Effects of maize genotypes, nitrogen rates and sources in yield, nutritional status, and fumonisins incidence.

The maize yield, nutritional status, and grain fumonisins concentration were evaluated in different genotypes, doses, and nitrogen sources (N) in two years and three locations. Two experiments were carried out in each area and year in an experimental design of a subdivided plot with four replications. One experiment involved a 4x2 factorial treatment: four nitrogen (N) doses (0, 80, 160, and 240 kg ha-1) in coverage and having urea as a source of N and two genotypes. Another experiment involved a 4x2 factorial treatment: four N sources: urea, urea covered with polymer, ammonium nitrate, and ammonium nitrate + urea (UAN), at a dose of 160 kg ha-1, in two genotypes. The genotype generally influenced maize yield more than N doses and sources, mainly due to the bushy stunt/corn stunt tolerance of AG7098 PRO2 and AG8677 PRO2. The N doses linearly increased the N leaf content. However, the N sources did not affect the N leaf content. The N doses and sources had no significant effect on the content of fumonisins, which was affected only by the genotypes in Sete Lagoas in 2016 (N doses experiment) and 2017 (N sources experiment). The hybrids, P3630H and AG8677PRO2 (Sete Lagoas, 2016, N doses experiment and 2017, N sources experiment, respectively) exceeded the Brazilian legislation for Maximum Tolerance Limit for fumonisins in corn grains, which is 5,000 µg kg-1. The best result was obtained with AG7098 PRO2, with yields (above 10,000 kg ha-1) and fumonisins consistently below 5,000 µg kg-1. Therefore, the selection of corn hybrids is a strategy to reduce the occurrence of fumonisins in the grains.

How omnivory affects the survival and choices of earwig Doru luteipes (Scudder) (Dermaptera: Forficulidae)? / Como a onivoria afeta a sobrevivência e escolhas da tesourinha Doru luteipes (Scudder) (Dermaptera: Forficulidae)?

Abstract Doru luteipes (Scudder, 1876) is an omnivorous predator that finds different food resources in the corn plant: eggs of Spodoptera frugiperda (J.E. Smith, 1797), uredospores of Puccinia polysora (Underw, 1897), and pollen. Knowing the survival and food preferences of this predator is essential to define its relevance as a biological control agent. We hypothesize that the foraging behavior and predatory capacity of D. luteipes may be affected when several food resources, especially eggs of S. frugiperda, uredospores of P. polysora, and pollen are concurrently in the same plant. The survival of D. luteipes in the nymph stage and their preference among food resources, often available in corn plants, were determined. To verify the survival of D. luteipes, newly hatched nymphs were fed exclusively with 1- uredospores of P. polysora, 2- eggs of S. frugiperda, 3- corn pollen, 4- a combination of uredospores + eggs, and 5- artificial diet (control). In another experiment, nymphs and adults of D. luteipes with 24 and 48 hours of fasting were individually released in the center of a container with four diets: 1- uredospores of P. polysora, 2- eggs of S. frugiperda, 3- corn pollen, 4- artificial diet, and maintained for 10 minutes, to evaluate the food choice and feeding time. The exclusive feeding with S. frugiperda eggs caused low nymph survival (8%), but the combination of P. polysora uredospores + S. frugiperda eggs allowed 58.3% survival. D. luteipes preferred feeding during the nighttime and the most significant proportions of choices by nymphs and adults were for pollen and diet, with adults spending more time eating pollen. These findings indicate that the trophic choices of D. luteipes are relevant to understand its contribution as an agent to control pest insects and fungal diseases in corn.

Resumo Doru luteipes (Scudder, 1876) é um predador onívoro, que encontra na planta do milho diferentes recursos alimentares: ovos de Spodoptera frugiperda (J.E. Smith, 1797), uredósporos de Puccinia polysora (Underw, 1897) e pólen. Para definição da relevância desse predador como agente de controle biológico, conhecer a sobrevivência e preferência alimentar é essencial. Nós hipotetizamos que o comportamento de forrageamento e a capacidade de predação de D. luteipes podem ser afetados quando uma mesma planta oferece ovos, uredósporos e pólen, concomitantemente. A sobrevivência de D. luteipes na fase de ninfa e sua preferência entre os recursos alimentares, frequentemente disponíveis nas plantas de milho, foram determinados. Para verificar a sobrevivência de D. luteipes, ninfas recém eclodidas foram alimentadas exclusivamente com 1- uredósporos de P. polysora, 2- ovos de S. frugiperda, 3- pólen de milho, 4- combinação de uredósporos + ovos e 5- dieta artificial (controle). Em outro experimento, ninfas e adultos de D. luteipes com 24 e 48 horas de jejum foram liberadas individualmente, em recipientes contendo quatro dietas: 1- uredósporos de P. polysora, 2- ovos de S. frugiperda, 3- pólen de milho, 4- dieta artificial e mantidas durante 10 min, sendo avaliados a escolha pelo alimento e o tempo de alimentação. A alimentação exclusiva com ovos de S. frugiperda ocasionou baixa sobrevivência das ninfas (8%), porém a combinação de uredósporos de P. polysora + ovos de S. frugiperda possibilitou sobrevivência de 58,3%. D. luteipes preferiu se alimentar durante o período noturno e as maiores proporções de escolhas das ninfas e dos adultos ocorreram no pólen e na dieta, sendo que os adultos gastaram mais tempo se alimentando de pólen. Estas descobertas indicam que as escolhas tróficas de D. luteipes são relevantes para compreender sua contribuição como agente de controle de insetos-praga e doença fúngicas em milho.

