Mutant alleles at the rugosus loci in pea affect seed moisture sorption isotherms and the relations between seed longevity and moisture content

Pea (Pisum sativum L.) mutant near-isogenic lines (RRrbrb, rrRbRb, rrrbrb) with lower starch but higher lipid contents, brought about by lesions in the starch biosynthetic pathway, had seed moisture sorption isotherms displaced below that of the wild type (RRRbRb). The negative logarithmic relationship between seed longevity and seed storage moisture content (%, f.wt basis), determined in hermetic storage at 65 degreesC, also differed: longevity in the mutant near-isogenic lines was poorer and less sensitive to moisture content than in the wild type (i.e. C-w was lower). The low-moisture-content limit (m(c)) to this relation also differed, being lower in the mutant near-isogenic lines (5.4-5.9%) than in the wild type (6.1%). In contrast, all four near-isogenic lines showed no difference (P >0.25) in the negative semilogarithmic relationship between equilibrium relative humidity (ERH) and seed longevity. It is concluded that the effect of these alleles at the r and rb loci on seed longevity. was largely indirect; a consequence of their effect on seed composition and hence on moisture sorption isotherms. However, this explanation could not be invoked at moisture contents below mc where differences in longevity remained substantial (RRRbRb double that of rrrbrb). Hence, these mutant alleles affected seed longevity directly at very low moisture contents.

Mutant alleles at the rugosus loci in pea affect seed moisture sorption isotherms and the relations between seed longevity and moisture content

Pea (Pisum sativum L.) mutant near-isogenic lines (RRrbrb, rrRbRb, rrrbrb) with lower starch but higher lipid contents, brought about by lesions in the starch biosynthetic pathway, had seed moisture sorption isotherms displaced below that of the wild type (RRRbRb). The negative logarithmic relationship between seed longevity and seed storage moisture content (%, f.wt basis), determined in hermetic storage at 65 °C, also differed: longevity in the mutant near-isogenic lines was poorer and less sensitive to moisture content than in the wild type (i.e. CW was lower). The low-moisture-content limit (mc) to this relation also differed, being lower in the mutant near-isogenic lines (5.4–5.9%) than in the wild type (6.1%). In contrast, all four near-isogenic lines showed no difference (P >0.25) in the negative semi-logarithmic relationship between equilibrium relative humidity (ERH) and seed longevity. It is concluded that the effect of these alleles at the r and rb loci on seed longevity was largely indirect; a consequence of their effect on seed composition and hence on moisture sorption isotherms. However, this explanation could not be invoked at moisture contents below mc where differences in longevity remained substantial (RRRbRb double that of rrrbrb). Hence, these mutant alleles affected seed longevity directly at very low moisture contents.

The competitive ability of pea-barley intercrops against weeds and the interactions with crop productivity and soil N availability

Grain legumes, such as peas (Pisum sativum L.), are known to be weak competitors against weeds when grown as the sole crop. In this study, the weed-suppression effect of pea–barley (Hordeum vulgare L.)intercropping compared to the respective sole crops was examined in organic field experiments across Western Europe (i.e., Denmark, the United Kingdom, France, Germany and Italy). Spring pea (P) and barley(B) were sown either as the sole crop, at the recommended plant density (P100 and B100, respectively), or in replacement (P50B50) or additive (P100B50)intercropping designs for three seasons (2003–2005). The weed biomass was three times higher under the pea sole crops than under both the intercrops and barley sole crops at maturity. The inclusion of joint experiments in several countries and various growing conditions showed that intercrops maintain a highly asymmetric competition over weeds, regardless of the particular weed infestation (species and productivity), the crop biomass or the soil nitrogen availability. The intercropping weed suppression was highly resilient, whereas the weed suppression in pea sole crops was lower and more variable. The pea–barley intercrops exhibited high levels of weed suppression, even with a low percentage of barley in the total biomass. Despite a reduced leaf area in the case of a low soil N availability, the barley sole crops and intercrops displayed high weed suppression, probably because of their strong competitive capability to absorb soil N. Higher soil N availabilities entailed increased leaf areas and competitive ability for light, which contributed to the overall competitive ability against weeds for all of the treatments. The contribution of the weeds in the total dry matter and soil N acquisition was higher in the pea sole crop than in the other treatments, in spite of the higher leaf areas in the pea crops.

