Evidence of Pyricularia oryzae adaptability to tricyclazole.

Pyricularia oryzae is the etiological agent of rice blast, the most destructive disease in rice crops and chemical control based on fungicide is the main method used in its management. The aim of this study was characterize pathogenicity and identify P. oryzae isolates adapted to tricyclazole. P. oryzae monosporic isolates were collected in the state of Tocantins and inoculated in international differentiating series of rice cultivars for determination of pathotypes. After, the same isolates were inoculated in the rice cultivar IRGA 424 to evaluate resistance to fungicide Bim® 750 BR (Tricyclazole - 250 g/ha) that was applied 24 and 48 hours after pathogen inoculation (hai). Leaf blast severity and infection efficiency were evaluated 9 days after inoculation (dai), latency period (2 dai) and sporulation intensity (7 dai). Nine different pathotypes were identified, predominantly as IA group. The latent period of isolates occurred between from 48 to 120 h. The application of tricyclazole, 24 hai reduced disease severity with the exception of the isolate Py 7.1. The great variability of the pathogen allowed for adaptation to this molecule and can increase its aggressiveness and should be considered to guide the integrated management of the disease.

Signaling defense responses of upland rice to avirulent and virulent strains of Magnaporthe oryzae.

Rice blast (Magnaporthe oryzae) can cause large losses in crop yields, especially in upland rice systems. Avirulent strains of M. oryzae can induce resistance to subsequent attacks by virulent strains in plants. This study aimed to investigate the defense responses in upland rice challenged with a virulent strain of M. oryzae after acclimation with an avirulent strain. The avirulent strain decreased rice blast severity in the challenged plants. Induced resistance was characterized by a hypersensitive response and early accumulation of phenolic compounds. Scanning electron microscopy showed that M. oryzae conidia germinate and form appressoria, but do not colonize leaf tissues. The activities of pathogenesis-related proteins, total phenolic compounds, and salicylic acid (SA) were affected by acclimation to the avirulent strain. The activities of ß-1,3-glucanase, phenylalanine ammonia-lyase, and peroxidase, as well as the SA levels explained most of the variability in the rice plant responses to M. oryzae. In addition, OsXa13, OsMAPKKK74, OsAOS2, OsACO7, and OsMAS1 expression was modulated depending on the virulence of the M. oryzae strains. This modulation in gene expression is critical for infection and some of these mechanisms are targeted by effectors, resulting in enhanced susceptibility and pathogen infection. These results have practical importance in plant-pathogen interaction studies to identify resistance-relevant mechanisms against M. oryzae in upland rice.

Screening of Beneficial Microorganisms to Improve Soybean Growth and Yield

Abstract The objective of this research was to identify the best microorganisms, alone or in mixture for total biomass gain (root + shoot), positive change in gas exchange, nutrient uptake (root, shoot and grain) and yield and yield components in the soybean crop. Trial under greenhouse conditions had the experimental design in a completely randomized scheme with 26 treatments and four replicates. The treatments consisted of the rhizobacteria BRM 32109, BRM 32110 and 1301 (Bacillus sp.), BRM 32111 and BRM 32112 (Pseudomonas sp.), BRM 32113 (Burkholderia sp.), BRM 32114 (Serratia sp.), Ab-V5 (Azospirillum brasilense) and 1381 (Azospirillum sp.), and the fungus Trichoderma asperellum (a mix of the isolates UFRA.T06, UFRA.T09, UFRA.T12 and UFRA.T52). Besides, the same isolates were combined in pairs, completing 16 combinations. Control treatments received no microorganism. Microorganisms applied isolated or in combination, provided biomass gain, positive gas exchange, increases in nutrients uptake at the shoot and grain, and improved grain yield and its components than control plants. Stood out the combination Ab-V5 + T. asperellum pool, which provided a 25% improvement in grain yield.

An approach on phytoalexins: function, characterization and biosynthesis in plants of the family Poaceae / Uma abordagem sobre fitoalexinas: função, caracterização e biossíntese em plantas da família Poaceae

ABSTRACT: Phytoalexins are compounds that have been studied a few years ago, which present mainly antimicrobial activity. The plants of the family Poaceae are the most geographically widespread and stand out for their economic importance, once they are cereals used as staple food. This family stands out for having a variety of phytoalexins, which can be synthesized via the shikimic acid (the phenylpropanoids), or mevalonic acid, being considered terpenoid phytoalexins. The characterization of these compounds with antimicrobial activity is carried out using chromatographic techniques, and the high-performance liquid chromatography (HPLC) coupled with mass spectrometry are the most efficient methods in this process. This research aimed to present an approach of the function, characterization and biosynthesis of phytoalexins in plants of the family Poaceae.

RESUMO: As fitoalexinas são compostos que vêm sendo estudados há alguns anos, apresentando principalmente atividade antimicrobiana. As plantas da família Poaceae são as geograficamente mais difundidas e se destacam por sua importância econômica, uma vez que são os cereais que compõe a base da alimentação, em todos os continentes. Essa família se destaca por apresentar uma variedade de fitoalexinas, sendo que as mais importantes são sintetizadas a partir da via do ácido chiquímico. A caracterização desses compostos com atividade antimicrobiana é realizada por meio de técnicas cromatográficas, sendo que a cromatografia líquida de alta eficiência (HPLC) acoplada com espectrometria de massas é a técnica mais eficiente nesse processo. O trabalho apresenta como objetivo uma abordagem da função, caracterização, biossíntese e aplicações das fitoalexinas em plantas da família Poaceae.