How omnivory affects the survival and choices of earwig Doru luteipes (Scudder) (Dermaptera: Forficulidae)? / Como a onivoria afeta a sobrevivência e escolhas da tesourinha Doru luteipes (Scudder) (Dermaptera: Forficulidae)?

Doru luteipes (Scudder, 1876) is an omnivorous predator that finds different food resources in the corn plant: eggs of Spodoptera frugiperda (J.E. Smith, 1797), uredospores of Puccinia polysora (Underw, 1897), and pollen. Knowing the survival and food preferences of this predator is essential to define its relevance as a biological control agent. We hypothesize that the foraging behavior and predatory capacity of D. luteipes may be affected when several food resources, especially eggs of S. frugiperda, uredospores of P. polysora, and pollen are concurrently in the same plant. The survival of D. luteipes in the nymph stage and their preference among food resources, often available in corn plants, were determined. To verify the survival of D. luteipes, newly hatched nymphs were fed exclusively with 1- uredospores of P. polysora, 2- eggs of S. frugiperda, 3- corn pollen, 4- a combination of uredospores + eggs, and 5- artificial diet (control). In another experiment, nymphs and adults of D. luteipes with 24 and 48 hours of fasting were individually released in the center of a container with four diets: 1- uredospores of P. polysora, 2- eggs of S. frugiperda, 3- corn pollen, 4- artificial diet, and maintained for 10 minutes, to evaluate the food choice and feeding time. The exclusive feeding with S. frugiperda eggs caused low nymph survival (8%), but the combination of P. polysora uredospores + S. frugiperda eggs allowed 58.3% survival. D. luteipes preferred feeding during the nighttime and the most significant proportions of choices by nymphs and adults were for pollen and diet, with adults spending more time eating pollen. These findings indicate that the trophic choices of D. luteipes are relevant to understand its contribution as an agent to control pest insects and fungal diseases in corn.

Doru luteipes (Scudder, 1876) é um predador onívoro, que encontra na planta do milho diferentes recursos alimentares: ovos de Spodoptera frugiperda (J.E. Smith, 1797), uredósporos de Puccinia polysora (Underw, 1897) e pólen. Para definição da relevância desse predador como agente de controle biológico, conhecer a sobrevivência e preferência alimentar é essencial. Nós hipotetizamos que o comportamento de forrageamento e a capacidade de predação de D. luteipes podem ser afetados quando uma mesma planta oferece ovos, uredósporos e pólen, concomitantemente. A sobrevivência de D. luteipes na fase de ninfa e sua preferência entre os recursos alimentares, frequentemente disponíveis nas plantas de milho, foram determinados. Para verificar a sobrevivência de D. luteipes, ninfas recém eclodidas foram alimentadas exclusivamente com 1- uredósporos de P. polysora, 2- ovos de S. frugiperda, 3- pólen de milho, 4- combinação de uredósporos + ovos e 5- dieta artificial (controle). Em outro experimento, ninfas e adultos de D. luteipes com 24 e 48 horas de jejum foram liberadas individualmente, em recipientes contendo quatro dietas: 1- uredósporos de P. polysora, 2- ovos de S. frugiperda, 3- pólen de milho, 4- dieta artificial e mantidas durante 10 min, sendo avaliados a escolha pelo alimento e o tempo de alimentação. A alimentação exclusiva com ovos de S. frugiperda ocasionou baixa sobrevivência das ninfas (8%), porém a combinação de uredósporos de P. polysora + ovos de S. frugiperda possibilitou sobrevivência de 58,3%. D. luteipes preferiu se alimentar durante o período noturno e as maiores proporções de escolhas das ninfas e dos adultos ocorreram no pólen e na dieta, sendo que os adultos gastaram mais tempo se alimentando de pólen. Estas descobertas indicam que as escolhas tróficas de D. luteipes são relevantes para compreender sua contribuição como agente de controle de insetos-praga e doença fúngicas em milho.

Thermo-resistant enzyme-producing microorganisms isolated from composting / Microrganismos produtores de enzimas termo-resistentes isolados de compostagem

Organo-mineral fertilizers supplemented with biological additives are an alternative to chemical fertilizers. In this study, thermoresistant microorganisms from composting mass were isolated by two-step procedures. First, samples taken at different time points and temperatures (33 days at 52 ºC, 60 days at 63 ºC, and over 365 days at 26 ºC) were pre-incubated at 80 oC for 30 minutes. Second, the microbial selection by in vitro culture-based methods and heat shock at 60 oC and 100 oC for 2h and 4h. Forty-one isolates were able to grow at 60 °C for 4h; twenty-seven at 100 °C for 2h, and two at 100 °C for 4h. The molecular identification by partial sequencing of the 16S ribosomal gene using universal primers revealed that thirty-five isolates were from eight Bacillus species, one Brevibacillus borstelensis, three Streptomyces thermogriseus, and two fungi (Thermomyces lanuginosus and T. dupontii). Data from amylase, phytase, and cellulase activity assays and the enzymatic index (EI) showed that 38 of 41 thermo-resistant isolates produce at least one enzyme. For amylase activity, the highest EI value was observed in Bacillus licheniformis (isolate 21C2, EI= 4.11), followed by Brevibacillus borstelensis (isolate 6C2, EI= 3.66), Bacillus cereus (isolate 18C2, EI= 3.52), and Bacillus paralicheniformis (isolate 20C2, EI= 3.34). For phytase, the highest EI values were observed for Bacillus cereus (isolate 18C2, EI= 2.30) and Bacillus licheniformis (isolate 3C1, EI= 2.15). Concerning cellulose production, B. altitudinis (isolate 6C1) was the most efficient (EI= 6.40), followed by three Bacillus subtilis (isolates 9C1, 16C2, and 19C2) with EI values of 5.66, 5.84, and 5.88, respectively, and one B. pumilus (isolate 27C2, EI= 5.78). The selected microorganisms are potentially useful as a biological additive in organo-mineral fertilizers and other biotechnological processes.

