Evaluation of in vitro methods to define the role of the cob and pedicel-placento-chalazal tissues in the amino acid supply to the developing maize endosperm

Abstract

Two in vitro methods that mimic the in vivo (field conditions) endosperm development of the Illinois High (IHP) and Illinois Low Protein (ILP) maize strains were evaluated. For the first method, immature endosperms, 9 days after pollination (DAP), were grown for 5 days on solid media containing a source of inorganic nitrogen (N) in the presence or absence of glutamine. On both culture media, the ILP endosperms accumulated more starch than the IHP endosperms. The same occurred with in vivo grown endosperms. In vitro ILP had the same zein content as IHP, reaching higher values than that observed at the same stage in vivo. The chromosome endoreduplication analysis of IHP and ILP endosperms in vitro cultured with this method, exhibited a mean ploidy level significantly lower than controls at the same stage for both strains. For the second method, ears were harvested at 4 and 9 DAP, cut into cob-blocks and cultured until 25 DAP. Both IHP and ILP kernels grown in vitro showed, for the specific strain, a phenotype similar to that observed in kernels grown at the same stage in field conditions. An experiment including 14 C -glutamine in the culture media of cob-blocks suggested that the cob and pedicel-placento-chalazal (PPCh) tissues may be involved in determining the ILP phenotype.