Plant diseases induced by fungi are among the most important limiting factors during pre- and post-harvest food production. For decades, synthetic chemical fungicides have been used to control these diseases, however, increase on worldwide regulatory policies and the demand to reduce their application, have led to searching for new ecofriendly alternatives such as the biostimulants. The commercial application of yeasts as biocontrol agents, has shown low efficacy compared to synthetic fungicides, mostly due to the limited knowledge of the molecular mechanisms of yeast-induced responses. To date, only two genome-wide transcriptomic analyses have characterized the mode of action of biocontrols using the plant model Arabidopsis thaliana, missing, in our point of view, all its molecular and genomic potential. Here we describe that compounds released by the biocontrol yeast Hanseniaspora opuntiae (HoFs) can protect Glycine max and Arabidopsis thaliana plants against the broad host-range necrotrophic fungi Corynespora cassiicola and Botrytis cinerea. We show that HoFs have a long-lasting, dose-dependent local, and systemic effect against Botrytis cinerea. Additionally, we performed a genome-wide transcriptomic analysis to identify genes differentially expressed after application of HoFs in Arabidopsis thaliana. Our work provides novel and valuable information that can help researchers to improve HoFs efficacy in order for it to become an ecofriendly alternative to synthetic fungicides.

Standard area diagrams (SADs) are plant disease severity assessment aids demonstrated to improve the accuracy and reliability of visual estimates of severity. Knowledge of the sources of variation, including those specific to a lab such as raters, specific procedures followed including instruction, image analysis software, image viewing time, etc., that affect the outcome of development and validation of SADs can help improve standard operating practice of these assessment aids. As reproducibility has not previously been explored in development of SADs, we aimed to explore the overarching question of whether the lab in which the measurement and validation of a SAD was performed affected the outcome of the process. Two different labs (Lab 1 and Lab 2) measured severity on the individual diagrams in a SAD and validated them independently for severity of gray mold (caused by Botrytis cinerea) on Gerbera daisy. Severity measurements of the 30 test images were performed independently at the two labs as well. A different group of 18 raters at each lab assessed the test images first without, and secondly with SADs under independent instruction at both Lab 1 and 2. Results showed that actual severity on the SADs as measured at each lab varied by up to 5.18%. Furthermore, measurement of the test image actual values varied from 0 to up to 24.29%, depending on image. Whereas at Lab 1 an equivalence test indicated no significant improvement in any measure of agreement with use of the SADs, at Lab 2, scale shift, generalized bias, and agreement were significantly improved with use of the SADs (P ≤ 0.05). An analysis of variance indicated differences existed between labs, use of the SADs aid, and the interaction, depending on the agreement statistic. Based on an equivalence test, the interrater reliability was significantly (P ≤ 0.05) improved at both Lab 1 and Lab 2 as a result of using SADs as an aid to severity estimation. Gain in measures of agreement and reliability tended to be greatest for the least able raters at both Lab 1 and Lab 2. Absolute error was reduced at both labs when raters used SADs. The results confirm that SADs are a useful tool, but the results demonstrated that aspects of the development and validation process in different labs may affect the outcome.

Cutaneous secretions produced by amphibians of the family Bufonidae are rich sources of bioactive compounds that can be useful as new chemical templates for agrochemicals. In crop protection, the use of elicitors to induce responses offers the prospect of durable, broad-spectrum disease control using the plant’s own resistance. Therefore, we evaluated the potential of methanolic extracts of cutaneous secretions of two species of amphibians of the family Bufonidae found in the Amazon biome—Rhaebo guttatus (species 1) and Rhinella marina (species 2)—in the synthesis of phytoalexins in soybean cotyledons, bean hypocotyls, and sorghum mesocotyls. Additionally, changes in the enzyme activity of β-1,3-glucanase, peroxidase (POX), and polyphenol oxidase (PPO) and in the total protein content of soybean cotyledons were determined. In the soybean cultivar ‘TMG 132 RR’, our results indicated that the methanolic extract of R. guttatus cutaneous secretions suppressed glyceollin synthesis and β-1,3-glucanase activity and increased POX and PPO activities at higher concentrations and total protein content at a concentration of 0.2 mg/mL. On the other hand, the methanolic extract of R. marina cutaneous secretions induced glyceollin synthesis in the soybean cultivars ‘TMG 132 RR’ and ‘Monsoy 8372 IPRO’ at 0.1–0.2 mg/mL and 0.2 mg/mL, respectively. The methanolic extract of R. marina cutaneous secretions also increased the specific activity of POX and PPO in ‘Monsoy 8372 IPRO’ and ‘TMG 132 RR’, respectively, and decreased the activity of β-1,3-glucanases in ‘Monsoy 8372 IPRO’. At 0.3 mg/mL, it stimulated phaseolin synthesis. The extracts did not express bioactivity in the synthesis of deoxyanthocyanidins in sorghum mesocotyls. The study in soybean suggests that the bioactivity in defense responses is influenced by cultivar genotypes. Therefore, these results provide evidence that extracts of cutaneous secretions of these amphibians species may contribute to the bioactivity of defense metabolites in plants.

