Chitosans of different molecular weight enhance potato (Solanum tuberosum L.) yield in a field trial

Physico-chemical features of chitosan affect its biological activity on plants. In this work, the influence of chitosan molecular mass in potato (Solanum tuberosum L.) yields was investigated. By using chitosan polymers of high (CH-1) and low (CH-2) molecular weight and a hydrolysed chitosan derivative (CHH), two experiments were performed under field conditions to determine the effect of these polymers on yields of two potato varieties, ‘Call White’ and ‘Santana’. For this purpose, the foliar spray of low doses of the derivatives at three cultivation moments was performed and several yield variables were determined at crop harvest. All three chitosan compounds increased the performance variables determined respect to the control, depending on the variable, the dose employed and the mass of the derivative evaluated. In most variables determined, the two lowest doses (200 and 325 mg/ha) provoked the highest increments above control. Chitosans also affected distribution of mass per tuber size, particularly; in ‘Santana’ variety the two lowest doses enhanced the commercial tuber sizes. Among the polymers, CH-1 caused the greatest increases in performance, while, compared to the polymer, CHH provoked higher yields. In conclusion, foliar application at low doses of high molecular weight and hydrolysed chitosan enhanced potato yield between 15-30%

Efecto de diferentes medios de cultivo sobre el desarrollo de Phytophthora nicotianae Breda de Haan

El objetivo del estudio fue determinar el efecto de diferentes medios de cultivo sobre el crecimiento, esporulación y secreción de enzimas hidrolíticas de Phytophthora nicotianae Breda de Haan. Para ello se emplearon los medios en estado sólido y líquido: Papa Dextrosa Agar (PDA), jugo de verduras (V8) y extracto de tabaco, combinados entre ellos y con suplemento de asparagina y carbonato de calcio. El mayor crecimiento del microorganismo se produjo en medio sólido con extracto de tabaco, pues alcanzó en menor tiempo el extremo de la placa; sin embargo, su crecimiento fue poco ramificado, a diferencia de los que contenían V8. Se comprobó que la biomasa producida fue mayor en los medios líquidos que contenían V8. El número de zoosporas estimadas en el momento en que el micelio alcanzó el borde de la placa fue significativamente mayor en el tratamiento que combinaba PDA con V8 y el menor valor se obtuvo al emplearse el extracto de tabaco. Al utilizarse la combinación del extracto de tabaco con V8, se obtuvieron las mayores actividades poligalacturonasa y xilanasa. Los resultados evidenciaron que los medios que favorecen la expresión de enzimas hidrolíticas, así como el crecimiento y esporulación de P. nicotianae, tienen V8 entre sus componentes, elemento de gran importancia, pues se disminuye el tiempo requerido para los ensayos y con ello el riesgo de contaminación de los experimentos. Palabras clave: Phytophthora nicotianae, medio de cultivo, crecimiento, esporulación, actividad enzimática.EFFECT OF DIFFERENT CULTURE MEDIA ON PHYTOPHTHORA NICOTIANAE BREDA DE HAAN DEVELOPABSTRACT: The effect of different culture media on Phytophthora nicotianae growth, sporulation, and hydrolytic enzymes secretion was studied. The liquid and solid culture media used were potato dextrose agar (PDA), vegetable juice (V8), and tobacco extract. They were combined one another and supplemented with asparagine and calcium carbonate. Phytophthora nicotianae growing on solid media containing only tobacco extract reached the plate edge in the shortest time; however, the mycelium was little branched, unlike the mycelium in the media containing V8. A greater biomass production was observed in liquid culture with V8. The zoospore number was significantly higher in the treatment combining PDA only with V8; the lowest number was obtained with tobacco extract. Polygalacturonase and xylanase activities were the highest when the liquid media contained the combination of tobacco extract and V8 juice. The culture medium V8 was shown to be useful to determine the enzymatic activity of the hydrolytic enzymes and the parameters of growth and sporulation of P. nicotianae; itreduced the time required for the trials and, consequently, the risk of contamination.Key words: Phytophthora nicotianae, culture media, growth, sporulation, enzymatic activity

Compatibilidad Quitosano-Bradyrhizobium aplicados a semillas y su efecto en el desarrollo vegetativo de soya (Glycine max (L.) Merrill)

