Twenty-Four Cycles of Mass Selection for Prolificacy in the Golden Glow Maize Population

Abstract

Maize (Zea mays L.) has the potential to produce an ear primordium at several nodes, and selection for increased prolificacy often increases grain yield. We have previously demonstrated the effectiveness of mass selection for increasing the number of active ear shoots in the ‘Golden Glow’ maize population. The objective of our research was to evaluate associated changes in ear and plant morphology after 24 cycles of mass selection for prolificacy in Golden Glow. Cycles 0, 6, 12, 18, 23, and 24 were grown in 1997 at two locations (Madison and Arlington, WI) at two planting densities (15 070 and 73 197 plants ha−1). At the lower planting density, the mean number of ears per plant increased from 1.61 at C0 to 4.93 at C24, and the response rate increased over the more recent cycles, mainly from C18 to C24. At C24, tiller number has increased, and lateral branches (terminating in ears) were located at approximately one node higher and two nodes lower on the main stalk compared with the original population. Total node number on the main stalk increased, and the internode length decreased over the 24 cycles, but the opposite occurred for lateral branches. At the lower planting density, ear diameter, ear length, and kernel size decreased by 0.03, 0.10, and 0.01 cm cycle−1, respectively, but total number of kernels per plant and dry kernel weight per plant increased significantly at a rate of 36.69 kernels cycle−1 and 5.60 g cycle−1 over the 24 cycles. Similar trends, but of lesser magnitude, were observed at the higher planting density. The changes in plant morphology observed across cycles of selection for prolificacy represent a general derepression of axillary meristematic growth in both main stalks and lateral branches.