Biochemical responses to ultraviolet‐C radiation and methyl jasmonate in Pinus radiata seedlings that accompany induced resistance to Diplodia pinea

Abstract

Irradiation of Pinus radiata seedlings with ultraviolet-C (UV-C) radiation or spray application of methyl jasmonate (MeJA) each resulted in induced resistance to subsequent wound inoculation with Diplodia pinea. Induced resistance was expressed by lower incidence of disease and by reduced size of stem lesions than in untreated seedlings. UV-C was more effective than MeJA and the induced resistance was greatest in seedlings that were irradiated with UV-C for 60 min, 1 week before pathogen inoculation. Induced resistance in the UV-C treated stems was concomitant with increases in peroxidase (POX) and polyphenol oxidase (PPO) activity but showed no correlation with concentrations of a-pinene and b-pinene or total phenolics. Furthermore, POX induction in stem tissue was cumulative and was greatest after three repeat treatments with UV-C at 6, 3 and 1 week before inoculation. In contrast to UV-C, MeJA induced a significant increase in b-pinene concentration in stem tissue but did not affect PPO activity. POX activity was induced by MeJA in stems, although to a lesser extent than by UV-C, but was not affected in needles. This appears to be the first report demonstrating the use of UV-C radiation to induce resistance to fungal infection in a coniferous species. The implications of the underlying differences between UV-C-and MeJA-mediated resistance to D. pinea are discussed.

Ultraviolet Radiation Effect on Seed Germination and Seedling Growth of Common Species from Northeastern Mexico

“…The sunflower and pine species were the most affected by UV-C radiation, decreasing their vigor and germinative power, with a high degree of deterioration in the pine seed. These results corroborate with those described by Reglinski et al [37], who demonstrated that the use of UV-C irradiation induces resistance to fungal infection in a conifer species (Pinus radiata). Similarly, Torres et al [38] and Cerero-Hernández [39] indicated that the percentage of normal plants in sunflowers was reduced when exposure to UV-C irradiation increased from 5 min to 60 min, which caused acute physiological stress, which led to a reduction in growth.…”

Enhancing resistance in Pinus radiata seedlings to terminal crook (Colletotrichum acutatum) using methyl jasmonate and ultraviolet‐C radiation

“…Jasmonates are known to induce physical and chemical defences in conifers, and MeJA application was shown to elevate concentrations of terpene and phenolic defence chemicals in radiata pine and to induce resistance against D. sapinea (Gould et al 2009) and also the large pine weevil Hylobius abietis (L.) (Zas et al 2014). Similarly, UV-C-induced resistance to D. sapinea in radiata pine was concomitant with increased activity of two defence-related enzymes, peroxidase and polyphenol oxidase (Reglinski et al 2013). Aside from crooking of the growing tip and needle death, infection of radiata pine with C. acutatum is also characterized by physiological symptoms including thickening of the stem and slowing down of apical growth (Nair and Corbin 1981).…”

“…Global trends towards reduced fungicide use have broadened interest in alternative control options including biotic and abiotic agents that stimulate natural plant disease resistance (Eyles et al 2010;Reglinski et al 2014). Spray application of chitosan (Reglinski et al 2004) or methyl jasmonate (MeJA) (Gould et al 2008(Gould et al , 2009), or irradiation with UV-C (Reglinski et al 2013), has each been shown to enhance resistance of P. radiata seedlings against infection caused by the fungal pathogen Diplodia sapinea (Fr.) Fuckel (syn.…”

Biosynthesis of D-Mannitol by Diplodia pinea

“…Diplodia pinea (D.pinea) is described as a pathogenic fungus capable of causing dieback, cankers, and tree death, in different Pinus species (Reglinski et al, 2013). The high incidence and severity of infection by D. pinea is associated with the spread of its spores by the action of rain and wind, in addition to being endophytic (asymptomatic condition) and transmitted by seedlings.…”

“…The high incidence and severity of infection by D. pinea is associated with the spread of its spores by the action of rain and wind, in addition to being endophytic (asymptomatic condition) and transmitted by seedlings. Besides, these fungi have become more aggressive under periods of plant stress (drought, excessive rain, hail, or some injury to the plant) (Reglinski et al, 2013;Smith et al, 2014).…”