Rice Tiller Number Research Articles

The Amino Acid Permease 5 (OsAAP5) Regulates Tiller Number and Grain Yield in Rice.

As fundamental nutrients, amino acids are important for rice (Oryza sativa) growth and development. Here, we identified the amino acid permease 5 (OsAAP5), that regulates tiller number and grain yield in rice. The OsAAP5 promoter sequence differed between indica and japonica rice varieties. Lower expression of OsAAP5 in the young leaf blade in indica varieties than in japonica varieties was associated with more tillers in indica than in japonica Down-regulation of OsAAP5 expression in japonica using RNA interference (RNAi) and clustered regularly interspaced short palindromic repeats led to increases in tiller number and grain yield, whereas OsAAP5 overexpression (OE) had the opposite effect. Both a protoplast amino acid uptake assay and HPLC analysis indicated that more basic (Lys, Arg) and neutral (Val, Ala) amino acids were transported and accumulated in the OE lines than in the wild type, but the opposite was observed in the RNAi lines. Furthermore, exogenous application of Lys, Arg, Val, and Ala in the OE lines substantially inhibited tiller bud elongation, but the effect was lost in the RNAi lines. Notably, concentrations of the cytokinins cis-zeatin and dihydrozeatin were much lower in the OE lines than in the wild type, whereas concentrations in the RNAi lines were higher. Thus, OsAAP5 could regulate tiller bud outgrowth by affecting cytokinin levels, and knockout of OsAAP5 could be valuable for japonica breeding programs seeking high yield and grain quality.

Altered expression of OsNPF7.1 and OsNPF7.4 differentially regulates tillering and grain yield in rice

The rice nitrate and di/tripeptide transporter (NPF) gene family plays an indispensable role in nitrogen transport and plant growth. In this study, 18 alternatively spliced OsNPF genes with 36 different forms of mRNAs were identified, and two of these, namely OsNPF7.1 and OsNPF7.4, showed opposite expression patterns in axillary buds under different nitrogen concentrations. Our results indicate that the expression levels of OsNPF7.1 and OsNPF7.4 determine the axillary bud outgrowth, especially for the second bud, and subsequently influence the tiller number in rice. The overexpression of either of the variants of OsNPF7.1 or the knockout of OsNPF7.4 increased the seedling biomass as well as the tiller number, filled grain number, and grain yield in rice. However, the RNAi-mediated silencing of OsNPF7.1 or the overexpression of either of the variants of OsNPF7.4 had an opposite effect. The overexpression of OsNPF7.1 or OsNPF7.4 could improve the uptake of nitrate, but the OsNPF7.4-overexpressing plants had lower biomass. It is possible that excessive nitrate in the OsNPF7.4-overexpressing plants led to the accumulation of amino acids in the leaf sheath, which inhibited seedling biomass. In addition, the reduced reutilization of nitrate in the seedlings also limited the plant biomass. However, the moderate increase in nitrate and amino acid concentrations in the OsNPF7.1-overexpressing plants could promote seedling biomass and enhance grain yield. In conclusion, our data suggest that different members in the NPF family have different roles in rice, and this study suggests an alternative way to modify rice architecture and enhance grain yield by regulating the expression of OsNPF7.1 and OsNPF7.4.

Populasi Serangga Hama dan Artropoda Predator pada Padi Rawa Lebak Sumatera Selatan yang Diaplikasikan Bioinsektisida dari Beauveria bassiana dan Insektisida Sintetik

Hanif et al, 2019. Population of Pest Insects and Predatory Arthropods Inhabiting Freshwater Swamp Rice of South Sumatra Treated with Bioinsectide of Beauveria bassiana and a Synthetic Insecticide. JLSO (8)1:31-38.Entomopathogenic fungi, Beauveria bassiana, could kill various species of insect pests, but their impact on predatory arthropods needs to be studied. The aim of this study was to compare population of pest insects and predatory arthropods inhabiting rice sprayed with bioinsecticide of B. bassiana and conventional rice field using a synthetic insecticides. Bioinsecticide was made from conidia of B. bassiana and sprayed on rice canopy. The plot of conventional farmers was sprayed with synthetic insecticides made from Abamektrin. The results showed that the application of bioinsecticide of B. bassiana was not proven to reduce the pest insect population. The abundance of natural enemies of pest insects, such as spiders and predatory insects was also more abundant in plots sprayed with bioinsecticide than conventional plots that used synthetic insecticide. The synthetic insecticides have been shown to reduce the abundance of predatory insects and spiders. Bioinsecticides containing carrier of liquid compost were proven to increase the growth and development of rice, which was an increase in the number of rice tillers per clump in plots applied by bioinsecticide. Thus, B. bassiana of bioinsecticide with liquid compost carrier material was safer and could maintain the abundance of predatory arthropods and increased rice growth.

