Gisela Muro-Pérez

Halophilic rhizobacteria from Distichlis spicata promote growth and improve salt tolerance in heterologous plant hosts

Rhizobacteria are central components of the plant microbiome and influence root development and function. Desciphering how rhizobacteria contribute to plant performance under adverse environments is a major research challenge. The aims of the present study were to isolate and characterize rhizobacteria from the halophilic grass Distichlis spicata and to test their possible growth promoting and salt protective properties in Arabidopsis thaliana, Cucumis sativus, and Citrullus lanatus. To determine their possible plant growth promoting properties, 38 rhizobacterial isolates were co-cultivated with Arabidopsis seedlings in vitro. Out of these, two halophilic bacteria, LBEndo1 and KBEcto4, were selected following their strong shoot and root biostimulation. 16S rRNA sequencing identified LBEndo1 as Bacillus sp. and KBEcto4 as Pseudomonas lini. Both strains improved growth under standard and saline conditions, which correlated with IAA and siderophore production, as well as phosphate solubilization. Additionally, the KBEcto4 strain expresses the ACC deaminase enzyme (acdS gene), and slightly increases auxin redistribution within Arabidopsis roots expressing an auxin-inducible gene construct. These data reveal the potential of saltgrass (Distichlis spicata) rhizobacteria to promote growth and confer salt tolerance to Arabidopsis and crop plants.

Effect of seed burial in different soils on the germination of three specially protected cactus species

Abstract Seedling establishment of many cactus species appears to be more frequent under canopies of nurse plants, which provide a less stressful microenvironment. Under these nurse plants, nutrient levels in the soil could be higher than in surrounding areas; these higher nutrient levels could promote higher seed germination. Seed burial under nurse plants may occur by seeds falling in the litter or in soil cracks; however, buried seeds are in the dark, which has been shown to inhibit seed germination for some cactus species. We measured germination percentage on nutrient-rich soil from under nurse mesquites and in soil from open spaces, and the effect of seed burial (buried and unburied seeds) on seed germination of three cactus species (Coryphantha durangensis, Peniocereus greggii, and Echinocereus longisetus) that grow under nurse plants in the Chihuahuan Desert. Echinocereus longisetus had very low germination across substrates. Coryphantha durangensis had higher germination on mesquite soil than on poor soil, and its buried seeds had lower germination than seeds on the soil surface. Germination of P. greggii seeds was higher on mesquite soil than on poor soil, and its buried seeds had lower germination than seeds on the soil surface.

EFECTO DE LA DENSIDAD DE SEMILLAS EN LA GERMINACIÓN DE TRES ESPECIES DEL GÉNERO ASTROPHYTUM (CACTACEAE)

Se colectaron frutos de poblaciones naturales de Astrophytum capricorne, A. myriostigma y A. ornatum en Coahuila, Durango e Hidalgo, respectivamente, con el objetivo de evaluar el efecto de la agrupacion de semillas en la germinacion, comparando tratamientos de 10 semillas agrupadas y 10 semillas no agrupadas (individuales). Las tres especies mostraron mayor porcentaje de germinacion en semillas individuales. La germinacion fue igual de rapida en semillas agrupadas e individuales para las tres especies. Estos resultados contrastan con el fenomeno de rivalidad entre hermanos que plantea la inhibicion de la germinacion en altas densidades como un mecanismo para evitar la competencia entre semillas hermanas con el fin de disminuir la competencia entre plantulas.