A soja está entre as principais culturas cultivadas no mundo e está sujeita à ocorrência de várias doenças, inclusive aquelas transmitidas por sementes, o que justifica o seu tratamento fitossanitário. Assim, objetivou-se verificar o efeito dos tratamentos com extratos das plantas medicinais cúrcuma (Curcuma longa L.) e alecrim (Rosmarinus officinalis L.) e do fungo medicinal Pycnoporus sanguineus em sementes de soja cultivar V Max convencional e V Max NK7059 transgênica. Os tratamentos foram realizados com os extratos hidroalcoólicos de cúrcuma e de alecrim e com o fungo medicinal P. sanguineus nas concentrações de 50, 100, 150 e 200 mL L-1 ; utilizou-se água como testemunha. As sementes foram imersas por cinco minutos em cada tratamento. Determinou-se a incidência de patógenos nas sementes pelo método do papel-filtro com congelamento, e também avaliou-se a porcentagem de plântulas normais, mortas e anormais. Os resultados para incidência de patógenos em sementes de soja indicaram a presença das leveduras Bacillus sp., Colletotrichum dematium, Penicillum sp. e Fusarium sp. O extrato de P. sanguineus foi eficiente no controle de Penicillium sp. para sementes de soja convencional. Para a cultivar transgênica, todos os extratos promoveram o controle de Fusarium spp., e os extratos vegetais reduziram a incidência de Colletotrichum dematium. Os tratamentos não influenciaram na germinação das sementes de ambas as cultivares. Esses extratos têm potencial para serem utilizados no controle alternativo de patógenos de sementes de soja.

2RESUMO -A homeopatização de óleos essenciais revela-se como uma alternativa para o controle de fitopatógenos e na indução de compostos de defesa em plantas, como as fitoalexinas. Neste sentido, o objetivo do trabalho foi de avaliar o efeito de soluções dinamizadas de Eucalyptus citriodora (EC) e Cymbopogon citratus (CC) na germinação de conídios de Alternaria solani e Corynespora cassiicola e na produção de fitoalexinas em soja. Para os testes foram utilizados os tratamentos homeopáticos: 6CH, 12CH, 30CH, 60CH, 100CH e 200CH de ambos os óleos. A porcentagem de germinação foi determinada 4 horas após incubação dos patógenos na presença dos tratamentos, em placas tipo Elisa a 25 ºC, e feita contagem de esporos em microscópio óptico. Para fitoalexinas, cotilédones de soja oriundos de sementes cultivadas em areia estéril foram cortados na superfície inferior e submetido aos tratamentos, permanecendo no escuro por 20 horas. A gliceolina formada foi extraída e determinada em espectrofotômetro. Todas as dinamizações aplicadas reduziram a germinação de ambos patógenos, chegando à redução de 59% em A. solani e 42% em C. cassiicola por CC 30CH. As dinamizações testadas não foram eficientes para indução de gliceolina, indicando maior potencial dos tratamentos sobre os patógenos em comparação a elicitação destes compostos de defesa. Baseando-se nestes resultados, é possível evidenciar o potencial de tratamentos homeopáticos no controle de A. solani e C. cassiicola. O processo de homeopatização manteve as propriedades antimicrobianas dos óleos testados. Palavras-chave: Eucalyptus citriodora. Cymbopogon citratus. Alternaria solani. Corynespora cassiicola. Controle alternativo de patógenos.ABSTRACT -The homeopathic use of essential oils is seen as an alternative in the control of plant pathogens and in the induction of such defensive plant compounds as phytoalexins. The aim of this study therefore, was to evaluate the effect of dynamised solutions of Eucalyptus citriodora (EC) and Cymbopogon citratus (CC) on conidial germination in Alternaria solani and Corynespora cassiicola, and on the production of phytoalexins in the soybean. The following homeopathic treatments from both oils were used in the tests: 6CH, 12CH, 30CH, 60CH, 100CH and 200CH. Germination percentage was determined four hours after incubation of the pathogens in the presence of the treatments using Elisa plates at 25 °C; spore counts were made by optical microscope. For the phytoalexins, soybean cotyledons from seeds grown in sterile sand were cut on their lower surface and subjected to the treatments, remaining in the dark for 20 hours. The gliceolin formed was extracted and determined by spectrophotometer. All the levels of dynamisation applied reduced germination in both pathogens, reaching 59% for A. solani and 42% for C. cassiicola with CC 30CH. The dynamisations under test were not efficient in gliceolin induction, demonstrating a greater potential of the treatments for pathogens, when compared to induction of these defensive compounds. Based on the resu...