Environmental Influences on Panicle Differentiation and Spikelet Number of Pennisetum americanum

Pearl millet (Pennisetum americanum (L.) Leeke) has a juvenilephase after which the time to panicle initiation is reducedby short daylengths. To understand more fully the mechanismunderlying temperature ? daylength interactions on panicle initiationand differentiation, plants were grown (a) at a range of constanttemperatures under a short daylength from sowing until afterpanicle differentiation and (b) at one temperature until 20d after emergence and then at a range of temperatures duringa 10 d exposure to short daylength. Temperature prior to panicle initiation determined the numberof leaves initiated on the main stem and the size of the apicaldome at the start of panicle initiation. The number of leaves,in turn, influenced the duration of the phase from panicle initiationto anthesis: this phase required a constant thermal time whenexpressed as day degrees per leaf. At anthesis, panicle lengthwas positively correlated with the number of leaves on the mainstem (and temperature) prior to panicle initiation. Changingthe temperature only during exposure to inductive daylengthsaffected the rate of growth of the apical dome so that panicledifferentiation began within 10 d at high temperature (30?C)whereas differentiation did not commence in 10 dat 21?C. Paniclesdeveloped normally if differentiation had commenced under inductivedaylengths whereas panicles were abnormal when plants were returnedto long daylengths after panicle initiation but before visibledifferentiation. Relative extension rates of the panicle during differentiationwere correlated positively with temperature. The results areconsistent with the hypothesis that panicle initiation dependson the apex attaining a critical size and that temperature,by determining the number of leaves initiated on the main stem,affects the size of the apical dome and thus the onset of panicleinitiation, the duration of paniclc differentiation and thenumber of spikelets differentiated. Key words: Pennisetum americanum, panicle differentiation, spikelet number     

水稻单株有效穗数和每穗粒数的QTL剖析

应用292个Lemont/特青F13重组自交系（RILs)及其含272标记的遗传连锁图谱部析单株有效穗数（PN）和每穗粒数（SNP）及其相关性状的遗传,所有性状呈现超亲分离,PN与SNP存在弱的负相关,检测到影响PN和SNP及其相关性状的QTL51个和互作位点45对,它们可以解释60％以上的性状总变异,SNP与其相关性状的QTL定位在一起,比较与SNP－QTL同一或相邻区域的QTL数,穗部枝梗数是长度性状的两倍,故前者对SNP的作用更大,仅有2个PN－QTL与SNP相关性状的QTL相邻,因此通过标记辅助选择有可能实现PN与SNP的有利重组,其中影响PN的QPn4和影响穗枝梗数和长度的QPbn3a,QPbn3和QPb14等主效QTL,在标记辅助选择中具有重要的应用价值,对通过标记辅助选择合理配置穗部性状TQL产生新的高产穗型进行了讨论。     

水稻产量库相关穗部性状的遗传分析

收人李源于珍汕97/明恢63的重组系群体中与产量库容有关的10个穗部性状的表现型数据。总体上,每穗颖花数与每穗二次枝梗数、每个二次枝梗上的颖花数、颖花密度有更大的相关性。对所研究的10个性状,两年间共检测到53个QTLs。约43.4%的QTLs能在两年同时检测到。5个染色体区域（第1染色体上G359-RG532和C567-C86-RG236,第2染色体上R712-RM29,第6染色体上P-RG424,第10染色体上C148-RM258）分别对多个穗部性状表现出效应。结果显示相关性状的QTLs大致定位在相似的染色体区域,这表明基因的多效性或紧密连锁是穗部性状间相关的遗传基因。在检测到的大量2位点互作对中,约18.2%在两年都能被检测到。不同性状的共同互作对的比例为8.7%～32.6%。在两年都能检测到2位点组合中,约26.7%的组合同时影响着多个性状,表现出多效效应。结果表明每个性状都由数个QTL、基因型与环境互作、大量的上位性互作所控制。     

