Annia Hernández-Rodríguez

Characterization of Pseudomonas chlororaphis from Theobroma cacao L. rhizosphere with antagonistic activity against Phytophthora palmivora (Butler)

To isolate and characterize rhizobacteria from Theobroma cacao with antagonistic activity against Phytophthora palmivora, the causal agent of the black pod rot, which is one of the most important diseases of T. cacao.

Assessment of the effect of chitosan of different molecular weights in controlling Rhizopus rots in tomato fruits

The effect of chitosan was evaluated in three isolates of Rhizopus stolonifer from infected tomatoes that were harvested in different regions of the state of Morelos, México. Changes in the membrane integrity of spores, modifications in pH media and the proteins released were analysed in each isolate against three different molecular weights of chitosan at three fixed concentrations. There was an observed decline in the integrity of spores in the presence of chitosan at all the concentrations evaluated. The protein released was different depending on the isolate, kind of chitosan and used concentration. There was a significant difference in the pH changes on the growth media for all the tested isolates. Chitosan of high molecular weight showed the best results to inhibit the infection caused by R. stolonifer on the tomato fruits. The severity of symptoms of soft rot was not related with the molecular weight of chitosan.

In vitro micrografting of apical and axillary buds of cacao

ABSTRACT This study aimed to evaluate in vitro grafting of Theobroma cacao where seedlings of the UF 677 genotype were used as the rootstock and apices or axillary buds of a Trinitarian genotype were used as scion. Three methods of grafting using scions from seedlings were evaluated. Apical grafts using apex and side grafts using apex displayed better graft success (95 and 80%, respectively). However, side grafts using axillary buds reached a greater height on average and a higher number of leaves per plant (1.76 cm and 3.72, respectively). Histological studies revealed new vascular elements at the graft union area. Side grafts with axillary buds provided the highest survival rate (82%) after the acclimatization step. A shoot of at least 1 cm with two leaves is required for plant survival after transfer to ex vitro conditions. Side grafting was carried out with axillary buds from adult trees and nursery plants. Only the grafts with buds from nursery grafted plants were successful, with a rate of 26%. Overall, side grafting with axillary buds is the most appropriate method for cacao micrografting. This method can be used for clonal propagation and for the establishment of in vivo and/or in vitro cacao germplasm collection.

Diazotrophic bacteria with activity promoting vegetable growth in Daucus carota L.

This study aimed at isolating diazotrophic bacteria with promoting activity of vegetal growth, associated to carrot culture. Samples were taken at 30, 60 and 115 days in a farm located in a rural area of the municipality of Manizales (Caldas). The diazotrophic bacteria were isolated in semi-solid culture media free of nitrogen. We described the macro and microscopic features of the obtained isolations, and identified them biochemically and molecularly. In addition, we evaluated indole compounds, nitrogenase activity and solubilization of phosphates. Gluconacetobacter diazotrophicus ATCC 49037 was used as a standard strain. We recovered 20 isolates associated to rhizosphere and 12 to rhizoplane. The molecular identification showed the presence of five genera: Rhizobium, Achromobacter, Bacillus, Enterobacter, and Stenotrophomonas. The production of indole compounds presented concentrations between 9.73 and 112.8 μg/mL. The standard strain showed a higher activity, with an indolic compound production of 172.5 μg/mL. Regarding nitrogenase activity, the isolates GIBI411, 394 and 399 had an activity greater or similar to the standard strain. The most efficient isolates in the solubilization of tricalcium phosphate were GIBI378 and 385. The solubilization of aluminum phosphate was assessed by the acid production index, with the isolates GIBI378, 391, 387 and 388 presenting the best behavior. The isolates found are potential candidates for the development of novel biotechnological processes to produce new alternative biofertilizers, considering the significant plant-growth promotion properties determined in this work.