RESUMEN
Blackberry is an economically important crop in Mexico, and its yield is substantially reduced by gray mold, a disease caused by Botrytis cinerea. One of the means to obtain B. cinerea-resistant plants is gamma irradiation. Shoot tips of in vitro-micropropagated blackberry plants (Rubus fruticosus 'Tupy') were irradiated with five doses of Cobalt-60 gamma radiation (0, 15, 30, 45, and 60 Gy) and cultured on Murashige and Skoog basal medium containing 1.0 mg l-1 benzylaminopurine and 0.06 mg l-1 indole-3-butyric acid (MSB medium). After 28 days of culture, survival was evaluated to determine mean lethal dose (LD50), and 200 shoots were further irradiated at the determined LD50 (30.8 Gy). After 28 days, the surviving shoots were micropropagated on MSB medium for 60 days. Non-irradiated shoots were screened for the in vitro selection of resistant B. cinerea, exposing them to different concentrations of sterile culture filtrate of B. cinerea (0, 2, 4, 6, 8, and 10 g l-1) for 28 days to determine mean lethal concentration (LC50), and the irradiated surviving shoots were further exposed to the determined LC50 (4.6 g l-1). Three surviving lines (rfgum5, rfgum6, and rfgum17) that did not present changes compared with the control shoots were micropropagated to obtain plantlets, which were further subjected to in vitro resistance assays using detached leaves inoculated with B. cinerea (1×103 spores ml-1). Plants of rfgum5 and rfgum6 mutant lines were highly resistant and presented similar growth to control plants. Therefore, this methodology is useful to obtain B. cinerea-resistant blackberry plants.
RESUMEN
Dalbergia congestiflora Pittier is a woody plant species grown in Mexico and Central America and widely used as timber wood and medicinal material. Since D. congestiflora is an endangered species, an in-vitro micropropagation technique is needed for mass propagation of D. congestiflora plantlets. Nodal segments of D. congestiflora stem cuttings grown in greenhouse conditions were disinfected with an appropriate protocol and in vitro established on Murashige and Skoog medium (MS) supplemented with 0.05 mg l-1 benzylaminopurine (BA). The explants showed 10% contamination with 90% survival, and the initial shoot was regenerated in 90% of them. Axillary buds of 45-day-old initial shoots were cultured on MS containing BA (0, 0.05, 0.1, 0.5, 1, 1.5 and 2 mg l-1) singly or in combination with α-naphthaleneacetic acid (NAA) (0, 0.1, 0.5 and 1 mg l-1). A higher shoot number (9.6 shoots/explant) was obtained on MS with 1 mg l-1 BA and 0.1 mg l-1 NAA. Rooting was investigated using half-strength MS, 2% sucrose and different concentrations of indole butyric acid (IBA) (0, 0.1, 0.5 and 1 mg l-1). After 30 days of culture, developing shoots were elongated and rooted in culture medium without IBA, with production of 3.2 roots/shoot. Micropropagated plantlets of D. congestiflora were successfully transplanted and acclimatized to a mixture of peat moss and perlite (2 : 1) with 100% relative humidity in greenhouse conditions with 80% survival at 30 days of culture. This micropropagation protocol will contribute to the conservation of D. congestiflora, and assure the mass propagation for sustainable usage of this species.
RESUMEN
We studied the effect of Rhizophagus irregularis on plant performance and volatile terpenes content of the Mexican native medicinal plant Satureja macrostema (Benth.) Briq. (Lamiaceae) in greenhouse conditions. The growth parameters considered in this research and the composition of volatile components were quantified monthly in mycorrhizal and non-mycorrhizal plants. The essential oil was collected from aerial parts and analyzed by gas chromatography-mass spectrometry. Colonization by R. irregularis significantly increased biomass, shoot and root length, and the amount of volatile terpenes. The more concentrated volatile terpenes were limonene, β- linalool, menthone, pulegone, and verbenol acetate. It is concluded that the use of R. irregularis allows optimal growth of S. macrostema plants in low fertility soils and increased production of the main components of the essential oil.
El efecto de Rhizophagus irregularis sobre el rendimiento vegetal y la producción de los terpenos volátiles de Satureja macrostema (Benth.) Briq. (Lamiaceae), una planta medicinal nativa mexicana, fue estudiado en condiciones de invernadero. Los parámetros de crecimiento considerados en esta investigación y los componentes volátiles, fueron cuantificados mensualmente en plantas con y sin micorrizas. El aceite esencial fue colectado de la parte aérea y fue analizado por técnicas de cromatografía de gases-espectrometría de masas. La colonización de R. irregularis aumentó significativamente la biomasa, longitud de tallo y raíz, y la cantidad de terpenos volátiles. Los terpenos volátiles mayoritarios fueron limoneno, β-linalol, mentona, pulegona y acetato de verbenol. Se concluye que el uso de R. irregularis permitió un óptimo crecimiento de las plantas de S. macrostema en suelos de baja fertilidad, con un aumento de los componentes principales del aceite esencial.
