Tradeoff between Biomass and Flavonoid Accumulation in White Clover Reflects Contrasting Plant Strategies

An outdoor study was conducted to examine relationships between plant productivity and stress-protective phenolic plant metabolites. Twenty-two populations of the pasture legume white clover were grown for 4½ months during spring and summer in Palmerston North, New Zealand. The major phenolic compounds identified and quantified by HPLC analysis were glycosides of the flavonoids quercetin and kaempferol. Multivariate analysis revealed a trade-off between flavonoid accumulation and plant productivity attributes. White clover populations with high biomass production, large leaves and thick tap roots showed low levels of quercetin glycoside accumulation and low quercetin:kaempferol ratios, while the opposite was true for less productive populations. The latter included stress-resistant ecotypes from Turkey and China, and the analysis also identified highly significant positive relationships of quercetin glycoside accumulation with plant morphology (root:shoot ratio). Importantly, a high degree of genetic variation was detected for most of the measured traits. These findings suggest merit for considering flavonoids such as quercetin as potential selection criteria in the genetic improvement of white clover and other crops

Quercetin glycoside accumulation in the leaves of 22 white clover populations.

<p>Quercetin glycoside accumulation in the leaves of 22 white clover populations.</p

Means, ranges, variance components (σ²_g) with associated standard errors (±SE), and line mean repeatability (<i>R</i>) for traits measured in 22 white clover populations.

<p>Q, quercetin; K, kaempferol; F, flavonols.</p

Mean monthly maximum and minimum temperatures (°C) and total monthly rainfall (mm) during the trial period from November 2003 to March 2004, at Palmerston North in New Zealand.

<p>Mean monthly maximum and minimum temperatures (°C) and total monthly rainfall (mm) during the trial period from November 2003 to March 2004, at Palmerston North in New Zealand.</p

Biplot displaying component vectors I and II based on standardized BLUP values for eight morphological and biochemical traits, measured in 22 white clover populations.

<p>The symbols represent the five population groups generated from cluster analysis. The directional vectors represent the traits F, flavonols; K, kaempferol; LW, leaf width; Q, quercetin; Q:K, quercetin:kaempferol ratio; RSR, root:shoot ratio; SW, shoot weight; TRD, tap root diameter.</p

Within-group population means for each trait based on the five clusters generated from cluster analysis of the 22 white clover population × eight trait BLUP adjusted mean matrix.

<p>Q, quercetin; K, kaempferol; F, flavonols.</p

Description of leaf sizes for the 22 white clover populations evaluated in the experiment.

<p>Description of leaf sizes for the 22 white clover populations evaluated in the experiment.</p

Box plots showing variation among the 22 white clover populations.

<p>(<b>A</b>) quercetin accumulation and (<b>B</b>) shoot weight. The top and bottom two populations for trait expression are indicated. B. line 1, Breeding Line 1. Mean (----).</p