Os fertilizantes organo-minerais suplementados com aditivos biológicos são uma alternativa aos adubos químicos. Neste estudo, microrganismos termoresistentes foram isolados de compostagem por procedimentos de duas etapas. Inicialmente, as amostras tomadas em diferentes períodos e temperaturas (33 dias a 52 ºC, 60 dias a 63 ºC e mais de 365 dias a 26 ºC) foram pré-incubadas a 80 oC por 30 minutos. Posteriormente, a seleção microbiana foi conduzida por métodos baseados em cultura in vitro e choque térmico a 60 oC e 100 oC por 2h e 4h. Quarenta e um isolados foram capazes de crescer a 60 °C por 4h; vinte e sete a 100 °C por 2h e dois a 100 °C por 4h. A identificação molecular por sequenciamento parcial do gene ribossomal 16S usando primers universais revelou que trinta e cinco isolados eram de oito espécies de Bacillus, um Brevibacillus borstelensis, três Streptomyces thermogriseus e dois fungos (Thermomyces lanuginosus e T. dupontii). Os dados dos ensaios de atividade de amilase, fitase e celulase e o índice enzimático (IE) mostraram que 38 dos 41 isolados termorresistentes produziram pelo menos uma enzima. Para a atividade da amilase, o maior valor de IE foi observado em Bacillus licheniformis (isolado 21C2, IE = 4,11), seguido por Brevibacillus borstelensis (isolado 6C2, IE = 3,66), Bacillus cereus (isolado 18C2, IE = 3,52) e Bacillus paralicheniformis (isolado 20C2, IE = 3,34). Para a fitase, os maiores valores de IE foram observados para B. cereus (isolado 18C2, IE = 2,30) e B. licheniformis (isolado 3C1, IE = 2,15). Em relação à produção de celulose, B. altitudinis (isolado 6C1) foi o mais eficiente (IE = 6,40), seguido por três Bacillus subtilis (isolados 9C1, 16C2 e 19C2) com valores de IE de 5,66, 5,84 e 5,88, respectivamente, e um B. pumilus (isolado 27C2, IE = 5,78). Pode-se inferir que os microrganismos selecionados são potencialmente úteis como aditivos biológicos em fertilizantes organo-minerais e outros processos biotecnológicos.

How omnivory affects the survival and choices of earwig Doru luteipes (Scudder) (Dermaptera: Forficulidae)?

Abstract Doru luteipes (Scudder, 1876) is an omnivorous predator that finds different food resources in the corn plant: eggs of Spodoptera frugiperda (J.E. Smith, 1797), uredospores of Puccinia polysora (Underw, 1897), and pollen. Knowing the survival and food preferences of this predator is essential to define its relevance as a biological control agent. We hypothesize that the foraging behavior and predatory capacity of D. luteipes may be affected when several food resources, especially eggs of S. frugiperda, uredospores of P. polysora, and pollen are concurrently in the same plant. The survival of D. luteipes in the nymph stage and their preference among food resources, often available in corn plants, were determined. To verify the survival of D. luteipes, newly hatched nymphs were fed exclusively with 1- uredospores of P. polysora, 2- eggs of S. frugiperda, 3- corn pollen, 4- a combination of uredospores + eggs, and 5- artificial diet (control). In another experiment, nymphs and adults of D. luteipes with 24 and 48 hours of fasting were individually released in the center of a container with four diets: 1- uredospores of P. polysora, 2- eggs of S. frugiperda, 3- corn pollen, 4- artificial diet, and maintained for 10 minutes, to evaluate the food choice and feeding time. The exclusive feeding with S. frugiperda eggs caused low nymph survival (8%), but the combination of P. polysora uredospores + S. frugiperda eggs allowed 58.3% survival. D. luteipes preferred feeding during the nighttime and the most significant proportions of choices by nymphs and adults were for pollen and diet, with adults spending more time eating pollen. These findings indicate that the trophic choices of D. luteipes are relevant to understand its contribution as an agent to control pest insects and fungal diseases in corn.

Resumo Doru luteipes (Scudder, 1876) é um predador onívoro, que encontra na planta do milho diferentes recursos alimentares: ovos de Spodoptera frugiperda (J.E. Smith, 1797), uredósporos de Puccinia polysora (Underw, 1897) e pólen. Para definição da relevância desse predador como agente de controle biológico, conhecer a sobrevivência e preferência alimentar é essencial. Nós hipotetizamos que o comportamento de forrageamento e a capacidade de predação de D. luteipes podem ser afetados quando uma mesma planta oferece ovos, uredósporos e pólen, concomitantemente. A sobrevivência de D. luteipes na fase de ninfa e sua preferência entre os recursos alimentares, frequentemente disponíveis nas plantas de milho, foram determinados. Para verificar a sobrevivência de D. luteipes, ninfas recém eclodidas foram alimentadas exclusivamente com 1- uredósporos de P. polysora, 2- ovos de S. frugiperda, 3- pólen de milho, 4- combinação de uredósporos + ovos e 5- dieta artificial (controle). Em outro experimento, ninfas e adultos de D. luteipes com 24 e 48 horas de jejum foram liberadas individualmente, em recipientes contendo quatro dietas: 1- uredósporos de P. polysora, 2- ovos de S. frugiperda, 3- pólen de milho, 4- dieta artificial e mantidas durante 10 min, sendo avaliados a escolha pelo alimento e o tempo de alimentação. A alimentação exclusiva com ovos de S. frugiperda ocasionou baixa sobrevivência das ninfas (8%), porém a combinação de uredósporos de P. polysora + ovos de S. frugiperda possibilitou sobrevivência de 58,3%. D. luteipes preferiu se alimentar durante o período noturno e as maiores proporções de escolhas das ninfas e dos adultos ocorreram no pólen e na dieta, sendo que os adultos gastaram mais tempo se alimentando de pólen. Estas descobertas indicam que as escolhas tróficas de D. luteipes são relevantes para compreender sua contribuição como agente de controle de insetos-praga e doença fúngicas em milho.

