Occurrence of fungi in bean seeds ‘Red Mexican’ and its effect on the germination

The seed-born fungi can be transmitted to long distances, also to reduce the viability of seeds. The objective of this study was to verify the occurring pathogens on common bean ‘Red mexican’ seed and evaluate its effect in the obtaining normal seedlings. Therefore, bean seeds 'Red mexican' were submitted to blotter test (25 seeds Gerbox-1) in four different dates. The design was completely randomized design (CRD) and each assessed data had eight replicates (Gerbox). The fungi incidence and obtaining normal seedlings were evaluated at 5 and 9 days, respectively. It was verified a larger incidence for Aspergillus sp. (19 to 57%) when compared to Cladosporium cladosporioides (11 to 29%). The incidence of the genus Aspergillus sp. and C. cladosporioides did not interfere in the percentage of normal seedlings, due to the escape mechanism of the seedlings to pathogens during the germination process.The seed-born fungi can be transmitted to long distances, for the transport of the same, in addition to harming seed viability. Therefore, the objective of this study was to verify the occurring fungi on common bean ‘Red mexican’ seed and evaluate its effect in the development of normal seedlings. Therefore, stored bean seeds ‘Red mexican’ were submitted to blotter test in four different dates. The design was completely randomized (CRD) and each assessed data had eight replicates. Each experimental unit (repetition) consisted in a Gerbox containing 25 seeds. The fungi incidence and development of normal seedlings were evaluated at 5 and 7 days, respectively. It was verified a larger incidence for Aspergillus sp. (19% to 57%) when compared to Cladosporium cladosporioides (11% to 29%). The incidence of the fungi Aspergillus sp. and C. cladosporioides did not interfere in the percentage of normal seedlings, due to the escape mechanism of the seedlings to pathogens during the germination process

Reaction of accessions of Manihot spp. to root-knot nematodes (Meloidogyne spp.)

