Tiller Development Research Articles

Rhizosphere microbial communities of canola and wheat at six paired field sites

Plant physical and chemical characteristics are known to alter rhizosphere microbial communities, but the effect of introducing canola (Brassica napus L.) into monoculture wheat (Triticum aestivum L.) rotations is not clear. Results from a field study in eastern Washington showed that winter canola (WC) influenced the bulk soil microbial community and differentiated it from the community associated with winter wheat (WW). Abundance of soil fungi, including mycorrhizae, was reduced with the introduction of WC. The objective of this research was to determine the differences and similarities in the rhizosphere microbial communities of WC and WW. Canola and wheat rhizosphere soil was collected from six dryland farms in Adams and Douglas Counties, WA. Each farm was a paired site with WC and WW grown in adjacent fields of the same soil type, landscape orientation, and crop history. Canola, or any non-cereal crop, had never been grown previously at the experimental sites. Rhizosphere microbial biomass and community composition, determined using phospholipid fatty acid analysis (PLFA), revealed differences associated with landscape position at the initial fall sampling when WC and WW were in the rosette and tiller development stages, respectively. However, data from spring samples, when WC and WW were in the early bolting and stem elongation growth stages, respectively, showed significant differences in microbial communities between WC and WW rhizosphere soils. Data suggest that initial (fall) microbial community composition were an artifact of previous histories of monocrop wheat production and varied with expected differences in landscape position. As the crops developed, microbial communities became more dissimilar and were differentiated by crop species. Our results show that WC can have significant effects on rhizosphere microbial biomass of specific microbial groups and community structure in wheat-based cropping systems, such as reductions in fungi and gram+ bacteria in some locations. Crop-related changes in the abundance of specific rhizosphere microbial groups may play a key role in the yield of subsequent crops, and overall soil health and nutrient turnover.

Effect of intermittent irrigation following the system of rice intensification (SRI) on rice yield in a farmer’s paddy fields in Indonesia

System of rice intensification (SRI) has been disseminated in many countries because of its high yield, although the mechanism of yield increase has yet to be fully understood. The aims of this study were to clarify the actual water management of a skilled SRI farmer in irrigated paddy field of Indonesia and to examine the effect of intermittent water management on rice growth and yield. Yield and yield components were compared in the field experiments in the farmer’s fields under intermittent (SRI) or flooded (FL) irrigation for 4 years from 2013 to 2016. The daily mean water depth of SRI plots during 0–40 days after transplanting showed very shallow (ca. 2 cm) or little lower than soil surface and continued to be lower than soil surface during reproductive stage when panicles were formed. The yield of SRI significantly exceeded that of FL for 4 years by 13% (P = 0.0004), so did the panicle numbers per area (P = 0.036). The yield increase in SRI was associated with the increased number of panicles, which should have resulted from enhanced tiller development under shallow water level during the vegetative stage. The increased number of panicles was, however, counteracted by the reduced number of spikelets per panicle and resulted in nonsignificant increase in the spikelet density, defined as number of spikelets per unit area of crop. This dampening change in spikelet number per panicle could have been caused by limited supply of either nitrogen or carbohydrate during the panicle development stage under the intermittent water supply. A greater yield increase by SRI could be expected by improving nutrient or water management during the reproductive stage.

Quantitative Changes in the Transcription of Phytohormone-Related Genes: Some Transcription Factors Are Major Causes of the Wheat Mutant dmc Not Tillering.

Tiller number is an important agronomic trait for grain yield of wheat (Triticum aestivum L.). A dwarf-monoculm wheat mutant (dmc) was obtained from cultivar Guomai 301 (wild type, WT). Here, we explored the molecular basis for the restrained tiller development of the mutant dmc. Two bulked samples of the mutant dmc (T1, T2 and T3) and WT (T4, T5 and T6) with three biological replicates were comparatively analyzed at the transcriptional level by bulked RNA sequencing (RNA-Seq). In total, 68.8 Gb data and 463 million reads were generated, 80% of which were mapped to the wheat reference genome of Chinese Spring. A total of 4904 differentially expressed genes (DEGs) were identified between the mutant dmc and WT. DEGs and their related major biological functions were characterized based on GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) categories. These results were confirmed by quantitatively analyzing the expression profiles of twelve selected DEGs via real-time qRT-PCR. The down-regulated gene expressions related to phytohormone syntheses of auxin, zeatin, cytokinin and some transcription factor (TF) families of TALE, and WOX might be the major causes of the mutant dmc, not tillering. Our work provides a foundation for subsequent tiller development research in the future.