Reduction in sucrose contents by downregulation of fructose-1,6-bisphosphatase 2 causes tiller outgrowth cessation in rice mutants lacking glutamine synthetase1;2

BackgroundOur previous transcriptomic analysis revealed that downregulation of nitrogen and carbon metabolism in the basal portions of the shoots inhibited cytosolic glutamine synthetase1;2 (GS1;2), which severely reduced rice tiller number. In the present study, we used rice mutants lacking GS1;2 (gs1;2 mutants) to determine the contribution of carbon metabolism to tiller growth.ResultsMetabolomic analysis indicated the effects of carbon metabolism disorder such as reductions in the levels of sugar metabolites (e.g., sucrose and glucose 6-phosphate) in the shoot basal portions of the gs1;2 mutant seedlings. Decrease in sucrose caused by the lack of GS1;2 was successfully restored to the wild-type levels by introducing OsGS1;2 cDNA into the mutants. In the basal portions of the shoots, the lack of GS1;2 caused low expression of cytosolic fructose 1,6-bisphosphatase2 (OscFBP2), which is a key cytosolic sucrose synthesis enzyme; it is especially important in the phloem companion cells of the nodal vascular anastomoses. NH4+ supply upregulated OscFBP2 expression in the shoot basal portions of the wild type but not in those of the gs1;2 mutants. Rice mutants lacking cFBPase2 presented with ~ 30% reduction in total cFBPase activity in the basal portions of their shoots. These mutants displayed reductions in sucrose levels of the basal portions of their shoots but not in their leaf blades. They also had relatively lower tiller numbers at the early growth stage.ConclusionsMetabolomic analysis revealed that the lack of GS1;2 reduced sucrose metabolism in the basal portions of the shoots. Our results indicated that sucrose reduction was caused by the downregulation of OscFBP2 expression in the basal portions of the gs1;2 mutant shoots. The reduction in sucrose content caused by the lack of cFBPase2 resulted in lower tiller number at the early growth stage. Therefore, adequate sucrose supply via cFBPase2 may be necessary for tiller growth in the basal portions of rice shoots.

Nitrogen application after low-temperature exposure alleviates tiller decrease in rice

Low temperature during the vegetative stage depresses the rice tillering, which decreases rice yield. The production and development of rice tillers can be closely related to the presence of nitrogen. Therefore, supplying rice with nitrogen after exposure to low temperatures may be an effective method to promote rice tillering. However, there is limited research about the effects of nitrogen application after low-temperature exposure on rice tillering. Water culture and field experiments were conducted using two rice varieties in each experiment; three temperatures (12 °C, 15 °C and 18 °C) and temperature durations (5, 10 and 15 days under 15 °C) were set in water culture experiments, and two temperatures (approximately 13 °C and 17 °C) were set in the field experiment. Two (40 mg N L−1 and 80 mg N L−1) and four (0, 20, 40 and 80 kg N ha−1) nitrogen levels after temperature treatment were applied in the water culture and field experiments, respectively. The results showed that low temperatures decreased rice tillering, nitrogen accumulation and yield, and higher stress strengths or longer low temperature durations led to greater tiller suppression. Nitrogen application after low-temperature stress enhanced the recovery of rice tillering. Four weeks after nitrogen application, the rice tiller number recovered to 87.90–92.92% of normal levels under 15 °C and to 70.39–73.85% of normal levels under 12 °C. Tillering in sensitive rice could be recovered to levels found at normal temperatures at the 10.5-leaf stage with increased nitrogen application after 5 days at 15 °C, whereas insensitive rice could be recovered without increased nitrogen. When low-temperature stress lasted for more than 10 days, increasing nitrogen application improved rice growth as well, although neither variety’s tillering recovered to normal levels. The correlation analysis also showed that the increase in tiller number was closely related to the increase in nitrogen accumulation (P < 0.01). Moreover, increasing the nitrogen application after low temperatures increased the rice nitrate reductase (NR) and glutamine synthase (GS) activities and nitrogen accumulation. The field experiment also showed that increasing the nitrogen application after low temperature could help rice yield recovery, but applying excessive nitrogen (more than 40 kg N ha-1 in this experiment) resulted in yield and nitrogen loss. These results highlighted the positive effects of nitrogen on rice growth recovery after low-temperature stress, which was affected by low temperature strength, duration and rice variety.