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Fitopatologia, Programa de Pós-Graduação em Fitopatologia, 2019.A mandioca (Manihot esculenta) é uma planta arbustiva, pertencente à família Euphorbiaceae. O produto comercial mais explorado desta cultura é o amido, fonte de reserva energética, o qual é acumulado nas raízes tuberosas. A produção mundial apresenta crescimento contínuo, devido a contribuição de alguns países africanos. No Brasil, é cultivada em quase todo território, representando uma das culturas de maior importância socioeconômica no país. Diversos fatores podem influenciar a produtividade da cultura, entre eles, problemas causados por patógenos, incluindo ataques por nematoides fitoparasitas que levam a reduções significativas na produtividade. Várias espécies de nematoides têm sido relatadas associadas à cultura da mandioca, em diferentes áreas geográficas. Evidências indicam que os nematoides das galhas (Meloidogyne spp.) são o grupo de nematoides mais importante que afetam a cultura, sendo as espécies M. incognita e M. javanica, consideradas as mais agressivas. Apesar da importância socioeconômica dessa cultura no Brasil, há ainda uma escassez de informações sobre a associação de nematoides fitoparasitas a plantas de mandioca, bem como ao comportamento dessas plantas ao parasitismo desses agentes. Assim, o objetivo deste estudo foi avaliar a reação de 10 acessos de Manihot spp. (UnB 201, UnB 031, M. fortalezensis, Quimera 1, Quimera 2, Quimera 3, UnB 220, UnB 360, UnB 519 e UnB 122), pertencentes à Coleção de Mandioca da Universidade de Brasília, a Meloidogyne incognita, M. javanica e M. enterolobii. Os estudos foram conduzidos em casa de vegetação da Estação Experimental de Biologia da Universidade de Brasília. A cultivar Pioneira considerada suscetível a Meloidogyne spp. foi incluída como um padrão de suscetibilidade. O experimento foi conduzido em delineamento inteiramente casualizado com 5 repetições. Após 40 dias do plantio, as plantas foram inoculadas separadamente com 5000 ovos de cada espécie do nematoide em suspensão depositada ao redor da planta. Sessenta dias após a inoculação, foram estimados o fator de reprodução (FR), o índice de galhas (IG), o índice de massa de ovos (IMO) e o número de ovos por grama de raiz (NOGR). O ensaio foi repetido um mês após. Os acessos expressaram diferentes reações ao parasitismo das três espécies do nematoide. Os acessos UnB 201, UnB 031, UnB 519 e UnB 122 mostraram-se suscetíveis (FR > 1,0) a M. javanica e a M. incognita. A espécie selvagem M. fortalezensis, os acessos UnB 220 e UnB 360 foram resistentes a todos os nematoides avaliados. Com exceção da 'Quimera 2', suscetível a M. incognita e ‘Quimera 3’ a M. javanica, as quimeras comportaram-se como resistentes a todas as espécies do nematoide avaliadas. Exceto a cultivar Pioneira, todos os acessos de mandioca avaliados foram resistentes a M. enterolobii.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) e Fundação Nagib Nassar para Desenvolvimento Científico e Sustentável (FUNAGIB).Cassava (Manihot esculenta) is a shrub, belonging to the family Euphorbiaceae. The most exploited commercial product of this crop is starch, a source of energy, which is accumulated in the tuberous roots. World production continues to grow, due to the contribution of some African countries. In Brazil, it is cultivated in almost all territory, representing one of the crops of greater socioeconomic importance. Several factors may influence crop yield, including problems caused by pathogens, as plant-parasitic nematodes that lead to significant yield reduction. Several species of nematodes have been reported associated with cassava crop in different geographic areas. Evidence indicates that the root-knot nematodes (Meloidogyne spp.) are the most important group of nematodes that affect the crop, being the species M. incognita and M. javanica, considered the most aggressive ones. Despite the socioeconomic importance of this crop in Brazil, there is still a lack of information on the association of plant-parasitic nematodes with cassava plants, as well as the behavior of these plants to the parasitism of these agents. Thus, the objective of this study was to evaluate the reaction of 10 accessions of Manihot spp. (UnB 201, UnB 031, M. fortalezensis, Chimera 1, Chimera 2, Chimera 3, UnB 220, UnB 360, UnB 519 and UnB 122), belonging to the Cassava Collection of the University Brasília, to Meloidogyne incognita, M. javanica and M. enterolobii. The studies were conducted in a greenhouse at the Biological Experimental Station of the University Brasilia. Cultivar Pioneira considered susceptible to Meloidogyne app. was included as a pattern of susceptibility. The experiment was conducted in a completely randomized design with 5 replicates. After 40 days of planting, the plants were inoculated separately with 5000 eggs of each nematode species deposited around the plant. Sixty days after inoculation, the reproduction factor (RF), gall index (GI), index of egg mass (IEM), number of eggs per gram of roots (NEGR) were estimated. The assay was repeated a month latter. The accessions expressed different reactions in relation to the parasitism of the three nematode species. The accessions UnB 201, UnB 031, UnB 519 and UnB 122 were susceptible (FR > 1.0) to M. javanica and to M. incognita. The wild species M. fortalezensis, the accessions 'UnB 220' and 'UnB 360' were resistant to all nematode species evaluated. Except for 'Chimera 2', which was susceptible to M. incognita and 'Chimera 3' to M. javanica, the chimeras behaved as resistant to all nematodes evaluated. Exception for cv. Pioneira, all accessions tested were resistant to M. enterolobii

Engineering Resistance against <i>Sclerotinia sclerotiorum</i> Using a Truncated NLR (TNx) and a Defense-Priming Gene

The association of both cell-surface PRRs (Pattern Recognition Receptors) and intracellular receptor NLRs (Nucleotide-Binding Leucine-Rich Repeat) in engineered plants have the potential to activate strong defenses against a broad range of pathogens. Here, we describe the identification, characterization, and in planta functional analysis of a novel truncated NLR (TNx) gene from the wild species Arachis stenosperma (AsTIR19), with a protein structure lacking the C-terminal LRR (Leucine Rich Repeat) domain involved in pathogen perception. Overexpression of AsTIR19 in tobacco plants led to a significant reduction in infection caused by Sclerotinia sclerotiorum, with a further reduction in pyramid lines containing an expansin-like B gene (AdEXLB8) potentially involved in defense priming. Transcription analysis of tobacco transgenic lines revealed induction of hormone defense pathways (SA; JA-ET) and PRs (Pathogenesis-Related proteins) production. The strong upregulation of the respiratory burst oxidase homolog D (RbohD) gene in the pyramid lines suggests its central role in mediating immune responses in plants co-expressing the two transgenes, with reactive oxygen species (ROS) production enhanced by AdEXLB8 cues leading to stronger defense response. Here, we demonstrate that the association of potential priming elicitors and truncated NLRs can produce a synergistic effect on fungal resistance, constituting a promising strategy for improved, non-specific resistance to plant pathogens