Effect of Sink Level on Root and Stalk Quality in Maize

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Abstract
Grain yield and resistance to root and stalk lodging currently require major emphasis in maize (Zea mays L.) breeding programs. Selection for high expression for one of these characters is often at the expense of the others. Oar objective was to evaluate the effect of grain sink level on root and stalk strength. Fourteen entries were grown including the CO, C4, C8, and Cll of MoSQA, a white endosperm synthetic population selected for high stalk crushing strength; the CO, C4, C8, and Cll of MoSQB, a yellow endosperm synthetic population selected for high stalk crushing strength; two single crosses with high root strength; two single crosses with low root strength; B73 ✕ Mo17, a high‐yielding, widely grown single cross; and ‘US13’ a lower yielding double‐cross hybrid with poor root and stalk strength. Grain sink levels were established by allowing open pollination (100% sink level), preventing pollination (0% sink level), and by physically removing the top half of the ear 10 d after pollination (50% sink level). Root strength was measured vertical root pulling resistance and stalk strength was determined by crushing a 2.5‐cm stalk section. Results from four environments indicated that vertical root pulling resistance declined linearly as sink level increased for all entries. Stalk crushing strength declined with increased sink level for all hybrids and for most of the cycles of MoSQA and MoSQB. Exceptions were Cycle 11 of both MoSQA and MoSQB for which stalk crushing strength was similar at all sink levels.