Synthesis, characterization and computational studies of 1,3-bis[(E)-furan-2-yl)methylene]urea and 1,3-bis[(E)-furan-2-yl)methylene]thiourea

Urea and thiourea derivatives: 1,3-bis[(E)-furan-2-yl)methylene]urea (BFMU) and 1,3-bis[(E)-furan-2-yl)methylene]thiourea (BFMT) were synthesized and characterized by spectrometry analyses (UV, IR, 1H NMR and 13C NMR). They were screened for antibacterial (Salmonella typhi, Staphylococcus aureus, Pseudomonas aeruginosa, Xanthomonas axonopodis and Streptococcus bovis) and antifungal (Fusarium oxysporum, Colletotrichum gloeosporioides and Cercospora zeae-maydis) activities. Quantum chemical calculations of frontier molecular orbital energies (EHOMO and ELUMO), and their associated global parameters were carried out by DFT levels of theory, with complete relaxation in the potential energy surface using 6-31G* basis set (DFT/B3LYP/6-31G*). Azomethine functional groups (C=N) appeared at δ 7.6 ppm and δ 7.0 ppm in the proton spectra, the peaks between δ 105 and δ 160 ppm of 13C spectra represent the methylene carbons (C=C). BFMU is a better inhibitor of P. aeruginosa and S. bovis, while BFMT is a better inhibitor of S. typhi, S. aureus and X. axonopodis and the fungi isolates (F. oxysporum, C. gloeosporioides and C. zeae-maydis) used. The global parameters agreed favorably with the experimental results, indicating the higher activity of BFMT.

PHYTOCHEMICAL AND ANTIMICROBIAL PROPERTIES OF LEAF EXTRACTS OF Calliandra calothyrsus, Leucaena diversifolia AND Sesbania sesban

Phytochemical compounds are secondary metabolites of plants useful as antimicrobial agents. Botanicals are being explored for bioactive compounds with antimicrobial properties against phytopathogens. Little information is available on the phytochemical and antimicrobial activity of Calliandra calothyrsus, Leucaena diversifolia and Sesbania sesban against Cercospora zeae-maydis and Xanthomonas campestris pv. musacearum. The aim of the study was to determine the phytochemical and antimicrobial properties of leaf extracts of C. calothyrsus, L. diversifolia and S. sesban against C. zeae-maydis and Xc. pv. musacearum. Dried leaves were extracted in methanol and aqueous solvents and screened for phytochemical and antimicrobial activity using Kirby-Bauer’s disk diffusion and poisoned food technique methods. Sesbania sesban extracts contained all the phytochemical tested; tannins, terpenoids, steroids, saponins, flavonoids, and alkaloids, Leucaena diversifolia lacked alkaloids while Calliandra calothyrsus lacked steroids and alkaloids. The extracts were active against Cercospora zeae-maydis and Xc.pv. musacearum with Sesbania sesban having greater radial inhibition activity. There was no significant difference in the antimicrobial activity between the lowest concentrations (25% and 25mg/ml) and highest concentrations (75% and 75mg/ml) in all the three plant extracts. Growth inhibition observed could be as a result of the different chemical compound observed in the extracts. Presence of alkaloids in Sesbania sesban could explain the greater growth inhibition of the pathogens under study. The results form the basis for further research that could lead to isolation and development of antimicrobial agents. Therefore, these plants can be used as an alternative to synthetic chemicals to control Cercospora zeae-maydis and Xanthomonas campestris pv. Musacearum.

Progresso temporal de doenças da cultura do milho

RESUMO O objetivo do presente trabalho foi avaliar o progresso temporal das doenças ferrugem polisora (Puccinia polysora), cercospora (Cercospora zeae-maydis), mancha branca (Pantoea ananatis) e helmintosporiose (Exserohilum turcicum) no milho, bem como sua correlação com as variáveis climáticas. O delineamento experimental foi o de blocos completos com tratamentos ao acaso. O modelo monomolecular foi o que melhor se ajustou às epidemias. Com os dados de severidade de cada doença, foram elaboradas correlações com as variáveis climáticas (DFtemp-dias favoráveis com temperatura entre 18-28ºC; DFumid-dias favoráveis com umidade relativa>60%; PrecAcc-precipitação acumulada; PrecDia- precipitação/dia e Prec10-precipitação>10mm) observadas durante o período de avaliação. Após as análises pôde-se inferir que a variável precipitação acumulada foi determinante para a ocorrência de epidemias das doenças estudadas.

