RESUMO
Despite the positive results of using elicitors to induce resistance against plant diseases, some factors have inhibited the popularization of their use in agriculture. There is an energetic cost related to the elicitors' induced response which can cause undesired effects on growth under low-pressure disease conditions. Elicitors can create phytotoxicity and show high variation in their efficiency between different genotypes within the same crop; in addition, the positive results related to the induced resistance may not repeat in field treatments, adding to the possibility that they are not economically viable. Thus, we carried out two experiments to investigate the technical and economic efficiency of acibenzolar-S-methyl (ASM) and its association with fungicides in the control of leaf diseases of susceptible and resistant wheat varieties, and as how it reflects on the photosynthetic and production performance of wheat. This study showed the limitations of incorporating ASM into foliar fungal disease control in economic terms. However, it was evident that ASM effectively induced plant resistance against Leaf Rust and Powdery Mildew in the field and can be considered a sustainable option for wheat cultivation. Even though its association with chemical control was not the best economic strategy the use of ASM is a tool that can be incorporated into wheat cultivation to minimize the emergence of fungicide-resistant pathogens due to the diversification of modes of action employed and reduce the toxic residue deposition to the environment and human health.
RESUMO
Despite recognizing the importance of genetic improvement in the production of barley grains, little information is available on the contribution of phenological development to the genetic improvement of Brazilian barley. Field experiments were carried out between 2011 to 2013, in the absence of biotic and abiotic stresses and with preventive lodging control. Five two-rowed spring barley cultivars, released between 1968 and 2008, were evaluated. Although there was no significant association in the cycle length (Emergence - Anthesis) of the cultivars with the year of release, the genetic improvement increased the proportion of the Doble ridge - Maximum number of spikelet primordia/Maximum number of spikelet primordia - anthesis period to the total time to anthesis. The period between DR-MNP was increased in modern cultivars, to the detriment of the Doble ridge - Maximum number of spikelet primordia period. However, the duration of the period between emergences to the double ridge (vegetative phase) was not altered in the analyzed period. Barley breeding in Brazil did not change the total number of leaves on the main stem but caused an increase in the number of leaves earlier in the development, favoring the high level of tillering. The leaf architecture of modern barley was altered towards a more vertical inclination (erectophilic canopy), allowing the penetration of photosynthetically active radiation into the crop canopy.
RESUMO
Galling insects gain food and shelter by inducing specialized anatomical structures in their plant hosts. Such galls often accumulate plant defensive metabolites protecting the inhabiting insects from predation. We previously found that, despite a marked natural chemopolymorphism in natural populations of Pistacia palaestina, the monoterpene content in Baizongia pistaciae-induced galls is substantially higher than in leaves of their hosts. Here we show a general up-regulation of key structural genes in both the plastidial and cytosolic terpene biosynthetic pathways in galls as compared with non-colonized leaves. Novel prenyltransferases and terpene synthases were functionally expressed in Escherichia coli to reveal their biochemical function. Individual Pistacia trees exhibiting chemopolymorphism in terpene compositions displayed differential up-regulation of selected terpene synthase genes, and the metabolites generated by their gene products in vitro corresponded to the monoterpenes accumulated by each tree. Our results delineate molecular mechanisms responsible for the formation of enhanced monoterpene in galls and the observed intraspecific monoterpene chemodiversity displayed in P. palaestina. We demonstrate that gall-inhabiting aphids transcriptionally reprogram their host terpene pathways by up-regulating tree-specific genes, boosting the accumulation of plant defensive compounds for the protection of colonizing insects.
Assuntos
Afídeos , Pistacia , Animais , Tumores de Planta , Terpenos , Regulação para CimaRESUMO
O trabalho teve por objetivo caracterizar o efeito alelopático do extrato aquoso de acículas de Pinus taeda na germinação e no desenvolvimento inicial de plântulas de aveia preta comum (Avena strigosa). O experimento foi conduzido no Laboratório de Bioquímica e Fisiologia Vegetal da Universidade Tecnológica Federal do Paraná (UTFPR), Campus de Pato Branco, utilizando o delineamento inteiramente casualizado, com tratamento fatorial (bifatorial com parcela subdividida no tempo), com três repetições, sob condições de temperatura, umidade e luminosidade controladas. Os tratamentos foram compostos por cinco concentrações (0, 25, 50, 75 e 100 por cento) de extrato bruto de acículas de pínus em estágio vegetativo (acícula verde), moderadamente decomposto (acícula seca) e em decomposição avançada (acícula decomposta). As avaliações foram realizadas a cada 24 horas. Foram avaliados os parâmetros porcentagem de germinação, velocidade média de germinação e comprimento de radículas e epicótilos das plântulas de Avena strigosa. O estágio de acícula verde afetou significativamente as variáveis avaliadas e esse problema aumentou com a concentração do extrato.
The purpose of this study was to verify the allelopathic effect of aqueous extract from the Pinus taeda needles on the germination and development of black oat (Avena strigosa) seedlings. The work was carried out at the Plant Physiology and Biochemistry Laboratory at the Federal Technological University of Paraná (UTFPR), Campus Pato Branco, using a completely randomized design with factorial distribution in three replicates, under temperature, humidity and light controlled conditions. The extract from the pine needles was composed of five percentages (0, 25, 50, 75 and 100 percent) from the crude extract (EB) dilution, composed of distilled water + pine needles in vegetative stage (green needles), moderately decomposed (dry needles) and in advanced decomposition (decomposed needles). The germination percentage, average speed of germination, the length of the primary roots and the length from the seedlings roots of Avena strigosa were evaluated. The stage of green needles affected the variables studied and showed linearly effect with the increasing concentration of the crude extract.
