Spikelets Research Articles

Genetic variability, heritability and trait associations in durum wheat (Triticum turgidum L. var. durum) genotypes

Information on the extent of genetic variability and heritability as well as correlation among agronomically important traits is a requirement to design a suitable plant breeding method. The present research was conducted at Sinana, Southeastern Ethiopia during the 2009 main crop growing season. The experimental material consisted of 16 durum wheat genotypes tested in a randomized complete block design with three replications. Twelve agronomic traits were included in the investigation. Highly significant differences were revealed among durum wheat genotypes for all traits studied, suggesting the possibility of improving durum wheat for these traits. Plant height and number of kernels per spike showed the highest phenotypic and genotypic coefficients of variations and genetic advance, whereas, days to maturity and test weight had the lowest values. Plant height exhibited highest heritability value of 98.3% while number of spikelets per spike showed minimum value of 36.4%. The genotypic correlations estimated showed positive association of grain yield with days for heading (r=0.50), harvest index (r=0.69) and kernels number per spike (r=0.81). Harvest index (1.13) and biomass (0.81) exhibited the highest positive and significant direct effect on grain yield. Hence, these traits could be considered as suitable selection criteria for the development of high yielding durum wheat varieties. Key words: Correlation coefficient, durum wheat, genetic advance, heritability, path coefficient.

Identification and pathogenicity assessment of Fusarium spp. sampled from durum wheat fields in Tunisia

Durum wheat is the major cereal crop cultivated in Tunisia; covering over 40% of the cereal growing areas. Durum wheat production remains below expectation due to its low productivity that is attributed to the chronically abiotic and biotic stresses. Fusarium head blight (FHB) caused by Fusarium spp. has become an important disease on durum wheat (Triticum turgidum L var. durum) in Tunisia, particularly during humid season. To identity the Fusarium species associated with FHB, samples were collected from five and six durum wheat fields in Northern Tunisia during 2004 and 2007 crop seasons, respectively. A total of 241 single spore cultures were isolated and seven different Fusarium spp. were identified using morphological traits and species-specific PCR assays. Pathogenicity of FHB causal agents was assessed on predominant durum wheat varieties. Aggressiveness of selected Fusarium isolates was investigated. Three durum wheat cultivars, characterized by different level of susceptibility to FHB, were artificially inoculated. Symptoms of FHB were rated as percentage of infected spikelets (PIS) at 7, 14 and 21 days after inoculation (DAI) and area under disease progress curve (AUDPC) was analysed. Fusarium culmorum was the dominant species representing 36.3% of all sampled isolates. All Fusarium species testedcaused visible infections to the durum wheat cultivars with significant difference in aggressiveness among species. F. culmorum was considered highly pathogenic with an AUDPC=243.7, followed by Fusarium pseudograminearum(AUDPC=216.7). The remaining species, which had <150 AUDPC, were moderately and weakly pathogenic. There were significant differences (P < 0.05) in aggressiveness among isolates within species suggesting that screening for resistance to FHB requires a mixture of several isolates within and amongFusarium species. Key words: Fusarium head blight (FHB), Fusarium species, pathogenicity, durum wheat.

Assessing phenotypic diversity of interspecific rice varieties using agro-morphological characterization

The aim of this study is to identify the phenotypic variability of 60 lowland NERICA varieties and 18 promising lines for better management of their genetic inheritance. The experimental design used was an augmented randomized complete block. Data on 23 agro-morphological traits were collected and analyzed. The analysis of variance showed highly significant differences (P<0.0001) between the variables and revealed the structure of the different genotypes from 11 quantitative discriminate traits. Cluster analysis and principal component analysis were carried out. The entries were grouped into three clusters irrespective of the level of backcrossing of genotypes. Eighty percent of lowland NERICA containing the desired characters adapted to lowland rice cultivation were grouped in cluster 1. The second cluster includes lowland NERICA varieties that can be grown in both upland and lowland ecologies, while the last group comprised only varieties close to their African parent and mainly adapted to the upland. Tillering at 60 days after sowing (DAS), plant height at maturity, maturity and spikelet fertility were the most discriminate and could therefore supplement a wide range of variables for genetic diversity study. Key words: Lowland NERICA, promising lines, agro-morphological descriptors, cluster

Estimation of correlation coefficients among seed yield and some quantitative traits inwheat (Triticum aestivum L.)

