Tolerância de bactérias diazotróficas simbióticas à salinidade in vitro

Abstract

RESUMOA busca de estirpes de bactérias diazotróficas simbióticas tolerantes à salinidade, em conjunto com a seleção de hospedeiros, tem por objetivo aumentar o desempenho da simbiose e manter a produtividade vegetal de forma sustentada em condições de estresse salino. Doze estirpes de bactérias diazotróficas de diferentes procedências foram estudadas quanto à tolerância a diferentes concentrações de NaCl em meios de cultura 79 e LB. As estirpes que apresentaram maior tolerância à salinidade (30 g L -1 ) em meio 79 foram: BR 6806 e BR 4007, ambas de crescimento rápido isoladas de solos do Nordeste brasileiro, UFLA 03-51 e UFLA 03-65, de crescimento rápido e UFLA 03-84, de crescimento lento, sendo as três últimas oriundas da Região Amazônica. Essas também estiveram entre as mais tolerantes em meio de cultura LB. A estirpe UFLA 03-84, selecionada em trabalhos prévios por sua alta eficiência para caupi (Vigna unguiculata), pode ser indicada para estudos de inoculação, visando a aumentar o rendimento dessa cultura em solos salinos. Os meios de cultura 79 e LB foram eficientes para avaliar a tolerância relativa de rizóbio a NaCl, mas o meio 79 é mais indicado, pois permite o crescimento de todas as estirpes. Pelos resultados, infere-se haver relação entre tolerância in vitro à salinidade e origem dos microssimbiontes, pois as estirpes BR 4007 e BR 6806, oriundas do Ceará, estiveram entre as mais tolerantes.Termos para indexação: Rizóbio, NaCl, estresse, Vigna unguiculata. ABSTRACTTolerance to salinity of diazotrophic bacteria and their host species could increase plant growth and sustainability in salt stressed soils. Twelve diazotrophic bacteria strains were studied regarding their tolerance to different NaCl concentrations in 79 and LB media. More tolerant (30 g L -1 ) strains in 79 medium were: the fast growers BR 6806 and BR 4007, isolated from northeast Brazil, UFLA 03-51 and UFLA 03-65, and slow growing strain UFLA03-84, being these last three isolated from Amazon region. These strains were among the most salt tolerant in LB medium. The high salt tolerance of strain UFLA 03-84, as well as its highest efficiency (biological nitrogen fixation) in cowpea symbiosis (Vigna unguiculata), indicates it can be assayed as inoculant to improve yields of this species at saline soils. Media 79 and LB were efficient to evaluate relative tolerance of rhizobia to NaCl, however 79 medium is more suitable as it allows growth of all strains.

Phenotypic and molecular fingerprinting of fast growing rhizobia of field-grown pigeonpea from the eastern edge of the Brazilian Pantanal

“…The same metabolic versatility was observed during the evaluation of the bacterial capacity to grow on the culture medium supplemented with different salt concentrations as the 13 bacterial isolates presented the capacity to grow on the YMA medium supplemented with 0.52 M NaCl. These results are in agreement with those found in previous studies evaluating the tolerance of tropical rhizobia from pigeonpea (Fernandes et al, 2003;Fernandes Jr. et al, 2012), cowpea (Nóbrega et al, 2004;Xavier et al, 2007, Florentino et al, 2010, and lentil (Jida and Assefa, 2011).…”

“…The evaluations of the in vitro bacterial tolerance simulated environment (salinity, high temperatures, antibiotic concentrations, etc.) are relatively cheap, require little space, are not time consuming, and can feasibly be conducted with a large number of bacterial isolates (Nóbrega et al, 2004, Xavier et al, 2007. Furthermore, the correlation between these results and field responses was recently demonstrated (Indrasumunar et al, 2012), indicating the relevance of these evaluations for rhizobial strains.…”

Phenotypic diversity and amylolytic activity of fast growing rhizobia from pigeonpea [Cajanus cajan (L.) Millsp.]

“…Temperatures higher than 40°C were easily reached at the tropical soils, the evaluation of in vitro tolerance to high temperatures may help in the selection of more stable strains to heat conditions (29). Regarding the salt tolerance evaluation, in vitro assays are cheap and feasible to large numbers of isolates, allowing the selection of potential strains to further field experiments, especially in soils with high salt content (17,29).…”

“…: 56302-970, Petrolina-PE, Brasil. ; E-mail: paulo.ivan@embrapa.br metabolism, high temperature and salt tolerance (11,12,17,29).…”

Effects that nutritional and saline gradients have on the growth of Passiflora mucronata Lam. and Canavalia rosea (Sw.) DC. found in the restinga of Brazil

“…This damage can be related to physiological and morphological characteristics specific to the taxonomic group to which this species belongs. While it is considered a species of nitrogen-fixing Fabaceae, its nodules are very sensitive to the presence of salt (Garg & Singla 2004;Nóbrega et al 2004). In fact, the number of nodules of C. rosea was lower in the saline solution.…”