Plant responses to pathogen attack: molecular basis of qualitative resistance

Pathogens attack plants to assimilate nutrients from them. All plant species have succeeded in overcoming pathogenic attack; therefore disease condition is not the rule but the exception. A co-evolutionary battle has equipped plants with sophisticated defense mechanisms and cognate pathogens with a corresponding arsenal of counter strategies to overcome them. Traditionally, plant-pathogen interaction has been associated with molecules involved in recognition processes giving rise to models such as the "Zig-zag Model". However, this model is being re-evaluated because it is not consistent with the complexity of the interaction. Current models propose a holistic view of a process where the response is not always determined by the interaction of two molecules. This review discusses the main aspects related to qualitative responses in the plant-pathogen interaction and the new proposed models

The greenhouse gas balance of the oil palm industry in colombia: a preliminary analysis. ii. greenhouse gas emissions and the carbon budget

In the preceding paper we examined carbon sequestration in oil palm plantations and in mill products and by-products as part of a study of the greenhouse gas balance of palm oil production in Colombia, showing how this has changed over time. Here, we look at the opposing processes of greenhouse gas (GHG) emission and calculate the resulting net carbon budget for the industry. The main emission sources, in decreasing order of magnitude, assessed using ‘default’ or ‘most probable’ options, were found to be land use change (40.9% of total), mill methane production (21.4%), direct use of fossil fuel (18.5%), indirect use of fossil fuel (11.9%) and nitrous oxide production (7.3%). The total (gross) emissions, expressed in carbon equivalents (Ceq.), were less than the amount of sequestered carbon, resulting in a positive net Ceq. balance. All oil palm growing regions showed a net gain with the exception of the western zone, where emissions due to land use change were judged to be substantial. Of the 11 alternative scenarios tested, only three resulted in Ceq. balances lower than the default and only two gave a negative balance

The greenhouse gas balance of the oil palm industry in colombia: a preliminary analysis. i. carbon sequestration and carbon offsets

Colombia is currently the world’s fifth largest producer of palm oil and the largest producer in South and Central America. It has substantial areas of land that could be used for additional oil palm production and there is considerable scope for increasing yields of existing planted areas. Much of the vegetation on land suitable for conversion to oil palm has a low biomass, and so establishing oil palm plantations on such land should lead to an increase in carbon stock, thereby counteracting greenhouse gas (GHG) emissions responsible for global warming. The first part of this study examines changes in carbon stock in Colombia resulting from expansion of oil palm cultivation together with factors (offsets) that act to minimize carbon emissions. The results are subsequently used to construct a net GHG balance

Estimation of transpiration in oil palm (Elaeis guineensis Jacq.) with the heat ratio method

Sap flow sensors were installed on the leaf petioles of 5-year-old oil palms (Elaeis guineensis Jacq.) to measure the xylem water flow for 12 days based on the heat ratio method (HRM). It was found that young leaves have higher sap flow rates, reaching values of over 250 cm3 h-1, and that sap flow fluctuations are directly related to weather conditions, particularly the vapor pressure deficit (VPD) component. It was observed that the sap flow rates remained constant and very close to 0 cm3 h-1 between 18:00 and 6:00 h and that the upward and downward movement of sap was faster during the day, with peak levels between 9:00 and 16:00 h. Under the evaluation conditions, the oil palm crop transpiration was estimated to be 1.15 mm H2O/ha-day. The HRM is a highly repeatable method and an useful tool to quantify the total oil palm transpiration. It could potentially be applied to irrigation

Determinación y aplicación de poliaminas en especies vegetales de interés agrícola y forestal

