 tillers per plant), shoot dry matter (by 82%), shoot N concentration (by 0.3% N), and total nutrient uptake (by 87%) at 51 days after sowing, regardless of topsoil thickness and fertiliser placement. In the furrow, RLD of repellent treatments was also nearly double that in wettable treatments when fertiliser was banded below the seed. Results suggest that preferential soil wetting of the furrow in repellent treatments favoured plant nutrient uptake under regular but low water supply.ConclusionWe conclude that for water-repellent soils with limited water supply, water harvesting techniques such as furrow sowing and banding wetting agents could boost water and nutrient uptake and early crop growth.

<i>BcBRC1a</i> is a negative regulator for tillering in non-heading Chinese cabbage

Shoot branching is a decisive factor for crop yield. Molecular mechanism for regulating shoot branching (tillering) needs to be determined. Plenty of previous studies have illustrated that <italic>BRANCHED1</italic> (<italic>BRC1</italic>) is a key integrator of shoot branching regulating signals. However, <italic>BcBRC1</italic> function in non-heading Chinese cabbage (<italic>Brassica campestris</italic> ssp.<italic> chinensis</italic>) (NHCC) remains unknown. Here, we defined two <italic>BRC1</italic> orthologs, <italic>BcBRC1a</italic> and <italic>BcBRC1b</italic>, from NHCC and focused on the <italic>BcBRC1a</italic> gene to describe its alternative splicing characteristic and structure. <italic>BcBRC1a</italic> was expressed rhythmically and mainly in leaf axils at the 'Maertou' cultivar tillering stage. <italic>BcBRC1a</italic>^{<italic>L</italic>} encoded a nuclear location protein. Its ectopic expression caused <italic>Arabidopsis</italic> growth inhibition and silencing <italic>BcBRC1a</italic> led to increased tiller numbers in 'Maertou'. Removing the shoot tips of NHCC caused axillary buds to be released from apical dominance and <italic>BcBRC1a</italic> expression down-regulation. Our research determined that <italic>BcBRC1a</italic> acts as a negative regulator for tillering in non-heading Chinese cabbage and sets the foundation for further studies.

A Rice Ancestral Genetic Resource Conferring Ideal Plant Shapes for Vegetative Growth and Weed Suppression.

To maximize crop growth, crops need to capture sunlight efficiently. This property is primarily influenced by the shape of the crops such as the angle, area, and arrangement of leaves. We constructed a rice (Oryza sativa L.) inbred line that displayed an ideal transition of plant shapes in terms of sunlight receiving efficiency. During vegetative growth, this line exhibited tiller spreading with increased tiller number, which formed a parabolic antenna-like structure. The architecture probably improved light reception efficiency of individuals compared with the recurrent parent. The line achieved not only acceleration of the vegetative growth, but also significant suppression of weed growth under the canopy. The increased light reception efficiency of the line has consequently reduced the amount of incident light to the ground and supplied significant competitiveness against weeds. The spread tillers became erect from the entry of the reproductive growth phase, adaptively sustaining light reception efficiency in thicker stands. The line carries a small chromosomal segment from Oryza rufipogon Griff., a putative progenitor of Asian cultivated rice. The introduced chromosome segment had little effect on grain yield and quality. Our results shed light on potentials hidden in the wild rice chromosome segment to achieve the valuable traits.

New insight to the use of oyster shell for removing phosphorus from aqueous solutions and fertilizing rice growth

