Past and prospects of forage maize breeding in Europe. II. History, germplasm evolution and correlative agronomic changes

Although maize was early recognized as an excellent forage plant soon after its introduction in Eu- rope, during a long time it was only bred for grain traits. However, the first recommendations of maize varieties for specific forage use are probably those given in the French VILMORIN-ANDRIEUX catalogues as early as the second mid of the 19th century. The 1940 Dutch variety list distin- guished several types of maize varieties and was already recommending three varieties for silage use. Whereas US hybrids were introduced in Europe in the early 1950s, the significant extension of silage maize cropping began after the release of early flint x dent hybrids such as INRA258 (1958) and a little later Brillant DK202, Capella, LG11, and Blizzard G188 (between 1965 and 1975). The increase went on until 1990, with a decrease or stabilization fol- lowing. The first generation of early European maize hy- brids was mostly often based on crosses between flint La- caune and dent Minnesota13 lines. The registration of Dea (1980) in France and a few years later Golda in Ger- many both illustrated tremendous changes in maize dent, and to a lesser extent flint, germplasm and marked the onset of a second era in European maize hybrid breeding. Iodent and BSSS origins were thus substituting for Min- nesota13. Correlatively, the era of 1980s was also marked by significant improvement of hybrid earliness. The actual maize breeding is characterized by a significantly greater introgression of medium late germplasm into early dent and flint maize lines. The beginning of this last period may be dated by the registration of Banguy (1992). The average genetic improvement in whole plant yield was close to 0.10 t/ha.year during the period between 1958 and 1988, but reached 0.17 t/ha.year between 1986 and 2004. In early maize, highly significant improvements of stalk standability, stalk rot and lodging resistance have been achieved between 1950 and 2004 in Europe. Physio- logical changes associated to these improvements are at least delayed senescence of leaves and stems, higher grain filling rate, and higher stress tolerance. Conversely to agronomic value, a steady decline in the average cell wall digestibility of hybrids was observed since the 1950s, and maize of the next future have to give a better balance between agronomic and feeding value traits.