Changes in genetic diversity during seven cycles of recurrent selection for grain yield in oat, Avena sativa L.

Variability for desirable alleles within elite breeding populations is a re quirement for long-term genetic improvement. Changes in genetic diversity w ere evaluated in a recurrent selection programme for enhanced grain yield i n oat, AL ena sativa L., using coefficient of parentage (r(p)) and restrict ion fragment length polymorphism (RFLP) based genetic similarity (s) estima tes. Both r(p) and s increased during seven cycles of recurrent selection, indicating a reduction in the level of genetic diversity within the populat ion. The relationship between generic diversity and agronomic performance w as also examined. Genetic similarity measures were poor predictors of the n ear-homozygous progeny performance and general and specific combining abili ty effects for three agronomic traits in the recurrent selection programme. in addition, there was no apparent trend for preferential selection of pro geny from either more similar or more diverse parents within a given cycle of selection. The overall reduction in genetic diversity in this population has not affected selection response for grain yield. Variability remaining at important loci or de novo variation are possible explanations for the c ontinued selection progress.