ACEITES ESENCIALES PROVENIENTES DE PLANTAS NATIVAS PARA EL CONTROL DE HONGOS FITOPATÓGENOS QUE AFECTAN A FRUTALES

El empleo constante y excesivo de fungicidas sintéticos en la industria fruti-hortícola ha provocado profundas alteraciones en el medio ambiente y en la salud humana. En este contexto, explorar fuentes naturales antifúngicas resulta de importancia económica y medioambiental. Se propuso estudiar la actividad de cinco aceites volátiles obtenidos de las especies vegetales nativas Dysphania ambrosioides, Baccharis frenguellii, Baccharis salicifolia, Lippia alba y Lippia turbinata contra hongos fitopatógenos de los géneros Botrytis, Colletotrichum, Rhizopus, Fusarium y Monilinia, aislados de frutillas y duraznos con sintomatología. La evaluación se realizó mediante el método de difusión en agar adaptado para muestras volátiles y se determinaron los porcentajes de inhibición fúngica para cada muestra en estudio utilizando el software ImageJ®. Se analizó el perfi l químico de cada aceite por CG-EM y se determinaron los compuestos mayoritarios. Los resultados indicaron un alto potencial antifúngico de todas las muestras evaluadas, particularmente el producto obtenido de L. alba.

Sexual and genotypic variation in terpene quantitative and qualitative profiles in the dioecious shrub Baccharis salicifolia

Terpenoids are secondary metabolites produced in most plant tissues and are often considered toxic or repellent to plant enemies. Previous work has typically reported on intra-specific variation in terpene profiles, but the effects of plant sex, an important axis of genetic variation, have been less studied for chemical defences in general, and terpenes in particular. In a prior study, we found strong genetic variation (but not sexual dimorphism) in terpene amounts in leaves of the dioecious shrub Baccharis salicifolia. Here we build on these findings and provide a more in-depth analysis of terpene chemistry on these same plants from an experiment consisting of a common garden with male (N = 19) and female (N = 20) genotypes sourced from a single population. Our goal in the present study was to investigate quantitative and qualitative differences in terpene profiles associated with plant sex and genotypic variation. For this, we quantified leaf mono- and sesquiterpene amount, richness, and diversity (quantitative profile), as well as the composition of compounds (qualitative profile). We found no evidence of sexual dimorphism in monoterpene or sesquiterpene profiles. We did, however, find significant genotypic variation in amount, diversity, and composition of monoterpenes, but no effects on sesquiterpenes. These findings indicated that genotypic variation in terpene profiles largely surpassed variation due to sexual dimorphism for the studied population of this species.

Impacts of Tamarix (L.) Litter and Mycorrhizal Amendments on Baccharis salicifolia (Ruiz & Pav.) Pers. Competitiveness and Mycorrhizal Colonization

Tamarix spp. are ecological threats in the Southwest U.S.A. because they displace native vegetation, increase soil salinity, and negatively affect soil microbial communities. After Tamarix L. removal, legacy effects often necessitate restoration to improve ecosystem services of Tamarix-impacted communities. Commercial mycorrhizae fungal inoculation has been recommended to improve restoration success, although inoculation treatments are rarely tested on lesser-known facultative riparian species. Our study asked two questions: (1) Can a commercial mycorrhizal fungal inoculant increase native Baccharis salicifolia (Ruiz & Pav.) Pers. (mule-fat) performance against Tamarix chinensis Lour. (i.e., tamarisk) and is this influenced by tamarisk leaf litter? (2) Is mycorrhizal colonization of mule-fat roots influenced by tamarisk stem density and leaf litter? A greenhouse experiment was performed with mule-fat cuttings in soil collected from a tamarisk monoculture. Treatments were factorial combinations of tamarisk stem densities (0, 1, 2, 3, 4 stems pot−1) with or without mycorrhizal inoculation and tamarisk litter. There were five replications and two greenhouse runs. The total biomass of both species was determined and mule-fat arbuscular mycorrhizal colonization rates were determined via the magnified intersection method. Increasing tamarisk biomass negatively affected mule-fat biomass, but there were interactions with tamarisk biomass, litter and mycorrhizal inoculation, with litter and inoculation increasing mule-fat growth at high tamarisk biomass. Arbuscular mycorrhizal colonization was high in all treatments, yet at higher tamarisk stem densities, inoculation and litter improved colonization. Interestingly, litter did not negatively impact mule-fat as predicted. Moreover, litter and mycorrhizal inoculum interacted with tamarisk to improve mule-fat growth at higher tamarisk biomass, suggesting an opportunity to improve restoration success when in competition with tamarisk.

Chemical profile of the volatiles of Baccharis salicifolia (Asteraceae) and interaction with Macrodactylus nigripes (Coleoptera: Melolonthidae)

Plant products or substances mediate interactions among organisms from different trophic levels, including phytophagous insects. These interactions have been cited in a chemical-ecology context for species of Coleoptera Melolonthidae. However, there are no previous reports of these interactions among melolonthid beetles species distributed in Mexico and host plants. For the above, the interaction between adults of ‘rose chafer’ Macrodactylus nigripes Bates (Coleoptera:Melolonthidae) and ‘seep willow’ shrub Baccharis salicifolia (Ruíz and Pav.) Pers. (Asteraceae) was recorded and the leaves volatiles of seep willow that might be involved in the attraction of these insects were extracted and identified. The sequence of behavior patterns that conforms this interaction was described. Females of M. nigripes emerge from the soil and flight to the leaves of seep willow shrubs. Each female settled on leaf and they place their mandibles on the leaf margin and start moving them from right to left to obtain small leaf fragments to ingest. In addition, females exhibit a similar ‘calling’ behavior as well as the others species. Following the females, males emerge from the soil and repeat the females’ behavior, approaching them for mating. A list of the leaves volatiles of seep willow was generated by solid phase microextraction (SPME) and coupled gas chromatography – mass spectrometry (GC-MS), where the most abundant chemicals were α-pinene, trimethylindan and cyclohexylbenzene. These compounds have been previously reported in other plant species, including some species considered as host plants for Melolonthidae.