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| Author(s): |
Monita Fiori de Abreu Tarazi
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2010-04-12 |
| Examining board members: |
Marcilio de Almeida;
Fernando Dini Andreote;
Welington Luiz de Araujo;
Nelson Barbosa Machado Neto;
Tsai Siu Mui
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| Advisor: | Marcilio de Almeida; Tsai Siu Mui |
| Abstract | |
The in vitro culture of plants by the control of environmental and nutritional factors, allows the study of the plant-bacteria interaction and the interpretation of possible morphophysiological changes in the microplants, from such interaction. However, the presence of endophytic bacteria in micropropagation is often characterized as harmful microbial contamination, which is promptly eliminated by the use of chemotherapeutics. This approach does not take into account the beneficial effects that endophytic bacteria can bring to the plant development, and annihilates the possibility of exploiting this potential in the in vitro environment. In general, due to its low culturability, endophytic bacterial communities require the use of culture-independent techniques for their study. In this context, this work aimed to prove the presence of bacterial endophytes in pineapple (Ananas comosus (L.) Merrill) cv. IAC Gomo-de-mel microplants considered axenics, and the effects of these in plant morphophysiology after antibiotictherapy. For this, PCR-DGGE, ARISA-PCR, cloning, sequencing, structural and ultrastructural analysis were used. The results showed that there is an endophytic bacterial community, composed of members of , , -proteobacteria, actinobacteria and cyanobacteria, which colonizes the microplants. The converging results of PCR-DGGE and ARISA-PCR showed that this community changed in its structure and diversity according to its niche of colonization and the period of cultivation of the host plant, without renewal of culture medium. The action of antibiotics influenced the bacterial community structure, promoting differential impacts on each bacterial group evaluated. Antibiotictherapy did not promote the total elimination of endophytic bacteria. However, the treatments caused changes in bacterial community, resulting in reduced growth of roots and other histological changes in the root system of the microplants. The ultrastructural analysis confirmed the presence of endophytic bacteria colonizing the intracellularly the leaf mesophyll and the cortex of roots, even after antibiotictherapy. Thus, it is concluded that in asymptomatic pineapple microplants there is an intracellular endophytic bacterial community, breaking the main paradigm of plant tissue culture, in which axenic microplants are mandatory. (AU) | |
| FAPESP's process: | 07/06731-6 - MOLECULAR CHARACTERIZATION OF ENDOPHYTIC BACTERIA AND ITS STUDY ON THE MORPHOGENIC PATHWAYS IN PINEAPPLE (ANANAS COMOSUS (L.) MERRILL) CV. IAC GOMO-DE-MEL CULTIVATED “IN VITRO”. |
| Grantee: | Monita Fiori de Abreu Tarazi |
| Support Opportunities: | Scholarships in Brazil - Doctorate |