The Pseudomonas aeruginosa antimetabolite L-2-amino-4-methoxy-trans-3-butenoic acid inhibits growth of Erwinia amylovora and acts as a seed germination-arrest factor

The Pseudomonas aeruginosa antimetabolite L-2-amino-4-methoxy-trans-3-butenoic acid (AMB) shares biological activities with 4-formylaminooxyvinylglycine, a related molecule produced by Pseudomonas fluorescens WH6. We found that culture filtrates of a P.aeruginosa strain overproducing AMB weakly interfered with seed germination of the grassy weed Poa annua and strongly inhibited growth of Erwinia amylovora, the causal agent of the devastating orchard crop disease known as fire blight. AMB was active against a 4-formylaminooxyvinylglycine-resistant isolate of E.amylovora, suggesting that the molecular targets of the two oxyvinylglycines in Erwinia do not, or not entirely, overlap. The AMB biosynthesis and transport genes were shown to be organized in two separate transcriptional units, ambA and ambBCDE, which were successfully expressed from IPTG-inducible tac promoters in the heterologous host P.fluorescens CHA0. Engineered AMB production enabled this model biocontrol strain to become inhibitory against E.amylovora and to weakly interfere with the germination of several graminaceous seeds. We conclude that AMB production requires no additional genes besides ambABCDE and we speculate that their expression in marketed fire blight biocontrol strains could potentially contribute to disease control.

Ideal culture conditions for Dicyma pulvinata conidia mass production

The objective of this work was to set up ideal conditions for conidia mass production of Dicyma pulvinata. Four isolates were compared in terms of their growth and conidia production on various substrates (grains of parboiled rice, common rice, maize and wheat, besides chipped maize and rice husk), temperatures (19, 22, 25, 28 and 31ºC), growth containers (aluminum trays, polypropylene bags and Erlenmeyers) and light regimes (continuous darkness, 6 and 12 hours of light/darkness, and continuous light). Temperature effects on conidia germination capacity were also evaluated. The experiments were done in randomized complete block designs, in factorial arrangements (isolates x treatments - substrates, containers, temperatures and light regimes), with four replicates. In general, parboiled rice and polypropylene bags provided the best development of the fungus. Complete darkness and 6 hours of light increased mycelial growth, whereas continuous light favored sporulation. All tested temperatures favored the cultures of the fungus, except 31ºC. Temperatures between 19 and 25ºC ensure spore germination of more than 76%.

Development of Sclerotium rolfsii sclerotia on soybean, corn, and wheat straw, under different soil temperatures and moisture contents

The objective of this work was to evaluate the effect of moisture and temperature on the development of Sclerotium rolfsii on soybean, corn, and wheat straw. Wheat straw produced the lowest number of sclerotia. Intermediate soil moisture level (70% of field capacity), and temperatures ranging between 25-30ºC favored sclerotia development. No sclerotia were formed at temperatures between 30-35ºC, on any type of straw.

Germination and development of pecan cultivar seedlings by seed stratification

Abstract: The objective of this work was to evaluate the effect of seed stratification on germination rate, germination speed, and initial development of seedlings of six pecan (Carya illinoinensis) cultivars under subtropical climatic conditions in southern Brazil. For stratification, the seeds were placed in boxes with moist sand, in a cold chamber at 4°C, for 90 days. In the fourteenth week after sowing, the emergence speed index, total emergence, plant height, stem diameter, and number of leaves were evaluated. Seed stratification significantly improves the germination potential and morphological traits of the evaluated cultivars.

Effect of temperature on percentage of germination of canistel seeds (Pouteria campechiana)

The canistel is a fruit originated in Mexico and Central America, being introduced in Brazil in 1986. The plants present medium size, however it can reach up to 15 meters of height; the leaves measure about 10 to 25 cm; the flowers are complete and small and the fruit presents yellow coloration when ripe, with whitish pulp and sweet flavor. The propagation can be realized by seed or grafting. In view of almost total absence of information about the culture and the possibility to have a commercial cultivation, the present work, was live in which the effect of the temperature was evaluated in the percentage of germination of the seeds. It was checked that the best averages were obtained in temperature of 30ºC and the minor in 15ºC, 20ºC and 40ºC could be considerate the worst of them.

Influence of the temperature in germination of seeds of jabuticaba tree

The jaboticaba tree (Myrciaria spp.) is originated from the center-south of Brazil and presents different types. It's a medium size tree, with tendency to form a crown with great number of branches. A characteristic considered as limitant for the commercial crop is the great juvenility, advicing producing good rootstocks of seedlings and graft wanted varieties, and other vegetative processes. With the purpose of evaluating the effect of temperature on germination of three clones of jaboticaba tree, was carried out a laboratorial research. It was observed influence of the temperature on germination. The highest percentage of germination was obtained at low temperature (15ºC and 20ºC). When it was used the temperature of 35ºC, two clones had only 8% of germination, while the other one was verified 35%. These values show the possibility of the ocurrence of variability among the clones of jaboticaba tree.