Genetic variability of quantitative traits and their contribution towards seed yield that may be used as criteria for yield improvement in wheat was investigated. Generation means analysis technique was applied to identify correlation (phenotypic and genetic) coefficients for seven quantitative traits in two wheat crosses and their reciprocals. The estimates of genetic correlation coefficients were found greater than the phenotypic one for all studied plant traits in both crosses and their reciprocals. Seed yield per plant was found positively correlated at phenotypic and genetic levels in cross V-95199 x PARI-73 and it’s reciprocal. In this cross, days to heading, peduncle length, spikelets per spike and seed yield per main spike were significantly influenced while harvest index showed negative association with seed yield per plant. The phenotypic and genetic correlation coefficients of cross Chakwal-86 x V-8060 and its reciprocal indicated that seed yield per plant had significantly positive strong association with all studied plant traits except specific flag leaf weight and days to heading. It is concluded that the inter relationship among traits both at phenotypic and genetic levels could efficiently be exploited for obtaining maximum seed yield per main spike, peduncle length, and harvest index which ultimately lead to improve crop yield. Key words: Wheat, direct and reciprocal crosses.

The Effect of Drought Stress on Grain Yield, Yield Components and Some Quality Traits of Durum Wheat (Triticum turgidum ssp. durum) Cultivars

Drought, one of the environmental stresses, is the most significant factor restricting plant production in the majority of agricultural fields of the world. Wheat is generally grown on arid-agricultural fields. Drought often causes serious problems in wheat production areas. A field study was conducted on clay-silt soil, in the Research Field, Southeastern Anatolia Agricultural Research Institute, in Diyarbakir during 1999-2000 growing season in order to evaluate genotypes for yield, yield components and some quality traits. Fourteen wheat (Triticum turgidum ssp. durum) cultivars were grown under well watered and natural drought conditions. Morphological traits were measured at anthesis and yield, yield components and quality traits were evaluated at ripening time. The flowering period was negatively associated with grain yield, while grain filling period, chlorophyll content, number of grains per spike and spikelets per spike were positively associated with grain yield under drought conditions. Moreover, the number of days to maturity was negatively associated with Drought Susceptibility Index (DSI), while Spike length was positively associated to DSI in drought conditions. DSI and relative yield (RY) values for grain yield were used to describe yield stability and yield potential. There were high variations in DSI and RY values within genotypes. DSI values for grain yield ranged from 0.82 to 1.07 and the mean RY values were 0.82 for well-watered plots and 0.87 for water stressed plots. The varieties ‘Gidara-II’, ‘Saricanak-98’, ‘Balcali-2000’, ‘Altintoprak-98’, ‘Aydin-93’ and ‘Harran-95’ showed high yield potential and stability (DSI mean RY).

Detection of unintended effects in genetically modified herbicide-tolerant (GMHT) rice in comparison with non- target phenotypic characteristics

