Sessile Spikelets Research Articles

Ischaemum dioecum (Poaceae: Andropogoneae): the most strangest new species from Northern Western Ghats, Maharashtra, India

Ischaemum dioecum, a new strange species from Northern Western Ghats, Maharashtra, India is described and illustrated. The most spectacular and unusual feature of the species is its dioecious breeding system i.e. male and female plants are sexually separate entities, which is being documented first time in the tribe Andropogoneae. Other distinguishing features are such as: sessile spikelets 1-flowered (only upper floret developed), palea bi-dentate with an arista from the sinus and pedicelled spikelet reduced or absent; stamens four with unusually filiform and elongated filaments, ca. 15 mm long; peduncle of male plants glandular and with tubercle-based bristles; style and stigma extraordinarily long each may be up to 14 mm long and pedicel 1/2–4/5 of the sessile spikelet. A table of morphological comparison and detailed discussion with allied species from Africa, India and Australia is given along with the keys to close genera. A detailed discussion on the similar case of dioecism in grasses; habitat characteristics, distribution of the populations and inter-specific interaction, adaptation and morphological affinities of I. dioecum is discussed with African, Indian and Australian taxa. It is apparently a narrow endemic species. Based on IUCN Red List Categories and Criteria, the species is assessed here as Critically Endangered (CR).

Ischaemum mistryi (Poaceae: Andropogoneae): A new remarkable species from Sub-Tropical Evergreen Forest, India

Ischaemum mistryi, a new species from the Sub-Tropical evergreen forest of Tilari Ghat, Maharashtra, India, is described and illustrated. This grass is unique with its leaves drooping, mostly congregated near the base, basal sheath villous, culms compressed at the base, lower glume of the sessile spikelet linear-lanceolate to oblongish tapering and slightly curled upwards, without a sub-apical ridge, nodules absent (if present 2–4 obscure) on its keels, and upper lemma of sessile spikelet bi-partite. Morphologically it is somewhat similar to I. mangaluricum, I. travancorense and I. barbatum. We provided a table of its detailed comparison with close species as mentioned above. According to IUCN Red List Categories and Criteria, we have assessed this new species as Critically Endangered (CR). The photo plates and illustration of the grass are given to facilitate its proper identification. A short discussion is also provided at the end.

<strong><em>Capillipedium yashwantraoi</em>, a new species of Poaceae from Madhya Pradesh, India</strong>

New species in the genus Capillipedium Stapf is described and illustrated from Amarkantak hills of Madhya Pradesh, India. New species is similar to Capillipedium assimile (Steud.) A.Camus and C. nagense Bor but mainly diverges by having 4–6 cm panicle, 2–2.5 cm racemes, about 11–13 pairs of sessile and pedicelled spikelets in each raceme; joints and pedicels without translucent groove, 2–2.5 mm sessile spikelets and 3–3.2 mm pedicelled spikelets. A taxonomic key for genus Capillipedium in India is given to facilitate easy identification of species.

<p><strong>A novel species of <em>Ischaemum </em>(Poaceae, Andropogoneae) from the northern Western Ghats, India, based on morphological and molecular data</strong></p>

Ischaemum amboliense (Poaceae, Andropogoneae), a new species of Muraina grass, is described and illustrated here. The new species is closely allied to I. travancorense but differs from it in having annual habit and erect posture, culm with sparsely hairy nodes, well-exerted racemes, lower glumes of sessile spikelets with 3–4 side nodules without ridges, upper glume of sessile spikelets with bicuspidate apex and margins with a membranous wing on one side of apical region and lower lemma of sessile spikelets winged on both sides towards the apex. A strict consensus tree obtained from the Maximum Likelihood and Bayesian analyses of trnLC–trnLD and ETS datasets supported the novelty of the species. Here, we provide a detailed morphological description, molecular phylogenetic analysis, distribution map, and photo-plates of the novel and allied species.

