Diallel Analysis of Afl atoxin Accumulation in Maize

Afl atoxin, a toxin produced by the fungus Asper- gillus fl avus Link:Fries, occurs naturally in maize (Zea mays L.). It is a potent carcinogen, and its presence markedly reduces the value of grain. Host-plant resistance to A. fl avus infection and subsequent afl atoxin accumulation is gener- ally considered a desirable means of reducing losses to afl atoxin. Maize germplasm lines with resistance to afl atoxin contamination have been developed in Mississippi. Four of the afl atoxin- resistant lines and six other lines were used as parents to produce a diallel cross. The diallel cross was evaluated for resistance to afl atoxin contamination in fi eld trials conducted in Missis- sippi in 2005 and 2006. General combining abil- ity (GCA) and specifi c combining ability (SCA) were highly signifi cant sources of variation each year. Reciprocal effects were not signifi cant in 2005 or in the combined analysis over years. In the analysis over years, GCA effects for reduced afl atoxin were highly signifi cant for the four lines developed as sources of resistance: Mp313E, Mp494, Mp715, and Mp717. The GCA effect for reduced afl atoxin was also highly signifi cant for Mo18W and NC408. These lines should be use- ful in developing maize lines and hybrids with resistance to afl atoxin contamination. Breeding methods that maximize the use of GCA should be effective in enhancing resistance to afl atoxin accumulation when using these germplasm lines.

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