Endoreduplication Occurs during Pod Wall Development in Temperate Grain Legumes

Differentiation to a specialized function in plant tissue isassociated with an increase in the DNA content of the cellsover the diploid state. Using flow cytometry, ploidy levelswere assessed during pod development in three white lupin genotypesunder three environmental conditions and in other lupin speciesand temperate grain legumes in one environmental condition.Endoreduplication was found in the pod walls of all genotypesstudied. Higher ploidy levels coincided with maximal growthof the pod. DNA replication was not related to the proportionof the pod that comprised walls. Endoreduplication also occurredin other temperate grain legumes with at least two DNA duplicationsduring the development of the pod walls. The biological significanceof endoreduplication in the pod walls of grain legumes is unknown,but could be related to the storage function of these organs.Copyright2000 Annals of Botany Company Lupinus species, Pisum sativum, Phaseolus vulgaris, Vicia faba, pod wall development, ploidy level, flux cytometry, Bis-benzimide Hoechst 33258     

Variability in Xanthomonads of Grain Legumes

Pulse xanthomonads could not be differed on the basis of their bacteriological propertries. Colonies from cowpea, mungbean, guar, and bean showed differences in virulence related to the degree of mucoidness than to the rate of multiplication. Very weakly virulent mutants of the bean fuscous pathogen produced distinctive reaction in bean pods. White mutants were as virulent as their yellow forms.     

Methyl Jasmonate Reduces Grain Yield by Mediating Stress Signals to Alter Spikelet Development in Rice

Jasmonic acid (JA) is involved in plant development and the defense response. Transgenic overexpression of the Arabidopsis (Arabidopsis thaliana) jasmonic acid carboxyl methyltransferase gene (AtJMT) linked to the Ubi1 promoter increased levels of methyl jasmonate (MeJA) by 6-fold in young panicles. Grain yield was greatly reduced in Ubi1:AtJMT plants due to a lower numbers of spikelets and lower filling rates than were observed for nontransgenic (NT) controls. Ubi1:AtJMT plants had altered numbers of spikelet organs, including the lemma/palea, lodicule, anther, and pistil. The loss of grain yield and alteration in spikelet organ numbers were reproduced by treating NT plants with exogenous MeJA, indicating that increased levels of MeJA in Ubi1:AtJMT panicles inhibited spikelet development. Interestingly, MeJA levels were increased by 19-fold in young NT panicles upon exposure to drought conditions, resulting in a loss of grain yield that was similar to that observed in Ubi1:AtJMT plants. Levels of abscisic acid (ABA) were increased by 1.9- and 1.4-fold in Ubi1:AtJMT and drought-treated NT panicles, respectively. The ABA increase in Ubi1:AtJMT panicles grown in nondrought conditions suggests that MeJA, rather than drought stress, induces ABA biosynthesis under drought conditions. Using microarray and quantitative polymerase chain reaction analyses, we identified seven genes that were regulated in both Ubi1:AtJMT and drought-treated NT panicles. Two genes, OsJMT1 and OsSDR (for short-chain alcohol dehydrogenase), are involved in MeJA and ABA biosynthesis, respectively, in rice (Oryza sativa). Overall, our results suggest that plants produce MeJA during drought stress, which in turn stimulates the production of ABA, together leading to a loss of grain yield.     

Effects of Strigolactones on Grain Yield and Seed Development in Rice

Journal of Plant Growth Regulation - Strigolactones (SLs) are well known as a class of endogenous phytohormones that regulate tiller bud outgrowth. Reduction of inorganic phosphate (Pi) induces the...     

The Development of Desiccation-tolerance and Maximum Seed Quality During Seed Maturation in Six Grain Legumes

‘Physiological maturity’, i.e. the time when seedsreach their maximum dry weight during development, occurredwhen maturation drying on the parent plant in the field hadreduced seed moisture content to approximately 60 per cent infaba bean (Vicia faba L.), lentil (Lens culinaris Medic.), chickpea(Cicer arietinum L.), white lupin (Lupinus albus L.), soya bean(Glycine max [L.] Merr.) and pea (Pisum sativum L.) The onsetof desiccation-tolerance, i.e. the ability of seeds to germinatefollowing harvest and rapid artificial drying, coincided withphysiological maturity, except in pea where it occurred a littleearlier at about 70 per cent moisture content. Maximum seedquality as determined by maximum viability, minimum seedlingabnormalities and maximum seedling size occurred in pea, chickpeaand lupin when seeds were harvested for rapid drying at physiologicalmaturity; but for maximum seed quality in the other speciesmaturation drying had to proceed further - to about 45 per centmoisture content in soya bean and to about 30 per cent moisturecontent in lentil and faba bean seed crops. Much of this variationamongst the six species, however, was due to differences inthe variation in maturity within each seed crop. Results forindividual pods showed that peak maturity, i.e. maximum seedquality following harvest and rapid artificial drying, was achievedin all six species once maturation drying had reduced the moisturecontent of the seeds to 45–50 per cent. In pea, faba beanand soya bean there was a substantial decline in viability andan increase in seedling abnormalities when harvest was delayedbeyond the optimal moisture content for harvest.     