Genome-wide identification of loci modifying spike-branching in tetraploid wheat

Key messageGenetic modification of spike architecture is essential for improving wheat yield. Newly identified loci for the ‘Miracle wheat’ phenotype on chromosomes 1AS and 2BS have significant effects on spike traits.The wheat (Triticum ssp.) inflorescence, also known as a spike, forms an unbranched inflorescence in which the inflorescence meristem generates axillary spikelet meristems (SMs) destined to become sessile spikelets. Previously, we identified the putatively causative mutation in the branched headt (bht) gene (TtBH-A1) of tetraploid wheat (T. turgidum convar. compositum (L.f.) Filat.) responsible for the loss of SM identity, converting the non-branching spike to a branched wheat spike. In the current study, we performed whole-genome quantitative trait loci (QTL) analysis using 146 recombinant inbred lines (RILs) derived from a cross between spike-branching wheat (‘Miracle wheat’) and an elite durum wheat cultivar showing broad phenotypic variation for spike architecture. Besides the previously found gene at the bht-A1 locus on the short arm of chromosome 2A, we also mapped two new modifier QTL for spike-branching on the short arm of chromosome 1A, termed bht-A2, and 2BS. Using biparental mapping population and GWAS in 302 diverse accessions, the 2BS locus was highly associated with coding sequence variation found at the homoeo-allele of TtBH-B1 (bht-B1). Thus, RILs that combined both bht-A1 and bht-B1 alleles showed additive genetic effects leading to increased penetrance and expressivity of the supernumerary spikelet and/or mini-spike formation.

Genetic dissection of QTLs associated with spikelet-related traits and grain size in sorghum

Although spikelet-related traits such as size of anther, spikelet, style, and stigma are associated with sexual reproduction in grasses, no QTLs have been reported in sorghum. Additionally, there are only a few reports on sorghum QTLs related to grain size, such as grain length, width, and thickness. In this study, we performed QTL analyses of nine spikelet-related traits (length of sessile spikelet, pedicellate spikelet, pedicel, anther, style, and stigma; width of sessile spikelet and stigma; and stigma pigmentation) and six grain-related traits (length, width, thickness, length/width ratio, length/thickness ratio, and width/thickness ratio) using sorghum recombinant inbred lines. We identified 36 and 7 QTLs for spikelet-related traits and grain-related traits, respectively, and found that most sorghum spikelet organ length- and width-related traits were partially controlled by the dwarf genes Dw1 and Dw3. Conversely, we found that these Dw genes were not strongly involved in the regulation of grain size. The QTLs identified in this study aid in understanding the genetic basis of spikelet- and grain-related traits in sorghum.

Ischaemum janarthanamii (Poaceae, Andropogoneae), a New Species from the Western Ghats, India: Evidence from Morphological and Molecular Data

Ischaemum janarthanamii S.A. Bokil, Datar & R.K. Choudhary, a new species belonging to family Poaceae, subfamily Andropogoneae is described and illustrated. It is morphologically similar to I. dalzellii and I. semisagittatum but differs from them in having geniculately ascending culms, lower glume of sessile spikelets winged on both sides, apex of upper glume of pedicelled spikelets mucronate, lower glume of pedicelled spikelets asymmetrically deltoid to oblong-lanceolate, joints of rachis linear-trigonous and bases of lower leave-blades hastate. Bayesian analysis of combined trnL c-d and ETS data sets supported the separation of the new species.

Sterile Spikelets Contribute to Yield in Sorghum and Related Grasses.

Sorghum (Sorghum bicolor) and its relatives in the grass tribe Andropogoneae bear their flowers in pairs of spikelets in which one spikelet (seed-bearing or sessile spikelet [SS]) of the pair produces a seed and the other is sterile or male (staminate). This division of function does not occur in other major cereals such as wheat (Triticum aestivum) or rice (Oryza sativa). Additionally, one bract of the SS spikelet often produces a long extension, the awn, that is in the same position as, but independently derived from, that of wheat and rice. The function of the sterile spikelet is unknown and that of the awn has not been tested in Andropogoneae. We used radioactive and stable isotopes of carbon, RNA sequencing of metabolically important enzymes, and immunolocalization of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) to show that the sterile spikelet assimilates carbon, which is translocated to the largely heterotrophic SS. The awn shows no evidence of photosynthesis. These results apply to distantly related species of Andropogoneae. Removal of sterile spikelets in sorghum significantly decreases seed weight (yield) by ∼9%. Thus, the sterile spikelet, but not the awn, affects yield in the cultivated species and fitness in the wild species.

