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.