Temporary immersion systems induce photomixotrophism during in vitro propagation of agave Tobalá

This study aimed to determine the photomixotrophic and physiological responses using different temporary immersion systems (TIS) during in vitro multiplication of agave Tobalá. The culture systems were SETIS™ bioreactor, Temporary Immersion Bioreactor (TIB), Monobloc Advance Temporary Immersion System, and semisolid culture medium as the control. At six weeks of culture, different physiological variables were evaluated: chlorophyll content, stomatal index, percentage of closed stomata, Phosphoenolpyruvate (PEP) and Rubisco during the multiplication stage, and survival percentage in the acclimatization stage. TIS increased multiplication rate (41%), stomatal index (44%), percentage of closed stomata (11%) and chlorophyll content (45%) with respect to the semisolid culture medium system. The highest PEP content (> 35%) was observed in temporary immersion (TI), whereas, Rubisco content, showed no differences among the culture systems evaluated. Regarding survival percentage during acclimatization, the highest shoot survival was obtained in TI, and all regenerate shoots were rooted ex vitro. This study shows that in vitro photomixotrophism was induced in TIS during the multiplication stage. In conclusion, SETIS™ bioreactor and TIB systems are an alternative for mass multiplication of A. potatorum; however, all TIS evaluated guarantee a high survival rate during acclimatization.

In Vitro Multiplication of Agave (A. marmorata and A. potatorum) by Temporary Immersion in SETIS™ Bioreactor

In Mexico, wild agaves are important for the production of alcoholic beverages known as mezcal and pulque. However, the propagation of agave seeds and pups is not enough to satisfy the national demand. Temporary immersion systems represent an agave micropropagation alternative that reduces the labor force, increases development, and improves the quality of seedlings. The use of the SETIS™ bioreactor in A. marmorata and A. potatorum improves the multiplication rate and allows rooting. Additionally, this bioreactor reduces the culture time, labor force, and reagents needed while maintaining high survival rates during the acclimatization phase.

Arbuscular Mycorrhizal Symbiosis Improves Ex Vitro Acclimatization of Sugarcane Plantlets (Saccharum spp.) under Drought Stress Conditions

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.

Arbuscular Mycorrhizal Fungi Induce Tolerance to Salinity Stress in Taro Plantlets (Colocasia esculenta L. Schott) during Acclimatization

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.

Comparison of Different Semi-Automated Bioreactors for In Vitro Propagation of Taro (Colocasia esculenta L. Schott)

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.