Plasticity in pollination processes - Effects of insect herbivory on cross- and self-pollination in Brassica rapa

Summary

How can plants maintain reproduction under stressful conditions? When pesticide use is reduced, insect herbivore presence in agricultural fields may increase. I studied how feeding by herbivorous insects affects various pollination processes in Brassica rapa (field mustard) and its subspecies pekinensis (Chinese cabbage).

Many plant species prefer cross-pollination for reproduction. Cross-pollination mixes genes and prevents inbreeding. However, self-pollination provides reproductive assurance: using own pollen is fast and independent of pollinators. Cross-pollination in Brassica rapa is facilitated by a diverse pollinator community. I found that insect herbivory can alter pollinator attraction, behaviour and community composition. Not all pollinators respond the same. The effects on pollinators and seed yield were dependent on plant genotype. To prevent self-pollination, Brassica rapa can recognise and reject self-pollen. I found that under insect herbivory, acceptance of self-pollen may increase.

In conclusion, my work shows that insect herbivore alters pollination processes in Brassica rapa, but that – dependent on plant genotype – this does not necessarily have a negative impact on pollination and seed yield.