Physiological Responses of Agave maximiliana to Inoculation with Autochthonous and Allochthonous Arbuscular Mycorrhizal Fungi

Abstract

The benefits of mycorrhizal interactions are only known in 8 of 210 recognized Agave taxa. We evaluated the effects of autochthonous and allochthonous arbuscular mycorrhizal fungi (AMF) on growth and nutrient assimilation in Agave maximiliana. The autochthonous consortium (Cn) of eight species was propagated from the rhizospheric soil of A. maximiliana, while Claroideoglomus claroideum (Cc) and Claroideoglomus etunicatum (Ce) were employed as allochthonous AMF. Six treatments were included in the study: Cn, Ce, Cc, Ce + Cc, Tf (fertilized control), and Tn (non-fertilized control, not inoculated). Mycorrhizal colonization increased over time, and the colonization percentages produced by Cn and the allochthonous AMF, both alone and mixed together, were equal at 6, 12, and 18 months. Height increased steadily and was higher in AMF-treated plants from seven months onward. Growth indicators of AMF-treated and AMF-free plants were equal at 6 months, but the beneficial effects of allochthonous and autochthonous AMF were evident in all growth indicators at 18 months and in sugar and mineral (P, K, Ca, Mg, and Fe) content. Arbuscular mycorrhizal fungi significantly improved all growth parameters of A. maximiliana regardless of the origin of the inoculums. This is the first study to report the positive effects of AMF colonization in A. maximiliana.

Keywords: AMF native consortium; Agave maximiliana; Claroideoglomus claroideum; Claroideoglomus etunicatum; biofertilizer.

Figure 1

Hyphae, vesicles, and spores of arbuscular mycorrhizal fungi (AMF). Abbreviations: consortium of autochthonous AMF of the Agave maximiliana rhizosphere (Cn), Claroideoglomus etunicatum (Ce), and Claroideoglomus claroideum (Cc) (a) AMF hyphae in the roots of A. maximiliana roots after six months of treatment (Cc). (b) AMF Hyphae and vesicles in A. maximiliana roots after 12 months of treatment (Cn). (c) Spores of Cn. (d) Spores of Ce. (e) Spores of Cc.

Figure 2

Fresh plant weight of Agave maximiliana at 6, 12, and 18 months after inoculation with arbuscular mycorrhizal fungi (AMF). Treatments: (1) consortium of autochthonous AMF of the A. maximiliana rhizosphere (Cn), (2) Claroideoglomus etunicatum (Ce), (3) Claroideoglomus claroideum (Cc), (4) C. etunicatum + C. claroideum (Ce + Cc), (5) control with fertilization and without mycorrhizal inoculation (Tf), and (6) control without fertilization or mycorrhizal inoculation (Tn). Age 6 months, n = 18; age 12 months, n = 13; age 18 months, n = 8. The bars represent the means ± standard error. An analysis of variance was followed by a means test (p ≤ 0.05). Different letters (by age) indicate significant differences between treatments.

Figure 3

Heights of Agave maximiliana plants over 18 months after being inoculated with arbuscular mycorrhizal fungi (AMF). Treatments: (1) consortium of autochthonous AMF of the A. maximiliana rhizosphere (Cn), (2) Claroideoglomus etunicatum (Ce), (3) Claroideoglomus claroideum (Cc), (4) C. etunicatum + C. claroideum (Ce + Cc), (5) control with fertilization and without mycorrhizal inoculation (Tf), and (6) control without fertilization or mycorrhizal inoculation (Tn). Ages 1–6 months, n = 18; ages 7–12 months, n = 13; ages 13–18 months, n = 8. Data are means ± standard error. Different letters (at 18 months) indicate significant differences between treatments.

Figure 4

Agave maximiliana plants of four treatments that included inoculation with arbuscular mycorrhizal fungi (AMF) and two control treatments. Treatments: (1) consortium of autochthonous AMF of the A. maximiliana rhizosphere (Cn), (2) Claroideoglomus etunicatum (Ce), (3) Claroideoglomus claroideum (Cc), (4) C. etunicatum + C. claroideum (Ce + Cc), (5) control with fertilization and without mycorrhizal inoculation (Tf), and (6) control without fertilization or mycorrhizal inoculation (Tn). (a) Plants at 6 months of treatment. (b) Plants at 12 months of treatment. (c) Plants at 18 months of treatment.