<p><strong>A new species of <em>Parahyparrhenia </em>(Poaceae: Andropogoneae) from India</strong></p>

Parahyparrhenia khannae, a new species of Andropogoneae (Poaceae: Andropogoneae) from the grassland of Ratlam and Jhabua districts of Madhya Pradesh, India is described and illustrated. The new species is similar to the Indian endemic species P. bellariensis in having dorsal groove in lower glume of sessile spikelet, but differs in having shorter plant height, lacerate membranous ligule, shorter leaf blade and raceme length, fewer homogamous spikelets, shorter sessile spikelet and anther length.

Fertility of Pedicellate Spikelets in Sorghum Is Controlled by a Jasmonic Acid Regulatory Module.

As in other cereal crops, the panicles of sorghum (Sorghum bicolor (L.) Moench) comprise two types of floral spikelets (grass flowers). Only sessile spikelets (SSs) are capable of producing viable grains, whereas pedicellate spikelets (PSs) cease development after initiation and eventually abort. Consequently, grain number per panicle (GNP) is lower than the total number of flowers produced per panicle. The mechanism underlying this differential fertility is not well understood. To investigate this issue, we isolated a series of ethyl methane sulfonate (EMS)-induced multiseeded (msd) mutants that result in full spikelet fertility, effectively doubling GNP. Previously, we showed that MSD1 is a TCP (Teosinte branched/Cycloidea/PCF) transcription factor that regulates jasmonic acid (JA) biosynthesis, and ultimately floral sex organ development. Here, we show that MSD2 encodes a lipoxygenase (LOX) that catalyzes the first committed step of JA biosynthesis. Further, we demonstrate that MSD1 binds to the promoters of MSD2 and other JA pathway genes. Together, these results show that a JA-induced module regulates sorghum panicle development and spikelet fertility. The findings advance our understanding of inflorescence development and could lead to new strategies for increasing GNP and grain yield in sorghum and other cereal crops.

A new variety of Schizachyrium (Poaceae: Andropogoneae) from South America, with notes on the infraspecific taxa of Schizachyrium tenerum

A new variety of Schizachyrium tenerum from South America is described and illustrated. The new taxon (S. tenerum var. muticum) differs from the other varieties of the species (S. tenerum var. tenerum and S. tenerum var. hirtiglume) mainly by the absence of awns in the sessile spikelets, which is a very unusual character in the genus. The new variety occurs in Venezuela, Bolivia, and Brazil. A taxonomic discussion and an identification key for the infraspecific taxa of S. tenerum are also presented, as well as illustrations of all varieties of the species. Additionally, Schizachyrium tenerum var. hirtiglume is reported for the first time for Colombia.

Specimen-based analysis of morphology and the environment in ecologically dominant grasses: the power of the herbarium.

Herbaria contain a cumulative sample of the world's flora, assembled by thousands of people over centuries. To capitalize on this resource, we conducted a specimen-based analysis of a major clade in the grass tribe Andropogoneae, including the dominant species of the world's grasslands in the genera Andropogon, Schizachyrium, Hyparrhenia and several others. We imaged 186 of the 250 named species of the clade, georeferenced the specimens and extracted climatic variables for each. Using semi- and fully automated image analysis techniques, we extracted spikelet morphological characters and correlated these with environmental variables. We generated chloroplast genome sequences to correct for phylogenetic covariance and here present a new phylogeny for 81 of the species. We confirm and extend earlier studies to show that Andropogon and Schizachyrium are not monophyletic. In addition, we find all morphological and ecological characters are homoplasious but variable among clades. For example, sessile spikelet length is positively correlated with awn length when all accessions are considered, but when separated by clade, the relationship is positive for three sub-clades and negative for three others. Climate variables showed no correlation with morphological variation in the spikelet pair; only very weak effects of temperature and precipitation were detected on macrohair density.This article is part of the theme issue 'Biological collections for understanding biodiversity in the Anthropocene'.