Modulation of plant architecture by the miR156f-OsSPL7-OsGH3.8 pathway in rice.

Tiller number and plant height are two of the main features of plant architecture that directly influence rice yield. Auxin and miR156, an extensively studied small RNA (smRNA), are both broadly involved in plant development and physiology, suggesting a possible relationship between the two. In this study, we identified a rice T-DNA insertion cluster and dwarf (cd) mutant that has an increased tiller number and reduced plant height. The T-DNA insertion was in close proximity to the miR156f gene and was associated with its up-regulation. Plants overexpressing miR156f resembled the cd mutant. In contrast, plants overexpressing an miR156f target mimic (MIM156fOE) had a reduced tiller number and increased height. Genetic analysis showed that OsSPL7 is a target of miR156f that regulates plant architecture. Plants overexpressing OsSPL7 had a reduced tiller number, while OsSPL7 RNAi plants had an increased tiller number and a reduced height. We also found that OsSPL7 binds directly to the OsGH3.8 promoter to regulate its transcription. Overexpression of OsGH3.8 and OsGH3.8 RNAi partially complemented the MIM156fOE and cd mutant phenotypes, respectively. Our combined data show that the miR156f-OsSPL7-OsGH3.8 pathway regulates tiller number and plant height in rice, and this pathway may allow crosstalk between miR156 and auxin.

Blocking amino acid transporter OsAAP3 improves grain yield by promoting outgrowth buds and increasing tiller number in rice.

SummaryAmino acid transporters (AATs) play indispensable roles in nutrient allocation during plant development. In this study, we demonstrated that inhibiting expression of the rice amino acid transporter OsAAP3 increased grain yield due to a formation of larger numbers of tillers as a result of increased bud outgrowth. Elevated expression of OsAAP3 in transgenic plants resulted in significantly higher amino acid concentrations of Lys, Arg, His, Asp, Ala, Gln, Gly, Thr and Tyr, and inhibited bud outgrowth and rice tillering. However, RNAi of OsAAP3 decreased significantly Arg, Lys, Asp and Thr concentrations to a small extent, and thus promoted bud outgrowth, increased significantly tiller numbers and effective panicle numbers per plant, and further enhanced significantly grain yield and nitrogen use efficiency (NUE). The promoter sequences of OsAAP3 showed some divergence between Japonica and Indica rice, and expression of the gene was higher in Japonica, which produced fewer tillers than Indica. We generated knockout lines of OsAAP3 on Japonica ZH11 and KY131 using CRISPR technology and found that grain yield could be increased significantly. These results suggest that manipulation of OsAAP3 expression could be used to increase grain yield in rice.

Two Splicing Variants of OsNPF7.7 Regulate Shoot Branching and Nitrogen Utilization Efficiency in Rice.

Rice includes 93 nitrate and peptide transporters family (NPF) members that facilitate the soil uptake and internal reallocation of nitrogen for growth and development. This study demonstrated that OsNPF7.7 had two splicing variants, and altered expression of each variant could regulate shoot branching and nitrogen utilization efficiency (NUtE) in rice. The expression of both variants was down-regulated in the buds by increased nitrogen level in the Japonica rice variety ZH11. The expression level of long-variant OsNPF7.7-1 was higher in panicles at reproductive stage, however, the expression level of short-variant OsNPF7.7-2 was higher in buds and leaves at vegetative stage compared to each other in ZH11. OsNPF7.7-1 was localized in the plasma membrane, whereas OsNPF7.7-2 was localized in the vacuole membrane. Furthermore, the results indicated that the expression level of each variant for OsNPF7.7 determined axillary bud outgrowth, and then influenced the rice tiller number. Overexpression of OsNPF7.7-1 could promote nitrate influx and concentration in root, whereas overexpression of OsNPF7.7-2 could improve ammonium influx and concentration in root. RNAi and osnpf7.7 lines of OsNPF7.7 showed an increased amount of amino acids in leaf sheaths, but a decreased amount in leaf blades, which affected nitrogen allocation and plant growth. The elevated expression of each variant for OsNPF7.7 in ZH11 enhanced NUtE using certain fertilization regimes under paddy field conditions. Moreover, overexpression of each variant for OsNPF7.7 in KY131 increased significantly the filled grain number per plant. Thus, increased each variant of OsNPF7.7 has the potential to improve grain yield and NUtE in rice.

