Mapping quantitative trait loci associated with compensatory responses in Arabidopsis thaliana

Background/Question/Methods: Plant tissue loss to herbivores is an important selective agent shaping plant phenotypes.  To date, most studies have focused on the evolution of defensive traits that reduce or prevent tissue damage by herbivores.  However, herbivores may also select for traits that allow plants to maintain fitness in the face of tissue loss.  Paige and Whitham (1987) provided convincing evidence that plants subjected to tissue loss by herbivores can, under some circumstances, compensate better in terms of growth and fitness (overcompensation) compared to their uneaten counter parts.  To understand the Quantitative trait loci (QTL’s) associated with compensatory responses, we screened recombinant inbred lines of Arabidopsis thaliana developed from a cross between Columbia (Col-4) and Landsberg erecta (Ler-0).  Columbia being an overcompensator and Landsberg erecta being an under compensator the RIL’s represented variation in compensatory responses. Herbivore damage was experimentally simulated and data on fitness (number of siliques) and related observations were recorded.

Results/Conclusions:

Compensatory responses varied significantly with few lines overcompensating (14 lines – including one of the parental lines) or undercompensating (9 lines including the other parental line), with the majority of the lines equally compensating (77 lines).  The initial data suggests presence of QTL’s associated with compensatory responses.  Using composite interval mapping the QTL’s associated with compensatory responses will be mapped.  Pairwise epistatic interactions will be identified between the identified QTL and all other markers to understand the percentage phenotypic variance accounted for by all the QTL for a given trait.  The results of this experiment will be discussed in light of evolutionary responses of plant-herbivore interaction.