Pseudomonas syringae pv. phaseolicola: from ‘has bean’ to supermodel

Pseudomonas syringae pv. phaseolicola causes halo blight of the common bean, Phaseolus vulgaris, worldwide and remains difficult to control. Races of the pathogen cause either disease symptoms or a resistant hypersensitive response on a series of differentially reacting bean cultivars. The molecular genetics of the interaction between P. syringae pv. phaseolicola and bean, and the evolution of bacterial virulence, have been investigated in depth and this research has led to important discoveries in the field of plant-microbe interactions. In this review, we discuss several of the areas of study that chart the rise of P. syringae pv. phaseolicola from a common pathogen of bean plants to a molecular plant-pathogen supermodel bacterium. Taxonomy: Bacteria; Proteobacteria, gamma subdivision; order Pseudomonadales; family Pseudomonadaceae; genus Pseudomonas; species Pseudomonas syringae; Genomospecies 2; pathogenic variety phaseolicola. Microbiological properties: Gram-negative, aerobic, motile, rod-shaped, 1.5 µm long, 0.7-1.2 µm in diameter, at least one polar flagellum, optimal temperatures for growth of 25-30 °C, oxidase negative, arginine dihydrolase negative, levan positive and elicits the hypersensitive response on tobacco. Host range: Major bacterial disease of common bean (Phaseolus vulgaris) in temperate regions and above medium altitudes in the tropics. Natural infections have been recorded on several other legume species, including all members of the tribe Phaseoleae with the exception of Desmodium spp. and Pisum sativum. Disease symptoms: Water-soaked lesions on leaves, pods, stems or petioles, that quickly develop greenish-yellow haloes on leaves at temperatures of less than 23 °C. Infected seeds may be symptomless, or have wrinkled or buttery-yellow patches on the seed coat. Seedling infection is recognized by general chlorosis, stunting and distortion of growth. Epidemiology: Seed borne and disseminated from exudation by water-splash and wind occurring during rainfall. Bacteria invade through wounds and natural openings (notably stomata). Weedy and cultivated alternative hosts may also harbour the bacterium. Disease control: Some measure of control is achieved with copper formulations and streptomycin. Pathogen-free seed and resistant cultivars are recommended. Useful websites: Pseudomonas-plant interaction http://www.pseudomonas-syringae.org/; PseudoDB http://xbase.bham.ac.uk/pseudodb/; Plant Associated and Environmental Microbes Database (PAMDB) http://genome.ppws.vt.edu/cgi-bin/MLST/home.pl; PseudoMLSA Database http://www.uib.es/microbiologiaBD/Welcome.html.

Two-photon excitation with pico-second fluorescence lifetime imaging to detect nuclear association of flavanols

Two-photon excitation enabled for the first time the observation and measurement of excited state fluorescence lifetimes from three flavanols in solution, which were ∼1.0 ns for catechin and epicatechin, but <45 ps for epigallocatechin gallate (EGCG). The shorter lifetime for EGCG is in line with a lower fluorescence quantum yield of 0.003 compared to catechin (0.015) and epicatechin (0.018). In vivo experiments with onion cells demonstrated that tryptophan and quercetin, which tend to be major contributors of background fluorescence in plant cells, have sufficiently low cross sections for two-photon excitation at 630 nm and therefore do not interfere with detection of externally added or endogenous flavanols in Allium cepa or Taxus baccata cells. Applying two-photon excitation to flavanols enabled 3-D fluorescence lifetime imaging microscopy and showed that added EGCG penetrated the whole nucleus of onion cells. Interestingly, EGCG and catechin showed different lifetime behaviour when bound to the nucleus: EGCG lifetime increased from <45 to 200 ps, whilst catechin lifetime decreased from 1.0 ns to 500 ps. Semi-quantitative measurements revealed that the relative ratios of EGCG concentrations in nucleoli associated vesicles: nucleus: cytoplasm were ca. 100:10:1. Solution experiments with catechin, epicatechin and histone proteins provided preliminary evidence, via the appearance of a second lifetime (τ2 = 1.9–3.1 ns), that both flavanols may be interacting with histone proteins. We conclude that there is significant nuclear absorption of flavanols. This advanced imaging using two-photon excitation and biophysical techniques described here will prove valuable for probing the intracellular trafficking and functions of flavanols, such as EGCG, which is the major flavanol of green tea.

Ethylene and 1-methylcyclopropene differentially regulate gene expression during onion sprout suppression

Onion (Allium cepa) is regarded as a nonclimacteric vegetable. In onions, however, ethylene can suppress sprouting while the ethylene-binding inhibitor 1-methylcyclopropene (1-MCP) can also suppress sprout growth; yet, it is unknown how ethylene and 1-MCP elicit the same response. In this study, onions were treated with 10 mu L L(-1) ethylene or 1 mu L L(-1) 1-MCP individually or in combination for 24 h at 20 degrees C before or after curing (6 weeks) at 20 degrees C or 28 degrees C and then stored at 1 degrees C. Following curing, a subset of these same onions was stored separately under continuous air or ethylene (10 mu L L(-1)) at 1 degrees C. Onions treated with ethylene and 1-MCP in combination after curing for 24 h had reduced sprout growth as compared with the control 25 weeks after harvest. Sprout growth following storage beyond 25 weeks was only reduced through continuous ethylene treatment. This observation was supported by a higher proportion of down-regulated genes characterized as being involved in photosynthesis, measured using a newly developed onion microarray. Physiological and biochemical data suggested that ethylene was being perceived in the presence of 1-MCP, since sprout growth was reduced in onions treated with 1-MCP and ethylene applied in combination but not when applied individually. A cluster of probes representing transcripts up-regulated by 1-MCP alone but down-regulated by ethylene alone or in the presence of 1-MCP support this suggestion. Ethylene and 1-MCP both down-regulated a probe tentatively annotated as an ethylene receptor as well as ethylene-insensitive 3, suggesting that both treatments down-regulate the perception and signaling events of ethylene.

