Influence of iron and copper on the activity of laccases in Fusarium oxysporum f. sp. lycopersici

ABSTRACT Fusarium oxysporum f. sp. lycopersici is a phytopathogenic fungus that causes vascular wilt in tomato plants. In this work we analyze the influence of metal salts such as iron and copper sulphate, as well as that of bathophenanthrolinedisulfonic acid (iron chelator) and bathocuproinedisulfonic acid (copper chelator) on the activity of laccases in the intra (IF) and extracellular fractions (EF) of the wild-type and the non-pathogenic mutant strain (rho1::hyg) of F. oxysporum. The results show that laccase activity in the IF fraction of the wild and mutant strain increased with the addition of iron chelator (53.4 and 114.32%; respectively). With copper, it is observed that there is an inhibition of the activity with the addition of CuSO4 for the EF of the wild and mutant strain (reduction of 82 and 62.6%; respectively) and for the IF of the mutant strain (54.8%). With the copper chelator a less laccase activity in the IF of the mutant strain was observed (reduction of 53.9%). The results obtained suggest a different regulation of intracellular laccases in the mutant strain compared with the wild type in presence of CuSO4 and copper chelator which may be due to the mutation in the rho gene.

Influence of iron and copper on the activity of laccases in Fusarium oxysporum f. sp. lycopersici

Fusarium oxysporum f. sp. lycopersici is a phytopathogenic fungus that causes vascular wilt in tomato plants. In this work we analyze the influence of metal salts such as iron and copper sulphate, as well as that of bathophenanthrolinedisulfonic acid (iron chelator) and bathocuproinedisulfonic acid (copper chelator) on the activity of laccases in the intra (IF) and extracellular fractions (EF) of the wild-type and the non-pathogenic mutant strain (rho1::hyg) of F. oxysporum. The results show that laccase activity in the IF fraction of the wild and mutant strain increased with the addition of iron chelator (53.4 and 114.32%; respectively). With copper, it is observed that there is an inhibition of the activity with the addition of CuSO4 for the EF of the wild and mutant strain (reduction of 82 and 62.6%; respectively) and for the IF of the mutant strain (54.8%). With the copper chelator a less laccase activity in the IF of the mutant strain was observed (reduction of 53.9%). The results obtained suggest a different regulation of intracellular laccases in the mutant strain compared with the wild type in presence of CuSO4 and copper chelator which may be due to the mutation in the rho gene.(AU)

Inheritance of resistance to Fusarium oxysporum f. sp. phaseoli Brazilian race 2 in common bean

Aiming to obtain information concerning the genetic control of the resistance of the bean (Phaseolus vulgaris L.) to the fungus Fusarium oxysporum f. sp. phaseoli, six crosses involving three resistant lines (Carioca MG, Esal 583 and Esal 566) and four susceptible to the fungus (Carioca, CNFC 10443, Uirapuru and Esal 522) were developed. The parental lines, the controls (Carioca MG and Carioca) and the F1, F2 and F3 generations were evaluated for reaction to Fusarium. For inoculation, root cuttings were immersed in a spore suspension. The evaluations were performed at 21 days after inoculation, by scale of notes ranging from 1.0, to 9.0 and genetic and phenotypic parameters were estimated. The heritability in the narrow sense ranged from 0.34 to 0.42 and in the broad sense of 0.76 to 0.97, showing that selection should be easy, since efficient inoculation and selection methods are used. The average degree of dominance was around 1.0 indicating the presence of dominance in the control of the character, although additive effects are also expressive.

Com o objetivo de obter informações a respeito do controle genético da resistência do feijoeiro (Phaseolus vulgaris L.) ao fungo Fusarium oxysporum f. sp. phaseoli, foram realizados seis cruzamentos envolvendo três linhagens resistentes (Carioca MG, ESAL 583 e ESAL 566) e quatro suscetíveis ao fungo (Carioca, CNFC 10443, Uirapuru e ESAL 522). As plantas dos genitores, das testemunhas (Carioca MG e Carioca) e das gerações F1, F2 e F3 foram avaliadas quanto à reação à murcha-de-fusarium utilizando a metodologia de inoculação de imersão de raízes na suspensão de esporos, com o corte do sistema radicular. As avaliações foram realizadas aos 21 dias após a inoculação, por meio de escala de notas variando de 1,0 (plantas sem sintomas) a 9,0 (plantas mortas). Com os dados obtidos, foram estimados parâmetros genéticos e fenotípicos. A herdabilidade no sentido restrito variou de 0,34 a 0,42 e no sentido amplo de 0,76 a 0,97, podendo considerar o caráter como de fácil seleção, desde que se adotem critérios eficientes de inoculação e avaliação das plantas. O grau médio de dominância foi próximo de 1,0 evidenciando a presença de dominância no controle do caráter, embora a presença de efeitos aditivos também seja expressiva.

