Pre-Breeding for Nematode Resistance in Beet

Abstract

Pre-breeding for partial resistance to the beet cyst nematode (BCN), Heterodera schachtii, included repeated mass selection in descendants of Beta vulgaris subsp. maritima accession BMH and preliminary studies on inheritance and mechanism of this resistance. The selection in accession BMH and in progenies of a cross with fodder beet resulted in rather high levels of partial resistance. The mean numbers of cysts per plant for the BMH selections and for progenies of a cross with fodder beet were 20-40070 and 15-30%, respectively, of those of the susceptible control varieties. The progenies of crosses between accession BMH and sugar beet were less advanced, and additional selection for bienniality may have decreased the progress in selection for BCN resistance. The resistant materials showed a wide variation in cyst size, and many of the cysts were considerably smaller than those on the susceptible control varieties. This phenomenon will reduce the multiplication rate of the nematodes. The numbers of cysts in progenies of pair crosses between accession BMH and cultivated materials generally were slightly below the mid-parent values. The results are discussed in the light of pre-breeding strategies and the possible application of marker-facilitated selection procedures.