Thermo-resistant enzyme-producing microorganisms isolated from composting

Abstract Organo-mineral fertilizers supplemented with biological additives are an alternative to chemical fertilizers. In this study, thermoresistant microorganisms from composting mass were isolated by two-step procedures. First, samples taken at different time points and temperatures (33 days at 52 ºC, 60 days at 63 ºC, and over 365 days at 26 ºC) were pre-incubated at 80 oC for 30 minutes. Second, the microbial selection by in vitro culture-based methods and heat shock at 60 oC and 100 oC for 2h and 4h. Forty-one isolates were able to grow at 60 °C for 4h; twenty-seven at 100 °C for 2h, and two at 100 °C for 4h. The molecular identification by partial sequencing of the 16S ribosomal gene using universal primers revealed that thirty-five isolates were from eight Bacillus species, one Brevibacillus borstelensis, three Streptomyces thermogriseus, and two fungi (Thermomyces lanuginosus and T. dupontii). Data from amylase, phytase, and cellulase activity assays and the enzymatic index (EI) showed that 38 of 41 thermo-resistant isolates produce at least one enzyme. For amylase activity, the highest EI value was observed in Bacillus licheniformis (isolate 21C2, EI= 4.11), followed by Brevibacillus borstelensis (isolate 6C2, EI= 3.66), Bacillus cereus (isolate 18C2, EI= 3.52), and Bacillus paralicheniformis (isolate 20C2, EI= 3.34). For phytase, the highest EI values were observed for Bacillus cereus (isolate 18C2, EI= 2.30) and Bacillus licheniformis (isolate 3C1, EI= 2.15). Concerning cellulose production, B. altitudinis (isolate 6C1) was the most efficient (EI= 6.40), followed by three Bacillus subtilis (isolates 9C1, 16C2, and 19C2) with EI values of 5.66, 5.84, and 5.88, respectively, and one B. pumilus (isolate 27C2, EI= 5.78). The selected microorganisms are potentially useful as a biological additive in organo-mineral fertilizers and other biotechnological processes.

Resumo Os fertilizantes organo-minerais suplementados com aditivos biológicos são uma alternativa aos adubos químicos. Neste estudo, microrganismos termoresistentes foram isolados de compostagem por procedimentos de duas etapas. Inicialmente, as amostras tomadas em diferentes períodos e temperaturas (33 dias a 52 ºC, 60 dias a 63 ºC e mais de 365 dias a 26 ºC) foram pré-incubadas a 80 oC por 30 minutos. Posteriormente, a seleção microbiana foi conduzida por métodos baseados em cultura in vitro e choque térmico a 60 oC e 100 oC por 2h e 4h. Quarenta e um isolados foram capazes de crescer a 60 °C por 4h; vinte e sete a 100 °C por 2h e dois a 100 °C por 4h. A identificação molecular por sequenciamento parcial do gene ribossomal 16S usando primers universais revelou que trinta e cinco isolados eram de oito espécies de Bacillus, um Brevibacillus borstelensis, três Streptomyces thermogriseus e dois fungos (Thermomyces lanuginosus e T. dupontii). Os dados dos ensaios de atividade de amilase, fitase e celulase e o índice enzimático (IE) mostraram que 38 dos 41 isolados termorresistentes produziram pelo menos uma enzima. Para a atividade da amilase, o maior valor de IE foi observado em Bacillus licheniformis (isolado 21C2, IE = 4,11), seguido por Brevibacillus borstelensis (isolado 6C2, IE = 3,66), Bacillus cereus (isolado 18C2, IE = 3,52) e Bacillus paralicheniformis (isolado 20C2, IE = 3,34). Para a fitase, os maiores valores de IE foram observados para B. cereus (isolado 18C2, IE = 2,30) e B. licheniformis (isolado 3C1, IE = 2,15). Em relação à produção de celulose, B. altitudinis (isolado 6C1) foi o mais eficiente (IE = 6,40), seguido por três Bacillus subtilis (isolados 9C1, 16C2 e 19C2) com valores de IE de 5,66, 5,84 e 5,88, respectivamente, e um B. pumilus (isolado 27C2, IE = 5,78). Pode-se inferir que os microrganismos selecionados são potencialmente úteis como aditivos biológicos em fertilizantes organo-minerais e outros processos biotecnológicos.

Expression analysis of phosphate induced genes in contrasting maize genotypes for phosphorus use efficiency.

Phosphorus is an essential nutrient for plant growth and development. The ability of plants to acquire phosphate (Pi) from the rhizosphere soil is critical in the Brazilian Cerrado characterized by acidic soil. The induction of Pi transporters is one of the earliest molecular responses to Pi deficiency in plants. In this study, we characterize the transcriptional regulation of six (ZmPT1 to ZmPT6) high-affinity Pi transporters genes in four Pi-efficient and four Pi-inefficient maize (Zea mays) genotypes. The expression analysis indicated that Pi-starvation induced the transcription of all ZmPT genes tested. The abundance of transcripts was inversely related to Pi concentration in nutrient solution and was observed as early as five days following the Pi deprivation. The Pi-starved plants replenished with 250 µM Pi for four to five days resulted in ZmPT suppression, indicating the Pi role in gene expression. The tissue-specific expression analysis revealed the abundance of ZmPT transcripts in roots and shoots. The six maize Pi transporters were primarily detected in the upper and middle root portions and barely expressed in root tips. The expression profiles of the six ZmPTs phosphate transporters between and among Pi-efficient and Pi-inefficient genotypes showed an absence of significant differences in the expression pattern of the ZmPTs among Pi-efficient and Pi-inefficient genotypes. The results suggested that Pi acquisition efficiency is a complex trait determined by quantitative loci in maize.

