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Rezistence jabloní vůči Venturia inaequalis, původci strupovitosti jabloně
Strouhal, Petr
Apples belong to the most important fruit species grown in a temperate zone. Like most cultivated botanical species, the domestic apple (Malus dometica Borkh.) is attacked by a number of pathogens. Apple scab caused by fungal pathogen Venturia inaequalis (Cooce) G. Winter belongs to the world's most important diseases of the apples. Chemical protection, which is based on the application of up to 20 treatments per vegetation in intensive orchards, represents a costly entry into the production of apples. Growing of apple scab resistant varieties is part of integrated plant protection and it is one of the ways to eliminate the negative effects of fungicides use on apple quality and on the environment and simultaneously produce quality and well-sold fruit. Therefore, the aim of the bachelor thesis is to elaborate a study focused on the issue of genetic mechanisms of resistance of apples to scab. The breeding of resistant apple varieties is based on two different genetic principles. The first principle is polygen-determined resistance, which is usually racially unspecific and persistent. However, donors of this resistance are difficult to define and the breeding process is significantly slower. Another option is racially-specific resistance controlled by some of the Rvi majorogens. Up to now, 18 different Rvi genes and their donors have been described. However, in apple resistant breeding, genes Rvi2, Rvi4, Rvi5, Rvi6 and Rvi10 are mainly used. But most of resistant varieties carry only gene Rvi6. The first varieties with resistance based on gene A were bred in the 1970s in the USA. In the Czech Republic, several dozen resistant varieties have been produced since 1980, mainly due to breeding programs in Station of apple breeding for disease resistence Institute of Experimenta Botany AS CR in Strizovice and in Research and Breeding Institute of Pomology. Holovousy Ltd. Most Moravian and Silesian farmers indicate the cultivation of at least one resistant variety. Nevertheless, it is clear from the data of the Czech Statistical Office that between 2012 and 2016 there was a significant decrease in the area of the two most common resistant varieties Topaz and Rubinola. The cause of this fact may be the breakdown of Rvi6 gene controlled resistance, the planting of other resistant varieties on significantly smaller areas, or lower fruit quality of resistant varieties. The occurrence of new V. inaequalis races has influenced the breeding strategies so that the breeding targets are resistant varieties with pyramidation of several majorgenes and polygenic resistance mechanism to scab.
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