Effect of Strawberry and Barley Defence Proteins on Nematode Pests

To reduce the use of chemicals in the control of phytophagous pests and diseases alternative strategies and new compounds have to be identified. We studied the effects of two defense proteins, the strawberry cystatin FaCPI-1 and the barley cystatin HvCPI-6 on plant nematodes. Both cystatins, expressed and purified as recombinant proteins from E. coli cultures, were used to perform in vitro assays on Meloidogyne spp., Xiphinema americanum and X. index. Nematode populations were collected from Chilean infected soils and subjected to increasing concentrations of the recombinant proteins (0, 1.5, 3 and 6 mu M), added to artificial diets. Nematode immobility, used as viability index, was evaluated 24 and 48 hours after treatment using a pipette tip to verify their response to physical stimulus. Each treatment consisted on 5 replicates using 10 nematodes in each dish. The results showed a nematoxic effect of both phytocystatins on the three species evaluated, although there were differences in the response of each nematode. X. americanum and Meloidogyne spp. showed an important reduction in their mobility index, even at the lowest concentration tested. In contrast, X. index was only significantly affected by the highest phytocystatin concentration tested, the number of immobilized nematodes being very few. These results will be further completed (data still not available) by the characterization of the proteolytic activity profile of the nematode species to determine the phytocystatin targets. Due to these promising results, these phytocystatin genes could be used as nematicidal transgenes to be stably expressed in plants, or to establish a large scale of protein production program for as alternative strategies for pest control.