Parameterising wheat leaf and tiller dynamics for faithful reconstruction of wheat plants by structural plant models

Structural 3D plant models aim at mimicking the dynamics of plant and crop structure based on experimental data. Such models can be interfaced with physical models to investigate plant-environment interactions. This work aimed at defining functions that represent the leaf and tiller development of individual wheat plants, and that could be fitted to the specific traits produced in a broad range of situations.A dataset of the dynamics of wheat plant (Triticum aestivum) architecture was collected for 55 experimental situations, including 11 growing seasons, three sowing densities, three sowing dates, and 13 commercial cultivars. Data were analysed to identify conserved patterns in the dynamics of leaf emergence and of tiller emergence and senescence.The broad range of conditions tested allowed us to evaluate the robustness of relationships proposed in previous studies and to identify novel patterns. Amongst them, we observed: (i) that leaf emergence dynamics may follow either a linear or a bilinear pattern for the same genotype. When a change in phyllochron occurred, it coincided with the initiation of the flag leaf; (ii) the delay between leaf and tiller emergence was not constant, but increased very regularly for successive phytomers; (iii) the number of leaves emerged at tillering cessation decreased with plant density but depended also on the final number of leaves on the main stem (MS) and marked differences existed between cultivars. Finally, we defined functions representing leaf and tiller dynamics with parameters that have a simple botanical interpretation and are easy to derive from field measurements. Assessing plant density, crop leaf stage at 5–6 dates and tiller population at 2 dates during the cycle provide the required data.This study defines a rationale to analyse and represent the dynamics of the architecture of individual wheat plants. The method can be used to determine the dynamics of architecture in 3D models and should be transposable to a wide range of cereal species.

Growth Analysis of Chloris elata

ABSTRACT: In Brazil, in agricultural areas where there is no establishment of cover crops in the off season, as well as in citrus orchards in the state of São Paulo, an increase in the infestation of Chloris elata has been observed. This is a perennial species, propagated by seeds and short rhizomes, erect and slightly caespitose. With the objective of evaluating the growth and development of plants from two accessions of C. elata, a greenhouse experiment was conducted. The experimental design was completely randomized, in a 2 (accessions of C. elata) x 15 (evaluation periods) factorial arrangement, with four replications. Fifteen destructive evaluations were performed 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91, 98, 112 and 126 days after sowing (DAS) both accessions of C. elata (Itaberaí from Goiás and Matão from São Paulo State). At each evaluation, four plants (replications) were randomly sampled and the height of the main culm, the number of tillers and inflorescences (flower+seed) per plant, the leaf area and dry matter of leaves, culms, roots, inflorescences and total (leaves+culms+roots+ inflorescences) were analyzed. The two accessions showed a slow initial development and growth (up to 63 DAS), mainly in root growth; however, the development of new tillers increased rapidly in the initial phase. During the first 63 DAS, the percentage distribution of dry matter was higher in the foliage, followed by culms and roots. In the final evaluation, the relation was culms followed by leaves, roots and inflorescences. Plants of Matão formed denser clumps, with culms of greater mass, while those from the Itaberaí showed higher height and greater foliage.