Carbohydrate Responsive Proteins in the Roots of Pennisetum americanum

The effect of changes in carbohydrate status on the synthesis of specific proteins was investigated in millet (Pennisetum americanum L., Leeke, Tift 23B₁E₁) seedlings grown in sterile solution culture. Carbohydrate status was altered by extended darkness and sucrose feeding. Root proteins from intact seedlings were labeled with [³⁵S]methionine, phenol-extracted, separated by two-dimensional gel electrophoresis, and visualized by autoradiography. In four separate experiments, two proteins showed a consistent change in labeling when root carbohydrate levels were varied between 200 and 1000 micromole hexose per gram residual dry weight. Labeling of the first protein (P₄₇, M_r 47 kD) increased as the carbohydrate levels rose above 500 micromole hexose per gram residual dry weight. Labeling of the second protein (P₃₄, M_r 34 kD) increased as carbohydrate levels declined from 500 to 200 micromole hexose per gram residual dry weight. Under extreme conditions, when carbohydrate levels fell below 100 micromole hexose per gram residual dry weight, the labeling pattern of most proteins was drastically altered. It is suggested that P₄₇ and P₃₄ are `carbohydrate responsive proteins,' i.e. proteins whose concentrations are controlled either directly or indirectly by tissue carbohydrate status. In contrast, the changes in protein labeling that occur once carbohydrate pools are depleted may be involved in adaptation to periods of prolonged starvation.     

异季条件下稻穗枝梗和颖花分化、退化及其形成的差异性研究

以19个水稻杂交组合为试验材料,通过大田条件下的分期播种,于抽穗期调查了稻穗枝梗、颖花分化、退化及形成有关性状,分析了各性状不同季节的变异及其相互关系。结果表明,单穗一次枝梗分化数、二次枝梗分化数、颖花分化数、一次枝梗退化数、二次枝梗退化数、颖花退化数、一次枝梗退化率、二次枝梗退化率、颖花退化率、一次枝梗形成数、二次枝梗形成数、一次枝梗颖花形成数、二次枝梗颖花形成数和单穗颖花总形成数等性状均存在较大的组合间差异和季节间变异,其中19个组合单穗颖花总形成数异季差异率变幅为5.12%~93.59%,平均变异率为34.19%;总体上,不同季节下二次枝梗各性状的变异性强,颖花性状其次,一次枝梗各性状变异性最小;根据异季条件下稻穗枝梗和颖花分化、退化及其形成性状的变异性,从大穗角度讨论了杂交稻新组合育种资源选择与利用问题。     

Spontaneous chlorophyll mutants of Pennisetum americanum: Genetics and chlorophyll quantities

Summary Thirteen spontaneously occurring chlorophyll deficient phenotypes have been described and their genetic basis was established. Ten of these — white, white tipped green, patchy white, white virescent, white striping 1, white striping 2, white striping 4, fine striping, chlorina and yellow virescent showed monogenic recessive inheritance and the remaining three — yellow striping, yellow green and light green seedling phenotypes showed digenic recessive inheritance. The genes for (i) white tipped green (wr) and yellow virescent (yv) and (ii) patchy white (pw) and white striping 1 (wst 1) showed independent assortment. Further, the genes for white (w), white tipped green (wr) and yellow virescent (yv) were inherited independently of the gene for hairy leaf margin (Hm).In the mutants — white tipped green, patchy white, white striping 1, white striping 2, fine striping, chlorina, yellow virescent, yellow striping, yellow green and light green phenotypes total quantity of chlorophyll was significantly less than that in the corresponding controls, while in white virescent there was no reduction in the mature stage. For nine of the mutants the quantity of chlorophyll was also estimated in F₁'s (mutant x control green). In F₁'s of six of the mutants — white tip, patchy white, chlorina, yellow virescent, fine striping and yellow striping the quantity of chlorophyll was almost equal to the wild type. In the F₁'s of three of the mutants — white striping 1, white striping 2 and light green an intermediate value between the mutant and wild types was observed. In yellow virescent retarded synthesis of chlorophyll, particularly chlorophyll a was observed in the juvenile stage. Reduced quantity of chlorophyll was associated with defective chloroplasts. In the mutants — white tipped green, white virescent, fine striping, chlorina, yellow striping, yellow green and light green defective plastids were also observed. In patchy white secondary destruction of chlorophylls and the presence of defective plastids were found to be associated with reduced chlorophyll quantity at maturity.Paper chromatographic studies of leaf flavonoids revealed some variation between the inbreds, but there were three common spots, 7, 8 and 9, except for PDP in which the spot 8 was absent. Chlorophyll deficient mutants differed from their respective controls in the absence of one or more of the spots present in the controls and in the presence of new spots in some of the mutants.Most of the chlorophyll mutants showed higher survival rate in the Kharif season than in Rabi season which was attributed to the higher mean day temperature and longer day light period in the Kharif season than in Rabi season.     

