Exploring mature plant resistance to control yellowing viruses in sugar beet

Summary

Yellowing viruses, transmitted through aphids, lead to yield decreases up to 50% in sugar beet. In sugar beet, a resistance mechanism against aphids is naturally present and called “Mature plant resistance (MPR)” but is only activated when plants become older. Within this PhD project we checked together with Cosun beet company, IRS, BBRO and SESvanderHave the prevalence of yellowing viruses in the Netherlands, the toxicity of MPR on aphids and the molecular changes in older sugar beet leaves.

Further studies are needed to unravel the exact molecular mechanism leading to MPR, but indications were found that the enzymatic browning reaction, caused by phenols and polyphenol oxidases that are presumably taken up by aphids from the leaves, leads to the death of the aphid. As MPR does not seem to be regulated by a resistance gene of QTL, breeding for higher of earlier MPR will probably be difficult. Our advice is therefore to exploit MPR in an integrated pest management strategy (IPM); e.g. spraying less insecticides on older sugar beet plants, sow sugar beets at an earlier timepoint so that the plants are older when the first aphid flight appears.

In addition, it would be interesting to further investigate external factors potentially leading to higher MPR (for example by stressing the plant for a short amount of time).