Genetic variation in constitutive and inducible pyrrolizidine alkaloid levels inCynoglossum officinale L.

Abstract

The constitutive pyrrolizidine alkaloid (PA) concentration of both shoots and roots differed significantly between 17 selfed families. The broad-sense heritability accounted for 33-43% of the variation in PA levels. Families also differed significantly in the amount and the direction of PA induction in both shoots and roots, 24 h after punching 15 holes in the leaves. We found a significantly negative relationship between the changes in PA content of the shoots and changes in PA content of the roots. The total PA content of the plants did not increase. We thus concluded that changes in PA distribution over the plant resulted from transport of PAs within the plant. The direction of transport differed between families: some transported PAs to the shoots, others to the roots. This makes it questionable whether PAs act as damage-induced defences. The effect of damage on the PA concentration is far less than the differences found between families in the constitutive PA concentration. This again strongly suggests that damage-induced defences inCynoglossum officinale do not play an important role. We argue that the general lack of attention that is given to genotype in induction experiments, has led to false conclusions.

Optimal Distribution of Defences: Are Plants Smart Investors?

“…The range in PA concentrations covered the whole range as found in leaves of C. offic inale (Van Dam et al 1994). Herbivory on discs with PAs was expressed relative to herbivory on control discs (Fig.…”

“…However, in a herbivore-free environ ment there was no significant negative genetic corre lation between PA content and growth in rosette plants of C. officinale (van Dam & Vrieling 1994). This indicates that the production costs of PAs may be too small to be measured under these circum stances.…”

“…The youngest leaf of the rosette has 50-190 times higher levels of pyrrolizidine alkaloids (PAs) than the oldest (van Dam, Verpoorte & van der Meijden 1994). Owing to their high PAlevels, the young leaves are avoided by generalist her bivores (van Dam et al 1995b).…”

“…Plant growth is maxi mized if the net production of each leaf over its life time is maximized. Chemical defences in the leaves increase the survival of the leaves in presence of her bivores (van Dam et al 1995a).…”

Variation in Lupinus arboreus alkaloid profiles and relationships with multiple herbivores

“…However, studies examining the heritability of defensive compounds typically use controlled environments to minimize environmental variation (e.g. Agren and Schemske, 1993;van Dam and Vrieling, 1994), or use clones (e.g., Maddox and Root, 1987), preventing the estimation of non-additive genetic effects (but see Nuñ ez-Farfán and Dirzo, 1994;Orians et al, 1996;Roche and Fritz, 1997, for studies that estimate narrow-sense heritability in the field). Few studies have simultaneously examined how environmental variation, population-level genetic differences, and maternal and paternal effects contribute to variation in defensive compounds.…”