Se realizaron diferentes ensayos para determinar el contenido y el efecto de las poliaminas (PA), putrescina, espermidina, espermina y cadaverina en los maices colombianos (Zeamayz), MB 510y MB 513 yen plántulas dormantes de Sietecueros, (Tibouchina lepidota) de varias edades. Se determinaron las PA en mazorcas de los dos maices mediante Cromatografía líquida de Alta Resolución (HPLC) durante la formación del óvulo, y el cuajado del grano. La putrescina fue la PA más concentrada en las mazorcas de los dos tipos de maíz, seguida de la espermidina y la espermina. La cadaverina se detectó, pero con valores no medibles. Las PA aplicadas sobre cultivos de maíz modificaron los patrones de crecimiento en las dos variedades utilizadas lográndose el desarrollo de mazorcas que normalmente no llenan grano, al igual que incrementos en el tamaño de las mazorcas y el número de granos llenos por mazorca. En plantas de maíz afectadas por heladas (temperaturas de -3°C/6 hrs.), el crecimiento en altura se suspendió, el follaje sufrió que maduras y disminuyóel número y tamaño de las mazorcas que formaron grano. Los tratamientos con PA revirtieron el efecto causado por la helada manteniéndose el crecimiento de las plantas y además se activaron mazorcas que normalmente no se desarrollan con lo cual se alcanzaron rendimientos superiores a los testigos.Different experiments in order to determine the polyamines (PA) putrescine (Put), spermidine, (Spd), spermine (Spm) and cadaverine (Cad) effect and concentration in corn (Zea maysJ cv. M8 510, c.v. M8 513 and a regional type; and in "Sietecueros" (Tibouchina lepidata) seedlings were made.PA were determined during ear of corn formation by High Performance Liquid Chromatography (HPLC). Put was the most abundant followed by Spd and Spm. Cad was detected but with unmeasurable values. Applied PA modified growth patterns of regional corn and so, ear of corns that normally don't fill out grain, was developed. Besides, there was sizeincrease and the number of grains in each ear of corn was higher. In corn plants, affected by chilling (_30 C/6 Hr), height growth was suspended, leaves were burn out and the number and size of corn ears decreased. PA treatments reverted the negative effect caused by chilling, keeping plant growth normal; furthermore, normally inactive ear of cornswere released, resulting in higher grain yield than in controls.In slow growing "Sietecueros" seedlings, PA applications released plant growth, reaching more than 100% of height increase in treated seedlings in relation to control

Changes in polyamine content are related to low temperature resistance in potato plants

Polyamine content and variation within a 48 hour simulated freezing stress were determined in plants with different low temperature resistance. Genotypes Solanum acaule, Solanum phureja, transgenic Solanum tuberosum c.v. Desiree with antifreezing trans-genes from Winter Flounder and the clone 88-35-7 (tbr- (atzimba) x (acl x phu ccc8l) were used for the experiment. Tolerant species 5. acaule was the only one that survived freezing stress (80% surviving tissue) the others had more than 50% of dead tissue by the end of the experiment. Clone 88-35-7 died slower than S. phureja and transgenic plants of Desiree. This response was related to free putrescine and free spermidine titters of 5. acaule plants and in less extend in clone 88-35-7 plants. Polyamine concentration was low and stable in sensitive plants (5. phureja and Desiree) within freezing condition. Soluble bound forms ofpolyamines were the source for Put and Spm increase in 5. acaule and 88-35-7 plants. As a result, soluble bound polyamine titer decreased with the freezing stress.En plantas de Solanum acaule, Solanum phureja, Solanum tuberosum c.v. Desireé, transformada con un gen que codifica para proteínas anticongelantes del pez lenguado del Ártico, y el clon 88-35-7 de genealogía (tbr-(atzimba) x (ad x phu ccc81), genotipos de papa con diferente grado de tolerancia a las temperaturas bajas, se determinó la variación en el contenido de poliaminas (PA) durante una helada simulada en fitorrón. La especie tolerante (5. acaule) fue la única que sobrevivió al tratamiento de temperaturas bajas (80% de tejido vivo), las demás especies tuvieron más de un 50% de muerte del tejido al final del experimento. El clon 88-35-7 tuvo una muerte de los tejidos más lenta que S. phureja y que Desireé. La supervivencia de los tejidos estuvo relacionada con los incrementos de los niveles de putrescina (Put) y espermina (Spm) libres observados en S. acaule y en menor medida en el clon. Los valores de PA en las plantas susceptibles (S. phureja y Desire transgenica) permanecieron bajos y constantes durante todo el tiempo de la condición extrema. La Fuente para el incremento en concentración de Put y Spm en S. acaule y en el clon 88-35-7 al parecer estuvo constituida por las formas ligadas solubles de las dos fitohormonas, que disminuyeron en la medida que avanzaba el tratamiento de frio

Chlorophyll a fluorescence and leaf temperature are early indicators of oil palm diseases

