Martha Elena Mora-Herrera

Salicylic acid enhances heat tolerance and potato virus X (PVX) elimination during thermotherapy of potato microplants

A modification of the standard thermotherapy used to eliminate virus from potato virus X (PVX)-infectedSolanum tuberosum microplants of the Mexican National Potato Program is described here. Microplants were cultured with or without 10-5 M salicylic acid (SA) for 4 wk, then subcultured without SA and exposed to 42 C for 30 days. Survival was more consistent in SA-treated microplants: among seven genotypes, 40% to 100% of SA-treated microplants and 0% to 96% of controls survived at the end of thermotherapy. SA also improved survival of the post-thermotherapy subculture. Among surviving microplants, SA increased the virus-free yield to 100% from 40% to 65% in the controls. In an additional 30 PVX(+) genotypes, 98% of surviving SA-treated microplants were virus-free after thermotherapy, compared to 75% of controls. SA-treated microplants had lower catalase activity and higher hydrogen peroxide (H2O2) levels.ResumenSe empleo termoterapia para eliminar el virus X de la papa (PVX), en plantas infectadas deSolanum tuberosum del Programa Nacional de Papa de México. Se cultivaron microplantas en presencia o ausencia de 10-5 M de ácido salicílco (SA) por cuatro semanas, posteriormente se subcultivaron en ausencia de SA y se expusieron a 42 C por 30 días. La sobrevivencia fue mas consistente en microplantas tratadas con SA: de siete genotipos al final de la termoterapia, 40% a 100% sobrevivieron en microplantas tratadas con SA y 0% a 96% en los testigos. SA también mejoró la sobrevivencia en el subcultivo posterior a la termoterapia. Entre las microplantas sobrevivientes, SA incremento el número de plantas libres de virus a 100% comparado con 40% a 65% en los testigos. Posteriormente en 30 genotipos (+) a PVX, 98% de las microplantas tratadas con SA fueron libres de virus después de termoterapia, comparado con 75% de los testigos. Microplantas tratadas con SA, tuvieron menor actividad catalasa y niveles mas altos de peroxido de hidrógeno (H2O2).

Hydrogen peroxide increases potato tuber and stem starch content, stem diameter, and stem lignin content

Field-grown potato plants were sprayed twice weekly, from 21 to 90 days after planting, with 5 or 50 mM hydrogen peroxide (H2O2) solutions. Relative to water-sprayed controls, the H2O2 treatments significantly enhanced tuber starch accumulation by between 6.7% and 30%, as determined by specific gravity or the anthrone spectrophotometric method. Pronounced effects of similar H2O2 treatments on aerial stem anatomy and starch content were also found in glasshouse experiments. H2O2 treated stems were up to 27% thicker than controls, mainly due to enlarged medullar parenchyma cells. Histochemical observations indicated that there were more starch grains in cortex and pith tissue of H2O2-treated stems. H2O2 also increased the number and size of xylem tracheary elements in the vascular bundles and the number of interfascicular fibers. Quantification using image analysis confirmed that stems of H2O2 treated plants contained up to 3.4-fold more starch and 62% more lignin. This new chemical treatment to promote starch accumulation has potential utility in potato crop production and research.ResumenPlantas de papa cultivadas en condiciones de campo se asperjaron dos veces por semana a partir de los 21 y hasta los 90 días después de la siembra, con soluciones de 5 o 50 mM de peroxido de hidrógeno (H2O2). Los tratamientos de H2O2 incrementaron significativamente la acumulación de almidón entre 6.7% y 30% con respecto a los controles que fueron asperjados con agua, de acuerdo a los métodos de gravedad específica o de antrona en espectrofotómetro. Se encontraron marcados efectos de tratamientos con H2O2, en la anatomía de tallos aéreos y en el contenido de almidón bajo condiciones de invernadero. Tallos tratados con H2O2 fueron hasta un 27% más gruesos que los controles, principalmente debido al alargamiento de las células de parénquima de la medula. Observaciones histoquímicas indicaron que hubo mas granos de almidón en corteza y tejido de medula en tallos tratados con H2O2. El H2O2 también incrementó el número y tamaño de elementos traqueales de xilema en los haces vasculares y el número de fibras interfasiculares. Las cuantificaciones usando análisis de imágenes confirmaron que tallos de plantas tratadas con H2O2 contuvieron hasta 3.4 veces mas almidón y 62% mas lignina que los controles. Este nuevo tratamiento químico para promover acumulación de almidón es potencialmente útil en la producción del cultivo de papa y en investigación.