Muka Air Optimum Pada System Of Rice Intensification (SRI)

Pengendalian muka air merupakan cara mengelola air di sawah SRI. Petani cenderung mengaplikasikan muka air yang berbeda tergantung pada praktek pengelolaan air setempat. Hal ini dapat berimplikasi pada pertumbuhan tanaman yang dapat terlihat dari jumlah anakan. Pada penelitian ini dilakukan pengamatan pada pembentukan anakan padi SRI di berbagai perlakuan muka air. Muka air dikendalikan menggunakan tabung mariot dengan set-point -12, -7, -5, -3, 0, dan +2 cm dari permukaan tanah. Hasil penelitian menunjukkan nilai kelembaban tanah (Ɵ) berfluktuasi karena adanya penerapan irigasi berselang dan perbedaan muka air. Hal tersebut mempengaruhi jumlah anakan yang terbentuk dimana laju pembentukannya bervariasi antara 0,21-0,29 anakan/hari. Anakan pertama muncul pada 18 hari setelah tanam (HST). Jumlah anakan terus meningkat hingga mencapai nilai maksimal pada 63-72 HST. Studi empirik ini menunjukkan bahwa pengendalian muka air pada -5 cm dari permukaan tanah di budidaya padi SRI merupakan pengelolaan air terbaik dalam produksi anakan dengan produktivitas lahan dan air tertinggi daripada penerapan muka air lainnya. Konsistensi produksi anakan dari awal pembentukan anakan hingga akhir dari musim tanam terlihat pada perlakuan ini.

Combination of modified nitrogen fertilizers and water saving irrigation can reduce greenhouse gas emissions and increase rice yield

The combined impacts of modified nitrogen (N) fertilizers and water saving irrigation (WSI) on greenhouse gas (GHG) emissions and grain yield of rice paddies have not previously been documented. GHG emissions from rice paddies under modified N fertilizers and WSI deserve attention because water and N are being used extensively to attain higher grain yield. A field experiment was conducted to evaluate the influence of modified N fertilizers and WSI on methane (CH4) and nitrous oxide (N2O) emissions and grain yield in rice paddies. Four treatments were applied: urea with conventional irrigation (U+CI), urea with shallow water depth with alternate wetting-drying water saving irrigation (U+SWD), polymer-coated controlled release urea with SWD (CRU+SWD), and nitrapyrin-urea composition plus hydroquinone with SWD (NU+HQ+SWD). Compared to U+CI, CH4 emissions significantly decreased by 26% and 31%, and N2O emissions increased by 52% and 42% under U+SWD in the early and late rice growing seasons respectively (p<0.05). Although SWD increased N2O emissions, total GHG emissions (TGHG) reduced by 20% and 25% in the two rice seasons under U+SWD, and GHG emission intensity (GHGI) decreased by 24% on average. Modified N fertilizer applications also affected grain yield and GHG emissions under SWD. Compared with U+SWD, CRU+SWD and NU+HQ+SWD reduced CH4, N2O emissions and TGHG by 28–49%, 12–44% and 26–45%, respectively, while grain yield increased by 6–35%. Reduction in CH4 emissions occurred because, compared to urea, CRU and NU+HQ can inhibit CH4 production and transport by controlling development of invalid tillers, while their nitrogen release patterns were more favorable for CH4 consumption. In summary, modified N fertilizers in combination with SWD are a win-win strategy to improve grain production while reducing GHG emissions in the rice cropping system.

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.

IPA1 functions as a downstream transcription factor repressed by D53 in strigolactone signaling in rice

Strigolactones (SLs), a group of carotenoid derived terpenoid lactones, are root-to-shoot phytohormones suppressing shoot branching by inhibiting the outgrowth of axillary buds. DWARF 53 (D53), the key repressor of the SL signaling pathway, is speculated to regulate the downstream transcriptional network of the SL response. However, no downstream transcription factor targeted by D53 has yet been reported. Here we report that IdealPlantArchitecture1 (IPA1), a key regulator of the plant architecture in rice, functions as a direct downstream component of D53 in regulating tiller number and SL-induced gene expression. We showed that D53 interacts with IPA1 in vivo and in vitro and suppresses the transcriptional activation activity of IPA1. We further showed that IPA1 could directly bind to the D53 promoter and plays a critical role in the feedback regulation of SL-induced D53 expression. These findings reveal that IPA1 is likely one of the long-speculated transcription factors that act with D53 to mediate the SL-regulated tiller development in rice.