In the process of safety assessments of genetically modified (GM) crops, particular attention should be paid to their unintended effects. This study was focused on detection of unintended effects in genetically modified herbicide-tolerant (GMHT) rice (Oryza sativa L. ssp. indica) Bar68 -1 in comparison with non-target phenotypic characteristics between Bar68 -1 and its unmodified counterpart, D68. The results showed that there were no significant differences between Bar68 -1 and D68 in most of the morphological or agronomic traits, including main culm length, main culm thickness, flag leaf length, tillering dynamics, seed setting, 1000-grain weight, grain length, grain width, length-width ratio of grain, brown rice length, brown rice width, length-width ratio of brown rice, grain yield, biomass of aerial part, yield, rate of seed germination and ratooning. There were statically significant differences between Bar68-1 and D68 in the parameters such as flag leaf width, spikelets per panicle, panicle length and harvest index, but the values of the changed traits are within rice normal ranges and in the same scales according to GB/T 19557.7 - 2004 from Chinese standard and SES from IRRI. Therefore, these differences were not considered biologically relevant. Results indicated that the unintended effects were not detected in Bar68-1 in this study. Key words: Unintended effects, safety assessment, biosafety, GM crops, herbicide tolerance, transgenic plant, rice (Oryza sativa L.), bar gene.

Epistasis and genotype-by-environment interaction of grain yield related traits in durum wheat

Genetic control of the number of heads per plant, spikelets per spike and grains per spike was studied in two durum wheat (Triticum durum Desf.) crosses, Inrat 69/Cocorit71 and Karim/Ben Bechir, respectively. Separate analyses of gene effects were done using means of four generations (parents P1 and P2, F1, F2, and the two reciprocal BC1) at two sites. A three-parameter model was inadequate to explain all traits except number of heads per plant in Inrat 69/Cocorit 71 at one site. In most cases a digenic epistatic model explained variation in generation means. Dominance effects and dominance ´ dominance epistasis (l) were more important than additive effects and other epistatic components. Considering the genotype-by-environment interaction, the interactive model was applied and found adequate in all majority of cases except spiklets per spike and grains per spike in Inrat 69/Cocorit71. The results of this study indicate that maintenance of heterozygosity is useful for exploitation of epistatic effects and adaptability to varied environmental conditions for spiklets per spike and grain per spike in the cross Karim/Ben Bechir. Estimates of narrow-sense heritability indicated that the genetic effect was larger than the environmental effect. The additive effect was the largest component of genetic effects. Key words: Genetic effects, epitasis, genotype-by-environment interaction,heritability, Triticum durum.

Space and Spikelets

Space and Spikelets

Genetic improvements for high yield and low soil nitrogen tolerance in rice ( Oryza Sativa L.) under a cold environment

Eight rice cultivars released in 1905, 1919, 1941, 1954, 1971, 1984, 1987 and 1988 were investigated to identify the traits that contributed to high yield and low soil nitrogen tolerance breeding under cold environment. They were grown in fields at three different nitrogen (N) fertilizer treatments, 0, 6 and 12 g N m −2 (0 N, 6 N and 12 N) in Sapporo, Northern Japan, in 2001 and 2002. All cultivars increased their grain yield (GY) with the increase in soil N availability, and better response to N was observed in modern cultivars released during 1984–1988 compared to old ones (1905–1954). Irrespective of N treatments, the modern cultivars showed better GY than the older ones. Absolute genetic gain was 2.15 or 2.94 g m −2 year −1 at 6 N and 12 N. Under 0 N treatment, although the magnitude of yield increase was small, the genetic gain in GY was still observed at 0.78 g m −2 year −1. The GY increments were achieved mainly through increasing the number of spikelets (SPK) which depends on the number of panicle (PAN) at any level, and the PAN could be increased by enhancing the number of tillers. The extinction coefficient ( k) showed that the older cultivars had a spreading plant type, on the other hand, the modern cultivars had an erect plant type which seemed to be a better plant structure in terms of light distribution. This change on plant structure would allow the modern cultivars to have a larger LAI with improved light capturing resulting in better GY in modern cultivars than the old cultivars having similar LAI with modern cultivars. These breeding strategies could work for the high-yielding rice breeding program under cold environments irrespective of soil nitrogen conditions.

