Soybean, Glycine max (L.) Merr., lines isogenic for dense (DE), normal (NL), and no (NO) pubescence developed from the cultivar ‘Tracy-M’ were used in free choice tests to determine their influence on corn earworm (CEW) Heliothis zea (Boddie) oviposition preference and distribution of eggs within plant canopy. Post oviposition performance of the isolines was determined. Of the total eggs deposited by CEW on excised leaves in a greenhouse oviposition arena, 64.5, 29.0, and 6.5% were on the DE, NL, and NO isolines, respectively. In a 614.2 m2 field cage study, 57.0, 30.9, and 12.1% of eggs deposited were on the DE, NL, and NO isolines, respectively. Within plant egg distribution was proportionally the same for the DE and NL isolines with 83.7, 13.5, and 3.8% of eggs deposited on leaves, stems, and fruiting structures, respectively. However, the within plant egg distribution on the NO isoline was 90.0, 0.9, and 9.3% deposited on leaves, stems, and fruiting structures, respectively. Isolines with the greater number of eggs senesced later, produced fewer pods and fewer seeds per pod than isolines with fewer eggs. However, isolines with the greater number of eggs produced larger seeds, which resulted in ca. the same total seed weight per plant as isolines with fewer eggs. There were no differences among isolines grown without oviposition for pod number, seed number, or seed weight. The strong ovipositional preference among the isolines, if properly developed and used, has potential for use in insect management programs.
Author notes
1 Entomologist
2 Geneticist, Soybean Production Research, USDA ARS, Stoneville, MS 38776.