Divergent Selection among Maize Seedlings for Nitrate Uptake

Abstract

Selection applied to seedlings grown under controlled environmental conditions may contribute to plant improvement provided agronomic traits are well correlated to the seedling selection trait. The objective of this research was to utilize techniques for screening maize (Zea mays L.) seedlings for induced NO3 uptake in order to evaluate direct and indirect effects of such selection on populations created. Two cycles of divergent mass selection were performed on the open‐pollinated maize populations ‘Jarvis Golden Prolific’. Resulting populations together with the original ‘Jarvis’ were evaluated under selection conditions in the laboratory and in field trials at three locations in each of 2 yr. Significant changes in the selection trait were observed (selection response = 13.3% per cycle) that were due primarily to effects on plant size. Realized heritabilities of the first generation of selection were 0.25 for high NO3 uptake and 0.10 for low NO3 uptake. Nitrate uptake and seedling size declined in both selection directions in the second cycle. Relative changes in uptake and reduction of NO3 differed between selection cycles. Correlated responses in yield, ear number, and grain N were observed in the field, but significant genotype ✕ environment (year, location, and N supply) interactions were evident. Response to N as measured by yield and N use parameters was not associated with selections based on seedling NO3 uptake.