Foliar Illumination Affects the Severity of Cameraria ohridella Damage Among Horse Chestnut Species

The influence of crown illumination on leaf damage of horse chestnut species (<i>Aesculus hippocastanum</i> L., <i>Aesculus glabra</i> Willd, <i>Aesculus flava</i> Aiton, <i>Aesculus pavia</i> L., <i>Aesculus</i> × <i>carnea</i> Hayne, <i>Aesculus parviflora</i> Walter, <i>Aesculus chinensis</i> Bunge) affected by ohrid leaf miner (<i>Cameraria ohridella</i> Deschka & Dymić) was studied using some accessions from the arboretum botanical tree collection. <i>A. hippocastanum</i>, <i>A. glabra</i>, <i>A. flava</i> had the lowest chl <i>a</i> content in the foliage on the sunlit side of the crown, while in <i>A. pavia</i>, <i>A. parviflora and A. chinensis</i> this indicator was the highest. The chl a content in the leaves of <i>A. hippocastanum</i> and <i>A. flava</i> under shaded conditions was 1.3 and 2.4 times higher than in the sunlit part, while in <i>A. pavia</i>, <i>A. parviflora</i> and <i>A. chinensis</i> the chl a content on the shaded side was 1.2, 1.6 and 1.3 times lower. The quantitative content of chl b in the sunlit part of the crown in <i>A. hippocastanum</i> and <i>A. flava</i> was significantly higher than in the other species. Moreover, while <i>A. flava</i> and <i>A. parviflora</i> had the highest chl b content in the foliage of the shaded part of the crown, <i>A. glabra</i> and <i>A</i>. × <i>carnea</i> had the lowest. Similarly, differences in proline levels were found in the leaves of different horse chestnut species on the sunny side of the crown. Higher proline levels in less infested species were identified. Water content imbalances due to feeding by leaf miners were most characteristic of the severely affected species. Chlorophyll fluorescence determination revealed high photochemical activity with an effective defense system in resistant species, while non-resistant species exhibited weak defense mechanisms in both sunlight and shade. To assess horse chestnut species the hyperspectral analysis indices (DSWI and SIPI) were also successfully applied. Changes in chl a and chl b content, proline levels, and leaf water-holding properties can be used to assess the resistance of horse chestnut species using classical physiological and biochemical methods. Hyperspectral analysis indices (DSWI and SIPI) can also be successfully applied.