Behavior of potato gametoclonal plants against the necrotic strain of potato Y potyvirus

A total of 59 Solanum tuberosum androgenetic plants have been obtained through anther culture, 47 of which derived from a tetraploid clone, seven from a diploid hybrid, and five from an anther-derived clone. About two thirds of the anther-derived plants were dihaploids, a few were monohaploids (5.08%) or aneuploids (6.78%), whereas the tetraploid genotype generated about a third of tetraploids. Seven hundred twenty seven R1 plants arisen from tubers of the androgenetic potatoes were mechanically inoculated with the necrotic strain of the potato Y potyvirus (PVYN) and grown in a glasshouse. Fifty days after inoculation, the presence of PVYN in R1 plants was detected by DAS-ELISA (Double Autibody Sandwich). Only three plants (0.4%) of genotype H2-258 exhibited local necrotic symptoms (hypersensitivity reaction) suggesting the presence of the Ny gene, and this extreme resistance is epistatic to hypersensitive resistance. The immunity (Ry-gene) to PVYN was retained through anther culturing and present at all levels of ploidy. The pattern of segregation for immunity was differentiated according to the ploidy level of the anther-derived plants. This changed segregation pattern may be due to a loss of resistance during the culturing, when an endoreduplication has taken place or to the possible regeneration from Second-division restituted unreduced microspores. Anyway, this segregation pattern must be taken into account when gametoclones are used in genetic studies.