Comparison among inbreeding systems in maize

Abstract

The use of less severe inbreeding systems than self-fertilization has been suggested as a means of developing more vigorous maize lines (Zea mays L.). To compare different inbreeding systems, nine traits were evaluated in inbred lines developed by full-sib mating (F=0.5), self-fertilization (F=0.5), half-sib mating (F= 0.305), from the following populations: BR 105, a synthetic variety, and ESALQ-PB 4 , which is a composite of wide genetic base. The means and genetic parameters comparisons showed no important advantages of full-sib crosses over selfing. The inbreeding depression values for grain yield were similar between these groups of lines and inferior for half-sib lines. The inbreeding depression rates / 1% of expected homozigosity were similar among the three inbreeding systems. We conclude, in view of large inbreeding depression showed by tropical populations of maize in Brazil, that it is more reasonable to allocate resources and time in breeding source populations than to use milder forms of inbreeding