Rice nitrate transporter OsNPF7.2 positively regulates tiller number and grain yield

BackgroundRice tiller number is one of the most important factors that determine grain yield, while nitrogen is essential for the crop growth and development, especially for tiller formation. Genes involved in nitrogen use efficiency processes have been identified in the previous studies, however, only a small number of these genes have been found to improve grain yield by promoting tillering.ResultsWe constructed over-expression (OX) lines and RNA-interference (Ri) lines, and selected a mutant of OsNPF7.2, a low-affinity nitrate transporter. Our analyses showed that rice tiller number and grain yield were significantly increased in OX lines, whereas Ri lines and mutant osnpf7.2 had fewer tiller number and lower grain yield. Under different nitrate concentrations, tiller buds grew faster in OX lines than in WT, but they grew slower in Ri lines and mutant osnpf7.2. These results indicated that altered expression of OsNPF7.2 plays a significant role in the control of tiller bud growth and regulation of tillering. Elevated expression of OsNPF7.2 also improved root length, root number, fresh weight, and dry weight. However, reduced expression of OsNPF7.2 had the opposite result on these characters. OsNPF7.2 OX lines showed more significantly enhanced influx of nitrate and had a higher nitrate concentration than WT. The levels of gene transcripts related to cytokinin pathway and cell cycle in tiller bud, and cytokinins concentration in tiller basal portion were higher in OX lines than that in WT, suggesting that altered expression of OsNPF7.2 controlled tiller bud growth and root development by regulating cytokinins content and cell cycle in plant cells. Altered expression of OsNPF7.2 also was responsible for the change in expression of the genes involved in strigolactone pathway, such as D27, D17, D10, Os900, Os1400, D14, D3, and OsFC1.ConclusionOur results suggested that OsNPF7.2 is a positive regulator of nitrate influx and concentration, and that it also regulates cell division in tiller bud and alters expression of genes involved in cytokinin and strigolactone pathways, resulting in the control over rice tiller number. Since elevated expression of OsNPF7.2 is capable of improving rice grain yield, this gene might be applied to high-yield rice breeding.

Mutations in the MIT3 gene encoding a caroteniod isomerase lead to increased tiller number in rice

Carotenoids not only play important roles in light harvesting and photoprotection against excess light, but also serve as precursors for apocaroteniod hormones such as abscisic acid (ABA) and strigolactones (SLs). Although light- and ABA-associated phenotypes of the carotenoid biosynthesis mutants such as albino, leaf variegation and preharvest sprouting have been studied extensively, the SLs-related branching phenotype is rarely explored. Here we characterized four allelic rice mutants named mit3, which exhibited moderately increased tiller number, semi-dwarfism and leaf variegation. Map-based cloning revealed that MIT3 encodes a carotenoid isomerase (CRTISO), the key enzyme catalyzing the conversion from prolycopene to all-trans-lycopene in carotenoid biosynthesis. Prolycopene was accumulated while all-trans-lycopene was barely detectable in the dark-grown mit3 seedlings. Accordingly, content of lutein and β-carotene, the two most abundant carotenoids, was significantly reduced. Furthermore, content of epi-5DS, a native SL, was significantly reduced in mit3. Exogenously applied GR24, a synthetic SL, could rescue the tillering phenotype of mit3. Double mutant analysis of mit3 with the SLs biosynthesis mutant d17 revealed that MIT3 controls tiller development upstream of the SLs biosynthesis pathway. Our results reveal that the tillering phenotype of mit3 is due to SL deficiency and directly link carotenoid deficiency with SL-regulated rice tillering.

