Physiochemical responses of Ailanthus altissima under the challenge of Verticillium dahliae: elucidating the decline of one of the world’s worst invasive alien plant species

Abstract

Natural infections of Verticillium spp. (Fungi, Ascomycota) on Ailanthus altissima have suggested to consider the biological control as a promising strategy to counteract this invasive plant, which is otherwise difficult to control by traditional mechanical and chemical treatments. Verticillium wilt is able to lead plants to death, throughout a pathogenic mechanism including vessel occlusions and production of degrading enzymes and phytotoxins. In this study, a 10 weeks open air pot experiment was set to investigate the ecophysiological and biochemical responses of Ailanthus trees artificially inoculated in the trunk with the V. dahliae strain VdGL16, previously isolated in Central Italy from the same host. Inoculated plants showed visible injuries starting from 2 weeks post inoculation (wpi), that progressively developed until a final severe defoliation. The fungal infection rapidly compromised the plant water status, and photosynthesis was impaired due to both stomatal and mesophyll limitations from 4 wpi, with subsequent detrimental effects also on PSII activity. Moreover, the disease altered the translocations of nutrients, as confirmed by cation and carbohydrate contents, probably due to a consumption of simple sugars and starch reserves without replacement of new photosynthesized. An accumulation of osmolytes (abscisic acid and proline) and phenylalanine (a precursor of phenylpropanoids) was also reported at 8 wpi, this being a response mechanism that needs to be further elucidated. However, the activation delay of such defence strategy inevitably did not avoid the premature defoliation of plants and the decline of physiochemical parameters, confirming the key role of Verticillium in Ailanthus decay.

Identification of key responsive leaf physiochemical traits for ozone sensitivity in 16 Italian cultivars of Triticum durum subjected to peak concentrations

“…The photosynthetic activity can be measured with leaf‐level gas exchange measurements, which also allows the determination of stomatal conductance ( g s ) and intercellular CO 2 concentration (C i ) (Sharkey, 2016). However, to obtain more complete information on the primary sites of damage in the photosynthetic apparatus, leaf gas exchange parameters were often combined with those of chlorophyll a fluorescence (Calzone et al., 2019; Cotrozzi et al., 2021; Guidi et al., 1997; Pisuttu, Lo Piccolo et al., 2023). The sensitivity to O 3 of photosystem II (PSII) has made this approach a crucial technique for unravelling how plants can react to oxidative damage, which can in part explain the effects of O 3 at macroscopic level (Bussotti et al., 2011).…”