Selection for Reduced Fusarium Ear Rot and Fumonisin Content in Advanced Backcross Maize Lines and Their Topcross Hybrids

Backcross breeding is an important method to improve elite cultivars for traits controlled by a small number of loci but has been used less frequently to improve quantitatively controlled traits. Resistances to Fusarium ear rot [caused by Fusarium verticillioides (Sacc.) Nirenberg (teleomorph Gibberella moniliformis Wineland)] and contamination by the associated mycotoxin fumonisin in maize ( Zea mays L.) are quantitatively inherited. We backcrossed the more resistant but unadapted inbred GE440 for four generations to the susceptible but agronomically elite commercial inbred FR1064. A selected set of 19 BC 4 F 1:3 lines had greater resistance to ear rot and fumonisin content than their recurrent parent FR1064. Topcrosses of the selected lines had greater resistance to Fusarium ear rot and similar grain yield compared to the topcross of the recurrent parent FR1064. We also genotyped selected lines at DNA markers linked to ear rot and fumonisin resistance quantitative trait loci (QTL) identified in the BC 1 generation of this cross to determine which QTL demonstrated allele frequency shifts due to selection. Markers linked to QTL on chromosomes 1 and 4 inherited the GE440 allele significantly more often than expected by random chance.