Tolerance to herbivory in lupin genotypes with different alkaloid concentration: Interspecific differences between Lupinus albus L. and L. angustifolius L.

Lupin genotypes accumulate alkaloids that act as feeding deterrents for several kinds of herbivores. Breeding sweet (low alkaloid) genotypes resulted in a greater dependence on pesticides. Besides the concentration of defensive chemicals, plants possess another way to deal with herbivory, to allocate post-damage resources to growth in order to reach compensation in biomass (tolerance).

These two ways to deal with herbivores were postulated as alternative strategies, as scarce resources allocated to one function (growth or secondary metabolism) would not be available for the other function. Genotypes could differ in the way they respond to herbivory; identifying those genotypes with greater ability to overcome the damage would be useful to decrease the use of pesticides.

The aim of this work was to compare tolerance to herbivory in Lupinus albus and Lupinus angustifolius genotypes with contrasting alkaloid concentration. Tolerance was evaluated by comparing growth and grain yield of field-grown cut and uncut plants. Cutting treatments were performed at flowering by cutting 50% of the upper shoot biomass (including the main apex, stems, flowers and leaves). Differences between species were found in their tolerance to herbivory. While L. angustifolius showed full compensation in growth or grain yield that allowed cut plants to equal controls biomass or yield after damage, simulated herbivory reduced growth and grain yield in L. albus.