Genes WHEAT FRIZZY PANICLE and SHAM RAMIFICATION 2 independently regulate differentiation of floral meristems in wheat

BackgroundInflorescences of wheat species, spikes, are characteristically unbranched and bear one sessile spikelet at a spike rachis node. Development of supernumerary spikelets (SSs) at rachis nodes or on the extended rachillas is abnormal. Various wheat morphotypes with altered spike morphology, associated with the development of SSs, present an important genetic resource for studies on genetic regulation of wheat inflorescence development.ResultsHere we characterized diploid and tetraploid wheat lines of various non-standard spike morphotypes, which allowed for identification of a new mutant allele of the WHEAT FRIZZY PANICLE (WFZP) gene that determines spike branching in diploid wheat Ttiticum monococcum L. Moreover, we found that the development of SSs and spike branching in wheat T. durum Desf. was a result of a wfzp-A/TtBH-A1 mutation that originated from spontaneous hybridization with T. turgidum convar. сompositum (L.f.) Filat. Detailed characterization of the false-true ramification phenotype controlled by the recessive sham ramification 2 (shr2) gene in tetraploid wheat T. turgidum L. allowed us to suggest putative functions of the SHR2 gene that may be involved in the regulation of spikelet meristem fate and in specification of floret meristems. The results of a gene interaction test suggested that genes WFZP and SHR2 function independently in different processes during spikelet development, whereas another spike ramification gene(s) interact(s) with SHR2 and share(s) common functions.ConclusionsSS mutants represent an important genetic tool for research on the development of the wheat spikelet and for identification of genes that control meristem activities. Further studies on different non-standard SS morphotypes and wheat lines with altered spike morphology will allow researchers to identify new genes that control meristem identity and determinacy, to elucidate the interaction between the genes, and to understand how these genes, acting in concert, regulate the development of the wheat spike.

A new species of Chrysopogon (Poaceae: Andropogoneae) from India

A new species of Chrysopogon from the lateritic hillocks of Kannur District, Kerala, India, is described and illustrated. It closely resembles C. tadulingamii, but differs mainly in having sessile spikelets with a ciliate, short-awned upper glume and a short-awned upper lemma, pedicelled spikelets with 7-nerved, awned lower glume, a short 3-nerved awnless, retrorsely ciliate upper glume and a retuse or bifid upper lemma. The new species also resembles C. asper in some characters, but differs in having acicular or linear leaf blades, rounded leaf sheaths, and sessile spikelets with short-awned upper glume and upper lemma. A key for identification of species in Chrysopogon from Kerala is also provided.

Fimbristylis tuckeri (Cyperaceae), a new sedge species from the Western Ghats, India

Fimbristylis tuckeri, a perennial fimbristyloid sedge from Nilgiri Biosphere Reserve and its environs in Western Ghats, India is described as a new species. It is similar to its closest morphological relative, F. filifolia Boeckeler but differs by the 5-angular scabrid culms, glumaceous involucral bracts and sessile spikelets. A detailed description, phenology, distribution, relevant notes and colour photographs are provided.

A new species of Themeda (Poaceae: Panicoideae) from the Eastern Ghats, India

Themeda odishae (Poaceae), a new species from the Mahendragiri hill ranges, Odisha (Orissa), India, is described and illustrated. It differs from T. mooneyi in shorter and hairy leaf blades, longer peduncle, length of sessile spikelet callus, number of pedicelled spikelets, and longer anthers. And from T. saxicola by its longer peduncle, number of racemes, number of pedicelled spikelets and hairy involucral spikelets.

The Genetic Basis of Composite Spike Form in Barley and 'Miracle-Wheat'.

Inflorescences of the tribe Triticeae, which includes wheat (Triticum sp. L.) and barley (Hordeum vulgare L.) are characterized by sessile spikelets directly borne on the main axis, thus forming a branchless spike. ‘Compositum-Barley’ and tetraploid ‘Miracle-Wheat’ (T. turgidum convar. compositum (L.f.) Filat.) display noncanonical spike-branching in which spikelets are replaced by lateral branch-like structures resembling small-sized secondary spikes. As a result of this branch formation ‘Miracle-Wheat’ produces significantly more grains per spike, leading to higher spike yield. In this study, we first isolated the gene underlying spike-branching in ‘Compositum-Barley,’ i.e., compositum 2 (com2). Moreover, we found that COM2 is orthologous to the branched headt (bht) locus regulating spike branching in tetraploid ‘Miracle-Wheat.’ Both genes possess orthologs with similar functions in maize BRANCHED SILKLESS 1 (BD1) and rice FRIZZY PANICLE/BRANCHED FLORETLESS 1 (FZP/BFL1) encoding AP2/ERF transcription factors. Sequence analysis of the bht locus in a collection of mutant and wild-type tetraploid wheat accessions revealed that a single amino acid substitution in the DNA-binding domain gave rise to the domestication of ‘Miracle-Wheat.’ mRNA in situ hybridization, microarray experiments, and independent qRT-PCR validation analyses revealed that the branch repression pathway in barley is governed through the spike architecture gene Six-rowed spike 4 regulating COM2 expression, while HvIDS1 (barley ortholog of maize INDETERMINATE SPIKELET 1) is a putative downstream target of COM2. These findings presented here provide new insights into the genetic basis of spike architecture in Triticeae, and have disclosed new targets for genetic manipulations aiming at boosting wheat’s yield potential.

