CHARACTERIZATION OF NEMATODE RESISTANCE GENES IN THE SECTION PROCUMBENTES GENUS-BETA - RESPONSE TO 2 POPULATIONS OF HETERODERA-SCHACHTII

Three species of the section Procumbentes genus Beta, nine monosomic a dditions, and five translocation lines were tested for resistance to t wo Heterodera schachtii populations. Nematode population 129-v (129-vi rulent) was selected for virulence to resistance gene(s) transferred f rom chromosome 1 of Beta procumbens to the diploid resistant sugar bee t KWS-NR1. This population is considered to be a pathotype. The unsele cted sib population 129-av (129-avirulent) was reared continuously on fodder rape, Brassica napus cv Velox. Monosomic additions with chromos ome 1 from the three species of the section Procumbentes were suscepti ble to population 129-v, regardless of the origin of the alien chromos ome. Translocations with a gene(s) for resistance from chromosome 7 of B. procumbens and B. webbiana were also susceptible to the pathotype. However, a monosomic addition with chromosome 7 of B. webbiana was re sistant to population 129-v. The three wild beets of the section Procu mbentes, Beta procumbens, Beta webbiana and Beta patellar is, also wer e highly resistant to the two populations. The results indicate the ex istence of just two different major genes for resistance to H. schacht ii in the entire Procumbentes section.