New Species of Paspalum (Poaceae: Panicoideae: Paniceae) from Brazil

Abstract During preparation for a revision of the genus Paspalum for America, two new taxa from Brazil were recognized as previously undescribed species. Paspalum plowmanii from Bahia, Goias, and Mato Grosso is related to P. macranthecium. from which it differs by its non-stipitate spikelets, with upper glume 3/4 the length of the spikelet, and by having a membranous upper glume and lower lemma. Paspalum filgueirasii from Goias, Brazil, is related to P. proximum Mez, from which it differs by having a single and erect raceme. Both species are described, illustrated, and compared with putatively related species. A key to the new species and related taxa of Paspalum is also presented.

Digitaria killeenii (Poaceae: Panicoideae: Paniceae), a New Species from Bolivia

Abstract Digitaria killeenii A. S. Vega et Rugolo, a new species from Bolivia, is described and illustrated. Additional micromorphological characters in the spikelets are also described. The presence of an apical, abaxial pair of stomata on the upper lemma and the presence of occasional brownish hairs on the lower palea constitute the first report in the genus Digitaria. The taxonomic position of D. killeenii is discussed and its inclusion in section Clavipilae (Stapf) Henrard is proposed. A comparative table and some remarks about the related taxa are included. Communicating Editor: Fred Barrie

Correlation of Spikelet Number per Panicle on the Order of Tillers with the Diameter of Shoot Apical Domes at Panicle Initiation in Rice

1穂穎花数の順位が主茎＞1次分げつ＞2次分げつになるのは穂首分化期（PI）の茎頂分裂組織（AD）の基部直径に関係づけられるのかを明らかにするために，穂数型品種のIR72と穂重型品種のIR65564-44-2-2の2つの水稲品種をポット栽培し，分げつ次位別の穎花数および1次枝梗数（PB），2次枝梗数とADの基部直径の関係を相関分析した．各ポットには1個体を栽培し，すべての分げつについて分げつ次位と出現した節位を記録した．主茎，主茎の第4，5，6，10葉節位から出現した1次分げつおよび主茎の第4，5，6葉節位から出現した1次分げつの第3葉節位から出現した2次分げつについて，PIにおけるADの基部直径，分化PB，分化穎花数などを調査した．PIにおけるADの基部直径はIR72では主茎が最も大きく，IR65564-44-2-2では主茎と主茎第5葉節位から出現した1次分げつが大きくなった．IR65564-44-2-2，IR72ともに分化PBの順位は主茎＞1次分げつ ＞2次分げつとなった．その結果，両品種においてそれぞれPIにおけるADの基部直径と1穂PBの間に正の相関関係が認められた．このことから1穂穎花数の順位が主茎＞1次分げつ＞2次分げつになるのはPIにおけるADの基部直径が分化PBと関係づけられる可能性があると結論した．

A New, Dioecious, Dimorphic Species of Licuala (Palmae) from Hainan, China

A description and illustration of a new species of Licuala, L. hainanensis, from Hainan, China is given. This species, endemic to Hainan, was previously confused with the widespread L. spinosa. The distribution of the new species is mapped, and it is compared and contrasted to morphologically similar species from Vietnam. Evidence is presented that L. hainanensis is both dioecious and sexually dimorphic, based on its flower and rachilla morphology. Other potential cases of sexual dimorphism in Licuala are discussed.

Phylogenetic Relationships of Zeugites (Poaceae: Centothecoideae) Inferred from Plastid and Nuclear DNA Sequences and Morphology

The genus Zeugites P. Browne encompasses ten species of neotropical grasses. To infer the phylogenetic relationships of the species, parsimony analyses of morphological data and DNA sequences from a nuclear region (ITS) and two non-coding plastid regions (the trnL intron and the trnL-trnF intergenic spacer) were undertaken for each data set separately and in combination. The combined analysis is presented as our preferred phylogenetic hypothesis because of its better resolution and higher support for the clades. Zeugites is monophyletic only if Calderonella sylvatica is included in it. Our analyses recover two major clades within Zeugites: Clade I, formed by Zeugites pittieri, Zeugites latifolia, Zeugites sylvatica (Calderonella sylvatica), Zeugites sagittata, and Zeugites capillaris; and Clade II, including Zeugites hackelii, Zeugites smilacifolia, Zeugites munroana, Zeugites pringlei, Zeugites mexicana, and Zeugites americana. The monospecific genus Pohlidium is strongly supported as sister of Zeugites (including Calderonella) but it is maintained as a different genus due to noticeable differences in spikelet and inflorescence morphology.