Inheritance of resistance to Fusarium oxysporum f. sp. phaseoli Brazilian race 2 in common bean

Aiming to obtain information concerning the genetic control of the resistance of the bean (Phaseolus vulgaris L.) to the fungus Fusarium oxysporum f. sp. phaseoli, six crosses involving three resistant lines (Carioca MG, Esal 583 and Esal 566) and four susceptible to the fungus (Carioca, CNFC 10443, Uirapuru and Esal 522) were developed. The parental lines, the controls (Carioca MG and Carioca) and the F1, F2 and F3 generations were evaluated for reaction to Fusarium. For inoculation, root cuttings were immersed in a spore suspension. The evaluations were performed at 21 days after inoculation, by scale of notes ranging from 1.0, to 9.0 and genetic and phenotypic parameters were estimated. The heritability in the narrow sense ranged from 0.34 to 0.42 and in the broad sense of 0.76 to 0.97, showing that selection should be easy, since efficient inoculation and selection methods are used. The average degree of dominance was around 1.0 indicating the presence of dominance in the control of the character, although additive effects are also expressive.

Com o objetivo de obter informações a respeito do controle genético da resistência do feijoeiro (Phaseolus vulgaris L.) ao fungo Fusarium oxysporum f. sp. phaseoli, foram realizados seis cruzamentos envolvendo três linhagens resistentes (Carioca MG, ESAL 583 e ESAL 566) e quatro suscetíveis ao fungo (Carioca, CNFC 10443, Uirapuru e ESAL 522). As plantas dos genitores, das testemunhas (Carioca MG e Carioca) e das gerações F1, F2 e F3 foram avaliadas quanto à reação à murcha-de-fusarium utilizando a metodologia de inoculação de imersão de raízes na suspensão de esporos, com o corte do sistema radicular. As avaliações foram realizadas aos 21 dias após a inoculação, por meio de escala de notas variando de 1,0 (plantas sem sintomas) a 9,0 (plantas mortas). Com os dados obtidos, foram estimados parâmetros genéticos e fenotípicos. A herdabilidade no sentido restrito variou de 0,34 a 0,42 e no sentido amplo de 0,76 a 0,97, podendo considerar o caráter como de fácil seleção, desde que se adotem critérios eficientes de inoculação e avaliação das plantas. O grau médio de dominância foi próximo de 1,0 evidenciando a presença de dominância no controle do caráter, embora a presença de efeitos aditivos também seja expressiva.

Biocontrol potential of salinity tolerant mutants of Trichoderma harzianum against Fusarium oxysporum

Exposing a wild-type culture of Trichoderma harzianum to gamma irradiation induced two stable salt-tolerant mutants (Th50M6 and Th50M11). Under saline conditions, both mutants greatly surpassed their wild type strain in growth rate, sporulation and biological proficiency against Fusarium oxysporum, the causal agent of tomato wilt disease. Tolerant T. harzianum mutants detained a capability to grow and convinced sporulation in growth media containing up to 69 mM NaCl. In comparison with their parent strain, characterization of both mutants confirmed that they have reinforced contents of proline and hydroxyproline, relatively higher sodium content compared to potassium, calcium or magnesium contents, higher level of total phenols. Electrophoretic analysis of total soluble proteins in the salt tolerance mutant Th50M6 showed different bands accumulated in response to 69 mM NaCl. Data also showed that mutants produce certain active metabolites, such as chitinases, cellulases, beta-galactosidases, as well as, some antibiotics i.e., trichodermin, gliotoxin and gliovirin. Trichoderma mutants significantly reduced wilt disease incidence and improved yield and mineral contents of tomato plants under both saline and non-saline soil conditions, as well as, under infested and natural conditions. T. harzianum mutants were also more efficient in dropping the F. oxysporum growth in rhizosphere compared to the wild type strain. Population density of both mutants in rhizosphere far exceeded that of T. harzianum wild type strain.

A exposição de uma cepa selvagem de Trichoderma harzianum à irradiação gama induziu dois mutantes tolerantes a sal (Th50M6 e Th50M11). Em condições salinas, os dois mutantes foram muito superiores à cepa selvagem em relação à velocidade de multiplicação, esporulação e eficiência contra Fusarium oxysporum, o agente causador da doença wilt do tomate. Os mutantes tolerantes foram capazes de multiplicação e esporulação em meio de cultura contendo NaCl até 69 mM. Em comparação à cepa selvagem, os dois mutantes possuíam conteúdo mais elevado de prolina e hidroxiprolina, conteúdo de sódio superior ao de potássio, cálcio ou magnésio e conteúdo elevado de fenóis totais. A análise eletroforética das proteínas totais solúveis no mutante Th50M6 apresentou bandas diferentes acumuladas em resposta a NaCl 69 mM. Os resultados também indicaram que os mutantes produzem alguns metabólitos ativos como quitinases, celulases, beta-galactosidades e antibióticos como tricodermina, gliotoxina e gliovirina. Os mutantes de Trichoderma reduziram significativamente a incidência da doença e melhoraram o rendimento e o conteúdo de minerais do tomate tanto em condições salinas como não-salinas e também em condições naturais e de infestação. Quando comparados à cepa selvagem, os mutantes de Trichoderma foram também mais eficientes em diminuir o crescimento de F. oxysporum na rizosfera.A densidade populacional de ambos mutantes na rizosfera excedeu muito a da cepa selvagem.