Evaluation of the Genotoxicity of Chitosan Nanoparticles for Use in Food Packaging Films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of the genotoxicity of cellulose nanofibers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Análise da presença de agentes mutagênicos nas águas do Rio Pitimbú/RN

The Pitimbu River is located at the oriental portion of the State of Rio Grande do Norte, including three importants cities named Macaíba, Parnamirim e Natal. Although its high importance as a water source, which supplys great part of the South Zone of the Natal city, this river receives a large quantity of domestic and industrial waste water without treatment. The Pitimbu River headhas its river-head located in the city of Macaiba, goes through Parnamirim, then it flowing into at the Jiqui Lake in Natal. The aim of this study was to evaluate, qualitatively and quantitatively, the environmental quality of the Pitimbu River by genotoxicity bio-assays, which are important tools for genetics toxicological evaluation. In this work, five samples sites, distributed along the river, were used to collect water samples. Another point site, located near Jiqui lake, was used to collect drinkable water, which was treated by CAERN, the water treatment entreprise of Rio Grande do Norte. The following assays where used to evaluate the quality of these samples: Allium cepa assay; Comet assay; Micronuclei (MN) assay; and Ames test. For the Allium cepa assay, sixteen specimes where used for each water sample from the sample sites. In this assay both microscopic, like cytogenetic damage, and macroscopic aspects, as morphological variation were evaluated. Red blood cells from periferical blood of the Crenicichla menezesi native specie were used not only for the MN assay, but also for the Comet assay. These fishes were collected at different points on the Pitimbu River and the negative control was developed using fishes of the same species that were bring to the laboratory and maintained for 100 days in the optimal experimental conditions. For the Ames test, TA100, YG1042, TA98 and YG1041 strains were used in the directed method without metabolic activation. The results found by the Allium cepa assay showed that two water sample sites induced increase of mitotic index (IM). Additionally, compared to the control, all the water samples increased the chromossomal aberrations frequency and/or micronucleus. Among the sample sites, two also showed an abnormal growth rate in its root and two samples induced morphological alteration. With the MN test in red blood cells, a high frequence of MN was observed in tree sample. By comparing all the results obtained on the water sample points and with the negative control, a significant variation on the MN frequency was observed. Positive results were also observed for the same sample to water test by the Comet assay. These results allow concluding that the proposed specie Crenicichla menezesi has a good profile as a bio-indicator for the evaluation of environmental water quality and the MN and comet test can be usuful for in situ evaluation. By the Ames test, it was possible to detect the mutagenic activity on the waters from the Pitimbu River in different levels of mutagenicity. This result suggests that this river has several substances that induced changes directly to the DNA. The mechanisms involved to this phenomenon could be by both processes, by changing of the reading frame and by nucleotide substitution. These data set indicate the presence of mutagenic agents, which can represent in risk to biot and human beens

Efeito de diferentes períodos de controle das plantas daninhas na produtividade da cultura da cebola

Foi realizado um experimento em Monte Alto-SP, visando estudar os efeitos de diferentes períodos de controle das plantas daninhas sobre a produção de bulbos da cultura da cebola (Allium cepa), cultivar 'Mercedes', no sistema de transplantio. O delineamento experimental utilizado foi o de blocos ao acaso, com quatro repetições. Parte dos tratamentos experimentais foi disposta num esquema fatorial 4 x 6, em que constituíram variáveis quatro períodos em que se fez o controle (0-0, 0-7, 0-14 e 0-21 DAT) e seis períodos em que se reiniciou o controle das plantas daninhas prolongando até a colheita: 28, 42, 56, 70, 84 e 98 DAT). Duas testemunhas foram adotadas: uma com controle e outra sem controle das plantas daninhas durante todo o ciclo da cultura. Lycopersicon esculentum, Portulaca oleracea, Eragrostis pilosa e Galinsoga parviflora foram as plantas daninhas mais importantes na área. Não houve interação entre os diferentes períodos de controle das plantas daninhas. O controle inicial destas plantas deve se prolongar até 14 DAT e ser reiniciado aos 28 DAT, a fim de prevenir reduções significativas na produtividade em relação à testemunha no limpo A convivência com as plantas daninhas durante todo o ciclo da cebola reduziu a produtividade em 94,5%.

Produtividade de híbridos de cebola em função da população de plantas e da fertilização nitrogenada e potássica

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeitos de doses de nitrogênio e potássio e densidade populacional sobre a classificação de bulbos de cebola

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Crescimento da cebola em função de doses de nitrogênio, potássio e da população de plantas em semeadura direta

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Acúmulo de macronutrientes pela cebola 'Optima' estabelecida por semeadura direta

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Distribuição espacial de Phytophthora nicotianae e reação de cultivares de cebola ao fungo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)