Microorganisms from corn stigma with biocontrol potential of Fusarium verticillioides.

The mycotoxigenic fungus Fusarium verticillioides is the primary maize pathogen and causes the maize stalk and ear rot diseases with significant economic losses. Furthermore, the excessive use of fungicides to control F. verticillioides constitutes threats to the environment and human health. Thus, sustainable alternatives such as biological control are needed to minimize the hazards associated with the current method. Although much is known about the vulnerability of the maize silks as a gateway for several fungal pathogens invading the developing grains, studies on the chemical properties of silk extracts and their resident microbiota are scarce. This study isolated and characterized bacteria and fungi that colonize the maize stigma to assess new potential biocontrol agents. The samples were collected from maize fields in the Brazilian localities of Sete Lagoas-MG, Sidrolândia-MS, Sertaneja-PR, and Goiânia-GO. One hundred sixty-seven microorganisms were isolated, 46% endophytic and 54% epiphytic. First, the antagonist activity was evaluated by the agar disc diffusion method performed in triplicate, and 83% of the isolates showed antagonist activity against F. verticillioides. Then, the 42 most efficient isolates were identified based on the partial sequencing of the bacterial 16S rRNA gene and fungi ITS region. The bacteria belong to the genera Bacillus (57.1%), Burkholderia (23.8%), Achromobacter (7.1%), Pseudomonas (2.4%), and Serratia (2.4%), while the fungi are Penicillium (2.4%), Candida (2.4), and Aspergillus (2.4%). The results showed that microorganisms from maize stigma might represent new promising agents for F. verticillioides control.

Fungivory: a new and complex ecological function of Doru luteipes (Scudder) (Dermaptera: Forficulidae) / Fungivoria: uma nova e complexa função ecológica de Doru luteipes (Scudder) (Dermaptera: Forficulidae)

We report the discovery that the earwig predator Doru luteipes (Scudder, 1876) (Dermaptera: Forficulidae) feed on Puccinia polysora Underw uredospore, the causal agent of Southern Rust of Corn (SRC), which is a primary disease affecting the maize crop in Brazil. We performed experiments in laboratory and greenhouse to test the effect of D. luteipes (1st/2nd and 3rd/4th instars, and adults) fungivory on the P. polysora uredospore concentration. All trials showed a significant reduction of the initial concentration of uredospore. There was a reduction in uredospore concentration with increase in number of D. luteipes feeding on them. We also tested the uredospore consumption by quantifying its percentage in the feces of D. luteipes. Nymphs of the 2nd, 4th instar and adults fed 88%, 85%, and 83.8% of the uredospore, respectively. For nymphs of the 3rd instar, the percentage of uredospore consumption (75.6%) was statistically significant compared with the other groups. In greenhouse experiment, at twenty-eight days after plant inoculation with 9.9 x 104 uredospores, the percentage of uredospore consumption was 81.7%. Our results confirmed the fungivory of D. luteipes on P. polysora uredospore. This is the first report of D. luteipes fungivory, which may play an important role in the biological control of P. polysora in corn.

Relatamos a descoberta de que o predador Doru luteipes (Scudder, 1876) (Dermaptera: Forficulidae) se alimenta de uredosporos de Puccinia polysora Underw, o agente causal da ferrugem polisora que é uma doença primária que afeta a cultura do milho no Brasil. Realizamos experimentos em laboratório e em casa de vegetação para testar o efeito da fungivoria de D. luteipes (1º/2º e 3º/4º iìstares e adultos) sobre a concentração de uredosporos de P. polysora. Todos os ensaios mostraram uma redução significativa da concentração inicial de uredosporos. Houve uma redução na concentração de uredosporos com o aumento do número de D. luteipes alimentando-se deles. Também testamos o consumo de uredosporos quantificando sua porcentagem nas fezes de D. luteipes. Ninfas do 2º e 4º ínstar, assim como adultos, alimentaram-se de 88%, 85% e 83,8% dos uredosporos, respectivamente. Para ninfas do 3º ínstar, a porcentagem de consumo de uredosporos (75,6%) foi estatisticamente significativo em comparação com os outros grupos. No experimento em casa de vegetação, aos 28 dias após a inoculação das plantas com 9,9 x 104 uredosporos, a porcentagem de consumo de uredosporos foi de 81,7%. Nossos resultados confirmaram a fungivoria de D. luteipes em uredosporos de P. polysora. Este é o primeiro relato de fungivoria de D. luteipes, que pode ter papel importante no controle biológico de P. polysora em milho.