On the Taxonomic Position of Panicum aristellum (Poaceae: Panicoideae: Paniceae)

Abstract In a recent treatment, the genus Panicum was restricted to subgenus Panicum based on molecular, morphological, and anatomical data. Also, other species of Panicum were transferred to different genera of the Paniceae, such as Dichanthelium, Hymenachne, Phanopyrum, and Steinchisma, while the remaining American species of Panicum were temporarily placed as incertae sedis taxa. Therefore, these incertae sedis species are in need of a new taxonomic status within the tribe. In this study, the taxonomic position of Panicum aristellum, an endemic species of central and southeastern Brazil, is evaluated using morphological and anatomical characters, together with sequence data from ndhF, a molecular marker from the chloroplast. The sequence of Panicum aristellum was analyzed together with other species of the subfamily Panicoideae. This species grouped with the genus Canastra in a well-supported clade. Several synapomorphies characterized the clade: caespitose plants, keeled sheaths, aristate spikelets, s...

Proteins and Carbohydrates in Developing Rice Panicles with Different Numbers of Spikelets: —Cultivar difference and the effect of nitrogen topdressing—

Proteins and carbohydrates in developing rice panicles were analyzed to see whether these parameters control spikelet number in rice. Two rice cultivars and 2 levels of nitrogen topdressing were used to obtain panicles with different numbers of spikelets. A japonica rice cultivar, Nipponbare, with topdressing (H) had 1.8 times more spikelets per panicle than that without topdressing (L). Moreover, the number of spikelets per panicle in an indica rice cultivar, Takanari, without topdressing was 2.7 times larger than that in Nipponbare-L. Panicles with more spikelets (LP) in Nipponbare-H and Takanari-L showed slower growth than those with few spikelets (SP) in Nippanbare-L in an early stage. LP, however, increased markedly in size thereafter, eventually exceeding SP, in length and fresh weight. Soluble protein content was higher in LP than SP in an early stage, but this difference was hardly detected in a late stage. No clear difference was observed in sugars or starch between LP and SP. Analysis of soluble and insoluble proteins by SDS-polyacrylamide gel electrophoresis showed that bands corresponding to insoluble proteins with a molecular weight about 42 kDa were present at higher intensities in LP than in SP. These results suggest that the spikelet number in rice is controlled by the soluble protein content in an early stage and insoluble proteins with a molecular weight of 42 kDa during panicle development, but not by the carbohydrates in developing panicles.

Molecular characterization of OsPRP1 from rice, which is expressed preferentially in anthers

A proline-rich protein-encoding cDNA encoded by a rice gene, OsPRP1, was isolated by PCR-mediated RNA subtraction hybridization strategy and rapid amplification of cDNA ends. The deduced protein consists of 224 amino acids with the highest level of proline residue (14.29%). Following the putative signal peptide, OsPRP1 contains two structural domains, of which the N-terminal domain lacks Pro-rich repetitive sequences, and the C-terminal domain has two repetitive proline-rich sequences of 18 amino acid residues with PEPK motifs. Southern blot and sequence analysis show that OsPRP1 exists as four copies in rice genome and is localized in rice chromosome 10. RT-PCR experiments reveal that OsPRP1 is expressed preferentially in spikelets and buds with lower levels in roots and leaves. In situ hybridization indicates that OsPRP1 transcripts are present at high levels in pollen mother cells (PMCs), meiotic PMCs, tapetal cells and vascular bundle cells of flower organs. The expression of OsPRP1 in anthers has temporal specificity. The transcripts are accumulated at high levels in PMCs, at the highest levels in meiotic PMCs and at undetectable levels in uninucleate pollen. In buds the transcripts are only detected in the epidermal cells of coleoptiles and leaf primordial.