Drought inhibition of tillering in Festuca arundinacea associated with axillary bud development and strigolactone signaling

Drought stress inhibits tiller formation and growth, but the underlying mechanism is not well understood. Tiller development and lateral branch growth in monocot and dicot species respectively involve two stages: axillary bud initiation and subsequent outgrowth. The objective of this study was to investigate whether drought-inhibition of tiller growth is mainly due to the suppression of axillary bud initiation or subsequent outgrowth in perennial grass species and to determine whether drought-inhibition of tiller development and growth in grass species are associated with strigolactone (SL) accumulation and signaling. Seedlings with one fully-expanded leaf without axillary buds and those with three-fully expanded leaves and two axillary buds were grown in 20% polyethylene glycol (PEG) solution to induce drought stress. Plant height, number of leaves, axillary buds, tillers and length of axillary buds were monitored during 21 d of stress. Both axillary bud initiation and outgrowth were inhibited by drought stress, with outgrowth being more sensitive to drought stress. qRT-PCR analysis showed that expression level of genes involved in axillary bud activity was down-regulated at 14 d of drought stress while genes involved in axillary bud dormancy was up-regulated. Strigolactone (SL) content was elevated under drought stress in crowns. qRT-PCR analysis showed that expression level of genes involved in SL biosynthesis and signaling transduction were up-regulated during drought stress. Axillary bud outgrowth was sensitive to drought stress and could be associated with SL signaling, contributing to drought-inhibition of tillering in perennial grass species.

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.

Ротационное орудие для поверхностной обработки почвы с эллипсовидными дисками

Analyzing a number of scientists’ research on development of disk tillers, working units of which make a complex spatial motion, we proposed the construction of rotary implement, which contains the elliptical wheels, fixed to the battery shaft is strictly at a certain angle. The article presents the structural scheme of this tool and theoretical dependences for the determination and justification of its basic parameters. The technical solution allows to mutually balance the axial loads, provides uniformity of soil tillage depth, improves the technological stability of instruments and the effectiveness of its work.&#x0D;

Homeobox Is Pivotal for OsWUS Controlling Tiller Development and Female Fertility in Rice.

OsWUS has recently been shown to be a transcription factor gene critical for tiller development and fertility in rice. The OsWUS protein consists of three conserved structural domains, but their biological functions are still unclear. We discovered a new rice mutant resulting from tissue culture, which hardly produced tillers and exhibited complete female sterility. The male and female floral organs of the mutant were morphologically indistinguishable from those of the wild type. We named the mutant srt1 for completely sterile and reduced tillering 1. Map-based cloning revealed that the mutant phenotypes were caused by a mutation in OsWUS. Compared with the two previously reported null allelic mutants of OsWUS (tab1-1 and moc3-1), which could produce partial N-terminal peptides of OsWUS, the srt1 protein contained a deletion of only seven amino acids within the conserved homeobox domain of OsWUS. However, the mutant phenotypes (monoculm and female sterility) displayed in srt1 were as typical and severe as those in tab1-1 and moc3-1. This indicates that the homeobox domain of SRT1 is essential for the regulation of tillering and sterility in rice. In addition, srt1 showed an opposite effect on panicle development to that of the two null allelic mutants, implying that the srt1 protein might still have partial or even new functions on panicle development. The results of this study suggest that the homeobox domain is pivotal for OsWUS function.

The Genetic Architecture of Barley Plant Stature.

Plant stature in temperate cereals is predominantly controlled by tillering and plant height as complex agronomic traits, representing important determinants of grain yield. This study was designed to reveal the genetic basis of tillering at five developmental stages and plant height at harvest in 218 worldwide spring barley (Hordeum vulgare L.) accessions under greenhouse conditions. The accessions were structured based on row-type classes [two- vs. six-rowed] and photoperiod response [photoperiod-sensitive (Ppd-H1) vs. reduced photoperiod sensitivity (ppd-H1)]. Phenotypic analyses of both factors revealed profound between group effects on tiller development. To further verify the row-type effect on the studied traits, Six-rowed spike 1 (vrs1) mutants and their two-rowed progenitors were examined for tiller number per plant and plant height. Here, wild-type (Vrs1) plants were significantly taller and had more tillers than mutants suggesting a negative pleiotropic effect of this row-type locus on both traits. Our genome-wide association scans further revealed highly significant associations, thereby establishing a link between the genetic control of row-type, heading time, tillering, and plant height. We further show that associations for tillering and plant height are co-localized with chromosomal segments harboring known plant stature-related phytohormone and sugar-related genes. This work demonstrates the feasibility of the GWAS approach for identifying putative candidate genes for improving plant architecture.