Assessing Late Vegetative and Tasseling Fungicide Application Timings on Foliar Disease and Yield in Indiana Corn

Gray leaf spot (Cercospora zeae-maydis) is a foliar disease of corn (Zea mays) that consistently reduces yields across the United States and is an annual concern in Indiana corn production. Field trials were conducted in West Lafayette, IN, over 3 years (2016 to 2018) to evaluate the effectiveness of 12-leaf collar stage (V12) foliar fungicide applications compared with tasseling (VT) applications for gray leaf spot management and yield. Results indicated that during years in which foliar disease severity was less than 4%, there was no effect of application timing on gray leaf spot severity. In 2018, when gray leaf spot levels exceeded 5%, significantly less disease was observed in treatments receiving VT applications compared with V12 applications. Application timing did not affect yield in any year of the experiment. In 2016, benzovindiflupyr + azoxystrobin + propiconazole resulted in greater yields compared with the nontreated control, and in 2018, pyraclostrobin + metconazole and benzovindiflupyr + azoxystrobin + propiconazole resulted in greater yields compared with the nontreated control. This research indicates that in high disease pressure environments and years, Indiana farmers may want to continue to apply fungicides at VT rather than apply prior to tassel.

Agronomic characters and disease management in second season corn using calcium, copper, manganese and zinc products

ABSTRACT Corn is a cereal whose productivity can be reduced by various diseases which has recommended treatments for control. The objective of this study was to analyze copper, zinc, calcium and manganese products for the management of Pantoea ananatis, Puccinia polysora and Cercospora zeae maydis in second season corn, and interference in agronomic characteristics. Commercial products made of amino acid chelated with 15% calcium, 5% copper, 15% manganese and 10% zinc, at the doses of 0.5 kg ha-1, 0.3 L ha-1, 0.4 kg ha-1 and 1 L ha-1, respectively, a treatment with fungicide (20% azoxystrobin and 8% cyproconazole at 0.3 L ha-1 + 25% propiconazole at 0.4 L ha-1), and a treatment with water were assayed. The experiments were carried out under field conditions for two consecutive years and in two simple hybrids, in soil supplemented with nutrients based on the chemical analysis. The plant height, stem diameter, number of rows per spike, number of grains per row of spike, productivity and mass of one thousand grains were evaluated. Disease severity was assessed with diagrammatic scales and calculated the area under the disease progress curves. In both years, there was no significant effect of chelates for agronomic traits and diseases severity. It is concluded that chelate-based calcium, copper, manganese and zinc products have no influence on agronomic characteristics and severity of the diseases evaluated in second season corn for those edaphoclimatic conditions.

Influência da época de semeadura na severidade de doenças foliares e na produtividade do milho safrinha

RESUMO Nas principais áreas produtoras de grãos, o milho tem sido cultivado em duas safras, sendo o milho verão (primeira safra) e o milho safrinha (segunda safra). Desta maneira com a cultura do milho o ano todo no campo, criou-se uma ponte verde, favorecendo o desenvolvimento e a permanência de pragas e doenças. A severidade de doenças podem limitar o desenvolvimento da cultura e comprometer a produtividade. O objetivo deste trabalho foi verificar a influência da época de semeadura na severidade de doenças foliares e na produtividade do milho safrinha, na região norte do Estado do Paraná em duas safras consecutivas, 2015 e 2016. Cercospora zeae-maydis, Pantoea annanatis e Exserohilum turcicun foram as principais doenças foliares observadas nos dois anos consecutivos na região norte do Estado do Paraná. Semeaduras realizadas até 10/03 apresentaram maiores severidades de Puccinia polysora e Pantoea annanatis, enquanto e Exserohilum turcicun foi mais acentuada em semeaduras após 10/03. Para Cercospora zeae-maydis a época de semeadura não demonstrou ter efetiva influência. Maiores índices produtivos foram alcançados quando a semeadura foi realizada precocemente.

Efficiency of fungicide chemical group in the preventive and curative control of Puccinia sorghi in corn and Cercospora zeae-maydis sporulation in different culture media

The chemical control of diseases is one of the most used measures, especially for a rapid and precise control. The objectives of this work were to verify the behavior of three chemical groups of fungicides applied in a preventive and curative way aiming the control of common corn rust and the sporulation of Cercospora zeae-maydis in different culture media. Two experiments were installed, one for chemical control and the other for sporulation. For the chemical control experiment, propiconazole, azoxystrobin, ciproconazole + azoxystrobin and benzovindiflupir + azoxystrobin were the fungicides preventively and curatively applied for the control of common corn rust in a random block experimental design with three replicates. In relation to cercosporiosis sporulation experiment, five culture media were used: potato sucrose agar (PSA), V8 agar juice (V8), (LCHA), corn leaf extract (CL) and seasoned tomato extract (STE) were used. Discs with Mycelial of the fungus were placed on the media and submitted to the 12-hour light/12-hour dark continuous dark in a double factorial (culture media and light treatments) experimental design with four replicates. The fungicides azoxystrobin and ciproconazole + azoxystrobin were efficient for up to 21 days after inoculation of P. sorghi, the fungicide azoxystrobin was efficient for the curative control of P. sorghi. The greatest sporulation of the fungus was verified in the medium with seasoned tomato extract submitted to the photoperiod.