Compensatory phenolic induction dynamics in aspen after aphid infestation

Area of Science:

• Plant Science
• Chemical Ecology
• Forestry

Background:

• Condensed tannins (CTs) are polyphenols contributing to plant defense against pathogens and herbivores.
• The role of CTs in aspen (Populus tremula) resistance against aphids and the relevance of constitutive versus induced levels remain unclear.
• Plant defense mechanisms involve complex chemical pools that vary significantly.

Purpose of the Study:

• To investigate the relationship between constitutive and induced condensed tannin (CT) levels in aspen and aphid fitness.
• To determine whether constitutive or induced CTs are more critical for plant resistance to aphid infestation.
• To explore the dynamics of phenolic compounds, including CTs and catechin, in response to aphid and mechanical damage.

Main Methods:

• Aspen genotypes with varying inherent CT production abilities were propagated.
• Plantlets were subjected to aphid infestation and mechanical leaf rupture.
• Foliar CT concentrations (constitutive and induced) and aphid fecundity were quantified and analyzed.

Main Results:

• Aphid fecundity was negatively correlated with CT and total phenolic (TP) concentrations, with TPs showing a more consistent relationship.
• TPs increased with damage, but CT induction was generally low, decreasing below constitutive levels in CT-rich genotypes.
• Catechin levels increased with aphid damage, negatively correlating with CT induction and positively with constitutive CTs and aphid fecundity.

Conclusions:

• Constitutive CT levels appear to be a more reliable indicator of aspen resistance to aphids than induced CT levels.
• The plant's inherent ability to produce and store CTs, potentially mediated by compounds like catechin, is crucial for defense.
• Different types of damage elicit distinct phenolic responses, highlighting the complexity of plant defense mechanisms.