穂肥窒素の増施および重点化による後期重点型施肥栽培が裸麦の分げつの有効化に及ぼす影響

裸麦品種トヨノカゼは穂肥を増施すると穂数が増加し，子実収量が増加する．本研究では，穂肥の増施および穂肥の重点化がどのように穂数を増加させているかを明らかにするため，2012/2013年と2013/2014年の2作期において，トヨノカゼを用い分げつの発生数や発生節位，分げつの有効化に係る形質を調査した．施肥は基肥−分げつ肥−穂肥の分施とし，基肥と穂肥の量を異にした処理区を設けた．その結果，穂肥を増施すると分げつを発生させた個体の割合が高まり，高位節においてまでも分げつの発生率が高まった．一方，同じ総施肥量のもと穂肥を重点化すると，高位節での発生率を高めた．有効分げつの展開葉数はどの処理区，発生節位においても5葉から8葉であり，1本の乾物重は主茎ではそのほとんどが1000 mg以上であった．分げつの糖含有率は有効分げつでは10～20％であったが，無効分げつでは乾物重の重いもので20％以上のものが，乾物重の軽いもので10％以下のものがあった．穂肥を重点化した4–2–6区では第1節，第3節，第4節からの1次分げつ発生率が高く，第1節1次分げつの多くが有効化した．一方，基肥を重点化した6–2–4区と比べて，1本の乾物重が500 mg前後の軽い有効分げつが多くみられ，一方で重い無効分げつも多かった．穂肥を増施し重点化する後期重点型施肥では主茎に加えて有効分げつを2本以上有する個体が多く，本法が穂数を確保するために有効な施肥方法であると考えられた．

Development of tillers formed in an inflorescence node of annual bluegrass (Poa annua L.)

Development of tillers formed in an inflorescence node of annual bluegrass (<i>Poa annua </i>L.)

Tillering and yield formation of a temperate Japonica rice cultivar in a Mediterranean rice agrosystem

Rice tillering is a crucial stage for yield formation. Deep understanding of the relationship between tillering dynamics and yield formation in a particular agrosystem is crucial to boost rice productivity. Research on rice tillering is mainly focused on tropical agrosystems whereas less is done in the Mediterranean, with direct water-seeding and Japonica cultivars. This study aims at characterizing tillering dynamics and identifying the main explanatory tillering traits of yield in a Mediterranean rice agrosystem, Ebro Delta (Northern Spain). A temperate Japonica cultivar grown in Spain, Gleva, was utilized. Plants and tillers were tagged to assess emergence and fertility ratios and grain yield; while changes in tillering number over time, yield and yield components for unit area were measured. Plant and tillering dynamics in the Ebro Delta rice fields can be accurately predicted through equations herein provided, which are based either on thermal time or leaf development. Plants grown under regional standard agricultural practices produced up to eight primary tillers of which two or three become productive. Maximum tiller number was the main explanatory variable of yield while high-yielding tillers within a plant are located on nodes with the highest emergence ratios and, after the main stem, they are the major contributors to yield. The decisive role of tiller development on yield along with the predictability of tiller dynamics raises options to optimize grain yield through tillering modulation. In this sense, results from this study suggests the promotion of early tillering followed by inhibition of late tillering as a strategy of tillering regulation.

