Relationships among phenotypic traits of sweet corn and tolerance to crowding stress

• Crowding stress tolerance (CST) has improved field corn yield over the last century.
• Sweet corn hybrids vary widely in CST, yet mechanisms of CST are unknown.
• Using 26 sweet corn hybrids, relations among 17 crop traits and CST were examined.
• Two groups of traits, ‘source-sink’ and ‘photosynthetic capacity’, relate to CST.

Crowding stress tolerance is defined as the extent to which the crop maintains yield per unit area as plant population density increases beyond standard levels. Sweet corn (Zea mays L.) hybrids grown for processing vary widely in tolerance to crowding stress; however, the mechanisms involved in crowding stress tolerance are unknown. The objective of the study was to determine the extent to which crop traits, individually and in combination, relate to crowding stress tolerance in processing sweet corn. Twenty-six modern shrunken-2 processing hybrids from eight sources were grown under conditions of crowding stress (i.e. 72,000 plants ha−1) over a three-year period. Seventeen crop traits measured from emergence to harvest were related to four measures of crowding stress tolerance, including ear mass, recovery, case production, and gross profit margin. Of individual crop traits, kernel mass plant−1 was among the best predictors of crowding stress tolerance in processing sweet corn, as long as sweet corn lines were grown at a uniformly high plant population. Two categories of traits related to crowding stress tolerance in sweet corn, including a ‘source-sink relationship’ factor and a ‘photosynthetic capacity’ factor. Factor regression showed the combination of traits loading into the source-sink relationship factor was positively related to ear mass, case production, and gross profit margin. This research points to the underlying mechanisms involved in crowding stress tolerance in processing sweet corn.