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 insegregating maize genetic materials. F1/F2 comparisons were made to evaluate the genetic materials and F1/F2andF2 mixtures of genotypes were formed to ensure allocompetition conditions. Moreover, two severe stresseswere applied: plant density and low inputs, in addition to full-inputs conditions. Prisma Fl and F2 were betteryielding materials than Funo Fl and F2, respectively. Until 13.33 plants m~(-2) there was an increase in Fl fieldyields, followed by lower yields in increased plant density, since modern hybrids tolerate greater plantpopulations. Significant interaction between genetic materials and plant density found in full-inputsexperiments, was eliminated under the strong low-inputs stress. The indications from Half-sib progenyevaluation showed strong relationship between progeny yield and both selected plants' yield and selectiondifferential. High selection differential was realized under low-inputs condition due to low performance oforiginal genetic materials. Strong allocompetition conditions may have a negative effect on HS progeny yieldingperformance, since mixtures of different genetic materials lead to lower yields. As a final conclusion, presentfindings 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 mustinclude SI and Full-sib progenies and selection of progeny plants must include not only the highest yieldingplants, but plants from the upper, mean and lower yielding areas of yield distribution, as well.