Variation for constitutive flavonols and morphological traits in a new white clover population

• The experiment showed repeated highly significant variation for the measured traits.
• There was only a weak negative correlation between biomass and flavonols.
• Both increased stress protective metabolites and selection for high herbage yield.
• The flavonoid biochemical pathway occurs in all crop plants.
• This finding could improve other economically important crops.

Breeding forage legumes combining high levels of stress-protective secondary metabolites and high herbage yield are possible. Previous findings suggested a trade-off between flavonol glycosides and biomass production in white clover (Trifolium repens L.), with population specific evidence indicating that association. The present study used a novel white clover first filial (F1) reciprocal cross (n = 130, 3 replications in pots) between the productive cultivar “Kopu II” and the cold- and drought stress-resistant population “Tienshan”. The conditions were non-limiting as the plants were watered at regular intervals as needed, to establish a baseline for both constitutive flavonol glycosides and above-ground biomass production. This study showed that the phenotypic correlation between the traits quercetin glycosides (Q) and shoot dry matter (SDM) although significant (P < 0.001) was weak with r2 = 0.0903 (9%). This suggests the possibility of improving white clover performance by increasing the levels of stress protective metabolites in tandem with selection for high yield. At a genotype level, constitutive quercetin (Q) glycoside accumulation in this white clover line is not a major constraint on DM production in the absence of moisture stress. This indicates that combining high DM yield and high constitutive levels of Q glycosides for abiotic stress protection is possible. This finding is significant to overcoming a key challenge in plant breeding: combining stress tolerance with increased herbage production.