SORGHUM VERTICILLIFLORUM: A NATURAL HOST OF SORGHUM YELLOW BANDING VIRUS IN VENEZUELA

Apparently virus- infected Sorghum verticilliflorum (wild sorghum) plants were observed at Maracay, Aragua State. These plants showed yellow speckles, chlorotic streaks and bands, stunting, and light necrosis. Symptomatic plants were collected, and extracts from these plants were mechanically inoculated to a range of plant species. A virus was transmitted at relatively low rate (7%) to wild sorghum and sorghum (S. bicolor) plants. Symptoms appeared 17-24 days after inoculation. Infected wild sorghum plants were sterile or had only a few spikelets. The virus was not transmitted by Rhopalosiphum maidis or Peregrinus maidis, nor was it found in progeny of seed from an infected plant. In agar double immunodiffusion tests forty-two isolates from wild sorghum reacted positively with antiserum to Sorghum yellow banding virus, SrYBV (Garrido et al., 2000). Examination of clarified viral concentrate of some isolates consistently revealed isometric particles 25 nm in diameter. SDS-PAGE analysis of protein extracted from these preparations yielded a single band with a mol. wt. of approximately 29 kDa. Based on these results, the virus is considered to be SrYBV (Garrido et al., 2000; Klaassen and Falk, 1989). Probably, S. verticilliflorum is an important host in the epidemiology of SrYBV in Venezuela, since it is a widely distributed weed in the country. This is the first report of S. verticilliflorum as natural host of SrYBV.

A Taxonomic Revision of the Eastern North American and Eastern Asian Disjunct Genus Brachyelytrum (Poaceae): Evidence from Morphology, Phytogeography and AFLPs

Abstract Morphological and phytogeographical data support the recognition of three distinct species in the genus Brachyelytrum: B. japonicum, B. erectum, and B. aristosum. Brachyelytrum japonicum is confined to eastern Asia and is characterized by narrow leaf blades (0.5–0.8 cm wide), long lower glumes (0.2–2.0 mm long), and long rachillas (6.8–8.8 mm long). Brachyelytrum erectum is distributed throughout much of the eastern United States, from northwestern Minnesota south to central Louisiana, east to northern Florida and north to northeastern New York. Brachyelytrum erectum is characterized by long hispid hairs (0.2–0.9 mm long) on the veins of the lemma, wide lemmas (0.8–1.8 mm wide), and a conspicuous lemma mid-vein. Brachyelytrum aristosum has a more northern distribution, occurring in southern Canada from southern Ontario to Newfoundland, the northern adjacent United States and through the Appalachian mountains to northwestern North Carolina. Brachyelytrum aristosum is characterized by short scaberu...

Novitates Gabonenses (32). A New Species of Panicum (Gramineae) from Gabon

villense Franch., but differed from this species, notably in the panicle being distinctly contracted and narrowly elliptic, sometimes almost linear in outline, only 2-5(-6) cm long and densely spikeled. On further examination (which included material from WAG, BR and K) it appeared that there were other characters that distinguished them from P. brazzavillense: the spikelets were always very small (1.0-1.2 mm long) and glabrous, the sheaths were distinctly shouldered, strongly striate and had glabrous margins, and the leaves were always stiff and inrolled. In P. brazzavillense the sheaths are not or slightly shouldered, have pilose margins and are less pronouncedly striate; the leaves are generally flat, and the panicle is open (or contracted only when young), usually larger and with slightly larger (1.2-1.7 mm long), hairy or occasionally glabrous spikelets. I therefore decided to describe this taxon, which appears to be endemic to coastal savanna's in Gabon from Port Gentil to