A review of potato propagation by means of seed, as distinct from clonal propagation by tubers

The vast majority of cultivated potatoes are vegetatively propagated, outbred autotretraploids. Disease problems dominate the maintenance of vegetative stocks. There have been recent proposals to propagate the crop by sexual seed in order to evade some of those disease problems. Some success has been achieved but controlled crosses are necessary to avoid inbreeding depression and seed propagation is not as cheap or simple as had been hoped. The idea has evoked wide interest throughout the tropics and has had some (and increasing) practical impact on China, India and Vietnam. There is a strong tendency to use 'tuberlets' borne on crowded nursery plants rather than to grow true seedlings. Some seedling families have looked locally attractive but it is not always realised that to use them implies the abandonment of about half the genetic variation, a heavy price to pay for disease avoidance. There is emerging recognition that vegetative and seed propagation are complementary rather than competitive and that good breeding programmes will therefore serve both. This review concentrates upon genetic/plant breeding aspects of propagation by seed, a subject hitherto largely neglected in the literature.