The excess amount of phosphorus (P) in water bodies can cause eutrophication, while the lack of P in soil can limit plant growth. Therefore, this study proposes to recover P from eutrophic lakes and use the recovered P as a fertilizer for rice growth in soil. In order to recover P from water bodies, oyster shell wastes (OySh) were used to prepare an adsorbent for P removal. The P-adsorbed adsorbent can then be used as fertilizer to release P to the soil slowly. This study investigates the feasibility of the OySh as both the P adsorbent and fertilizer, and involves four major experiments: the characterization of the OySh, adsorption experiments, toxicity tests, and pot experiments for rice growth. The OySh was thermally treated to improve its adsorption capacity for P, and the OySh calcined at 800 °C (OySh-800) showed noticeably high P adsorption. The P adsorption to the OySh-800 was quantified in batch experiments under various conditions and column experiments using natural lake water. The potential use of P adsorbed OySh-800 (P-OySh-800) as a P fertilizer was assessed by its toxicity test using bioluminescent bacteria and earthworms and pot experiments for rice growth. X-ray diffraction and X-ray photoelectron spectroscopy analyses revealed that P adsorption by the OySh-800 was achieved by the reaction between P and the calcium in the OySh-800, which formed Ca(PO3)2 and Ca4.885(PO4)3(OH)0.654. The P adsorption on the OySh-800 took 72 h to reach the equilibrium, and the maximum P adsorption capacity was 228.15 mg/g, which was higher than that of other adsorbents used for P removal. In the column experiment, a breakthrough point was reached in 20 h, and 73.6% of the P in the lake water was removed. The toxic effects of the OySh-800 determined by Allivibrio fischeri (EC50 of 896 mg/L) decreased after P adsorption (EC50 of 28 300 mg/L for P-OySh-800). When the OySh-800 and P-OySh-800 were applied at 0%–0.42% in soil, the toxic effects of both adsorbents on earthworms were negligible. The application of the P-OySh-800 at the medium level (i.e., 0.1 g/kg-soil) significantly promoted rice growth (i.e., increased tiller number). The application of organic wastes (i.e., OySh-800) as value-added materials to remove P from water and subsequently supply P for rice cultivation can address two environmental issues with P, excess of P in water bodies causing eutrophication and lack of P in the soil.

Divergent responses of tiller and grain yield to fertilization and fallow precipitation: Insights from a 28-year long-term experiment in a semiarid winter wheat system

Tillering is an important phenological stage, which is strongly related to the yield in spike components and final grain yield during winter wheat growth. Precipitation during the fallow season (fallow precipitation) influences tillering in winter wheat on the semi-arid Chinese Loess Plateau. However, little work has been done regarding tiller number changes under various types of fertilization and amounts of fallow precipitation on a long-term scale. Effects of fallow precipitation and fertilization on tiller were investigated in a winter wheat (Triticum aestivum L.) system in a 28-year field study (1990 to 2017) in a semiarid agro-ecosystem. Tiller number, spike number and grain yield were measured in four fertilization conditions: control without fertilizer (CK); mineral nitrogen fertilizer alone (N); mineral phosphorus fertilizer alone (P); mineral nitrogen and phosphorus fertilizer together (NP). Based on the long-term annual fallow precipitation, dry years (<mean annual fallow precipitation) and wet years (>mean annual fallow precipitation) were distinguished. Phosphorus fertilization alone significantly increased the mean annual tiller number (23%), and the increase in tiller number was higher in wet years (29%) than in the dry years (17%). However, nitrogen fertilization alone had little effect on mean tiller number, while nitrogen and phosphorus together significantly increased mean annual tiller number (30%), mean tiller number in wet years (45%) and mean tiller number in dry years (17%). Tiller number was significantly and positively correlated with fallow precipitation in dry years for all fertilizer treatments, whereas it was weakly and either positively or negatively correlated with fallow precipitation in wet years depending on the treatment. This study found positive correlations between tiller number and fallow precipitation in the CK and NP treatments, and it found negative correlations between tiller number and fallow precipitation in the treatments with nitrogen fertilization alone or phosphorous fertilization alone in wet years. Understanding the impacts of fallow precipitation and fertilization on tiller development shed light on ways to improve crop production in rain-fed agricultural regions.

