INHERITANCE OF MAYSIN CONTENT IN SILKS OF MAIZE INBREDS RESISTANT TO THE CORN-EARWORM

Genetic information is needed on maysin, a compound in maize, Zea mays L., silks that is antibiotic to corn earworm larvae, Helicoverpa (for merly Heliothis) zea (Boddie), to assist in the process of breeding fo r resistance to this pest. This study was initiated to elucidate the i nheritance of maysin content in the silks of a cross between two maize inbreds (GT114 and GT119) having resistance to the com earworm. Rever sed phase high performance liquid chromatography (HPLC) procedures wer e used to quantify the maysin concentration of silks from individual p lants in the parent, F1, F2, and first backcross generations of the cr oss GT114 x GT119. A model assuming dominance at a single locus for lo w maysin content which is expressed only when a dominant modifier is p resent was proposed to explain the segregation ratios obtained in the F1 and first backcrosses of GT114 x GT119. This model also provided a fit for maysin data previously generated from a cross between inbreds F6 and F44. Observations of selfed families in the backcross of GT114 x GT119 to the low maysin parent confirmed the two-locus model (one fa ctor with dominance for low maysin expressed only when a modifier gene is also present) as a plausible explanation for inheritance of silk m aysin in the cross. The process of selection for high maysin will be c omplicated somewhat by the presence of a gene which modifies the expre ssion of dominance unless a method of easily identifying the gene, ind ependent of maysin content, can be developed.