Stress Conditions for Improvement of Mass Breeding Method in Maize

摘要

Mass selection during early stages of genotype evaluation is essential for maize breeding programs. The purpose of this study was to determine the proper conditions for mass selecting useful genotypes in segregating maize genetic materials. F1/F2 comparisons were made to evaluate the genetic materials and F1/F2 and F2 mixtures of genotypes were formed to ensure allocompetition conditions. Moreover, two severe stresses were applied: plant density and low inputs, in addition to full-inputs conditions. Prisma F1 and F2 were better yielding materials than Funo F1 and F2, respectively. Until 13.33 plants m^-2 there was an increase in F1 field yields, followed by lower yields in increased plant density, since modern hybrids tolerate greater plant populations. Significant interaction between genetic materials and plant density found in full-inputs experiments, was eliminated under the strong low-inputs stress. The indications from Half-sib progeny evaluation showed strong relationship between progeny yield and both selected plants? yield and selection differential. High selection differential was realized under low-inputs condition due to low performance of original genetic materials. Strong allocompetition conditions may have a negative effect on HS progeny yielding performance, since mixtures of different genetic materials lead to lower yields. As a final conclusion, present findings indicated that selection of genotypes must be practiced under conditions of high selection differential. The original population mean is not as important as the selection differential. Extended experimentation must include S1 and Full-sib progenies and selection of progeny plants must include not only the highest yielding plants, but plants from the upper, mean and lower yielding areas of yield distribution, as well.