Identification of novel plant architecture mutants in barley

In grasses, biomass and grain production are affected by plant architecture traits such as tiller number, leaf size and orientation. Thus, knowledge regarding their genetic basis is a prerequisite for developing new improved varieties. Mutant screens represent a powerful approach to identify genetic factors underpinning these traits: the HorTILLUS population, obtained by mutagenesis of spring two-row cultivar Sebastian, is a valuable resource for this purpose in barley. In this study, 20 mutant families from the HorTILLUS population were selected and evaluated for tiller number, leaf angle and a range of other plant architecture and agronomic traits using an unreplicated field design with Sebastian as a check cultivar. Principal Component Analysis revealed strong relationships among number of tillers, upper canopy leaf angle, biomass and yield-related traits. Comparison to the Sebastian background revealed that most mutants significantly differed from the wild-type for multiple traits, including two mutants with more erect leaves and four mutants with increased tiller number in at least one phenological stage. Heatmap clustering identified two main groups: the first containing the two erect mutants and the second containing Sebastian and the high-tillering mutants. Among the high-tillering mutants, two showed significantly higher biomass and grain yield per plant compared to Sebastian. The selected mutants represent promising materials for the identification of genetic factors controlling tillering and leaf angle in barley.

Evaluation of arsenic remediation, morphological and biochemical response by Vetiveria zizanoides L. plants grown on artificially arsenic contaminated soil: A field study

The present study evaluated arsenic (As) remediation capacity of Vetiveria. zizanoides plants from artificially contaminated soil (0, 50, 100, 250, 500, 1000 mg kg−1) after various durations ie. 30, 60 and 90 d. Plants were found effective, maximum As removal being 71% after 90 d when grown in 50 mg kg−1 As. Plant growth was not affected at lower As levels (up to 250 mg kg−1) and V. zizanoides plants grown at 50 mg kg−1 have shown increase in number of tillers (43%), biomass (30%) and plant height (26%) compared to control after 90 days. Thiobarbituric acid reactive metabolites (TBARM) content has not shown any change in As exposed plants up to 30 d, maximum increase in TBARM content was found in roots and shoots of the V. zizanoides plants as 84% and 79% after 90 d when grown at 1000 mg kg−1 As contaminated plot. The activities of antioxidant enzymes, superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase and catalase were found to increase in response to As stress in a coordinated manner. Besides, various non- enzymatic antioxidants also provided defense to plants against As stress. High As accumulation and tolerance potential of V. zizanoides from artificially contaminated soil coupled with large biomass and root system, suggests its feasibility for the revegatation/remediation of As contaminated soils of West Bengal (India).

Molecular cloning and functional characterization of TaIRI9 gene in wheat (Triticum aestivum L.).

The vernalization of wheat is one of the important factors that determine the planting region, introduction and cultivation techniques of wheat. However, the known vernalization genes (molecular marker) cannot precisely distinguish the vernalization requirement of winter wheat cultivars. Therefore, it is important to explore new vernalization genes and elucidate the mechanism of vernalization regulation. To explore the gene network in the vernalization pathway, we screened TaIRI9 (ice recrystallization inhibitor protein) gene associated with the expression profile of vernalization treatment of winter wheat Jing 841. Overexpression of TaIRI9 in wild type wheat resulted in reduced plant height, increased tiller number and delayed heading days. After 4°C vernalization treatment for 30, 35, 45 or 50days, TaIRI9 overexpression lines showed increased vernalization requirement and delayed heading time than wild type, indicating that TaIRI9 may affect vernalization process of wheat. In addition, the expression of the TaIRI9 genes were analyzed in winter Jing 841, strong winter wheat cultivar Xindong 18 and ten recombinant inbred lines (RILs, Hussar×Yanzhan1). The data showed that the expression of TaIRI9 was positively associated with the requirement of vernalization. These results indicated that TaIRI9 regulates heading and flowering time in wheat by promoting VRN2 and inhibiting flowering promoter VRN1 and VRN3 and may be involved in wheat vernalization regulation pathway.

APICAL SPIKELET ABORTION (ASA) Controls Apical Panicle Development in Rice by Regulating Salicylic Acid Biosynthesis.