Heterogeneity of Primary Branch Development and Spikelet Survival in Rice Panicle in Relation to Assimilates of Primary Branches

Two high yielding semi-dwarf rice varieties namely IR-36 andJava, and one traditional tall indica rice variety, Akul, werecultivated in the dry and wet seasons, respectively, in 1987under irrigated field conditions. A few days after visible panicleinitiation, the panicle on the main shoot was dissected outto measure development, growth, soluble carbohydrates, aminoacid and phosphate contents of individual primary branches.Primary branch developmnent was quantified by noting the averagetime to anthesis of spikelets on the branch. The pattern ofdevelopment was hierarchical with each successive branch dominatingthe one immediately below it and hence, the measure of developmentincreased in an acropetal fashion from the bottom to the topin all varieties. However, in comparison to the developmentallyadvanced distal branches, the branches at the proximal regionhad the potential to generate larger numbers of spikelets, althoughactual potential to produce grains in them was quite poor. Almost2 weeks prior to mean anthesis, the gradient in assimilate concentrationof the primary branches was found to increase acropetally frombottom to top and correlated negatively with the developmentalscore (high score indicates less development and vice versa).During the following week, the situation reversed and a higherconcentration of assimilates was found in the lower branchesthan in the upper. Subsequent observations taken before meananthesis showed assimilate contents to be correlated positivelywith the developmental score. The role of assimilates in spikeletdevelopment on the primary branches has been discussed and itis concluded that there is no clear causative relationship betweenassimilate concentration and spikelet development. In the postanthesis period, little difference in assimilate concentrationof the branches was observed. The presence of a higher concentrationof assimilates did not help spikelet survival on the proximalbranches any more than that on the distal. Key words: Rice, spikelet, primary branch, anthesis, assimilates     

Cytogenetics of a factor for syncyte formation and male sterility in Pennisetum americanum

Summary Male sterility in Pennisetum americanum (L.) Leeke, inbred line IP 482, was found to be inherited as a monofactorial recessive phenotype. Homozygosity for the gene designated ms 2, produced in addition to pollen abortion, plasmodial tapetum, plasmodial pollen mother cells, delayed and asynchronous meiotic development, desynapsis and blockage of meiosis. Plasmodial PMCs resulted from the fusion of PMCs at pachytene.     

New sources of dwarfing genes in pearl millet (Pennisetum americanum)

Summary Thirteen naturally occurring dwarf lines of pearl millet [Pennisetum americanum (L.) Leeke], identified from the world collection, varied for several morphological and agronomic characters. Extreme dwarfs were characterized by a tufted growth habit which could be distinguished from the time of germination, while the other dwarf lines could be distinguished only after anthesis. The F₁ hybrids between the tall and dwarf genotypes were tall, indicating that dwarfness is a recessive trait. In 10 out of the 13 crosses, the F₂ segregation ratio was three tall to one dwarf (31) suggesting that the dwarfness is controlled by a single recessive gene, while the height differences in 3 of the dwarfs (IP 8056, IP 8210 and IP 8214) were controlled by more than one gene as they showed continuous variation for plant height in F₂. When the remaining 10 single gene dwarfs were crossed to either d ₁ (Tift 238) or d ₂ (Tift 23 DB) dwarfs, only 2 crosses produced tall F₂ hybrids and they segregated for height in F₂ indicating that these 2 dwarfs are non-allelic to d ₁ and d ₂. Reciprocal crosses of these 2 dwarfs produced tall F₁ hybrids and showed a dihybrid segregation of 934 in F₂ indicating that the dwarfing genes of these 2 parents are non-allelic to each other. These non-allelic dwarfs were assigned the gene symbols d ₃ (IP 10401), and d ₄ (IP 10402).Submitted as J.A. No. 429 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)     

