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Submitted to: CIMMYT Symposium Proceedings
Publication Type: Proceedings Publication Acceptance Date: 3/29/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Asynchronous floral development and abortion of fertilized ovaries are responsible for much of the kernel loss caused by drought during flowering in maize. Inhibition of silk elongation and ear growth at low water potential both contribute to the failure of silks to emerge during pollen shed. Because this delay in silk emergence, rather than loss of pollen availability, pollen viability, or silk receptivity generally limits kernel set, selection for genotypes which exert silks in advance of pollen shed (protogyny) should be beneficial. Modern maize genotypes tolerate up to 6 days of protogyny without loss of silk receptivity. Rapid and sustained ovary growth also is essential to maintain kernel set during drought. A decrease in assimilate production in droughted plants coupled with inhibition of carbohydrate metabolism within the ovaries leads to a dramatic decrease in carbohydrate partitioning to the ear, and ultimately, kernel abortion. While it has been possible to reverse the effects of drought on kernel abortion by supplying sucrose via stem infusion, attempts to increase kernel set in droughted plants by increasing assimilate supply per kernel naturally under field conditions have not proven successful. The ear of maize competes poorly for available assimilates. Selection for genotypes with rapid ear growth relative to vegetative growth at anthesis is a practical method to improve ear silk strength. Current research on the molecular basis for inhibition of ovary carbohydrate metabolism and the role of cytokinins in controlling ovary growth may provide new molecular targets for improving drought tolerance in maize. |
