Soil salinity is a problem that affects soil fertility and threatens agri-food crop production worldwide. Biotechnology, through plant micropropagation and the use of biofertilizers such as arbuscular mycorrhizal fungi (AMF), is an alternative to increase productivity and induce tolerance to salinity stress in different crops. This study aimed to evaluate the effect of different doses of the fungus Glomus intraradices on the ex vitro development of taro (Colocasia esculenta L. Schott cv. Criolla) plantlets under salinity stress during the acclimatization stage. In vitro-obtained C. esculenta plantlets were inoculated at different doses (0, 100, and 200 spores per plantlet) of G. intraradices during acclimatization. At 60 d of acclimatization in the greenhouse, plantlets were exposed to 100 mM NaCl salinity stress for 10 d. After the stress period, plantlet development, colonization percentage, and biomass were evaluated. In addition, the content of chlorophyll, carotenoids, proteins, proline, glycine-betaine, soluble phenols, and antioxidant capacity were quantified. The results showed differences in the developmental, physiological, and biochemical variables evaluated; however, no changes in total protein content were observed. Spore colonization showed that the symbiotic association has positive effects on the development of plantlets with or without salinity stress. This symbiotic interaction contributes to salinity stress tolerance in C. esculenta plantlets. The early application of AMF in in vitro-obtained taro plantlets is an alternative to increase or maintain the productivity of this crop in saline soils.

Taro is important for its nutritional content, medicinal use, and bioethanol production. The aim of the present study was to compare different semi-automated bioreactors (SABs) during in vitro multiplication of C. esculenta. The SABs used were temporary immersion bioreactors (TIBs), SETIS™ bioreactors and ebb-and-flow bioreactors; semi-solid culture medium was used as a control treatment. At 30 d of culture, different developmental variables, determination of chlorophyll, stomatal content, and survival percentage during acclimatization were evaluated. SABs increased the shoot multiplication rate relative to the semi-solid medium; however, the SETIS™ bioreactor showed the highest shoot production, with 36 shoots per explant, and the highest chlorophyll content. The stomatal index was higher in the semi-solid medium compared to the SABs, while the percentage of closed stomata was higher in the SABs than in the semi-solid culture medium. The survival rate during acclimatization showed no differences among the culture systems assessed, obtaining survival rates higher than 99%. In conclusion, the SETIS™ bioreactor showed the highest multiplication rate; however, other bioreactor alternatives are available for semi-automation and cost reduction for micropropagation of C. esculenta.

The symbiotic associations between arbuscular mycorrhizal fungi (AMF) and plants can induce drought stress tolerance. In this study, we evaluated the effect of Glomus intraradices, a mycorrhizal fungus, on the ex vitro development and survival of sugarcane plantlets subjected to drought stress during the acclimatization stage of micropropagation. In vitro obtained sugarcane plantlets (Saccharum spp. cv Mex 69–290) were inoculated with different doses of G. intraradices (0, 100, and 200 spores per plantlet) during greenhouse acclimatization. Sixty days after inoculation, plantlets were temporarily subjected to drought stress. We evaluated the survival rate, total chlorophyll, total protein, carotenoids, proline, betaine glycine, soluble phenolic content, and antioxidant capacity every 3 days for 12 days. Symbiotic interaction was characterized by microscopy. Our results showed that the survival rate of inoculated plants was higher in 45% than the treatment without mycorrhizae. Total chlorophyll, protein, proline, betaine glycine content, and antioxidant capacity were increased in AMF inoculated plants. The soluble phenolic content was higher in non-inoculated plants than the treatment with mycorrhizae during the drought stress period. Microscopy showed the symbiotic relationship between plant and AMF. The early inoculation of 100 spores of G. intraradices per sugarcane plantlet during the acclimatization stage could represent a preconditioning advantage before transplanting into the field and establishing basic seedbeds.