Strategies for Improving Drought Resistance in Grain Legumes

This review distills recent information on drought resistance characteristics of grain legumes with a view toward developing appropriate genetic enhancement strategies for water-limited environments. First, the possible adaptations that allow grain legumes to better cope with drought stress are summarized. It is suggested that there are considerable gains to be made in increasing yield and yield stability in environments characterized by terminal drought stress by further exploiting drought escape, by shortening crop duration. Many traits conferring dehydration avoidance and dehydration tolerance are available, but integrated traits, expressing at a higher level of organization, are suggested to be more useful in crop improvement programs. Possible genetic improvement strategies are outlined, ranging from empirical selection for yield in droughted environments to a physiological genetic approach. It is suggested that in view of recent advances in understanding drought resistance mechanisms, the latter strategy is becoming more feasible. It is concluded that use of this recently derived knowledge in a systematic manner can lead to significant gains in yield and yield stability of the world's major grain legumes, as they are mainly grown (and will continue to be grown) under rain-fed conditions.     

Moderate Salinity Stress Reduces Rice Grain Yield by Influencing Expression of Grain Number- and Grain Filling-Associated Genes

Journal of Plant Growth Regulation - Soil salinity is an environmental stress severely impacting on rice grain yield. However, limited information is available on how salinity affects expression...     

Nitrogen Nutrition and Xylem Transport of Nitrogen in Ureide-producing Grain Legumes

Xylem sap composition was examined in nodulated and nonnodulated cowpea (Vigna unguiculata [L.] Walp.) plants receiving a range of levels of NO₃ and in eight other ureide-forming legumes utilizing NO₃ or N₂ as sole source of nitrogen. A ¹⁵N dilution technique determined the proportions of plant nitrogen derived from N₂ in the nodulated cowpeas fed NO₃. Xylem sap composition of NO₃-fed, nodulated cowpea varied predictably with the relative extents to which N₂ and NO₃ were being utilized. The ratios of asparagine to glutamine (N/N) and of NO₃ to ureide (N/N) in xylem sap increased with increasing dependence on NO₃ whereas per cent of xylem nitrogen as ureide and the ratio of ureide plus glutamine to asparagine plus NO₃ (N/N) in xylem sap increased with increasing dependence on N₂ fixation. The amounts of NO₃ and ureides stored in leaflets, stems plus petioles, and roots of cowpea varied in a complex manner with level of NO₃ and the presence or absence of N₂ fixation. All species showed higher proportions of organic nitrogen as ureide and several-fold lower ratios of asparagine to glutamine in their xylem sap when relying on N₂ than when utilizing NO₃. In nodulated (minus nitrate) cowpea and mung bean (Vigna radiata [L.] Wilczek) the percentage of xylem nitrogen as ureide remained constant during growth but the ratio of asparagine to glutamine varied considerably. The biochemical significance of the above differences in xylem sap composition was discussed.     

Effects of Grain Development and Thermal History on Grain Maturation and Seed Vigour of Pennisetum americanum

Studies were made of the viability and vigour of seeds of pearlmillet (Pennisetum americanum) harvested at different stagesof grain development and from different controlled-temperatureenvironments. Seed viability and vigour of the next generationwere dependent on the extent of grain development at harvest.Where grain had developed for only one-third of the potentialgrain-filling period before harvest, seed viability and vigourwere greatly reduced. Harvest at or after the middle of grain-fillingdid not reduce seed viability or vigour. The temperature atwhich the grains had developed did not affect seed viability,but grains that had developed at 21/16 °C (day/night) producedseedlings of greater height and dry weight than those from grainswhich had developed at higher temperatures.     

