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Agronomic Features of Two Maize Synthetics Selected for High and Low Stalk-Crushing Strengh¹

Maize (Zea mays L.) stalk lodging remains a major production-limiting problem despite progress in improving standability. Efforts to improve stalk quality may result in the production of maize with undesirable agronomic features. Two Missouri maize stalk-quality synthetics (MoSQA and MoSQB), were grown at Newark and Georgetown, DE, to determine if any changes in agronomic characteristics were associated with selection for high and low stalkcrushing strength in an environment other than Missouri. Plants from three levels of selection (C₆ low = 6th cycle of selection for low crushing strength, C6 high = 6th cycle of selection for high crushing strength, and CIO high = 10th cycle of selection for high crushing strength) and the original population (C₀) were evaluated for each synthetic. Plants were grown at 37 064 and 74 129 plants ha^–1 at both locations. Both synthetics responded significantly to selection for high crushing strength. Rind puncture pressure values (kg) of MoSQA taken 3 weeks after midsilking were 12.4 (C₆ low), 17.0 (C₀), 19.1 (C₆ high), and 22.2 (C₁₀ high). The corresponding values for MoSQB were 10.5, 15.0, 17.1, and 18.1. A significantly higher percentage of soft and lodged stalks was associated with low crushing strength selections compared with high crushing strength selections. The percentage of soft stalks decreased by 2.8% per cycle for MoSQA and 3.5% per cycle for MoSQB from C₀ to C₁₀ high. Stalk lodging was not increased at the high plant density for either synthetic due to the improved stalk quality following selection for high crushing strength. A significant increase in kernel yield for MoSQA with selection for high stalk-crushing strength was associated with increased plant height. An undesired significant increase in ear height, plant height, and a delay in maturity occurred for MoSQB. The MoSQA kernel yield increased 8.6% from C₀ to C₁₀ high with no consistent changes in ear height or maturity. However, a nonsignificant 3.1% kernel yield increase for MoSQB from C₀, to C₁₀, high was accompanied by a kernel moisture increase of 44.9%. Plant height, ear height, plant maturity, and yield should be carefully monitored when selecting for improved stalk quality in maize.

Key Words: Zea mays L. • Kernel yield • Kernel moisture • Lodging • Stalk quality • Rind puncture pressure

² Former research assistant and associate professor, respectively, Dep. of Plant Science, Univ. of Delaware, Newark, DE 19717-1303.

Received for publication March 18, 1985.