Mutation breeding for yield and Phytophthora infestans (Mont.) de Bary foliar resistance in potato (Solanum tuberosum L-cv. Golden Wonder) using computerized image analysis in selection

Using visual selection for off-types and image analysis to select against m aturation mutants, a line combining improved late blight resistance and yie ld was isolated in an in vitro mutagenesis programme from a population of 2 101 putative mutants. The adventitious regenerants from mutagenesis treatme nt, including spontaneous mutants (somaclonal variants), were subjected to serial subculture of the apical bud in vitro and two cycles of apical cutti ngs in vivo to breakdown chimeras. The selected line was stable in trials o ver five years; others were unstable or failed to combine improvement in la te blight resistance with high yield. Leaf and tuber image analysis was use d to characterize selected lines. Lines that differed most from cv. Golden Wonder in yield and late blight resistance were more easily distinguished f rom the control by image analysis. The role of image analysis in negative s election and in determination of the relatedness of mutants to the control is discussed.