Induction of defense mechanisms in seedlings of oilseed winter rape inoculated with Phoma lingam (Leptosphaeria maculans)

Abstract

The aim of this study was to find the biochemical markers of blackleg, evoked by the fungus Leptosphaeria maculans in seedlings of oilseed winter rape. Analyses of antioxidant enzymes activity and reactive oxygen species detection were performed 24, 48 and 72 h after inoculation. Moreover, measurements of the total pool of phenolic compounds, transcinnamic acid and ferulic acid were carried out. The results proved the virulence of Ph L5 isolate towards the rape seedlings. An increase in total phenolic content, including trans-cinnamic acid, was observed 24 h after inoculation. High activity of phenylalanine ammonia-lyase is probably another symptom of the defense mechanisms, despite the fact that it was not accompanied by elevated phenolics level, which were probably rapidly exhausted during Phoma lingam inoculation. A drop in phenolics content was balanced by higher activity of SOD, CAT and non-specific peroxidases. Enhanced activity of these enzymes was a response to the reactive oxygen species overproduction. ROS accumulation in indirectly inoculated first true leaves after inoculation may suggest a systemic defense response.

An explanation for the natural de-bittering of Hurma olives during ripening on the tree

“…This parameter ranged in Hurma olives between 30-40% ( Figure 2) whereas Erkence had around 50%. Phoma fungus causes irregular necrotic patches in fruits, a drop in phenolic compounds and an increase in peroxidase and polyphenoloxidase activity (Bugbee, 1975;Hura et al, 2014). Also, an anthracnose disease originated by Colletottrichum acutatum gives rise to desiccated fruits (Moral et al, 2014) but Hurma olives look like dry-salted olives rather than mummified fruit.…”

Biochemical defense mechanisms induced in winter oilseed rape seedlings with different susceptibility to infection with Leptosphaeria maculans

“…In response to a necrotroph attack and increased production of ROS the host cells trigger defense mechanisms involving enzymatic and non-enzymatic antioxidants [7,11]. The cause of lower O $À 2 content in the true leaves of the resistant 'Liclassic' cultivar was probably its effective dismutation to hydrogen peroxide by SOD.…”

“…This applies mainly to hydrogen peroxide, the most stable ROS which, being also a signaling molecule, can move freely through the cell walls and membranes, bringing about positive or negative physiological effects in healthy and remote parts of the plant [9,10]. Therefore, elevated ROS level during pathogenesis is accompanied by changes in enzymatic activity (catalase, peroxidase, SOD) and nonenzymatic antioxidants [1,11,12]. Another possible route for the neutralization of reactive oxygen species, especially hydrogen peroxide, is their participation in the process of phenolics incorporation into the cell wall [13].…”

O Papel Das Enzimas Antioxidantes Na Defesa Das Plantas Contra Insetos Herbívoros E Fitopatógenos

“…Estes estudos reforçam a hipótese que a classe III tem um importante papel na defesa de plantas e que pode servir como marcadores enzimáticos em resposta a estressores bióticos (SAATHOFF et al, 2013). HURA et al (2013) analisando a resposta bioquímica de plântulas de colza após inoculação de esporos do fungo Phoma lingam (Leptosphaeria maculans) observaram que houve aumento na atividade de peroxidase somente 72 horas após a inoculação e que este aumento ocorreu em resposta a alta produção de H 2 O 2 que ativou o sistema de defesa da planta, devido ao ataque do estressor biótico.…”