Effects of nitrogen supply on growth, contents of phenolic compounds and pathogen (scab) resistance of apple trees

Abstract

The effect of long-term N-supply on growth, scab resistance and phenolic compounds in the leaves of two apple cultivars was studied. The different pools of phenylpropanoids (hydroxycinnamic acids, dihydrochalcones) and flavonoids (flavonols, catechins, procyanidins) were quanitfied by HPLC from non-infected and inoculated leaves representing different ontogenetic stages. Scab incidence was also evaluated. Strictly following the carbon-nutrient-balance hypothesis, apple trees responded to high N-supply with increased shoot growth and with a reduced accumulation of total phenolic compounds in their leaves. This was shown for the cultivar 'Golden Delicious', which is susceptible to the scab disease caused by Venturia inaequalis, and for the resistant cultivar 'Rewena'. Whereas high N-fertilization increased the susceptibility of 'Golden Delicious', it did not decrease the resistance of 'Rewena' despite of the pronounced reduction of phenolic concentrations. Thus, a simple C trade off between growth-related metabolism and secondary metabolism cannot solely explain changes in defensive potential.

Seasonal changes in phenolic compounds in the leaves of scab-resistant and susceptible apple cultivars

“…In contrast, the maximum value of catechin in pear leaves was obtained only at the beginning of September (Colaric et al , 2007 (Table 2). Leser and Treutter (2005) reported that the resistant cultivar Rewena contained more catechins than Golden Delicious.…”

“…Previous investigations have shown that high N-nutrition reduced flavonoid accumulation in leaves. This situation is positively correlated to increased susceptibility to scab (Ru¨hmann et al 2002;Leser and Treutter 2005;Strissel et al 2005). The content of phenolics in a plant may be influenced by cultivation conditions (environmental conditions and cultivation techniques).…”

Lower nitrogen nutrition determines higher phenolic content of organic apples Juozas Lanauskas1, Darius Kviklys1, Mindaugas Liaudanskas2, Valdimaras

“…Apple trees respond to a high N-supply by increased shoot growth and the reduced accumulation of total phenolic compounds in their leaves (Leser, Treutter 2005). The application of N might cause a decrease in the content of some phenolics and in the percentage of blush skin of apples (Awad, De Jager 2002).…”

Non- Chemical Management of Apple Scab- A Global Perspective

“…Heavy nitrogen fertilization supports tree and fruit growth and therefore is a prominent controlling tool for yield. An enhanced vegetative growth of apple trees, however, is often correlated with an increasing susceptibility to pathogens such as V.inaequalis (Leser and Treutter, 2005). This may be due to the concomitant decrease of phenolic compounds by high nitrogen uptake (Leser and Treutter, 2005) indicating that environmental conditions favouring plant growth reduce investment of carbon for defence.…”

“…An enhanced vegetative growth of apple trees, however, is often correlated with an increasing susceptibility to pathogens such as V.inaequalis (Leser and Treutter, 2005). This may be due to the concomitant decrease of phenolic compounds by high nitrogen uptake (Leser and Treutter, 2005) indicating that environmental conditions favouring plant growth reduce investment of carbon for defence. Kumar and Gupta (1986) observed that a high level of potassium fertilizers increased resistance of apple tree to scab but a similar effect was not obtained with high levels of phosphorus fertilization.…”