Genetic progress in Dutch crop yields

Abstract

Crop yields are a result of interactions between genetics, environment and management (G×E×M). As in the Netherlands differences between potential yield and actual farm yields (yield gaps) are relatively small, progress in genetic potential is essential to further increase farm yields. In this paper we study the progress in yields of newly released varieties in official Dutch variety trials as a proxy for the progress in genetic yield potential, i.e., yield under absence of water and nitrogen limitation and pests and diseases. The use of yields from variety trials as a proxy for genetic yield potential is justified as these are well managed and because water is hardly limiting under Dutch climate–soil conditions. We compared the genetic yield progress of winter wheat (Triticum aestivum L.), spring barley (Hordeum vulgare L.), ware and starch potato (Solanum tuberosum L.) and sugar beet (Beta vulgaris L.) over the past ca. 30 years (ca. 1980–2010) with the developments in on-farm yields over the same period. GenStat 14th edition was used to perform modified joint regression analyses (mjra) and residual (or restricted) maximum likelihood (reml) analyses of yields in order to separate year (i.e., climate and/or management) effects from variety effects. Genetic progress in yield has been linear with ca. 100 and 60kgha−1year−1 (15% moisture), respectively, for winter wheat and spring barley, 580kgha−1year−1 payment weight for starch potato, and, partly non-linear for sugar beet, i.e., 80–170kg sugarha−1year−1 depending on resistance type of the varieties. We also analyzed significant year effects (corrected for genetic progress) for most crops in the variety trials, which point at an effect of climate (environment) and/or management in addition to the genetic effect. Farm yields of winter wheat, spring barley and starch potato have increased linearly over the last decades, with ca. 90, 70 and 320kgha−1year−1 (in the same units as above). Increase in sugar yields on farms was concave (20–230kgha−1year−1) and spectacular over the last 10 years. For ware potatoes the genetic yield increase was only 20kg dry matterha−1year−1 and reliable farm statistics for dry matter yields are lacking. We conclude that for the main crops in the Netherlands genetic progress in yield potential of varieties newly released over the past three decades has been substantial and largely linear. Farm yields for these crops also continued to increase, at approximately the same rates, but could not always keep pace with the combined genetic and year effects (G×E×M) in variety trials, suggesting a widening yield gap.