Defoliation Effects on Grain Filling of R‐nj Color‐Selected Maize Strains

Abstract

Grain yield in maize (Zea mays L.) is often related to rate and duration of grain filling, which can be influenced by selection for R‐nj aleurone color expression. This study was conducted to determine how modifying the source/sink ratio affects grain‐filling characteristics and R‐nj color expression from two genetic backgrounds. Field experiments were conducted at Fargo, ND, with six synthetic strains derived from NDSF (early maturing) and NDSC (late maturing) and divergently selected for R‐nj color expression. A single plant from each plot was tagged and pollinated with bulked pollen from ‘Cudu’, a source homozygous for R‐nj. Three defoliation treatments (0, 50, and 100%) were applied at silking. Four sequential 15‐kernel samples (five each from the apical, mid‐ear, and basal sections of the ears) were taken at 3‐ to 4‐d intervals from alternate kernel rows during the linear phase of grain filling and at kernel maturity. Combined analyses of data over years indicated that source reduction (defoliation) reduced color intensity (CI), rate of dry matter accumulation (RDMA), and kernel weight. Strains selected for high color expression had higher RDMA and kernel weight than low color selections. As expected, the CI ratings corresponded to color selection groups. Color expression was positively correlated with RDMA and kernel weight. Results suggest that R‐nj color expression is related to sugar concentration in the endosperm during kernel development, and that selection for differences in color expression may be a simple, inexpensive means of modifying RDMA.