Variability among maize hybrids differing in canopy architecture for above-ground dry matter and grain yield

Dry matter and grain yields are among the traits most commonly used to eval uate maize (Zen mays L.) hybrid performance. Production of both dry matter and grain yield is often influenced by hybrid size. The efficiency with whi ch a hybrid allocates accumulated dry matter into economic grain yield has a large influence on potential grain production. The objective of this work was to quantify dry matter grain yield and harvest index of 17 hybrids rep resenting a range of canopy architectures. A field experiment was conducted on clay loam soil at the E. A. Lods Agronomy Research Center, Ste. Anne de Bellevue, Quebec in 1997 and 1998. Hybrids were arranged in a randomised c omplete block; design and included 11 newly developed leafy reduced-stature (LRS), four non-leafy reduced-stature (NLRS), one conventional (Pioneer Br and 3979), and one late-maturing big leaf (LMBL) hybrids. In both years, ge nerally above-ground dry matter was greater for the taller LMBL and Pioneer Brand 3979 than for the shorter hybrids, but greater grain yields were mea sured for both thr taller and five of the 11 LRS hybrids. Moreover grain yi elds averaged over canopy groups were not differ ent. The shorter hybrids h ad greater assimilate allocation to the grain than the taller (especially L MBL) hybrids, and this was evident in their harvest index values. However w ithin the LRS group, hybrids differed for both dry matter and grain yield w ith some being similar to the NLRS hybrids while others were similar to tl- ie taller Pioneer Brand 3979 hybrid. The hypothesis that the changes in dry matter allocation seen in two LRS hybrids evaluated in previous studies (B EGNA et al., 1997a,b) is a condition of all LRS hybrids was rejected. While these hybrids show considerable potential in this: regard some careful sel ection for the production of commercial hybrids is required.