Fungivory: a new and complex ecological function of Doru luteipes (Scudder) (Dermaptera: Forficulidae) / Fungivoria: uma nova e complexa função ecológica de Doru luteipes (Scudder) (Dermaptera: Forficulidae)

We report the discovery that the earwig predator Doru luteipes (Scudder, 1876) (Dermaptera: Forficulidae) feed on Puccinia polysora Underw uredospore, the causal agent of Southern Rust of Corn (SRC), which is a primary disease affecting the maize crop in Brazil. We performed experiments in laboratory and greenhouse to test the effect of D. luteipes (1st/2nd and 3rd/4th instars, and adults) fungivory on the P. polysora uredospore concentration. All trials showed a significant reduction of the initial concentration of uredospore. There was a reduction in uredospore concentration with increase in number of D. luteipes feeding on them. We also tested the uredospore consumption by quantifying its percentage in the feces of D. luteipes. Nymphs of the 2nd, 4th instar and adults fed 88%, 85%, and 83.8% of the uredospore, respectively. For nymphs of the 3rd instar, the percentage of uredospore consumption (75.6%) was statistically significant compared with the other groups. In greenhouse experiment, at twenty-eight days after plant inoculation with 9.9 x 104 uredospores, the percentage of uredospore consumption was 81.7%. Our results confirmed the fungivory of D. luteipes on P. polysora uredospore. This is the first report of D. luteipes fungivory, which may play an important role in the biological control of P. polysora in corn.

Relatamos a descoberta de que o predador Doru luteipes (Scudder, 1876) (Dermaptera: Forficulidae) se alimenta de uredosporos de Puccinia polysora Underw, o agente causal da ferrugem polisora que é uma doença primária que afeta a cultura do milho no Brasil. Realizamos experimentos em laboratório e em casa de vegetação para testar o efeito da fungivoria de D. luteipes (1º/2º e 3º/4º iìstares e adultos) sobre a concentração de uredosporos de P. polysora. Todos os ensaios mostraram uma redução significativa da concentração inicial de uredosporos. Houve uma redução na concentração de uredosporos com o aumento do número de D. luteipes alimentando-se deles. Também testamos o consumo de uredosporos quantificando sua porcentagem nas fezes de D. luteipes. Ninfas do 2º e 4º ínstar, assim como adultos, alimentaram-se de 88%, 85% e 83,8% dos uredosporos, respectivamente. Para ninfas do 3º ínstar, a porcentagem de consumo de uredosporos (75,6%) foi estatisticamente significativo em comparação com os outros grupos. No experimento em casa de vegetação, aos 28 dias após a inoculação das plantas com 9,9 x 104 uredosporos, a porcentagem de consumo de uredosporos foi de 81,7%. Nossos resultados confirmaram a fungivoria de D. luteipes em uredosporos de P. polysora. Este é o primeiro relato de fungivoria de D. luteipes, que pode ter papel importante no controle biológico de P. polysora em milho.

Fungivory: a new and complex ecological function of Doru luteipes (Scudder) (Dermaptera: Forficulidae)

Abstract We report the discovery that the earwig predator Doru luteipes (Scudder, 1876) (Dermaptera: Forficulidae) feed on Puccinia polysora Underw uredospore, the causal agent of Southern Rust of Corn (SRC), which is a primary disease affecting the maize crop in Brazil. We performed experiments in laboratory and greenhouse to test the effect of D. luteipes (1st/2nd and 3rd/4th instars, and adults) fungivory on the P. polysora uredospore concentration. All trials showed a significant reduction of the initial concentration of uredospore. There was a reduction in uredospore concentration with increase in number of D. luteipes feeding on them. We also tested the uredospore consumption by quantifying its percentage in the feces of D. luteipes. Nymphs of the 2nd, 4th instar and adults fed 88%, 85%, and 83.8% of the uredospore, respectively. For nymphs of the 3rd instar, the percentage of uredospore consumption (75.6%) was statistically significant compared with the other groups. In greenhouse experiment, at twenty-eight days after plant inoculation with 9.9 x 104 uredospores, the percentage of uredospore consumption was 81.7%. Our results confirmed the fungivory of D. luteipes on P. polysora uredospore. This is the first report of D. luteipes fungivory, which may play an important role in the biological control of P. polysora in corn.

Resumo Relatamos a descoberta de que o predador Doru luteipes (Scudder, 1876) (Dermaptera: Forficulidae) se alimenta de uredosporos de Puccinia polysora Underw, o agente causal da ferrugem polisora que é uma doença primária que afeta a cultura do milho no Brasil. Realizamos experimentos em laboratório e em casa de vegetação para testar o efeito da fungivoria de D. luteipes (1º/2º e 3º/4º iìstares e adultos) sobre a concentração de uredosporos de P. polysora. Todos os ensaios mostraram uma redução significativa da concentração inicial de uredosporos. Houve uma redução na concentração de uredosporos com o aumento do número de D. luteipes alimentando-se deles. Também testamos o consumo de uredosporos quantificando sua porcentagem nas fezes de D. luteipes. Ninfas do 2º e 4º ínstar, assim como adultos, alimentaram-se de 88%, 85% e 83,8% dos uredosporos, respectivamente. Para ninfas do 3º ínstar, a porcentagem de consumo de uredosporos (75,6%) foi estatisticamente significativo em comparação com os outros grupos. No experimento em casa de vegetação, aos 28 dias após a inoculação das plantas com 9,9 x 104 uredosporos, a porcentagem de consumo de uredosporos foi de 81,7%. Nossos resultados confirmaram a fungivoria de D. luteipes em uredosporos de P. polysora. Este é o primeiro relato de fungivoria de D. luteipes, que pode ter papel importante no controle biológico de P. polysora em milho.

Thermo-resistant enzyme-producing microorganisms isolated from composting.

