Use of southern parents in a short-season soybean breeding program is facilitated with long-day screening

Elite northern-by-southern soybean crosses may increase genetic diversity while maintaining performance. The objective of this study was to test a long-day selection method which would generate populations containing southern germplasm adapted in maturity to short-season areas. Long-daylength-insensitive lines (MG 00 to 0) were crossed to southern determinate cultivars (MG IV to VI) and of 909 F2 plants grown under 20-h incandescent long daylength (ILD), 34 were ILD-insensitive and non-dwarf. Progeny from selected ILD-insensitive plants were intermated and the resulting modified double cross F2 populations were grown in the field and were of late MG I adaptation. The ILD-screening technique was useful for generating early-maturing populations from parents with divergent maturity.