Effects of seedling age and cultivation density on agronomic characteristics and grain yield of mechanically transplanted rice

Delayed transplantation frequently occurs in mechanically transplanted rice in China, leading to a significant reduction in grain yield. Thus, determining how to compensate grain yield loss is crucial for improving rice cultivation technology. A field experiment was conducted to investigate the effects of cultivation density and seedling age on agronomic traits and grain yield of mechanically transplanted rice. With increasing seedling age, rice tiller number, pre-anthesis dry matter accumulation, remobilization efficiency and contribution to grain yield, as well as post-anthesis photosynthesis amount decreased, causing reductions in the number of effective panicles, the total number of grains per panicle, the sink capacity per tiller, and grain yield. In rice transplanted at 30- and 35-day seedling ages, increasing cultivation density significantly enhanced the number of effective panicles and grain yield. Additionally, there existed strong, positive correlations between sink capacity per tiller and pre-anthesis dry matter remobilization efficiency and pre-anthesis dry matter contribution to grain yield. We conclude that in addition to cultivation density, enhancing the amount of pre-anthesis dry matter and the remobilization efficiency could be feasible for mitigating grain yield loss caused by delayed transplantation.

Overexpression of the leucine-rich receptor-like kinase gene LRK2 increases drought tolerance and tiller number in rice.

SummaryDrought represents a key limiting factor of global crop distribution. Receptor‐like kinases play major roles in plant development and defence responses against stresses such as drought. In this study, LRK2, which encodes a leucine‐rich receptor‐like kinase, was cloned and characterized and found to be localized on the plasma membrane in rice. Promoter–GUS analysis revealed strong expression in tiller buds, roots, nodes and anthers. Transgenic plants overexpressing LRK2 exhibited enhanced tolerance to drought stress due to an increased number of lateral roots compared with the wild type at the vegetative stage. Moreover, ectopic expression of LRK2 seedlings resulted in increased tiller development. Yeast two‐hybrid screening and bimolecular fluorescence complementation (BiFC) indicated a possible interaction between LRK2 and elongation factor 1 alpha (OsEF1A) in vitro. These results suggest that LRK2 functions as a positive regulator of the drought stress response and tiller development via increased branch development in rice. These findings will aid our understanding of branch regulation in other grasses and support improvements in rice genetics.

Rice Dwarf Virus P2 Protein Hijacks Auxin Signaling by Directly Targeting the Rice OsIAA10 Protein, Enhancing Viral Infection and Disease Development.

The phytohormone auxin plays critical roles in regulating myriads of plant growth and developmental processes. Microbe infection can disturb auxin signaling resulting in defects in these processes, but the underlying mechanisms are poorly understood. Auxin signaling begins with perception of auxin by a transient co-receptor complex consisting of an F-box transport inhibitor response 1/auxin signaling F-box (TIR1/AFB) protein and an auxin/indole-3-acetic acid (Aux/IAA) protein. Auxin binding to the co-receptor triggers ubiquitination and 26S proteasome degradation of the Aux/IAA proteins, leading to subsequent events, including expression of auxin-responsive genes. Here we report that Rice dwarf virus (RDV), a devastating pathogen of rice, causes disease symptoms including dwarfing, increased tiller number and short crown roots in infected rice as a result of reduced sensitivity to auxin signaling. The RDV capsid protein P2 binds OsIAA10, blocking the interaction between OsIAA10 and OsTIR1 and inhibiting 26S proteasome-mediated OsIAA10 degradation. Transgenic rice plants overexpressing wild-type or a dominant-negative (degradation-resistant) mutant of OsIAA10 phenocopy RDV symptoms are more susceptible to RDV infection; however, knockdown of OsIAA10 enhances the resistance of rice to RDV infection. Our findings reveal a previously unknown mechanism of viral protein reprogramming of a key step in auxin signaling initiation that enhances viral infection and pathogenesis.

The Effect of Different Weed Management Strategies on the Growth and Yield of Direct-Seeded Dry Rice (Oryza sativa)

Weed management is a primary concern in direct seeded rice (DSR) cropping because weed growth becomes a major constraint on crop yield. A two year field study was set up to evaluate the effect of various weed control measures on crop growth, grain yield and grain quality of DSR. The experiment involved five different weed control measures: hand weeding, hoeing, inter-row tine cultivation, inter-row spike hoeing and herbicide treatment (Nominee 100 SC). The extent of weed control (compared to a non-weeded control) ranged from 50-95%. The highest crop yield was obtained using hand weeding. Hand weeding, tine cultivation and herbicide treatment raised the number of fertile rice tillers formed per unit area and the thousand grain weight. Tine cultivation provided an effective and economical level of weed control in the DSR crop.

