Identification of Rhizobia Isolated from Nodules of Mexican Commercial Soybean Varieties

Rhizobia, crucial for nitrogen fixation in leguminous plants, play a vital role in soybean cultivation. This study, conducted in Mexico, a major soybean importer, aimed to identify bacteria from nodules of five soybean varieties in high-production regions. Multilocus sequence analysis (MLSA) was employed for enhanced species resolution. The study identified six Bradyrhizobium species: Bradyrhizobium japonicum USDA 110, Bradyrhizobium japonicum USDA 6, Bradyrhizobium elkanii USDA 76, Bradyrhizobium neotropicale, Bradyrhizobium lablabi, and Bradyrhizobium icense. Bradyrhizobium japonicum USDA 110 predominated in the soils, displaying symbiotic preference for the Huasteca 400 variety. However, phylogenetic analysis didn't reveal a clear association between strains, soil, and soybean variety. This research sheds light on the diversity of rhizobia in Mexican soybean cultivation, contributing to the understanding of symbiotic relationships in soybean production systems.

In vitro Mutagenesis for the Improvement of Agave Genus

Biotechnological techniques provide a viable alternative to help improve and increase the production of plant species of agricultural and economic importance,which have been affected over the years by climate change,increasing their susceptibility to pests and/or diseases,generating losses in production as well as a decrease in their regenerative and genetic diversity.The application of biotechnological techniques such as in vitro mutagenesis offers a viable option for the generation of crops that are resistant to the different factors caused by abiotic and biotic stress.In vitro mutagenesis has been used in an efficient way to generate genetic changes in different plant species.However,these methods have not been studied thoroughly in crops of agro-industrial interest,such as agave,which represents an economic resource of national importance and are considered as endemic species of Mexico.Therefore,this literary review aimed to focus on the studies that have been used for the genetic improvement of this species via mutagenesis techniques in plants in the agave genus.Therefore,the objective was to set a precedent for future genetic studies that aim to obtain more productive regenerants for various industries,such as food and pharmaceutical.It is also of great interest to compile information from basic research that helps understand and elucidate a model of possible defense mechanisms that are activated in the Agave genus.

Effects of Plant Extracts and Beauveria bassiana on the Activity of Defense-Related Enzymes in Solanum lycopersicum L.during Interaction with Fusarium oxysporum f.sp.lycopersici

The objective to this work was to evaluate the enzymatic activity in the culture of Solanum lycopersicum L.infected with Fusarium oxysporum after the combined application of Beauveria bassiana and plant extracts.Solanum lycopersicum plantlets were transplanted 15 days after the emergency.Five days after transplanting,Beauveria bassiana spores were applied at a concentration of 1×10^(7)spores mL^(−1)onto soil(along with A.indica(N)and P.auritum(H)leaf extracts)where S.lycopersicum plants were planted.Eight days after transplanting,spores of F.oxysporum strain were applied at a concentration of 1×10^(6)spores mL^(−1)to soil where S.lycopersicum plants were growing.The development of S.lycopersicum plants was monitored for 114 days,whereby a randomized complete block treatment design was used,the roots of the plants were crushed with liquid nitrogen,after which UV/VIS spectrophotometry was used to determine protein concentration,as well as the activity ofβ-1,3-glucanases,peroxidases(POX,EC1.11.1.7),catalase and chitinases.The treatments combining B.bassiana and A.indica and P.auritum extracts,had a significant difference in enzymatic activity levels,thus contributing to better defense mechanisms and a greater protection to S.lycopersicum plants in the presence of F.oxysporum.The application of B.bassiana and plant extracts to the ground mitigated damage caused by F.oxysporum on S.lycopersicum plants.

Antifungal Potential of Beauveria bassiana on Solanum lycopersicum L. Infected with Fusarium oxysporum f. sp. lycopersici

The objective of this work was to evaluate the effect of Beauveria bassiana(Bb 1205)on controlling Fusarium oxysporum f.sp.lycopersici(Fol 17108)in tomato plants in greenhouse conditions.Inoculation of Bb 1205 was the most promising among the agronomic variables and expression of the activity of the enzymesβ-1,3-glucanases and chitinases.Inoculation of Bb 1205 occurred at a concentration of 1×108 conidia·mL−1,which was administered onto the leaves,directly into the soil and via injection.Infection with Fol 17108 occurred with 1×106 spores·mL−1,which were added directly to the soil.Spectrophotometry was used for measuring agronomic parameters,namely activity of chitinases andβ-1,3-glucanases in foliage and roots.When Bb 1205 was added to the soil,the chlorophyll index and aerial part length showed significant differences.In addition,it was determined that root length,fresh weight of foliage,flower,and fruit count increased 82 days after inoculation(dai).Chitinase activity induced by Bb 1205 in leaves and roots of tomato plants infected with Fol 17108 was observed when injected into the stem at 32 dai(41.8 and 11.6-fold,respectively).Inoculation on the foliage showed a 10-fold increase ofβ-1,3-glucanases in the roots after 82 dpi.As for leaves,a 3.8-fold increase was found when the stem was inoculated.In the different in vivo applications,Bb 1205 activated its defenses by expressing the chitinase enzymes andβ-1,3-glucanase,thus reducing the damage caused by Fol 17108,demonstrating increase plant growth thereafter.