Organo-mineral fertilizers supplemented with biological additives are an alternative to chemical fertilizers. In this study, thermoresistant microorganisms from composting mass were isolated by two-step procedures. First, samples taken at different time points and temperatures (33 days at 52 ºC, 60 days at 63 ºC, and over 365 days at 26 ºC) were pre-incubated at 80 oC for 30 minutes. Second, the microbial selection by in vitro culture-based methods and heat shock at 60 oC and 100 oC for 2h and 4h. Forty-one isolates were able to grow at 60 °C for 4h; twenty-seven at 100 °C for 2h, and two at 100 °C for 4h. The molecular identification by partial sequencing of the 16S ribosomal gene using universal primers revealed that thirty-five isolates were from eight Bacillus species, one Brevibacillus borstelensis, three Streptomyces thermogriseus, and two fungi (Thermomyces lanuginosus and T. dupontii). Data from amylase, phytase, and cellulase activity assays and the enzymatic index (EI) showed that 38 of 41 thermo-resistant isolates produce at least one enzyme. For amylase activity, the highest EI value was observed in Bacillus licheniformis (isolate 21C2, EI= 4.11), followed by Brevibacillus borstelensis (isolate 6C2, EI= 3.66), Bacillus cereus (isolate 18C2, EI= 3.52), and Bacillus paralicheniformis (isolate 20C2, EI= 3.34). For phytase, the highest EI values were observed for Bacillus cereus (isolate 18C2, EI= 2.30) and Bacillus licheniformis (isolate 3C1, EI= 2.15). Concerning cellulose production, B. altitudinis (isolate 6C1) was the most efficient (EI= 6.40), followed by three Bacillus subtilis (isolates 9C1, 16C2, and 19C2) with EI values of 5.66, 5.84, and 5.88, respectively, and one B. pumilus (isolate 27C2, EI= 5.78). The selected microorganisms are potentially useful as a biological additive in organo-mineral fertilizers and other biotechnological processes.

How omnivory affects the survival and choices of earwig Doru luteipes (Scudder) (Dermaptera: Forficulidae)?

Doru luteipes (Scudder, 1876) is an omnivorous predator that finds different food resources in the corn plant: eggs of Spodoptera frugiperda (J.E. Smith, 1797), uredospores of Puccinia polysora (Underw, 1897), and pollen. Knowing the survival and food preferences of this predator is essential to define its relevance as a biological control agent. We hypothesize that the foraging behavior and predatory capacity of D. luteipes may be affected when several food resources, especially eggs of S. frugiperda, uredospores of P. polysora, and pollen are concurrently in the same plant. The survival of D. luteipes in the nymph stage and their preference among food resources, often available in corn plants, were determined. To verify the survival of D. luteipes, newly hatched nymphs were fed exclusively with 1- uredospores of P. polysora, 2- eggs of S. frugiperda, 3- corn pollen, 4- a combination of uredospores + eggs, and 5- artificial diet (control). In another experiment, nymphs and adults of D. luteipes with 24 and 48 hours of fasting were individually released in the center of a container with four diets: 1- uredospores of P. polysora, 2- eggs of S. frugiperda, 3- corn pollen, 4- artificial diet, and maintained for 10 minutes, to evaluate the food choice and feeding time. The exclusive feeding with S. frugiperda eggs caused low nymph survival (8%), but the combination of P. polysora uredospores + S. frugiperda eggs allowed 58.3% survival. D. luteipes preferred feeding during the nighttime and the most significant proportions of choices by nymphs and adults were for pollen and diet, with adults spending more time eating pollen. These findings indicate that the trophic choices of D. luteipes are relevant to understand its contribution as an agent to control pest insects and fungal diseases in corn.

Fungivory: a new and complex ecological function of Doru luteipes (Scudder) (Dermaptera: Forficulidae).

We report the discovery that the earwig predator Doru luteipes (Scudder, 1876) (Dermaptera: Forficulidae) feed on Puccinia polysora Underw uredospore, the causal agent of Southern Rust of Corn (SRC), which is a primary disease affecting the maize crop in Brazil. We performed experiments in laboratory and greenhouse to test the effect of D. luteipes (1st/2nd and 3rd/4th instars, and adults) fungivory on the P. polysora uredospore concentration. All trials showed a significant reduction of the initial concentration of uredospore. There was a reduction in uredospore concentration with increase in number of D. luteipes feeding on them. We also tested the uredospore consumption by quantifying its percentage in the feces of D. luteipes. Nymphs of the 2nd, 4th instar and adults fed 88%, 85%, and 83.8% of the uredospore, respectively. For nymphs of the 3rd instar, the percentage of uredospore consumption (75.6%) was statistically significant compared with the other groups. In greenhouse experiment, at twenty-eight days after plant inoculation with 9.9 x 104 uredospores, the percentage of uredospore consumption was 81.7%. Our results confirmed the fungivory of D. luteipes on P. polysora uredospore. This is the first report of D. luteipes fungivory, which may play an important role in the biological control of P. polysora in corn.

Characterization and phylogenetic affiliation of Actinobacteria from tropical soils with potential uses for agro-industrial processes.

Secondary metabolites produced by Actinobacteria of tropical soils represent a largely understudied source of novel molecules with relevant application in medicine, pharmaceutical and food industries, agriculture, and environmental bioremediation. The present study aimed to characterize sixty-nine Actinobacteria isolated from compost and tropical soils using morphological, biochemical, and molecular methods. All the isolates showed high variation for morphological traits considering the color of pigments of the aerial and vegetative mycelium and spore chain morphology. The enzymatic activity of amylase, cellulase, and lipase was highly variable. The amylase activity was detected in 53 (76.81%) isolates. Eighteen isolates showed enzymatic index (EI) > 4.0, and the isolates ACJ 45 (Streptomyces curacoi) and ACSL 6 (S. hygroscopicus) showed the highest EI values (6.44 and 6.42, respectively). The cellulase activity varied significantly (P ≤ 0.05) among the isolates. Twenty-nine isolates (42.02%) showed high cellulase activity, and the isolates ACJ 48 (S. chiangmaiensis) and ACJ 53 (S. cyslabdanicus) showed the highest EI values (6.56 for both isolates). The lipase activity varied statistically (P ≤ 0.05) with fourteen isolates (20.29%) considered good lipase producers (EI > 2.0). The isolate ACSL 6 (S. hygroscopicus) showed the highest EI value of 2.60. Molecular analysis of partial 16S rRNA gene sequencing revealed the existence of 49 species, being 38 species with only one representative member and 11 species represented by one or more strains. All species belonged to three genera, namely Streptomyces (82.61%), Amycolatopsis (7.25%), and Kitasatospora (10.14%). The present results showed the high biotechnological potential of different Actinobacteria from tropical soils.