Comparative Proteomic Analysis Reveals Nitrogen Fertilizer Increases Spikelet Number per Panicle in Rice by Repressing Protein Degradation and 14-3-3 Proteins

The spikelet number per panicle is established in the early stages of panicle development. Nitrogen fertilizer application before panicle initiation is known to increase spikelet number, which is one of the most important traits in rice productivity determination. However, the basic proteomic mechanism remains poorly understood. The present study shows that nitrogen fertilizer significantly increased spikelet number and grain yield in rice. Proteomic variations were further analyzed in young panicles at the secondary panicle branch initiation and spikelet meristem initiation under nitrogen fertilizer treatment. Proteomic analysis identified 63 proteins with significant differential accumulation in young panicles under nitrogen fertilizer treatment. Proteolysis represents the largest functional category, which suggests that protein degradation is an important pathway in the response to nitrogen fertilizer. Importantly, nitrogen fertilizer significantly reduced 14-3-3 proteins, which interact with key enzymes associated with carbon and nitrogen metabolism, and the rice FT homologue Hd3a. Real-time PCR revealed that Hd3a signaling is also repressed by nitrogen fertilizer in leaves. This study contributes to a better understanding of the regulation of nitrogen fertilizers in the flowering pathway leading to panicle development. The identification of novel genes provides new insight into the profound impacts of nitrogen fertilizer on panicle development in rice.     

Structural Changes of the Grain Associated with Black Region Formation in Pennisetum americanum

The structure and ontogeny of grains of Pennisetum americanumare described with particular reference to the black regionon the abgerminal surface of the grain. Darkly pigmented materialwas deposited in the cells of the chalazal pad at black regiondevelopment. This colour development was associated with thecrushing of the transfer cells of the basal endosperm by theembryo and the cessation of transfer of ¹⁴C-labelled assimilateinto the grain. It is proposed that the growth of the embryointo the basal endosperm transfer cells and the subsequent accumulationof the pigmented material are the mechanisms by which graingrowth is halted.     

Collection and evaluation of Pearl Millet (Pennisetum americanum) Germplasm from Ghana

An expedition to Ghana was undertaken during August 1981 to collect mainly the early-maturing pearl millet, Pennisetum americanum. The collection team travelled extensively in most of the pearl millet-growing areas of the eastern and northern provinces of Ghana. The mission was planned to coincide with harvesting so that early-maturing landraces could be obtained from farmers’ fields. Seed samples of late-maturing pearl millet were also obtained from local markets. Early-maturing pearl millet is traditionally intercropped with groundnut (Arachis hypogaea), sorghum (Sorghum bicolor) or late-maturing pearl millet. Pearl millet grain is used in several traditional food preparations: thick porridge called tô, a thin, fermented porridge calledkoko, and a deep-fried pancake calledmarsa. Landrace populations grown by the farmers were mixtures of several types. The material collected varied considerably for shapes, sizes and colors of spikes and grains. Of the 284 samples collected, 227 were grown in a uniform nursery at Patancheru: they flowered in 39–140 days, grew 120–315 cm tall, spikes were short (6–53 cm) and conical, grains were large, globular and gray with starchy endosperm. The samples belong to race globosum and serve as a good source of genes for earliness and large-grain size.     

Trisomic categories in pearl millet (Pennisetum americanum (L.) Leeke)

Summary In pearl millet [Pennisetum americanum (L.) Leeke], in the open pollinated and crossed progenies of autotriploids, desynaptics and translocation heterozygotes, two primary trisomics, one each of secondary and tertiary trisomics, two primary trisomics with interchanges, two interchange secondary trisomics, and three interchange tertiary trisomics were located. These categories were determined on the basis of chromosomal associations formed at meiosis. In one other trisomic, its category, whether tertiary or interchange trisomy, could not be determined. Some of these categories, like the secondary trisomy and interchange tertiary trisomy, are reported for the first time.     

