A maize gene controlling silk browning in response to wounding.

ROWNING is a common degradative phenomenon of injured cIr senescent ' vegetable tissue (SZENT-GYORGYI 1969). I t is due to enzymatic oxidation of polyphenolics resulting in quinones which form brown colored complexes with protein. When fresh corn silks (stigmas) were ground in an aqueous solution and allowed to stand, it was observed that the brei normally turned brown. Occasionally, ground silks from certain inbreds were found which did not turn brown hut remained yellow-green (i.e., no change in color). Later, it was learned that the browning or nonbrowning phenotypes could be determined on the plant by cutting back fresh silks, as in preparation for controlled pollination, and observing the cut ends after about 15 minutes. In this instance, cut ends become brown in the browning phenotype and remain unchanged in the ncnbrowning. The distinction between browning and nonbrowning types is also evident with senescent silks of mature ears. In this case, senescent silks from the browning type appear very dark brown while nonbrowning are tan in color. This study was conducted to determine the inheritance and chemical basis of the browning and nonbrowning response to wounding of corn silks. We will show that the browning response is controlled by a single dominant locus which permits, primarily, the synthesis of dihydroxyl flavoaes by the silks and that when the silks are injured these flavones are enzymatically oxidized resulting in brown pigment formation. The nonbrowning type will he shown to be due to a recessive allele which when homozygous blocks the synthesis of the dihydroxyl flavones. Absence of the flavone substrates precludes brown pigment formation in response to wounding.