Bud rot (BR) caused by Phytophthora palmivora and lethal wilt (LW) whose causal agent is unknown, are two diseases currently posing a threat to the oil palm (Elaeis guineensis. Jacq) industry. BR, first reported in 1964, has destroyed more than 85,000 ha. LW, first reported in 1994 in the Llanos Orientales in Colombia, has destroyed more than 5,000 ha. Chlorophyll a fluorescence is useful as a provider of information about the efficiency of the photosynthetic process when plants are subjected to biotic or abiotic stresses. Oil palms affected by BR and LW showed anomalies in the photosynthetic system, manifested by reductions in Fv/FM and ΦPSII. Changes in ΦPSII, variable fluorescence yield (Fv) and maximum fluorescence in light-adapted leaves (FM’) were observed from the start of BR infection. The most sensitive and early indicators of LW disease were leaf temperature and basal fluorescence (F0). Fv/F0 significantly changed in diseased palms, indicating problems with movement of electrons through the electron transport chain. Leaf temperature changed in response to both diseases, but variation was greater in LW. We concluded that damage to the photochemical system caused by the diseases affected the processes by which the plant captures and transports energy, causing a physiological imbalance in the plant reflected in the observed variations in chlorophyll a fluorescence and leaf temperature. The two parameters began to change early in the onset of BR and before visual symptoms appeared in LW, which is very important to the management of both diseases, the foundation of which is early detection

Impacts of the dry season on the gas exchange of oil palm (iElaeis guineensis/i) and interspecific hybrid (iElaeis oleifera/i x iElaeis guineensis/i) progenies under field conditions in eastern Colombia

Elaeis guineensis palms and its interspecific hybrid (E. oleifera × E. guineensis) were planted in 2004 in the Cuernavaca farm of Unipalma S.A., located in the municipality of Paratebueno Cundinamarca, Colombia). The palms were planted in two fields: Mecasaragua and Aurora. The first field has never been irrigated, and the second one (Aurora) has always been floodirrigated during the dry season according to the parameters of the plantation. In this study, physiological parameters (gas exchange and water potential) were assessed in three seasons of the year 2013 (dry season, dry-to-wet transition season and wet season). Significant gas exchange differences were found among the seasons in the field with no irrigation (Mecasaragua). Likewise, differences between the genetic materials were observed during the dry season. For example, the hotosynthesis decreased by 75% compared with the palms planted in the irrigated field. No differences among seasons or materials were found in the irrigated field (Aurora). E. guineensis palms were more sensitive to water stress compared with the O×G interspecific hybrid. Both genetic materials responded rapidly to the first rains by leveling their photosynthetic rates and demonstrated an excellent capacity to recover from water stress

Physiological responses of oil palm (Elaeis guineensis Jacq.) seedlings under different water soil conditions

Water supply is the main yield-limiting factor of oil palm crops. A water deficit affects virtually all aspects of metabolism and plant structure, while a water excess leads to waterlogging, an abiotic stress that affects crop production because of a reduction of oxygen in the soil. To determine the effect of water stress on the physiology of oil palms (Elaeis guineensis) during the nursery stage, clones from three embryogenic lines of three different ortets (LE 33-7, LE 28-59 and LE 16-79) were subjected to four water conditions (moderate deficit, field capacity, partial and continuous waterlogging) for 60 days under a completely randomized split-plot design with four replications. The gas exchange, vegetative growth and nutrient content variables were evaluated. There was no interaction between the water conditions and embryogenic lines for any variable. The moderate water-deficit stress significantly reduced the stomatic conductance, photosynthesis, transpiration and growth. Under waterlogged conditions, the seedlings developed root aerenchyma and pneumatophores as adaptation mechanisms, and their gas exchange or their micronutrient reduction and assimilation processes (with the exception of copper) were not affected. However, under permanent waterlogging, the seedlings had poor growth because of higher leaf respiration rates and probably pneumatophore maintenance and imitations in the absorption and transport of macronutrients. while the plants under partial waterlogging exhibited a growth pattern similar to that observed under optimal soil moisture conditions

CO2 soil emission under different methods of oil palm replanting

Colombian oil palm plantations have started a largescalereplanting phase. The replanting process has an effect onthe disposal of biomass, plant health management, and agroecological conditions due to the disturbance that is generated.This document addresses soil respiration (CO2 flux) as a responsevariable of crop replanting. Seven renovation methods used inColombia were tested. The measurements were taken over timeafter the disturbance and planting of the new crop. This study wascarried out in the municipality of Tumaco between August of 2009 and June of 2011 using 7 methods of renovation and 4 stages of crop development. The CO2 flow was measured at 12 points in each plot. There were no significant differences for the CO2 emission among the replanting methods. The average value for respiration was 929 mg CO2 m-2 h-1 (± 270.3); however, significant differences were found over time.This response was not related to fluctuations of soil temperatureand moisture; therefore, there should be an associated responseto biotic factors (microbial organisms) not established in thisstudy. The values suggested that the soil of the plots under areplanting process emitted considerable quantities of carbon intothe atmosphere, but the emissions declined over time and, in turn,were offset by the photosynthesis of the new crop (14 μ CO2 m-2s-1 ± 1.4, data not shown), creating an overall positive carbon balance