Maturity and harvest indices in papaya Maradol

[SPA] El incremento en la producción de papaya Maradol en México crea la necesidad de generar conocimientos para mejorar su manejo poscosecha, un aspecto importante es el momento oportuno para realizar la cosecha para asegurar que los frutos maduren adecuadamente y alcancen sus atributos de calidad característicos. Los objetivos fueron conocer los cambios de los componentes de los atributos de calidad que ocurren en el proceso de maduración, conocer si estos componentes se mantienen cuando cambian las condiciones de manejo tecnológico de la parcela y determinar estados tempranos de maduración para usarlos como índices de cosecha. Se usaron frutos de dos parcelas comerciales, la parcela 1 emplea tecnología intermedia y destina su producto a mercado local, la parcela 2 se utiliza tecnología alta y destina su producto a mercado de exportación. Los frutos se recolectaron en estado inmaduro y en madurez fisiológica, se almacenaron a 23 oC hasta que llegaron a estados intermedios y madurez de consumo. Se determinaron azúcares totales, azúcares reductores, sólidos solubles totales, color y firmeza. Los azúcares y los sólidos solubles totales fueron más altos en la localidad 2 alcanzando más del 12 % de Brix en los estados de madurez de consumo. Los valores de firmeza de la pulpa fueron muy semejantes en los frutos de las dos localidades y permite diferenciar a los cuatro últimos estados de maduración. Todos los componentes del color en la pulpa (L*, a*, b*) marcan notoriamente el inicio de la maduración pero tienen la desventaja de requerir un muestreo destructivo. La escala b* permite diferenciar el inicio de la maduración en la cáscara cuando adquiere valores cercanos a 32. Los estados 1, 2 y 3 pueden ser utilizados como índices para el momento de la cosecha tanto para fines comerciales como para fines de investigación. [ENG] The increase in papaya Maradol production in Mexico creates the necessity to generate knowledge to improve postharvest handling systems. An important aspect is the determination of the exact moment to harvest in order to assure that the fruits mature properly and reach their typical attributes of quality. The objectives of the present work were to define the changes in quality attributes that occur in the process of maturation, to know if these components stay when the handling conditions change from one plantation to another and to determine early stages of maturation to use them as harvest indices. Fruits of two comercial plantations were used, plantation 1 where intermediate handling technology was used oriented to local market, plantation 2 where high handling technology was used oriented to export markets. The fruits were collected in immature and physiological maturity stages, they were stored at 23 oC until they reach the stage of intermediate consumption maturity. Total sugars, reducing sugars, total soluble solutes, color and firmness were determined. Sugars and total soluble solutes were higher at plantation 2, reaching values of 12% Brix at the stage of consumption maturity. The values of firmness of the flesh were very similar in the fruits of the two plantations and data allow the clear differentiation of four stages of maturation. All the component of the color in the flesh (L*, a*, b*) allow the confirmation of well-known marks of the beginning of maturation but they have the disadvantage to require a destructive sampling. The scale b* measured in the skin allows to differentiate the beginning of maturation when it reaches values around 32. Stages 1, 2 and 3 can be used as harvest índices for commercial aims as well as for research purposes.Se extiende el agradecimiento: al Profr. Raúl Monforte Peniche (Grupo Agropecuario Sucilá SPR de CV) por proporcionar los frutos y las facilidades para la realización de este trabajo

Multiple Effects of Cadmium on the Photosynthetic Apparatus of Avicennia germinans L. as Probed by OJIP Chlorophyll Fluorescence Measurements

The toxic effects of cadmium on the photosynthetic apparatus of Avicennia germinans were evaluated by means of the chlorophyll fluorescence transient OÐJÐIÐP. The chlorophyll fluorescence transients were recorded in vivo with high time resolution and analyzed according to the OJIP-test that can quantify the performance of photosystem II. Cadmium-treated plants showed a decrease in yield for primary photochemistry, TR 0 /ABS. The performance index of photosystem II (PSII), PI ABS , decreased due to cadmium treatment. This performance index is the combination of the indexes of three independent parameters: (1) total number of active reaction centers per absorption (RC/ABS), (2) yield of primary photochemistry (TR 0 /ABS), and (3) efficiency with which a trapped exciton can move an electron into the electron transport chain (ET 0 /TR 0 ). Additionally, the F 0 /F v registered the highest sensitivity to the metal, thus indicating that the water-splitting apparatus of the oxidizing side of PSII is the primary site of action of cadmium. In summary, cadmium affects several targets of photosystem II. More specifically the main targets of cadmium, according to the OJIPtest, can be listed as a decrease in the number of active reaction centers and damage to the activity of the water-splitting complex

RAP2.4a Is Transported through the Phloem to Regulate Cold and Heat Tolerance in Papaya Tree (Carica papaya cv. Maradol): Implications for Protection Against Abiotic Stress.

