Search for morphological, biochemical, and microbiological markers of resistance of raspberry cultivars to Botrytis cinerea Pers.

To accelerate the breeding process, studies were conducted to identify morphological, biochemical, and microbiological markers of raspberry resistance to Botrytis cinerea Pers . The research objects were leaves of cultivars and forms diff ering in their resistance to gray mold. Using optical microscopy, we found that the abaxial surface of resistant cultivar leaves had multiple trichomes (hairs) not only along the veins, but also in the interveinal spaces. Moreover, closely spaced yellow glandules were discovered there as well. On the abaxial leaf surface of susceptible cultivars, rare trichomes were located along the primary leaf vein (midrib). No glandules were observed. Electron microscopy convincingly demonstrated that the adaxial side of resistant cultivars was so densely covered with intertwined hairs of diff erent lengths that the plant cuticle was not visible. In susceptible cultivars, the hairs were sparse, and the cuticle could be seen. The correlation analysis between the mineral content in the leaves and the extent of damage to raspberry cultivars by Botrytis cinerea revealed a medium and weak dependence between these indicators. Thus, they cannot be used as reliable markers of resistance to gray mold of fruits. As a result of metabolomic profi le analysis, resistant cultivars were found to contain an increased amount (1.5-23.6 times) of compounds with antimicrobial (fungicidal) action in the composition of the epicuticular layer of leaves. They are as follows: lignoceric, decanoic (capric), pelargonic acids, as well as ethyl gallate, arabinofuranose, 1-butanamine. These compounds can be considered biochemical markers of resistance to B. cinerea and used for early seedling disease diagnosis. Strains of cultivated endophytic bacteria forms with established antifungal activity against Botrýtis cinérea were isolated from the leaves of the resistant cultivar Zhar-Ptica and selected form No. 11-165-10.