Effect of supplemental irrigation on the relationships between leaf ABA concentrations, tiller development and photosynthate accumulation and remobilization in winter wheat

Drought after the jointing stage restricted the growth and yield formation in wheat. Supplemental irrigation (SI) at Z31 (Zadoks Stage 31) reduced the ABA concentrations in the leaves of the inferior tillers (T3 and T10) and improved the survival rate of the tillers. Additional SI at Z60 reduced the ABA concentrations in the flag leaves of ear-bearing stems after anthesis and increased the assimilate accumulation and the 1000-grain weight. These two SIs increased the yield by 16.7–32.2 % compared with a rainfed control (W0). Delaying the first SI from Z31 to Z34 or Z39 reduced the ABA concentrations in the leaves of the main stem and superior tillers (T1 and T2) but increased the ABA concentrations in the leaves of the inferior tillers at Z45 and reduced the survival rate of the tillers. Delaying SI from Z31 and Z60 (W1) to Z34 and Z69 (W2) increased the partitioning of the recent (14C-labelled) assimilate to the stems plus sheaths and stalk plus glume at anthesis and the grains at maturity and increased the 1000-grain weight and the grain yield significantly. However, if SI was applied too late, i.e., at Z39 and Z77 (W3), the redistribution of the recent assimilate from the vegetative organs to the grain after anthesis and the grain yield at maturity were reduced. These data suggested that: (1) a lower soil moisture at the early jointing stage elevated the ABA concentrations in the inferior tillers and inhibited their growth; (2) if SI was applied too late (W3) senescence of the inferior tillers could not be halted; and (3) low ABA concentrations in the leaves during the later grain filling following the late SI (W3) were correlated with a reduced transfer of assimilates from the vegetative organs to the grain, leading to a significant reduction in the grain weight at maturity.

Winter Wheat Photosynthesis and Grain Yield Responses to Spring Freeze

Spring freeze events seriously limit the growth, development, and grain yield of winter wheat (Triticum aestivum L.). A 2‐yr field experiment with two contrasting cultivars: XM21 (low‐temperature resistant) and XZ24 (low‐temperature sensitive), was conducted using an air temperature control device designed to allow investigation of the physiological and grain yield responses to spring freeze. The plants were grown in the field and subjected to a 5‐d spring freeze episode (approximately 8°C lower than the ambient temperature) at jointing stage (Zadoks scale 31). Spring freeze significantly decreased gas exchange rates and maximum quantum efficiency of photosystem II in wheat leaves of both cultivars. Under spring freeze, the yield loss was 12 to 14% in XZ24 vs. 5 to 6% in XM21. Greater yield loss in XZ24 coincided with a greater reduction of tiller and spike number in XZ24 than in XM21. Spring freeze occurring at jointing stage depressed the photosynthetic capacity of the leaves when measured at the end of the 5‐d period and again at 7 d later, resulting in lowered number of effective tillers, and eventually decreasing the grain yield. The genetic and/or bio‐physiochemical basis for the different sensitivity of tiller development to spring freeze between the two cultivars could be further exploited for breeding new wheat cultivars tolerant to spring freeze stress.

Emergence and seed yield of redtop as affected by row spacing and sowing rate

Seed yield of grass is determined by environmental and cultivation factors. The aim of this study was to determine the effect of sowing rate and row spacing on germination in establishment year and development of generative tillers and seed yield of redtop (Agrostis gigantea Roth = A. alba) in the two consecutive production years. Two replicate experiments were performed for 3 years in the same locality in Poland (51°54′N; 17°12′E). The first experiment was established in 2005, with seed production for two successive years (2006 and 2007). The entire experiment was repeated, being established again in 2007 and seed production measured in 2008 and 2009. In both experiments, redtop was sown with row spacings of 24 and 48 cm (factor 1), in sowing of 0.8, 1.6 and 2.4 kg ha−1 (factor 2). The study indicated that at the smallest sowing rate 0.8 kg ha−1 and row spacing 24 cm, field emergence index was the highest (26.3%). The lack of response of the total seed yield from two consecutive production years to sowing rate indicates that in redtop grown for seed, sowing in the amount of 0.8 kg ha−1 is sufficient. Increasing the row spacing from 24 to 48 cm resulted in a reduction in the density of generative tillers in the first and second production years. The row spacing of 48 cm was more favourable for seed yield in the first year, whereas 24 cm in the second year. In view of the increase in the total seed yield from two consecutive production years by 9.5% at the row spacing of 24 cm as compared with 48 cm, the row spacing of 24 cm should be regarded as recommended. Also, higher green matter of autumn regrowth can be obtained at a row spacing of 24 cm than at 48 cm.