Development of Heterodera schachtii in sugar beet genotypes with varying levels of resistance.

The beet cyst nematode (BCN, Heterodera schachtii) is a major pest of sugar beet in many production areas around the world. BCN is mainly managed by growing tolerant sugar beet cultivars. These cultivars are not only tolerant, but also show a 30-60% lower nematode reproduction in comparison to susceptible cultivars. To better understand the mechanisms of different levels of resistance, development of H. schachtii in susceptible, resistant and tolerant sugar beet cultivars was studied in a series of climate chamber experiments. Seedlings were grown in 100-ml-containers with sand and inoculated in the 2-leaf stage with 500 BCN second-stage juveniles. Nematode development was evaluated at weekly intervals until the first generation was completed. In summary, 1) resistance and partial resistance did not affect root penetration rate of H. schachtii, 2) resistance frequently interrupted the development of juveniles and almost completely prevented the development of adult females, 3) partial resistance changed the sex ratio in favour of males and delayed the development of females, 4) resistance and partial resistance reduced the number of developed cysts and the cyst content and 5) sugar beet genotypes with partial resistance could be differentiated according to the average number of eggs and juveniles per cyst. The project was funded by the Federal Ministry of Food and Agriculture through the Fachagentur Nachwachsende Rohstoffe e. V. (FKZ 22022812).