Panicle degradation causes severe yield reduction in rice. There are two main types of panicle degradation: apical spikelet abortion and basal degeneration. In this study, we isolated and characterized the apical panicle abortion mutant apical spikelet abortion (asa), which exhibits degeneration and defects in the apical spikelets. This mutant had a pleiotropic phenotype, characterized by reduced plant height, increased tiller number, and decreased pollen fertility. Map-based cloning revealed that OsASA encodes a boric acid channel protein that showed the highest expression in the inflorescence, peduncle, and anther. RNA-seq analysis of the asa mutant vs wild-type (WT) plants revealed that biological processes related to reactive oxygen species (ROS) homeostasis and salicylic acid (SA) metabolism were significantly affected. Furthermore, the asa mutants had an increased SA level and H2O2 accumulation in the young panicles compared to the WT plants. Moreover, the SA level and the expression of OsPAL3, OsPAL4, and OsPAL6 genes (related to SA biosynthesis) were significantly increased under boron-deficient conditions in the asa mutant and in OsASA-knockout plants. Collectively, these results suggest that the boron distribution maintained by OsASA is required for normal panicle development in a process that involves modulating ROS homeostasis and SA biosynthesis.

Narrow Leaf21, encoding ribosomal protein RPS3A, controls leaf development in rice.

Leaf morphology influences photosynthesis, transpiration, and ultimately crop yield. However, the molecular mechanism of leaf development is still not fully understood. Here, we identified and characterized the narrow leaf21 (nal21) mutant in rice (Oryza sativa), showing a significant reduction in leaf width, leaf length and plant height, and increased tiller number. Microscopic observation revealed defects in the vascular system and reduced epidermal cell size and number in the nal21 leaf blade. Map-based cloning revealed that NAL21 encodes a ribosomal small subunit protein RPS3A. Ribosome-targeting antibiotics resistance assay and ribosome profiling showed a significant reduction in the free 40S ribosome subunit in the nal21 mutant. The nal21 mutant showed aberrant auxin responses in which multiple auxin response factors (ARFs) harboring upstream open-reading frames (uORFs) in their 5'-untranslated region were repressed at the translational level. The WUSCHEL-related homeobox 3A (OsWOX3A) gene, a key transcription factor involved in leaf blade lateral outgrowth, is also under the translational regulation by RPS3A. Transformation with modified OsARF11, OsARF16, and OsWOX3A genomic DNA (gDNA) lacking uORFs rescued the narrow leaf phenotype of nal21 to a better extent than transformation with their native gDNA, implying that RPS3A could regulate translation of ARFs and WOX3A through uORFs. Our results demonstrate that proper translational regulation of key factors involved in leaf development is essential to maintain normal leaf morphology.

The potential of plant growth-promoting microbes from South Kalimantan acid sulfate soil in enhancing the growth of rice plants

Rhizobacteria and dark septa endophytic (DSE) fungi isolated from indigenous plant of acid sulfate soil (ASS) in South Kalimantan has potency as an adaptive plant growth promoter. The study aimed to test the effectiveness of the rhizobacteria and DSE in improving swamp rice growth in ASS. Inpara 2 rice variety was used in greenhouse experiment using randomized complete design. Inoculants and compost were applied to the potential ASS-filled pot. The observed parameters were plant height, tillers number, rice straw and root weight, as well as root length. The plant height at 14 and 21 days after transplanting (DAT) was significantly higher in three rhizobacteria treatments over three DSEs and uninoculated treatment. All rhizobacteria significantly increased tiller number, rice straw and root weight, and length compared to control. The DSE GS1-2 significantly improved tiller number, as well as, root weight, and length over control. Rhizobacterium KM19.2 revealed highest effect on rice straw fresh and dry weight, root fresh weight and length. Rhizobacterium PD5.3.1 produced highest plant height at 14, 21, and 56 DAT as well as, tiller number and root dry weight. Therefore, the rhizobacteria and DSE GS1-2 could be used as a promising bio-fertilizer for improving swamp rice growth in ASS.

