MAJOR GENES FOR RESISTANCE TO BEET NECROTIC YELLOW VEIN VIRUS (BNYVV)IN BETA-VULGARIS

Inheritance of resistance to beet necrotic yellow vein virus (BNYVV) w as studied in segregating F2 and backcross families obtained from cros ses between resistant plants of the sugar beet selection Holly-1-4 or the wild beet accession Beta vulgaris subsp. maritima WB42 and suscept ible parents. Greenhouse tests were carried out, in which seedlings we re grown in a mixture of sand and infested soil. Virus concentrations of BNYVV in the rootlets were estimated by ELISA. To discriminate resi stant and susceptible plants, mixtures of normal distributions were fi tted to log(10) virus concentrations, estimated for segregating F1, F2 and BC populations of both accessions. The hypothesis that Holly-1-4 contained one single dominant major gene was accepted. For WB42, resul ts fitted with the hypotheses that resistance was based on either one (or more) dominant major gene(s) showing distorted segregation, or two complementary dominant genes, which are both required for resistance. Resistance from WB42 appeared to be more effective against BNYVV than resistance from Holly-1-4.