Effect of Controlled-release Nitrogen Fertilizer on Methane Emission from Paddy Field Soil

An experimental study was conducted to investigate the effect of Controlled Release Nitrogen Fertilizer on CH4 emission from a rice paddy field soil using pot experimental setup. The experiment is designed with three fertilizer types, i.e., controlled-release nitrogen fertilizer (Neem oil coated urea) and urea (U) and organic fertilizers like Gliricidia sepium, cowpea, Farmyard manure etc. There are two rice cultivars Uma and Jyothy were used for the pot experiment. Each experiment replicate triply. Methane flux was measured at different growth stages for the two rice cultivar by one-time application of CRNF compared with Urea and Organic fertilizer. The methane emission was noted at different rice growth stages. Finally the total CH4 emission from the cultivar is also calculated. CH4 emission was decreased at vegetative stage, gradually increased at reproductive stage and decreased at grain filling to maturity. Methane emission was higher from Heading to flowering, accounting for 35.21% to 41.53% of total cumulative emission. CRNF significantly affect the biometric characters like tiller number, plant height, biomass, and yield in rice by using CRNF. Rice yields increased by 11.43 and 11.11% for Uma and Jyothy rice respectively.

Peningkatan Hasil Padi di Tanah Sulfat Masam melalui Kombinasi Perlakuan Lindi dan Olah Tanah

&lt;p&gt;ABSTRACT&lt;br /&gt; &lt;br /&gt;Tidal swamp lands containing acid sulphate is easily become idle land, which can be fixed by reducing oxidation process of pyrite (FeS2). The pyrite oxidation causes disturbance on the growth and yield of rice plant. An experiment was conducted by means soil leaching in order to reduce accumulation of pyrites. The research had been conducted in Simpang Jaya village, Barito Kuala District in 2012 using a split plot design with three replications. As the main plot was leaching, and no leaching treatment, while as the subplot was soil tillage, i.e., 1) control, 2) weeds cleared without tillage, 3) soil tillage at a depth of 15 cm, and 4) soil tillage at a depth of 30 cm. The results showed that the leaching treatment combined with tillage at a depth of 15 cm or 30 cm increased the number of rice tillers, shoot dry weight, and number of panicles per hill, and number of seeds per hill, thus the leaching treatment was able to increase rice production.&lt;/p&gt;&lt;p&gt;Keywords: acid sulphate, leaching, pyrite, tidal swamp land&lt;/p&gt;

Optimized nitrogen managements and polyaspartic acid urea improved dry matter production and yield of indica hybrid rice

Reasonable management of nitrogen (N) and the development of N fertilizers with higher use efficiency are the two main methods to increase rice yield. The effects of optimized nitrogen management (ONM) and polyaspartic acid urea treatment (PAU) on rice dry matter production and grain yield under different soil conditions in Sichuan, China, were studied in 2013. When the different N management regimes were applied there were differences in the rice tiller number, dry matter production, and yield observed. At Shehong, ONM3 (a 15% increase in the N rate over the farmer’s fertilizer practice) had the highest grain yield, and significantly (P<0.05) increased the percentage of effective tillers, biomass yield, the ratio of leaf lamina at anthesis and maturity stages, amount of post-anthesis transfer of accumulated dry matter into the grain (APA), and panicles per meter square. ONM2 (a 15% reduction in the N rate over the farmer’s fertilizer practice) significantly (P<0.05) increased the percentage of effective tillers, panicles per meter square, and grain yield at Wenjiang, as the rice plants had a reasonable amount of pre-anthesis stored dry matter from the vegetative organs to redistribute to the grain and APA. At both sites, PAU3 (polyaspartic acid urea (PASP-urea) spilt-applied in four stages) improved the grain yield due to an increase in APA, panicles per meter square, and spikelets per panicle. It was shown through correlation analysis that at both sites the grain yield was correlated positively with the panicles per meter square and APA (P<0.01). Therefore, it can be concluded that the increase in panicles per meter square and APA were the causes of the improved grain yields. PASP-urea promoted rice production, and PAU3 was suitable for use with different soils. Based on these results, the effect of spilt-applied N during the middle and later stages largely depended on the soil fertility, and the spilt-applied N being used at a suitable rate that was beneficial for improving the rice yield.

