engleski

Quality preservation in FHB attack due to antioxidant system

Biotic stress leads to the formation of ROS which can harm the plants. Due to that plants have evolved an antioxidant defense system that includes non-enzymatic compounds, like ascorbate, glutathione, tocopherol, carotenoids, flavonoids and enzymes such as superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POD), ascorbate peroxidase (APX) and polyphenol oxidase (PPO). Six winter wheat varieties, representing commercial Croatian wheat classes with different intrinsic qualities, were subjected to Fusarium Head Blight (FHB) stress. Sampling was done at the 14th day of the FHB stress when the first symptoms occurred. Antioxidant properties of both treatments (control and FHB) were investigated to document the effect of FHB resistance to protein components (albumins, gliadins, ω-, α-, γ- gliadins, glutenins, HMW-GS and LMW-GS) which were detected by RP-HPLC method. The plants of all six varieties under test showed less or no symptoms of FHB till the 14th day of the FHB stress, when two wheat varieties progressively enlarged symptoms up to 90% till 26th dai (days after inoculation) and due to that they were characterized as FHB-susceptible. Very low FHB severity was obtained by 'Kraljica', 'Olimpija' and 'Vulkan' (20% symptoms at 26th dai), while 'Sana' showed moderate susceptibility (35%). The decline in CAT activity was in correlation with the increase of H2O2 in more resistant varieties ('Olimpija' and 'Vulkan'). The activity of APX increased with the appearance of symptoms in 'Kraljica', 'Golubica', 'Bc Anica', while the activity of APX declined in 'Olimpija' in FHB treatment in comparison to control. However, there was significant increase in FHB treatment in comparison to control, in respect to phenols, POD and H2O2 for all varieties, except for POD in 'Sana' and H2O2 in 'Golubica'. Varieties 'Golubica' and 'Vulkan' exhibited higher PPO activity in FHB treatment in comparison to control despite the presence of enlarged phenol content in FHB treatment in all varieties. The accumulation of MDA content was higher in two susceptible varieties than in tolerant varieties, with one exception. After harvest, gliadin level in FHB treatment in comparison to control increased in four varieties ('Kraljica', 'Sana', 'Golubica', 'Anica'). There was a significant effect of FHB on percentage of glutenins showing a respective reduction in comparison to control of 5%, 20% and 16% of 'Kraljica', 'Golubica' and' Bc Anica', respectively, while HMW subunits decreased in those three varieties (9.93, 14.61 and 20.33%, respectively) including 'Sana' (8.79%). LMW subunits were not largely affected as HMW, but 'Olimpija', 'Golubica' and 'Bc Anica' showed statistically significant decrease. It is interesting that in both treatments the most susceptible variety had the lowest amount of phenol content and PPO activity among other varieties. Due to the role of polyphenols as secondary plant metabolites that play a role in the protection of plants against pathogen, they were higher in genotypes with better preserved protein quality. The protein components of 'Vulkan' and Olimpija' were untouched which could be due to high PPO activity which could participate in detoxification of phenolic acids induced by pathogen attack.

FHB ; wheat ; protein ; antioxidant capacity

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