Distribution of Xiphinema americanum and Related Species in North America

All species of the Xiphinema americanum-group and their synonyms are listed. The North American species reported are listed by state or province. Among these species, X. rivesi has the most widely reported distribution. Six species (X. diffusum, X. floridae, X. laevistriatum, X. luci, X. shell, and X. tarjanense) have been reported from only Florida. The reports of X. pachtaicum, X. sheri, and X. luci did not include morphometrics and need to be confirmed; X. brevicolle from California was identified before Lamberti and Bleve-Zacheo described 15 new species in 1979 and similarly needs to be confirmed. Because of the proliferation of species in this group, reports of X. americanum (sensu stricto) before 1979 are questionable. Extraction techniques for longidorids are discussed.     

Light-Induced Chloroplast [alpha]-Amylase in Pearl Millet (Pennisetum americanum)

In pearl millet (Pennisetum americanum) seedlings light induces the appearance of a leaf [alpha]-amylase isozyme. The leaf [alpha]-amylase isozyme was present in enriched amounts in isolated chloroplast but it could not be detected in isolated etioplasts. The chloroplast [alpha]-amylase was present in both mesophyll and bundle-sheath chloroplasts. Preliminary characterization indicated that molecular properties of chloroplast [alpha]-amylase were like those of a typical [alpha]-amylase. The plastidic [alpha]-amylase had a molecular mass of 46 kD, pH optimum of 6.2, required Ca2+ for activity and thermostability, but lost activity in the presence of ethylenediaminetetracetate. Plastidic [alpha]-amylase activity after sodium dodecyl sulfate-polyacrylamide gel electrophoresis could be renatured in situ by Triton X-100. Western blot analysis demonstrated that this protein was antigenically similar to a maize seed [alpha]-amylase. In vivo [35S]methionine labeling of bundle-sheath strands isolated from light-grown leaves followed by immunoprecipitation revealed that bundlesheath strands synthesized plastidic [alpha]-amylase de novo.     

Enhanced plant regeneration in pearl millet (Pennisetum americanum) by ethylene inhibitors and cefotaxime

Cefotaxime, a cephalosporin antibiotic, and different ethylene inhibitors, such as silver nitrate, cobalt chloride, nickel chloride and O-acetyl salicylic acid, significantly delayed the loss of regeneration potential in embryogenic cultures of Pennisetum americanum. In the presence of these chemicals, ethylene content in the atmosphere of the culture vessel was less than that of the control. Cefotaxime, silver nitrate and O-acetyl salicyclic acid did not have any effect on callus growth based on fresh weight, while growth based on dry weight was enhanced by O-acetyl salicyclic acid.Abbreviations ASA O-acetyl salicylic acid - BA benzyladenine - CW coconut water - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - NAA -naphthaleneacetic acid - MS Murashige and Skoog     

Effect of Temperature During Various Growth Stages on Grain Development and Yield of Pennisetum americanum

In controlled temperature glasshouses plant morphology, gramdevelopment and yield of pearl millet (Pennisetum americanum)were markedly affected by temperature during three stages ofplant growth: vegetative, stem elongation, and grain development.High temperature (to 33/28 °C day/night) during all threegrowth stages lowered grain yields by reducing basal tillering,numbers of grains per inflorescence, and single grain weight.Low temperature (21/16 °C) during the vegetative stage increasedbasal tillering and, as a result, total grain yield per plant.However, low temperature during the stem elongation stage reducedspikelet fertility and influorescence length, and thereby reducedthe potential main shoot grain yield. Low temperature duringgrain development increased the grain filling period and grainyield. The rate of grain filling did not vary over the rangeof 21/16 to 33/28 °C. Although plant morphology and grainyield were markedly affected by pre-anthesis thermal environment,grain development was not. At all temperatures ethanol-solublecarbohydrates stored in the stem were depleted during earlygrain development.     

DNA and RNA Levels in Bundle Sheath and Mesophyll Cells of Pearl Millett (Pennisetum americanum)

The DNA content of bundle sheath cells and mesophyll protoplasts from the C₄ plant pearl millet (Pennisetum americanum, Tift 23DB) was determined by microspectrophotometry to be 1.8 to 2.3 and 3.2 to 4.0 picograms/nucleus, respectively. Measurement of RNA by ultraviolet spectroscopy indicated that bundle sheath cells contain twice as much RNA as mesophyll cells.