Effect of Water Stress Induced by Polyethylene Glycol on Growth, Proline Accumulation in Agave americana L.

The effect of water deficit was determined on both in vitro and soil seedling as well as in cells in suspension of Agave americana L.In order to do the establishment of cells,the formation of callus was induced;for it two auxins were evaluated:2,4-dichlorophenoxyacetic acid(2,4-D)and 4-mino-3,5,6-trichloropicolinic acid(picloram)at three concentrations(0.25,0.5 and 0.75 mg L−1)in three explants(leaf,root and meristems)cultured in MS semisolid medium.The callogenesis response was related to the type and section of the explant,as well as the regulator used,and a cell suspension was established using 0.5 mg L−1 naphthaleneacetic acid(NAA)+0.5 mg L−1 Benzylaminopurine(BAP).Seedlings were exposed to polyethyleneglycol(15%and 30%w/v)with a water potential of−0.87 and−2.67 MPa,respectively,under soil conditions.Water stress was applied through restricted irrigation.Fresh weight,root system growth,and chlorophyll concentration were some of the parameters that were affected by the effect of water deficit on A.americana L.Chlorophyll concentration values were significantly decreased by 15 at 30%PEG(19.6 SPAD units)compared to the control treatment.In in vitro plants,the highest concentration of proline was found in the roots,being the treatment with 30%polyethylene glycol where the highest concentration of this osmoregulator was obtained(62.5 mg g−1 DW).Under restricted irrigation conditions,an increase in proline concentration was observed both in the aerial part(2.2μg 100 g−1 DW)and in the root system(1.8μg 100 g−1 DW).However,the concentrations found were approximately ten times greater,less than those found under in vitro conditions.Therefore,the accumulation of proline can be considered an indicator of stress in Agave Americana L.growth in vitro.

Morphometric and Biochemical Changes in Agave americana L.Plantlets Induced By Ethyl Methanesulfonate

A.americana L.is a crop with very little genetic variability.In order to evaluate the effect of ethyl methanesulfonate(EMS)to induce variability in in vitro plantlets of A.americana,different explants(meristems,leaves and roots)were evaluated for the production of callus.MS medium supplemented with ANA(2.68μM)and BAP(2.68μM)was used.Callus obtained from apical meristem were treated with 15 mM EMS for two hours after which shoot formation was induced using 2,4-D(0.11μM)and BAP(44μM).The EMS induced variations in the morphometric and morphological parameters of the plantlets obtained,with 60%of the plantlets presenting differences such as dwarfism and different leaf forms,without the presence of spines,as well as an increase in fructan content of 30%with respect to the control plantlets.PAL was increased and this activity is related with higher anthocyanins concentration in A.americana L.plantlets.

Selection and Analysis of Polymorphisms in Somaclonal Variants of Agave americana Resistant to Fusarium oxysporum via an Ethyl Methanesulphonate Treatment

Agave americana L.callus were exposed to different concentrations of ethyl methanesulphonate(EMS)0,15,30,45 and 60 mM and to different times of exposure(2 and 4 h).The viability and capacity of shoot formation were shown to be affected when the callus were exposed to high concentrations(30–60 mM).Only the callus exposed to 15 mM EMS presented shoot formation;the exposure time of two hours produced the largest quantity of shoots regenerated per callus(21 shoots/callus).In order to generate somaclonal variants resistant to Fusarium oxysporum,a selection pressure was applied through of a culture filtrate(CF)of 100 ppm of the fungus.This was made in callus obtained in the treatment with 15 mM EMS during 2 h of exposure.The CF caused oxidation and necrosis in 71.25%of the callus;however,they were capable of generating shoots(3.5 shoots/callus).Molecular markers type RAPD,ISSR and DAMD were used to evaluate the genetic variation arising from the mutations caused by EMS on control plants and 16-month-old somaclonal variants.The polymorphic information content(PIC)for each one of the initiating groups was:0.28(DAMD),0.09(ISSR)and 0.14(RAPD).DAMD revealed a greater percentage of polymorphism than RAPD and ISSR.Polymorphic bands were detected in the somaclonal variants.This indicated that the EMS caused genetic variation in the regenerated plants conferring resistance to them against Fusarium oxysporum.

Encapsulation of Immature Somatic Embryos of Coffea arabica L.for in Vitro Preservation

The present study aimed to develop a protocol for somatic embryogenesis and encapsulation of coffee embryos(Coffea arabica L.),for the conservation of genotypes with characteristics of commercial interest.Somatic embryos were induced from leaf explants in Murashige and Skoog medium(MS)supplemented with 1 mg·L^(−1) of 2,4-dichlorophenoxiacetic acid(2,4-D)combined with 2 mg·L^(−1) of benzyladenine(BA).Somatic embryos(SE)at the globular stage were encapsulated in a sodium alginate matrix;two treatments were tested:MS+5 mg·L^(−1) BA+1 mg·L^(−1) NAA+3%(w/v)alginate,and MS+7 mg·L^(−1) BA+5.7 mg·L^(−1) indoleacetic acid(IAA)+3%(w/v)alginate.Alginate was complexed with 100 mM calcium chloride(CaCl_(2)).Viability of the encapsulated SE was determined by staining with 0.01%fluorescein diacetate(FDA)after 0,15,30,and 45 days of storage at 4℃.Embryo viability was 100%in both treatments.