Diversidade e potencial biotecnológico de fungos endofíticos de cacau (Theobroma cacao L.)

Abstract

Endophytes are all microorganisms, culturable or not, that inhabit the interior of plant tissues, causing no harm to the host, and that do not develop external structures, excluding in this way, nodulating bacteria and mycorrhizal fungi. Theobroma cacao L. is important to food and cosmetic industry due the fact that it is used for production of cacao butter. Considering the importance of cacao and associated endophytic fungal community studies, the objectives of this work were to: i) study the diversity on endophytic community of cacao; ii) evaluate the potential of this community to biological control of Crinipellis perniciosa, causal agent of witches' broom disease and other phytopathogens and iii) study the interaction endophyte-pathogen and endophyte-host. The work began with isolation of the cacao endophytic fungi that was characterizated based on morphological and molecelar characters. The diversity was evaluated by rDNA (ITS1, ITS2 e 5.8 subunit regions) analyses (ARDRA and sequencing). The ARDRA analysis generated 64 haplotypes, which included at least 16 species. Following, antagonistic endophytic fungi from cacao were selected in vitro against C. perniciosa. It was observed that in 145 evaluated isolates, 38.6% was classified as antagonic, while 13.1% were classified as parasitic. After the selection, isolates were used for secondary metabolites extraction and further characterization. Also, detection of δ-(L-α-aminoadipil)-L-cisteinil-D-valin (ACV) gene, which is the precursor of β-lactans, antibiotics like penicilins and cephalosporins, was carried out. The amplification of this gene generated a fragment of 600pb in 9.1% of the isolates evaluated. Some isolates were further evaluated against phytophathogenic fungi (Colletotrichum falcatum, C. sublineorum, Erythricium salmonicolor, Rhizoctonia solani, Ceratocystis paradoxa, Phytophthora sp., P. parasitica, P. palmivora and Fusarium moniliforme). Only C. sublineorum of sorghum and Ceratocystis paradoxa of sugarcane were in vitro inhibited by the endophytes 42.3 and 2, respectively. The investigation of the penetration and colonization ability of endophytic fungus 42.3 on susceptible cacao comum was carried out, using RAPD and SEM techniques. The penetration of the fungus was initiated between 3 and 6 hours after inoculation. The interaction between cacao endophyte 42.3 with C. perniciosa 281 (pathogenic), was evaluated by SDS-PAGE, aiming the detection of expressed proteins by pathogen and endophyte. The SDS-PAGE allowed the visualization of bands expressed in the interaction, when the microorganisms were grown together. In the presence of the endophyte growth substrate, C. perniciosa do not express visible proteins or, at least, distinguishable in SDS-PAGE, but the co-cultive of these fungi generated non observed bands in previously analysis.

Foliar endophytic fungi from Hevea brasiliensis and their antagonism on Microcyclus ulei

“…Proof of mutualism of endophyte-host symbioses has been inconclusive in most cases, but plant communities would probably not survive many environmental stresses without these symbioses. During the last decade, the question of possible symbiosis began to be answered with the detection of positive effects of endophytic microorganisms on plant growth and development (Gasoni and Gurfinkel 1997;Franken et al 1998;Varma et al 1999), resistance to biotic stresses (Maki 2006), and biological control of plant disease by fungi (Azevedo et al 2000;Benhamou and Brodeur 2000) or bacteria (Rajkumar et al 2005;Bergsma-Vlami et al 2005;Biondi 2004;Kaewchai et al 2009). Recent evidence has shown that endophytic fungi restrict both in vitro and in vivo growth of cacao pathogens and limit the damage they cause Evans et al 2003;Mejía et al 2003;Holmes et al 2004Holmes et al , 2006Rubini et al 2005;Tondje et al 2006) highlighting their status as a new source of biological control agents against the fungal pathogens of this tropical tree (Mejía et al 2008).…”

Fungos Endófitos Em Plantas Ornamentais Tropicais Na Bahia

“…(Assunção, 2010) e Vitis labrusca (Lima, 2010); Guignardia spp. em muitos hospedeiros (Wickert et al, 2009;Costa, 2003); Lasiodiplodia theobromae em Theobroma cacao (Maki, 2006); Pestalotiopsis microspora, P. maculans e Pestalotiopsis sp. em raízes de Vellozia compacta (Rodrigues, 2010), folhas de Musa spp.…”

“…Segundo Maki (2006), a estrutura da comunidade endófita varia em função do ambiente ao qual a planta está adaptada, bem como, das oscilações de fatores abióticos, tais como, temperatura, regime de chuvas que determinam a predominância de espécies de microrganismos presentes no ambiente. A riqueza e a composição de fungos endófitos estão relacionadas às estações do ano (Assunção, 2010).…”

Fungos endofíticos em folhas de cafeeiro: diversidade e potencial entomopatogênico sobre a broca do café

“…Barbosa (2005), informa que os endofíticos podem estabelecer relação mutualística com seus hospedeiros, recebendo nutrientes e proteção e produzindo compostos químicos como enzimas, alcaloides e antibióticos. Maki (2006), informa que os microrganismos endofíticos são responsáveis por promoção de crescimento através da síntese de fitormônios e fixação de nitrogênio, além de produção de compostos de defesa bioquímica induzida como peroxidases, H2O2, fenilalanina, amônio liases (FAL), proantocianidinas e fenilpropanóides. Informa ainda, que os endofíticos são estudados no mundo todo como fortes candidatos a agentes de controle biológico de fitopatógenos, uma vez que ocupam os mesmos nichos ecológicos destes.…”