How Frequent Are Superior Genotypes in Plant Breeding Populations?

Summary A search of plant breeding literature has produced 69 examples in which reasonable judgements could be made as to potential for genetic advance. The crops covered are all inbreeders (predominantly cereals) or outbred clones. The average potential for genetic advance (roughly 60 % of examples were favourable) seemed to be far higher than would usually be expected and to indicate therefore that excellent new crop varieties should be more frequent than experience suggests. The discrepancy may be partly explained by various biases but the main conclusion is that superior genotypes are indeed fairly frequent but that selection efficiency is too low to take better advantage of them.