CLAVATA Signaling Ensures Reproductive Development in Plants across Thermal Environments

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氮肥基追比与灌浆中期高温胁迫对小麦产量和品质的影响

以优质强筋小麦品种‘济麦20’为供试材料,研究了不同氮肥基追比（基肥：追肥为1：1、1：2、1：5）和灌浆中期高温胁迫对小麦籽粒产量和品质的影响.结果显示,灌浆中期高温胁迫处理能显著降低小麦千粒重、籽粒产量以及籽粒的淀粉含量、支链淀粉含量、支链淀粉/直链淀粉比例,峰值粘度、稀懈值、最终粘度也相应降低,而籽粒蛋白质含量相应提高,导致淀粉品质变劣而面团的流变学特性得以改善;在基追比例1：1的基础上增大拔节期氮素追施比例,能显著提高小麦常温和高温胁迫下籽粒产量,缓解高温胁迫对小麦千粒重和籽粒产量的不良影响,而对小麦籽粒面团流变学特性及面粉的粘度指标影响甚微.研究表明,适当提高拔节期氮肥追施比例可有效减缓灌浆中期高温胁迫对小麦产量的负面影响,但对小麦籽粒品质影响较小.     

Plant Regeneration from Leaf Explants of Three Grain Legumes on Same Medium

The regeneration potential of leaves of moth bean, pigeonpea and grass pea was studied on Murashige and Skoog’s (MS) medium supplemented with various combinations of auxins and cytokinins. Regeneration of shoots was obtained mainly on MS medium supplemented with high auxin and low cytokinin levels. However, frequency of response varied not only in the three legume species but also in their varieties studied. Roots were induced on regenerated shoots by transferring them to MS basal medium. Complete plant regeneration was observed in the three legumes in a short duration of 60–70 days.     

Characterization of Bacterial Community Structure in Rhizosphere Soil of Grain Legumes

Molecular techniques were used to characterize bacterial community structure, diversity (16S rDNA), and activity (16S rRNA) in rhizospheres of three grain legumes: faba beans (Vicia faba L., cv. Scirocco), peas (Pisum sativum L., cv. Duel) and white lupin (Lupinus albus L., cv. Amiga). All plants were grown in the same soil under controlled conditions in a greenhouse and sampled after fruiting. Amplified 16S rDNA and rRNA products (using universal bacterial primers) were resolved by denaturing gradient gel electrophoresis (DGGE). Distinct profiles were observed for the three legumes with most of the bands derived from RNA being a subset of those derived from DNA. Comparing the total bacterial profiles with actinomycete-specific ones (using actinomycete-specific primers) highlighted the dominance of this group in the three rhizospheres. 16S PCR and RT-PCR products were cloned to construct libraries and 100 clones from each library were sequenced. Actinomycetes and proteobacteria dominated the clone libraries with differences in the groups of proteobacteria. Absence of β-subdivision members in pea and γ-subdivision members of proteobacteria in faba bean rhizosphere was observed. Plant-dependent rhizosphere effects were evident from significant differences in the bacterial community structure of the legume rhizospheres under study. The study gives a detailed picture of both residing and „active” bacterial community in the three rhizospheres. The high abundance of actinomycetes in the rhizospheres of mature legumes indicates their possible role in soil enrichment after the legumes are plowed into the soil as biofertilizers.     

Reproductive Development in Lolium temulentum L.: Spike Morphogenesis and Grain Set Limitations

Reproductive development in cereals is not easy to investigatebecause their quantitative response to environmental factorsmakes it difficult to synchronize the plants. In this paper,one of our aims was to assess whether Lolium temulentum strainCeres, a qualitative long-day grass, could serve as a modelof reproductive development for cereals. The morphological patternsfrom floral transition to seed set were studied. A flowering scale was established to evaluate developmentalrate during spike morphogenesis. Apex growth was found to increaseaccording to biphasic kinetics; double ridge appearance markedthe beginning of an exponential phase. Developmental progression and apical growth rate were both increasedby giving repeated long days. In contrast, the final numberof lateral spikelets (20–25) could not be manipulatedafter the beginning of long-day treatment. When plants were kept in continuous light from the beginningof induction, double ridges appeared on the fifth 24 h cycle.Spikelet initiation began in the upper mid-part of the spike,and then extended acro- and basipetally. The phase of spikeletinitiation lasted 6 d, with l?5 to 1?9 spikelets being produceddaily. Within each spikelet, florets were initiated at an averagerate of l?3 primordia per day and developed acropetally. Thefirst signs of apical site degeneration were observed in themost developed upper spikelets just before heading. Ear emergenceoccurred between the 20th and 25th cycles of continuous light;anthesis was observed 6 or 7 d later. The proportion of floretssetting grain averaged about 40%. Grains were produced mainlyin the lower spikelets while the upper mid-part of the inflorescenceshowed a much lower fertility rate. Complex developmental gradients described in this paper suggestthat L. temulentum could serve as a model of reproductive developmentin cereals, with the added advantage of flowering in responseto a single long-day. Key words: Lolium temulentum L., spike morphogenesis, spikelet number, floret number, grain set     

Copper Nanoparticle Application Enhances Plant Growth and Grain Yield in Maize Under Drought Stress Conditions

Journal of Plant Growth Regulation - Abiotic stresses, including drought, detrimentally affect the growth and productivity of many economically important crop plants, leading to significant yield...     