Modulating tiller formation in cereal crops by the signalling function of fertilizer nitrogen forms

Cereal crop yield comprises interrelated components, among which the number of tillers is highly responsive to nitrogen fertilization. We addressed the hypothesis of whether the supply of different nitrogen forms can be employed to manipulate the tiller number in cereal crops. Relative to urea or ammonium, exclusive supply of nitrate increased tiller number in hydroponically-grown barley plants. Thereby, tiller number correlated positively with the root-to-shoot translocation rate of endogenous cytokinins. External supply of a synthetic cytokinin analog further stimulated tillering in nitrate-containing but not in urea-containing nutrient solution. When the cytokinin analog 6-benzylaminopurine riboside was externally supplied to roots, its translocation to shoots was 2.5 times higher in presence of nitrate than in presence of urea or ammonium, suggesting that cytokinin loading into the xylem is affected by different nitrogen forms. We then translated this finding to field scale, cultivated winter wheat in four environments, and confirmed that nitrate fertilization significantly increased tiller number in a dose-dependent manner. As assessed in 22 winter wheat cultivars, nitrogen form-dependent tiller formation was subject to substantial genotypic variation. We conclude that cytokinin-mediated signaling effects of fertilizer nitrogen forms can be employed as a management tool to regulate the tiller number in cereal crops.

OsPIN9, an auxin efflux carrier, is required for the regulation of rice tiller bud outgrowth by ammonium.

The degree of rice tillering is an important agronomic trait that can be markedly affected by nitrogen supply. However, less is known about how nitrogen-regulated rice tillering is related to polar auxin transport. Compared with nitrate, ammonium induced tiller development and was paralleled with increased 3 H-indole-acetic acid (IAA) transport and greater auxin into the junctions. OsPIN9, an auxin efflux carrier, was selected as the candidate gene involved in ammonium-regulated tillering based on GeneChip data. Compared with wild-type plants, ospin9 mutants had fewer tillers, and OsPIN9 overexpression increased the tiller number. Additionally, OsPIN9 was mainly expressed in vascular tissue of the junction and tiller buds, and encoded a membrane-localised protein. Heterologous expression in Xenopus oocytes and yeast demonstrated that OsPIN9 is a functional auxin efflux transporter. More importantly, its RNA and protein levels were induced by ammonium but not by nitrate, and tiller numbers in mutants did not respond to nitrogen forms. Further advantages, including increased tiller number and grain yield, were observed in overexpression lines grown in the paddy field at a low-nitrogen rate compared with at a high-nitrogen rate. Our data revealed that ammonium supply and an auxin efflux transporter co-ordinately control tiller bud elongation in rice.

HIGH-TILLERING AND DWARF 12 modulates photosynthesis and plant architecture by affecting carotenoid biosynthesis in rice.

Photosynthesis and plant architecture are important factors influencing grain yield in rice (Oryza sativa L.). Here, we identified a high-tillering and dwarf 12 (htd12) mutant and analyzed the effects of the HTD12 mutation on these important factors. HTD12 encodes a 15-cis-ζ-carotene isomerase (Z-ISO) belonging to the nitrite and nitric oxide reductase U (NnrU) protein family, as revealed by positional mapping and transformation experiments. Sequence analysis showed that a single nucleotide transition from guanine (G) to adenine (A) in the 3' acceptor site between the first intron and second exon of HTD12 alters its mRNA splicing in htd12 plants, resulting in a 49-amino acid deletion that affects carotenoid biosynthesis and photosynthesis. In addition, compared with the wild type, htd12 had significantly lower concentrations of ent-2'-epi-5-deoxystrigol (epi-5DS), a native strigolactone, in both roots and root exudates, resulting in an obvious increase in tiller number and decrease in plant height. These findings indicate that HTD12, the rice homolog of Z-ISO, regulates chloroplast development and photosynthesis by functioning in carotenoid biosynthesis, and modulates plant architecture by affecting strigolactone concentrations.