Horner, T.W.Frey, K.J.2014-09-052014-09-052007Agronomy Journalhttp://hdl.handle.net/123456789/5377Substantial reduction of the variety-location interaction affecting genotypic progress resulted from proper subdivision of Iowa into subregions, following a procedure described herein. For example, optimum subdivision into four parts resulted in a reduction of 30%. Implications with respect to a breeding program were briefly discussed. The data involved 9 locations, 5 years and oat varieties previously selected for wide adaptability.enArticle