Plants respond to stress through metabolic and morphological changes that increase their ability to survive and grow. To this end, several transcription factor families are responsible for transmitting the signals that are required for these changes. Here, we studied the transcription factor superfamily AP2/ERF, particularly, RAP2.4 from Carica papaya cv. Maradol. We isolated four genes (CpRap2.4a, CpRAap2.4b, CpRap2.1 and CpRap2.10), and an in silico analysis showed that the four genes encode proteins that contain a conserved APETALA2 (AP2) domain located within group I and II transcription factors of the AP2/ERF superfamily. Semiquantitative PCR experiments indicated that each CpRap2 gene is differentially expressed under stress conditions, such as extreme temperatures. Moreover, genetic transformants of tobacco plants overexpressing CpRap2.4a and CpRap2.4b genes show a high level of tolerance to cold and heat stress compared to non-transformed plants. Confocal microscopy analysis of tobacco transgenic plants showed that CpRAP2.4a and CpRAP2.4b proteins were mainly localized to the nuclei of cells from the leaves and roots and also in the sieve elements. Moreover, the movement of CpRap2.4a RNA in tobacco grafting was analyzed. Our results indicate that CpRap2.4a and CpRap2.4b RNA in the papaya tree have a functional role in the response to stress conditions such as exposure to extreme temperatures via direct translation outside the parental RNA cell

Bioaccumulation and effect of cadmium in the photosynthetic apparatus of Prosopis juliflora

In the present study Prosopis juliflora plants grown in hydroponics solution were exposed to 50,100 and 1000 μM CdCl2. The cadmium uptake, transport and toxicity on the photosynthetic activities in the plants were measured at 48 h after starting cadmium treatments. The results showed that the concentration of Cd2+ in P. juliflora tended to increase with addition of Cd2+ to hydroponics solution. However, the increase of Cd2+ in roots and leaves varied largely. In this sense, the accumulation of Cd2+ in P. juliflora roots increased significantly in proportion with the addition of this metal. In contrast a relatively low level of Cd2+ transportation index, and bioaccumulation factor were found in P. juliflora at 48 h after of treatments. On the other hand the maximum photochemical efficiency of photosystem II (Fv/Fm) and the activity of photosystem II (Fv/Fo) ratios in P. juliflora leaf treated with Cd2+ not showed significantly changes during the experiment. These results suggested that the photosynthetic apparatus of P. juliflora was not the primary target of the Cd2+ action. Further studies will be focused in understanding the participation of the root system in Prosopis plants with the rhizosphere activation and root adsorption to soil Cd2+ under natural conditions

Subcellular accumulation patterns of CpRAP proteins fused to GFP in <i>Nicotiana tabacum</i> plants.

<p>The leaves or roots of tobacco seedlings after 8 days of germination were taken under different light sources Transmitted light is observed in the horizontal first line, DAPI staining is observed in the second horizontal line and GFP is observed in the third horizontal line. DAPI staining or GFP fluorescence of leaf or root is shown for tobacco transformed plants that they carry different CpRAP genes (the <i>CpRap2</i>.<i>1</i>, <i>CpRap2</i>.<i>10</i>, <i>CpRap2</i>.<i>4a</i> and <i>CpRap2</i>.<i>4b</i> gene) in their genome. The fluorescence of GFP and DAPI staining were taken at 40X on an Olympus FV1000 confocal microscope. Wild-type tobacco plants were used as a control.</p

Transcriptional expression of different genes in the sap of <i>Carica papaya</i> and <i>in vitro</i> translation from sap.

<p>A) PCR from Genomic DNA, Total RNA, and cDNA of leaf and sap in the absence or presence of DNase I. Nomenclature: 1. 1 Kb ladder (Promega); 2. PCR of DNase I treated Genomic DNA; 3. PCR of Genomic DNA; 4. PCR of DNase I treated total RNA; 5. PCR of total RNA; 6. PCR of cDNA synthesized from DNase I treated total RNA; 7. PCR of DNase I treated Sap RNA; 8. PCR of Sap RNA; 9. PCR of cDNA synthesized from DNase I treated RNA sap. B) RT-PCR analysis of CpRap genes in sap or the whole plant of <i>C</i>. <i>papaya</i> exposed to 4°C and 40°C. Quantification values of CpRap genes were normalized with the 18S gene. All analyses were performed with three biological replicates. C) Total RNA, comparison of tissue vs sap separated on a 1% agarose gel after electrophoresis with ethidium bromide. 28 and 18 S rRNA are mark by the arrows. D) Immunoblot analysis after <i>in vitro</i> translation of GST-PLCd1PHD with sap of <i>C</i>. <i>papaya</i>. Recombinant GST-PLCd1PHD was loaded as a control (C), 20 μl of the in vitro translation reactions were loaded, minus RNA added to the sap, with RNA and sap and RNA only.</p