In vitro conservation and regeneration of potato germplasm is important in breeding programs. The objective of this study was to assess the combined effect of paclobutrazol (PAC) and silver nanoparticles (AgNPs) during reduced-growth conservation and their in vitro ability to regenerate S. tuberosum after conservation treatments. For the conservation system, apices were used as explants in Murashige and Skoog culture media with different combinations of PAC (0, 0.5, 1 and 2 mg L⁻¹) and AgNPs (0, 50, 100 and 200 mg L⁻¹). At six months of culture, plant length, number of lateral branches, number of leaves and roots, root length, stomatal density and total chlorophyll content were assessed. For regeneration, explants were internodes cultured in medium with only 2 mg L⁻¹ benzyladenine (BA). At 60 d of culture, the response percentage, number of shoots per explant and shoot length were assessed. For in vitro conservation, the combination of 2 mg L⁻¹ PAC and 50 mg L⁻¹ AgNPs was the best treatment, whereas for in vitro regeneration, the highest number of shoots was in explants that were treated with 1 or 2 mg L⁻¹ PAC with 50 mg L⁻¹ AgNPs. In conclusion, PAC and AgNPs are alternatives for in vitro S. tuberosum conservation, and their evaluation in other species recalcitrant to the effect of ethylene is recommended.

Chitosan nanoparticles (CsNPs) are biocompatible, biodegradable, and non-toxic natural polymers at low concentrations with diverse applications in in vitro plant tissue culture. This study aims to evaluate the effect of CsNPs during in vitro multiplication of sugarcane (Saccharum spp.) using temporary immersion bioreactors. CsNPs were evaluated at concentrations of 0, 25, 50, 100, and 200 mg L⁻¹ in Murashige and Skoog liquid culture medium. After four weeks of culture, response percentage, the number of shoots per explant, shoot length, number of leaves per explant, dry matter, chlorophyll content, β-carotene content, lipid peroxidation, phenolic content, hydrogen peroxide content, and antioxidant capacity were evaluated. The results showed that the highest response percentages were obtained in the treatments with 0, 25, and 50 mg L⁻¹ CsNPs, whereas the lowest response percentages were obtained in the treatments with 100 and 200 mg L⁻¹ CsNPs. Concentrations of 25 and 50 mg L⁻¹ CsNPs promoted cell growth and differentiation, whereas 100 and 200 mg L⁻¹ CsNPs inhibited it. Chlorophyll content increased by 25 and 50 mg L-1 CsNPs, whereas β-carotene content increased by 100 and 200 mg L⁻¹ CsNPs. Lipid peroxidation and antioxidant capacity increased with increasing CsNP concentrations. The phenolic content increased by 100 mg L⁻¹ CsNPs, whereas the hydrogen peroxide content decreased with increasing CsNP concentrations. In conclusion, CsNPs are an alternative for stimulating tissue growth and differentiation during the in vitro multiplication of sugarcane.

Raspberry (Rubus idaeus L.) micropropagation is an alternative for obtaining plantlets with high genetic and phytosanitary quality. The objective of this study was to establish a protocol for the micropropagation of raspberry (Rubus idaeus L.) using the temporary immersion bioreactor, under intermittent immersion periods and different culture medium volumes. The effect of the liquid medium using the TIB and semisolid was evaluated. Different immersion frequencies and culture medium volumes per explant were evaluated in the TIB. In all treatments, the number of shoots per explant, shoot length, number of leaves per explant, percentage of hyperhydricity, and chlorophyll and β-carotene content at multiplication stage were evaluated. The generated shoots, without a root system, were transferred to the acclimatization stage. The results show that the TIB with an immersion frequency of 2 min every 8 h and a volume of 25 mL of culture medium per explant had the best developmental parameters, with 5.75 shoots per explant, a shoot length of 3.44 cm, and 2% hyperhydricity. The highest chlorophyll and β-carotene content was observed in the TIB at different immersion frequencies of 4, 8 and 12 h, with 25 and 50 mL per explant. Survival percentages higher than 96% were observed in all methods evaluated. In conclusion, the evaluated immersion system is an efficient alternative for R. idaeus micropropagation, without using a rooting stage.