Caracterització del comportament reològic del suc de taronja concentrat a baixes temperatures. Efecte del procés de clarificació

Els sucs de taronja són els de major demanda dins el mercat espanyol i en la majoria de mercats a nivell mundial. Generalment, aquests sucs es comercialitzen amb polpa en suspensió i amb un contingut en sòlids solubles al voltant de 10-12ºBrix. No obstant, per a facilitar el transport i conservació durant l’emmagatzematge, s’obtenen concentrats en forma industrial, i posteriorment es dilueixen afegint aigua fins a la concentració requerida. Les indústries també obtenen sucs clarificats i concentrats que serveixen, entre d’altres, per a preparar mescles. Els sucs concentrats s’obtenen per extracció o premsat del suc i posterior clarificació i concentració mitjançant una etapa d’evaporació, assolint-se finalment productes al voltant dels 65ºBrix. En el procés d’elaboració el suc canvia contínuament de contingut en sòlids solubles i és sotmès a diverses temperatures, motius pels quals variaran les seves propietats, que depenen en gran mesura d’aquests dos paràmetres. Aquest treball d’investigació descrit fins ara, es complementarà amb l’estudi de les alternatives de tecnologia i enginyeria disponibles en la fabricació del suc de taronja concentrat. Aquesta tasca servirà per aprofundir en el coneixement tant del producte objecte de l’estudi com de la seva producció, a més a més d’aplicar sobre un cas concret els coneixements adquirits al llarg dels cinc anys de formació en el camp de l’enginyeria alimentària.

Influence of the substrate in germination of lychee seeds

The lychee is, all over the world, considered as the "queen of the fruits" due to the delicacy of its appearance and flavor. Although it was only recently that it started to have economical importance in Brazil, the lychee is already calling the attention of numerous farmers, mainly those who cultivate citric fruits and/or sugarcane in the State of São Paulo, due to the constant and at the same time growing necessity of finding new alternative crops. Considering that the commercial cultivation of lychee plants in the field requires the previous obtainment of rootstocks viewing to reduce the genetic variability and the length of the juvenile period displayed by plants resulting directly from the seeds, finding ways to improve the germination performance of lychee seeds for the production of rootstock plants is of considerable economic importance. Thus, the objective of this experiment was to test five substrates for the germination of lychee seeds: (1) vermiculite, (2) washed sand, (3) filter paper, (4) carbonized rice hull, and (5) sphagnum. The results showed that the period of time required by a lychee seed to germinate is a short one thus reinforcing the importance of providing a suitable substrate for the germination to take place. It was found that the substrates which apparently allowed the best combinations of water and oxygen availability for the seeds - washed sand and carbonized rice hull - were those leading to the fastest and highest germination values.

A germination study of herbicide-resistant field poppies in Spain

Field poppy, Papaver rhoeas L., is a very common weed in winter cereals in North-Eastern Spain. Its control is becoming difficult due to expanding herbicide resistance. To control field poppies there are alternative strategies such as non-chemical control that take into account the weed emergence period. However, there is a lack of knowledge of P. rhoeas emergence patterns in semi-arid conditions. Thus, here we conducted pot experiments on the emergence of P. rhoeas. We aimed to describe the emergence period and to quantify the emergence of a susceptible and of a herbicide-resistant P. rhoeas population at two locations in Catalonia, Spain, from 1998 to 2001 and until 2004 at one of them. Therefore, pots containing seeds of both populations were established at the two locations and emergence was recorded monthly. We studied the origin of the population, the sowing location, the effect of cultivation and the sowing year. First, we found that the main emergence peaks in our experiments occurred in autumn, accounting for between 65.7 and 98.5% of the annual emergence from October to December, and only little emergence was recorded in spring. This emergence pattern is different from those found in the literature corresponding to Northern European countries, where in some cases main flushes occur only in autumn, in spring and winter or only in spring. The emergence was mainly affected by cultivation, but the effect of light stimulus was observed several months later. As a consequence, cultivation should be done in early autumn, promoting emergence during the whole autumn and winter so that emerged seedlings can be controlled before sowing a spring crop. Second, most experiments showed that the emergence was significantly higher in the first autumn than in the following seasons, e.g. 4.1% emergence in the first year and only 2.1, 2.3, 0.5 and 0.6% new emergence at one of the locations for the second, third, fourth and fifth years. Thus, after having a severe P. rhoeas infestation causing a big seed rain, emergence should be stimulated by autumn cultivation in the following season and seedlings controlled by trying to deplete the soil seed bank as much as possible. Despite the fact that emergence will be staggered throughout several years and that there was a significant relationship between rainfall and emergence, so that dry years will cause a smaller emergence rate of the weed, these findings define a cultural management strategy to reduce P. rhoeas infestations and to contribute to integrated weed management strategies combining it with other tools.