Application of Controlled-Release Nitrogen Fertilizer Decreased Methane Emission in Transgenic Rice from a Paddy Soil

A pot experiment was conducted to investigate the effect of nitrogen fertilizer on CH4 emission from a paddy soil under greenhouse conditions. The experiment was designed with two fertilizer types, i.e., controlled-release nitrogen fertilizer (CRNF) and urea (U), and two rice cultivars, i.e., herbicide-resistant transgenic rice (japonica line B2) and its parent conventional rice (japonica cv Xiushui 63). Compared with control (urea), one-time basal application of CRNF increased tiller number, plant height, biomass, and yield in rice and significantly decreased total CH4 emission from the paddy soil. The total CH4 emission was significantly lower from the transgenic cultivar than that from the conventional cultivar. It is suggested that CRNF and herbicide-resistant transgenic rice are helpful in mitigating CH4 emission from the paddy soil.

THIS1 is a putative lipase that regulates tillering, plant height, and spikelet fertility in rice

Proper branching and successful reproductive growth is of great importance for rice productivity. Substantial progress has been made in uncovering the molecular mechanisms underlying tillering control and spikelet sterility. However, rice tillering is developmentally controlled, and how it is regulated coordinately with reproductive growth remains unclear. This study characterized a rice mutant, the most obvious phenotypes of which are high tillering, reduced height, and infertile spikelets (named this1). Similarly to the high tiller number and dwarf mutants in rice, the increased tiller number of this1 plants is ascribed to the release of tiller bud outgrowth rather than to increased tiller bud formation. In the this1 mutant, however, the accelerated rate of branching was delayed until the stem elongation stage, while other mutants lost the ability to control branching at all developmental stages. The seed-setting rate of this1 was less than half that of the wild type, owing to defects in pollen maturation, anther dehiscence, and flower opening. Histological analyses showed that the mutation in this1 resulted in anisotropic cell expansion and cell division. Using a map-based cloning approach, This1 was found to encode a class III lipase. Homology searches revealed that THIS1 is conserved in both monocots and eudicots, suggesting that it plays fundamental role in regulating branch and spikelet fertility, as well as other aspects of developmental control. The relative change in expression of marker genes highlighted the possibility that This1 is involved in phytohormone signalling pathways, such as those for strigolactone and auxin. Thus, This1 provides joint control between shoot branching and reproductive development.

Dynamic analysis of QTLs on tiller number in rice (Oryza sativa L.) with single segment substitution lines

Twelve single segment substitution lines (SSSLs) in rice, which contain quantitative trait loci (QTLs) for tiller number detected previously, were used to study dynamic expression of the QTLs in this study. These SSSLs and their recipient, Hua-Jing-Xian 74 (HJX74), were used to produce 78 crossing combinations first, and then these combinations and their parents were grown in two planting seasons with three cropping densities. Tiller number was measured at seven developmental stages. QTL effects including main effects (additive, dominance and epistasis), QTL×season and QTL×density interaction effects were analyzed at each measured stage. The additive, dominant and epistatic effects of the 12 QTLs as well as their interaction effects with the seasons and with the densities all display dynamic changes with the development. Eight QTLs are detected with significant additive effects and/or additive×season and/or additive×density interaction effects at least at one developmental stage, and all QTLs have significant dominant and epistatic effects and/or interaction effects involved in. For most of the QTLs dominant effects are much bigger than additive effects, showing overdominance. Each QTL interacts at least with eight other QTLs. Additive and dominant effects of these QTLs are mostly positive while epistatic effects are negative and minor. Most of the QTLs show significant interactions with planting seasons and cropping densities, but the additive effects of QTLs Tn3-1 and Tn3-2, the dominant effects of QTL Tn7 and Tn8, and the epistatic effects of 14 pairs of QTLs are stable across seasons and the dominant effect of QTL Tn3-3 and the epistatic effects of QTL pairs Tn2-1/Tn6-2, Tn2-1/Tn9 and Tn3-3/Tn6-3 are nearly consistent across cropping densities. This paper is the first report of dynamics on dominances and epistasis of QTLs for tiller number in rice and provides abundant information, which is useful to improve rice tiller number via heterosis and/or QTL pyramiding.