Genetic variation of horse chestnut and red horse chestnut and trees susceptibility to Erysiphe flexuosa and Cameraria ohridella

Phenolic-Based Discrimination between Non-Symptomatic and Symptomatic Leaves of Aesculus hippocastanum Infested by Cameraria ohridella and Erysiphe flexuosa

The herbivore Cameraria ohridella (kingdom Animalia) and the pathogen Erysiphe flexuosa (kingdom Fungi) are considered pests and biotic stressors of Aesculus hippocastanum (chestnut trees). The impact of both pests on the accumulation of secondary metabolites in chestnut leaves was investigated. Specifically, the interactive effect of both pests on metabolite accumulation and their potential role in enhancing the resistance of chestnut trees to biological stress was the focus of this study. Aesculus hippocastanum leaves with varying degrees of Cameraria ohridella infestation and Erysiphe flexuosa infection were used in this research. Leaf samples were collected during the plant vegetative growth phase and evaluated for pest infection and secondary metabolite content. Eight main polyphenols were identified in the leaves: (1) neochlorogenic acid, (2) (-)-epicatechin, (3) procyanidin trimer A-type, (4) procyanidin tetramer A-type, (5) quercetin-3-O-arabinoside, (6) quercetin-3-O-rhamnoside, (7) kaempferol-3-O-arabinoside, and (8) kaempferol-3-O-rhamnoside. It was found that the accumulation of metabolites, primarily those derived from epicatechin and quercetin, during the initial vegetation phase (up to 11.05 or 09.05), strongly depended on the later degree of pest infection. The differences observed in the metabolite dynamics in the chestnut leaves, depending on the extent of infection, indicate the development of a metabolic response mechanism in chestnut trees to biological stress.

Biotic and abiotic factors causing the collapse of Robinia pseudoacacia L. veteran trees in urban environments

Robinia pseudoacacia L. is an interesting example of how one plant species can be considered invasive or useful depending on its environment. In the past this tree species was planted for decorative purposes and for wood in Poland. For many years it was recommended in poor and degraded habitats because it facilitated late-successional plant species. The aim of this study was to verify if black locust can still be regarded as a resistant tree species in urban greenery. The health condition of old tree specimens growing along streets and in parks was compared. The occurrence of pests and pathogens on R. pseudoacacia trees was assessed and the content of mineral elements in leaves was examined. The research results showed that the health of black locust trees growing in the urban environment in Polish cities, especially along streets (in comparison to park sites), deteriorated significantly due to the interaction of harmful biotic and abiotic factors. Increased level of toxic metals (Fe, Zn, Pb, Mn and Cd) in plant tissues and the accumulation of pests and pathogens negatively influenced the health of R. pseudoacacia.

Genetic variation and association mapping of waterlogging tolerance in chrysanthemum

Forty-five molecular markers were detected significantly associated with chrysanthemum' waterlogging tolerance, and four favorable parental lines were identified as potential donors for improving waterlogging tolerance in chrysanthemum. The productivity of chrysanthemum is downgraded by waterlogging soils, which has driven a search for germplasm showing an enhanced level of waterlogging tolerance (WT). As yet little is known regarding the mode of inheritance of WT in chrysanthemum. The study set out to characterize the extent of genetic variation for WT represented in a collection of one hundred chrysanthemum accessions by testing them under both greenhouse and field conditions. A membership function value of waterlogging (MFVW), which integrated a wilting index, a chlorosis score and the proportion of dead leaf in waterlogged plants, was used as a measure of WT. The variation for MFVW among plants grown in the greenhouse (two experiments) was generally higher than that generated in field-grown (one experiment) plants. The MFVW broad sense heritability was 0.82, and the phenotypic coefficient of variation (31.8 %) was larger than the genetic one (28.8 %). Association mapping (AM) identified 45 markers related to WT: 25 by applying the general linear model (GLM) + principal component (PC) model, 16 by applying the mixed linear model (MLM), 31 by applying the MLM + Q matrix model and 12 by applying the MLM + PC model. Of the associated markers, eight and two were predictive in two and three experiments within all models, respectively; the proportion of the phenotypic variance explained by the eight associations ranged from 6.3 to 16.4 %. On the basis of their harboring all four of the leading markers E2M16-2, SSR150-6, E19M16-1 and E10M10-12, the varieties 'Nannong Xuefeng', 'Qx097', 'Nannong Xunzhang' and 'Finch' were identified as potential donors for future improvement of WT in chrysanthemum.