四种植物淬取物对尼日利亚仓贮甲虫的生物活性

Acute food shortage due to the inability to protectand preserve crops fromquality and quantity deteriora-tion arising from microbial,vertebrate and insect pestinfestations has been a pri mordial problem confrontingNigeria and other developing countries in the tropics(Talukder&Howse,1994;Adedire,2001).Insect pests cause a great deal of losses of storedfood products,especially in the tropics where foodproducts usually are susceptible to attack during thestorage phase of the crops(Sighamony et a…     

Effect of High Temperature Stress at Anthesis on Grain Yield and Biomass of Field-grown Crops of Wheat

Spring wheat (Triticum aestivumL., ‘Chablis’) wasgrown under field conditions from sowing until harvest maturity,except for a 12-d period [70–82 days after sowing (DAS)coinciding with anthesis] during which replicated crop areaswere exposed to a range of temperatures within two pairs ofpolyethylene-covered temperature gradient tunnels. At 82 DAS,an increase in mean temperature from 16 to 25 °C duringthis treatment period had no effect on above-ground biomass,but increased ear dry weight from 223 to 327 g m^-2and, at 83DAS, reduced root biomass from 141 to 63 g m^-2. Mean temperatureover the treatment period had no effect on either above-groundbiomass or grain yield at maturity. However, the number of grainsper ear at maturity declined with increasing maximum temperaturerecorded over the mid-anthesis period (76–79 DAS) and,more significantly, with maximum temperature 1 d after 50% anthesis(78 DAS). Grain yield and harvest index also declined sharplywith maximum temperature at 78 DAS. Grain yield declined by350 g m^-2at harvest maturity with a 10 °C increase in maximumtemperature at 78 DAS and was related to a 40% reduction inthe number of grains per ear. Grain yield was also negativelyrelated to thermal time accumulated above a base temperatureof 31 °C (over 8 d of the treatment from 5 d before to 2d after 50% anthesis). Thus, grain fertilization and grain setwas most sensitive to the maximum temperature at mid-anthesis.These results confirm that wheat yields would be reduced considerablyif, as modellers suggest, high temperature extremes become morefrequent as a result of increased variability in temperatureassociated with climate change.Copyright 1998 Annals of BotanyCompany Triticum aestivum, spring wheat, temperature, grain number, grain yield, root growth.     

Genetic Architecture of Delayed Senescence,Biomass, and Grain Yield under Drought Stress in Cowpea

The stay-green phenomenon is a key plant trait with wide usage in managing crop production under limited water conditions. This trait enhances delayed senescence, biomass, and grain yield under drought stress. In this study we sought to identify QTLs in cowpea (Vigna unguiculata) consistent across experiments conducted in Burkina Faso, Nigeria, Senegal, and the United States of America under limited water conditions. A panel of 383 diverse cowpea accessions and a recombinant inbred line population (RIL) were SNP genotyped using an Illumina 1536 GoldenGate assay. Phenotypic data from thirteen experiments conducted across the four countries were used to identify SNP-trait associations based on linkage disequilibrium association mapping, with bi-parental QTL mapping as a complementary strategy. We identified seven loci, five of which exhibited evidence suggesting pleiotropic effects (stay-green) between delayed senescence, biomass, and grain yield. Further, we provide evidence suggesting the existence of positive pleiotropy in cowpea based on positively correlated mean phenotypic values (0.34< r <0.87) and allele effects (0.07< r <0.86) for delayed senescence and grain yield across three African environments. Three of the five putative stay-green QTLs, Dro-1, 3, and 7 were identified in both RILs and diverse germplasm with resolutions of 3.2 cM or less for each of the three loci, suggesting that these may be valuable targets for marker-assisted breeding in cowpea. Also, the co-location of early vegetative delayed senescence with biomass and grain yield QTLs suggests the possibility of using delayed senescence at the seedling stage as a rapid screening tool for post-flowering drought tolerance in cowpea breeding. BLAST analysis using EST sequences harboring SNPs with the highest associations provided a genomic context for loci identified in this study in closely related common bean (Phaseolus vulgaris) and soybean (Glycine max) reference genomes.