Germination : a means to improve the functionality of oat

Selostus: Idättämällä voi muokata kaurasta uudenlaisia elintarvikeraaka-aineita

Evaluation of winter temperatures on apple budbreak using grafted twigs

Temperature is the main climate factor related to induction, maintenance and dormancy release in apple (Malus domestica Borkh.). The inadequate chilling exposure in apples causes budbreak problems, resulting in decrease in yield potential. Thus, the knowledge of physiological principles and environmental factors determining the dormancy phenomenon, especially winter temperature effects, it is necessary for the efficient selection of cultivars in a productive region. In addition, it is indispensable to adapt the orchard management aiming to decrease the problems caused by lack chilling during winter. The objective of this study was to evaluate the influence of different thermal conditions during the dormancy period on budbreak of apple cultivars. One-year-old twigs of 'Castel Gala' and 'Royal Gala' cultivars, grafted on M7 rootstock, were submitted to temperatures of 5, 10 and 15ºC for different exposure periods (168; 336; 672; 1,008 and 1,344 hours). After treatments execution, the plants were kept in a greenhouse at 25ºC. Budbreak was quantified when accumulated 3,444; 6,888; 10,332; 13,776; 17,220 and 20,664 GDHºC after temperature treatments. The cultivars responded differently to temperature effect during the winter period. The temperature of 15ºC during winter shows a greater effectiveness on 'Castel Gala' apple budbreak while in the 'Royal Gala' apples the temperatures of 5 and 10ºC show better performance. 'Castel Gala' cultivar (low chilling requirement) may supply its physiological necessities, may be capable to budburst, even when subjected to higher temperatures in relation to 'Royal Gala' apples (high chilling requirement).

Effect of GA3, KNO3, and removing of basal point of seeds on germination of sweet granadilla (Passiflora ligularis Juss) and yellow passion fruit (Passiflora edulis f. flavicarpa)

Passiflora seeds germinate erratically presenting difficulties for their handling in a greenhouse. The effect of removing of basal point of seeds (RB) and pre-imbibition of seeds of sweet granadilla and yellow passion fruit in 50, 100, 200, and 400 mg mL-1 solutions of gibberellic acid (GA3) or 0.1% KNO3 solution was studied. The experiment was conducted in greenhouses in La Plata, Colombia. Two accessions PrJ1 and PrJ2 of sweet granadilla were evaluated. There were calculated the final percentage of germination (PG), mean germination time (MGT), and the mean germination rate (MGR). The leaf area and dry mass of seedlings were measured 22 days after sowing (das); with this data, specific leaf area and relation root/shoot were calculated. In all cases, the highest germination percentages were achieved treating seeds with KNO3 (89, 92, and 87% for yellow passion fruit, PrJ2, and PrJ1, respectively), but the increase in MGR (3.3 germinated seeds per day) and the decrease in MGT (16 days) were only significant for PrJ1. RB had a significant reduction of PG in all cases (28, 12, and 33% for passion fruit, PrJ2 and PrJ1, respectively). With the increase in the concentration of GA3, PG was reduced for two accessions of sweet granadilla, for yellow passion fruit this trend was not clear, no treatment with GA3 showed significant differences with the control. Leaf area (24.07 cm2) and dry mass of seedlings (135 mg) were significantly higher than seeds previously treated with KNO3 only for PrJ1.The solution of KNO3 0,1% is recommended to improve the germination and initial growth of granadilla seedlings.

In vitro pollen germination and pollen viability in passion fruit (Passiflora spp.)

The use of Passiflora species for ornamental purposes has been recently developed, but little is known about pollen viability and the potential for crossing different species. The objective of this study was to evaluate the pollen viability of six Passiflora species collected from different physiological stages of development through in vitro germination and histochemical analysis using dyes. The pollen was collected in three stages (pre-anthesis, anthesis and post-anthesis). Three compositions of culture medium were used to evaluate the in vitro germination, and two dyes (2,3,5-triphenyltetrazolium chloride, or TTC, and Lugol's solution) were used for the histochemical analysis. The culture medium containing 0.03% Ca(NO3) 4H2O, 0.02% of Mg(SO4 ).7H2O, 0.01% of KNO3, 0,01% of H3BO3, 15% sucrose, and 0.8% agar, pH 7.0, showed a higher percentage of pollen grains germinated. Anthesis is the best time to collect pollen because it promotes high viability and germination. The Lugol's solution and TTC dye overestimated the viability of pollen, as all accessions showed high viability indices when compared with the results obtained in vitro.