Exogenous H2O2 in Phytoplasma-Infected Potato Plants Promotes Antioxidant Activity and Tuber Production Under Drought Conditions

H2O2-mediated symptoms and antioxidant responses were examined in phytoplasma-infected potato plants under drought conditions. In vitro phytoplasma-infected or uninfected plants were transferred to a greenhouse and sprayed twice a week with H2O2. Phytoplasma decreased water potential, catalase (CAT) activity and increased H2O2 content significantly. H2O2 significantly enhanced minitubers weight and starch content in phytoplasma-infected plants. Under drought conditions, minitubers produced by H2O2-sprayed phytoplasma-infected plants had significantly more starch than the controls. Minitubers weight was reduced in both uninfected and infected plants, but H2O2 in the presence of phytoplasma significantly enhanced minitubers weight, CAT activity, and H2O2 content. H2O2 treatment induced higher internal H2O2 concentration, which was associated with positive effects on infected minitubers, such as weight, reduction of number, starch content, sprouting, and tolerance to drought a signal role for H2O2 in lessening symptoms is suggested.ResumenSe estudiaron los síntomas en plantas de papa infectadas con fitoplasma y las respuestas antioxidantes mediados por H2O2 bajo condiciones de sequia. Plantas in vitro infectadas y no, con fitoplasma, fueron transferidas a invernadero y asperjadas dos veces por semana con H2O2. El fitoplasma disminuyó el potencial hídrico, la actividad catalasa (CAT) e incremento significativamente el contenido de H2O2. H2O2 incremento significativamente el peso de los minitubérculos y el contenido de almidón en plantas infectadas con fitoplasma. Bajo condiciones de sequía, los mintuberculos producidos por plantas infectadas con fitoplasma y asperjadas con H2O2, tuvieron significativamente más almidón que los controles. El peso de los minitubérculos se redujo en plantas no infectadas e infectadas, sin embargo, H2O2 significativamente incremento el peso de los minitubérculos, la actividad CAT y contenido de H2O2 en presencia de fitoplasma. El tratamiento de H2O2 indujo más altas concentraciones de H2O2 interno, que estuvo asociado con efectos positivos en minitubérculos infectados, tales como peso, reducción del número, contenido de almidón, brotación y tolerancia a sequía, se sugiere una función de señal del H2O2 en la disminución de síntomas.

Short and Long Term Effects of Salicylic Acid on Protection to Phytoplasma Associated Stress in Potato Plants

Salicylic acid (SA) activated the plant defense response in potato against phytoplasma attack, reduced infection symptoms, favored photosynthates translocation and improved the quality of tubers. SA induced effects at short and long terms and it was equally efficient when it was first applied on in vitro culture followed of transplanting or directly sprayed on greenhouse conditions. Low levels of exogenous SA (0.1 and 0.001 mM) showed higher biological activity. The reduction of damage was associated to high hydrogen peroxide and ascorbic acid contents, together with reduction of peroxidase activity suggesting an important role of SA on the regulation of these molecules and counteracting the pathogens effects.

Bactericidal effect of silver nanoparticles against the propagation of Clavibacter michiganensis infection in Lycopersicon esculentum Mill

This study explored the use of silver nanoparticle as a bactericidal against the propagation of Clavibacter michiganensis onto tomatoes (Lycopersicon esculentum Mill). In Mexico, tomato production covers about 73% of the total vegetable production but it is affected by outbreak of bacteria canker caused by Clavibacter michiganensis subspecies michiganensis (Cmm). Silver ions possess inhibitor properties, bactericides and high specter antimicrobials. In this study, 6 groups of culture were prepared using 6 different petri dishes where silver nanoparticles of varying concentrations (120, 84, 48, 24, 12 and 0 μg) were added. Furthermore, each group was observed for 20 min, 1, 2, 12 and 24 h. The optimum concentration is 84 μg, which shows an average of 2 Cmm colonies after 20 min. Further increase to 120 μg shows no significant change. However, the average colonies was observed for 48 μg after 1, 2, 12, and 24 h. The obtained results indicate that silver nanoparticles are a promising inhibitor, bactericide and high a specter antimicrobial for treatment or prevention of Cmm.

Changes in Hydrogen Peroxide Levels and Catalase Isoforms Expression are Induced with Freezing Tolerance by Abscisic Acid in Potato Microplants

Martha E. Mora-Herrera1,2, Humberto Lopez-Delgado1, Ernestina Valadez-Moctezuma3 and Ian M. Scott4 1Programa Nacional de Papa, Instituto Nacional de Investigaciones Forestales Agricolas y Pecuarias, (INIFAP), Metepec 2Centro Universitario Tenancingo, Universidad Autonoma del Estado de Mexico, Carr. Tenancingo-Villa Guerrero Km 1.5 Tenancingo, 3Departamento de Fitotecnia, Universidad Autonoma Chapingo, Chapingo, 4Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Ceredigion, 1,2,3Mexico 4UK