Maize endophytic bacteria as mineral phosphate solubilizers.

In the present study, we demonstrated the in vitro activity of endophytic phosphate-solubilizing bacteria (PSB). Fifty-five endophytic PSB that were isolated from sap, leaves, and roots of maize were tested for their ability to solubilize tricalcium phosphate and produce organic acid. Partial sequencing of the 16S rRNA-encoding gene showed that the isolates were from the genus Bacillus and different species of Enterobacteriaceae. The phosphate solubilization index on solid medium and phosphate solubilization in liquid medium varied significantly among the isolates. There was a statistically significant difference (P ≤ 0.05) for both, the values of phosphate-solubilizing activity and pH of the growth medium, among the isolates. Pearson correlation was statistically significant (P ≤ 0.05) between P-solubilization and pH (R = -0.38), and between the gluconic acid production and the lowering of the pH of the liquid medium at 6 (R = 0.28) and 9 days (R = 0.39). Gluconic acid production was prevalent in all the PSB studied, and Bacillus species were most efficient in solubilizing phosphate. This is the first report on the characterization of bacterial endophytes from maize and their use as potential biofertilizers. In addition, this may provide an alternative strategy for improving the phosphorus acquisition efficiency of crop plants in tropical soils.

Genomic variability of Pantoea ananatis in maize white spot lesions assessed by AFLP markers.

Measures to control maize white spot (MWS) caused by Pantoea ananatis are preferentially based on resistant cultivars. A lack of knowledge on the genetic variability of pathogens could interfere with the development and utilization of controlling strategies in this pathosystem. The main goals of this study were to investigate the genetic variability of 90 P. ananatis isolates from three different eco-geographical regions of Brazil by amplified fragment length polymorphism (AFLP), and to determine the presence of a universal P. ananatis plasmid in isolates from tropical Brazil. Analysis of genetic similarity by AFLP allowed us to categorize the 90 isolates into two groups. However, no correlation between the collecting sites and genetic groupings was observed. The polymorphism percentage found in P. ananatis ranged between 24.64 and 92.46%, and genetic diversity was calculated to be 0.07-0.09. The analysis of molecular variance showed that 99.18% of genetic variability was within the populations, providing evidence that evolutionary forces were acting on these populations. All P. ananatis isolates showed the P. ananatis universal plasmid (280 or 352 kb). This is the first report on the presence of a universal P. ananatis plasmid from MWS lesions in the tropical area.

Characterization of the inaA gene and expression of ice nucleation phenotype in Pantoea ananatis isolates from Maize White Spot disease.

Maize White Spot (MWS), a foliar disease caused by Pantoea ananatis, could cause up to 60% yield loss. Some strains of P. ananatis harboring the ice nucleation gene inaA catalyze the formation of ice nuclei, causing tissue damage at temperatures slightly below freezing. Little is known about the relationship between the presence of the ina gene in this maize pathogen and its expression during the phenomenon of ice nucleus formation. Here, we attempted to verify the presence of the inaA gene and the expression of phenotype in vitro. The identity of the isolates and the presence of the inaA gene were determined by P. ananatis species-specific primers. The expression of the inaA gene was assessed in vitro by the visualization of ice-crystal formation in water at subzero temperatures. A total of ninety P. ananatis isolates from MWS lesions were characterized. The presence of the inaA gene was confirmed by gel electrophoresis of the 350-400-bp PCR products. The inaA primers did not lead to DNA fragment amplification in three isolates. The ice nucleation phenotype was expressed in 83.34% of the isolates carrying the inaA gene. Our study showed that the ice nucleation in P. ananatis isolated from MWS lesions was dependent on the presence of a functional ina gene in the genome. We also found evidence indicating that some P. ananatis strains have a mutated form of the inaA gene, producing a non-functional ice nucleation protein. This is the first report on inaA gene characterization in P. ananatis isolates from Maize White Spot.

Heterologous expression of an insecticidal gene from the armed spider (Phoneutria nigriventer)

Insect-pests are global problems that cause severe damage to crop plants, and their control is commonly based on chemical insecticides. However, negative effects of pesticides on the environment and human health emphasize the necessity to develop alternative methods for insect-pest control. In the present study, a gene coding for the insecticidal peptide TX4(6-1) of the Brazilian armed spider (Phoneutria nigriventer) was cloned in fusion with maltose binding protein (MBP) and expressed in Escherichia coli. The affinity purified protein MBP-GlyTX4 was cleaved with the Xa factor and used for a bioassay against Spodoptera frugiperda and rabbit immunization. Five micrograms GlyTX4 protein injected into the hemocoel of larvae and abdominal cavity of adults produced trembling and uncoordinated movements immediately after injection and all adult insects died after 12h. After two days, larvae became paralyzed and the epidermal color changed to dark brown. Furthermore, the development stage was prolonged for two weeks. Alternatively, slices of maize leaves were imbibed with 15 micrograms of the recombinant protein cleaved with the Xa factor and used as diet for larvae. In this experiment, all larvae died in about 30 minutes. Polyclonal antibodies anti-MBP-GlyTX4 were effective for recognizing MBP and GlyTX4 in whole cell extract from E. coli expressing the recombinant protein.