Introduction. Chitosan and plant growth promoting rhizobacteria are recognized as agricultural biostimulants for the biological benefits they provide to plants. Objective. To evaluate the combined application of chitosan concentrations and the Azofert-S® inoculant on soybean seeds, on the survival of Bradyrhizobium elkanii and the vegetative growth of the plants. Materials and methods. The research was developed in the plant growth room of Plant Physiology and Biochemistry Department of the Instituto Nacional de Ciencias Agricolas, Cuba, in 2016. The effect of chitosan and Azofert-S® inoculant applied to soybean seeds was determined on the number of viable bacteria in seeds and the behavior of morphoagronomic and physio-biochemical indicators related to the nodulation and vegetative development of plants. Results. The chitosan concentrations evaluated in the compatibility test did not affect the number of viable cells in the seeds, except for 500 and 1000 mg l-1, which improved the bacteria survival at the beginning of the test and 500 mg l-1 at ten days of seed storage. The latter concentration also benefited root and stem length, leaf area, and nitrate reductase enzymatic activity in leaves. The combined application of Azofert® - chitosan and seed inoculation alone enhanced the concentration of nitrogen and other nutrients in nodules and trifoliolus. The concentration of flavonoids and total phenols increased with the concentration of 10 mg l-1 of chitosan, although it decreased the concentration of total soluble and reductive carbohydrates in leaves. Conclusion. The biostimulants were compatible when applied on seeds at the time of sowing and benefited the nodulation, nutrition, and vegetative development of soybeans plants, depending on the concentration of the polymer.Introducción. El quitosano y las rizobacterias promotoras del crecimiento vegetal son reconocidos bioestimulantes agrícolas por los beneficios biológicos que aportan a las plantas. Objetivo. Evaluar la aplicación conjunta de concentraciones de quitosano y el inoculante Azofert-S® sobre semillas de soya, en la supervivencia de Bradyrhizobium elkanii y el desarrollo vegetativo de las plantas. Materiales y métodos. La investigación se desarrolló en el cuarto de crecimiento de plantas del Departamento de Fisiología y Bioquímica Vegetal del Instituto Nacional de Ciencias Agrícolas de Cuba, en el año 2016. Se determinó el efecto del quitosano y el inoculante Azofert-S® aplicados a semillas de soya, en el número de bacterias viables en las semillas y en el comportamiento de indicadores morfoagronómicos y fisio-bioquímicos relacionados con la nodulación y el desarrollo vegetativo de las plantas. Resultados. Las concentraciones de quitosano evaluadas en el ensayo de compatibilidad no afectaron el número de células viables en las semillas, excepto 500 y 1000 mg l-1, que mejoraron la supervivencia de la bacteria al comienzo del ensayo y 500 mg l-1 a los diez días de almacenamiento de las semillas. Esta última concentración benefició también la longitud radical y del tallo, el área foliar y la actividad enzimática de la nitrato reductasa en hojas. La aplicación combinada de Azofert® - quitosano y la sola inoculación de las semillas incrementó la concentración de nitrógeno y otros nutrientes en nódulos y trifoliolos. La concentración de flavonoides y de fenoles totales aumentó con la concentración de 10 mg l-1 de quitosano, aunque redujo la concentración de carbohidratos solubles totales y reductores en las hojas. Conclusión. Los bioestimulantes resultaron compatibles cuando se aplicaron sobre semillas en el momento de la siembra y beneficiaron la nodulación, la nutrición y el desarrollo vegetativo de las plantas de soya, en dependencia de la concentración del polímero

Chitosans of different molecular weight enhance potato (Solanum tuberosum L.) yield in a field trial

Physico-chemical features of chitosan affect its biological activity on plants. In this work, the influence of chitosan molecular mass in potato (Solanum tuberosum L.) yields was investigated. By using chitosan polymers of high (CH-1) and low (CH-2) molecular weight and a hydrolysed chitosan derivative (CHH), two experiments were performed under field conditions to determine the effect of these polymers on yields of two potato varieties, ‘Call White’ and ‘Santana’. For this purpose, the foliar spray of low doses of the derivatives at three cultivation moments was performed and several yield variables were determined at crop harvest. All three chitosan compounds increased the performance variables determined respect to the control, depending on the variable, the dose employed and the mass of the derivative evaluated. In most variables determined, the two lowest doses (200 and 325 mg/ha) provoked the highest increments above control. Chitosans also affected distribution of mass per tuber size, particularly; in ‘Santana’ variety the two lowest doses enhanced the commercial tuber sizes. Among the polymers, CH-1 caused the greatest increases in performance, while, compared to the polymer, CHH provoked higher yields. In conclusion, foliar application at low doses of high molecular weight and hydrolysed chitosan enhanced potato yield between 15-30%

The effect of size and acetylation degree of chitosan derivatives on tobacco plant protection against Phytophthora parasitica nicotianae

Enzymatic degradation of chitosan polymer with Pectinex Ultra SPL was used to obtain derivatives with biological potential as protective agents against Phytophthora parasitica nicotianae (Ppn) in tobacco plants. The 24 h hydrolysate showed the highest Ppn antipathogenic activity and the chitosan native polymer the lowest. The in vitro growth inhibition of several Phytophthora parasitica strains by two chitosans of different DA was compared. While less acetylated chitosan (DA 1%) fully inhibited three P. parasitica strains at the doses 500 and 1000 mg/l the second polymer (DA 36.5%) never completely inhibited such strains. When comparing two polymers of similar molecular weight and different DA, again the highest antipathogenic activity was for the less acetylated polymer. However, degraded chitosan always showed the highest pathogen growth inhibition. Additionally, a bioassay in tobacco seedlings to test plant protection against Ppn by foliar application demonstrated that partially acetylated chitosan and its hydrolysate induced systemic resistance and higher levels of glucanase activity than less acetylated chitosan. Similarly, when treatments were applied as seeds coating before planting, about 46% of plant protection was obtained using chitosan hydrolysate. It was concluded that, while less acetylated and degraded chitosan are better for direct inhibition of pathogen growth, partially acetylated and degraded chitosan are suitable to protect tobacco against P. parasitica by systemic induction of plant resistance