Characterization of a Multiseeded (msd1) Mutant of Sorghum for Increasing Grain Yield

ABSTRACTSorghum [Sorghum bicolor (L.) Moench] has branched panicles with primary, secondary, and tertiary branches. These inflorescence branches are composed of a terminal triplet spikelet, consisting of one sessile (directly attached to the branch) and two pedicellate (spikelets attached to the branch through a short pedicel), followed by one or more spikelet pairs (one sessile and one pedicellate). In BTx623, and most sorghum lines, only the sessile spikelets can develop into seeds and the pedicellate spikelets, occasionally developing anthers, eventually abort. Here, we report the isolation and characterization of a stable multiseeded (msd1) mutant of sorghum (in BTx623 background, referred to as wild‐type [WT]) in which both sessile and pedicellate spikelets are fertile. In addition, this mutant displayed increased length and total number of primary and secondary inflorescence branches. Genetic analysis showed that this multiseeded mutation is a recessive trait. Pedicellate spikelets in msd1 mutants exhibited complete flower with functional ovary and anthers, of which 75 to 95% can develop into viable seeds. The individual msd1 seeds are smaller than WT; however, the results indicated that this reduction in seed weight can be compensated by the increase in seed number. The total seed weight per panicle in msd1 mutants was increased by 30 to 40% as compared to the WT. Further experiments are needed to demonstrate whether the msd1 mutation can increase grain yield under field conditions.

Synflorescence analysis in South American species of <i>Andropogon</i> section <i>Leptopogon</i> (Andropogoneae, Poaceae): a tool to identify different ploidy levels

In southern South America, Andropogon sect. Leptopogon is represented by both diploid and hexaploid species. In order to compare the synflorescence structures and floral arrays in relation to ploidy levels in species of Andropogon , the section Leptopogon was used as model. In this study, the synflorescence structure was typologically characterized. The structural analysis was based on the typology system developed by Troll and Weberling, which has proved useful in describing inflorescences. A comparative analysis of the variations observed in the structure of the synflorescence and a morphometric analysis using principal component analysis were carried out. These results revealed that diploid and hexaploid species present differences mainly in the following parameters: synflorescence length, number of internodes of the enrichment zone main axis, number of internodes and length of paracladia of the trophotagma, number of long paracladia per unit of inflorescence, length of hairs on articulated rachis internodes, pedicellate spikelet length, pedicellate spikelet width, pedicel width, length of hairs on pedicel, sessile spikelet length, awn length and floral system arrangements. This study provides a useful tool to distinguish between diploid and hexaploid species of Andropogon sect. Leptopogon . We propose naming the group of diploid species from Central and South America as the Andropogon selloanus complex.

<p class="HeadingRunIn"><strong>New record for <em>Eriochrysis</em> (Poaceae: Andropogoneae) in the State of Rio Grande do Sul, Brazil, and a key to the species of <em>Eriochrysis</em> in Brazil</strong></p>

The genus Eriochrysis Beauvois (1812: 8) (Poaceae: Andropogoneae) includes ca. seven species from America, Africa, and India (Clayton & Renvoize 1986). It is characterized mainly by inflorescences with golden-brown to light-brown trichomes, and heterogamous spikelets: sessile spikelets with a bisexual flower and pedicelled spikelets with a pistillate flower. Six species of the genus occur in Brazil (Filgueiras & Welker 2012), of which three were previously reported for the State of Rio Grande do Sul: E . cayennensis Beauvois (1812: 8), E . holcoides (Nees 1829: 324) Kuhlmann (1922: 89) and E . villosa Swallen (1966: 90) (Welker & Longhi-Wagner 2012).