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Projects / Programmes source: ARIS

Flavonoids and their synthesis as a mechanism of resistance of apples to apple scab

Research activity

Code Science Field Subfield
4.03.00  Biotechnical sciences  Plant production   

Code Science Field
B006  Biomedical sciences  Agronomics 
B390  Biomedical sciences  Phytotechny, horticulture, crop protection, phytopathology 
Keywords
secondary metabolites, phenolics, apple, apple scab, HPLC-MS, enzymes
Evaluation (rules)
source: COBISS
Researchers (11)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  14033  PhD Metka Hudina  Plant production  Researcher  2008 - 2009  660 
2.  25505  PhD Jerneja Jakopič  Plant production  Junior researcher  2008 - 2010  214 
3.  23631  PhD Maja Mikulič Petkovšek  Plant production  Researcher  2008 - 2009  397 
4.  14541  PhD Gregor Osterc  Plant production  Researcher  2008 - 2009  347 
5.  17771  Dragutin Plasajec    Technical associate  2008 - 2009  43 
6.  20496  Tomaž Pliberšek    Technical associate  2008 - 2009 
7.  29419  PhD Valentina Schmitzer  Plant production  Junior researcher  2008 - 2010  154 
8.  07552  PhD Anita Solar  Plant production  Researcher  2008 - 2009  521 
9.  06404  PhD Franci Štampar  Plant production  Researcher  2008 - 2009  1,186 
10.  11759  PhD Valentina Usenik  Plant production  Researcher  2008 - 2009  425 
11.  20165  PhD Robert Veberič  Plant production  Head  2008 - 2010  578 
Organisations (1)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  0481  University of Ljubljana, Biotechnical Faculty  Ljubljana  1626914  67,269 
Abstract
Apple scab caused by the fungus Venturia inaequalis /Cooke/ G. Winter is a frequent occurring apple-tree disease in the world. This disease can cause tremendous loss of yield and can degrade fruit quality. Fruit growers tried to minimize the importance of this disease in several ways using frequent chemical treatment with fungicides, resistant/tolerant genotypes or induction of defense mechanisms by treating plants with triggering agents. Although intensively belabored in the past 50 years, the biochemical principle of scab-resistance is not known. Phenolic compounds and especially flavonoids play a role in the resistance of apples to the fungus causing scab. Especially in a resistant variety of plant relative to a susceptible variety the phenolics accumulate at a faster rate. The phenolic derivatives can oxidize and react with proteins thus causing the loss of enzyme function of the aggressors. Their other function is that they can be deposited inside the cell wall as an important first line in plant defense against infection. Phenylalanine-ammonia-lyase (PAL) which connects the primary and secondary metabolism catalyzes the conversion of the amino acid phenylalanine into cinnamic acid, which produces a variety of phenolic compounds with structural and defense-related functions, including flavonoids, phytoalexins, and lignin. However, derivatives of cinnamic acids are the precursors for a broad variety of secondary metabolites, and the activity of PAL alone therefore provides only limited information with respect to flavonoid formation. To get a more comprehensive insight into the changes occurring in flavonoid metabolism during infection with fungus causing apple scab also activity of other enzymes. With our project we would like to investigate the response of the plant to the infection with fungus that causes apple scab. With the help of HPLC-MS we will detect phenolics that increase in concentration after the infection. At the same time we will try to estimate the activity of key enzymes in flavonoid synthesis pathway. Consequently, with knowledge about the synthetic pathway of phenolics and their response to scab infection, we will becoming more sophisticated in the approaches and tools for targeted modifications of specific pathway branches in order to achieve a particular desired metabolic profile resulting in higher resistance to the disease. This will enable us with technological measures to stimulate an early response, increasing the resistance level and consequently reducing the amounts of fungicides in apple production.
Significance for science
We have developed and optimized the method for identification of individual phenolic compounds on high performance liquid chromatograph coupled with mass spectrometer. In this way, we analyzed all the major phenolic components, which are represented in the leaves and fruits of apples. The results of individual experiments in the general scope of the study exposed several important scientific findings which were successfully published in international journals and presented at various scientific and professional meetings. The results showed that the infection with apple scab modified the profile in plant tissue. Almost all the analyzed phenolic compounds increased their levels as a result of the infection with apple scab. The largest increase was observed in hydroxycinnamic acids, even up to 4.9 times compared to healthy tissue, followed by flavan-3-ols, which have increased up to 2.8 times and dihydrochalcones which have increased up to 1.4 times. In collaboration with researchers from the Technical University in Vienna, we introduced a new method of determining the activity of many important enzymes of phenylallanin metabolism in fruit skin. Enzymes analyzed were as follows: phenylalanine ammonia lyase (PAL), 3-hydroxylase flavanon (FHT), dihydroflavonol 4-reductase (DFR), flavonol synthase (FLS), chalcone synthase (CHS), chalcone isomerase (CHI), dihidrohalkon 2 - O-glucosyltransferase (D2GT) and peroxidase (POD). The results of enzyme activity indicate that the infection caused significantly higher enzyme activity of most of the analyzed enzymes in infected tissues compared with healthy tissue. In general, young plant parts, such as leaves and fruits possessed higher enzyme activity and higher concentrations of phenols, which is associated with greater resistance to pathogens. When comparing organic and integrated production, higher levels of phenols and a higher antioxidant activity in organic apples was measured compared to the ones produced in an integrated technology. Our results show, that the plant response to stress factors, such as apple scab infection or organic production is in increased synthesis of hydroxycinnamic acids and flavonoids. With the aid of these the plants develop their own defense mechanism against pathogens. Our results make an important contribution to a precise knowledge of the physiology and metabolism of secondary metabolites in apple in relation to the fungus Venturia inaequalis.
Significance for the country
Apple scab, caused by the fungus Venturia inaequalis, is still one of the most severe diseases of apple. Because of the number of mandatory sprayings with fungicides, especially in wet years, large financial costs as well as a burden on the environment have to be considered. Knowledge on key phenolics and enzymes involved in their synthesis is essential for the study of host-pathogen interactions, which in turn is linked to greater resistance of plants. Our study on the natural defense mechanisms of apple to these pathogens contribute significantly to a more detailed knowledge in the field of biotechnological sciences and implement this knowledge into new technological processes. The positive effects of treating the apple trees with sodium bicarbonate, resulting in a lower rate of infection with apple scab on leafs and fruit, could be transferred to the fruit growers' practice. In this way, the number of fungicidal sprayings could significantly be reduced. Comparison of the integrated and organic fruit production showed that the latter contained higher level of phenolic compounds and had a higher antioxidant potential in apple fruit. Therefore, from the nutritional and health perspective, we recommend organic produce; in addition, it is environmentally friendly and provides living environment for wild organisms, since the introduction of synthetic pesticides and fertilizers is prohibited. The importance of secondary metabolites in the production of high quality and healthy fruit is essential, because of their effects on increased resistance of plants and consequently a reduced use of fungicides and insecticides in fruit growing production. Organic food is gaining importance, from a viewpoint of a healthy diet and more efficient energy use as well as conservation of the environment it is significant that we grow those cultivars of agricultural plants, which reduce the use of fungicides and insecticides. All these aims lead to higher awareness and sustainable development.
Most important scientific results Annual report 2008, final report, complete report on dLib.si
Most important socioeconomically and culturally relevant results Annual report 2008, final report, complete report on dLib.si
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