Genetic Variation in Testcrosses and Relationship between Line per se and Testcross Performance for Resistance to Gibberella Ear Rot in Maize

Gibberella ear rot (GER), caused by Fusarium spp., is a major concern in maize production in Central Europe, and development of hybrid cultivars having GER resistance is an important breeding goal. The objectives of the present study were to (i) evaluate the variation in testcross performance (TP) of European maize germplasm for GER resistance and deoxynivalenol (DON) contamination, (ii) estimate variance components, heritabilities, and correlations of these traits, and (iii) examine the relationship between line per se performance (LP) and TP. Testcrosses of 30 diverse flint inbred lines with two dent inbred testers were evaluated in four environments under artificial inoculation. Data were recorded on severity of GER and concentration of DON. There was substantial GER development and the range of both traits was greater for LP than TP. Estimates of genotypic and genotype x environment interaction variances were significant for testcrosses with both testers. Genotypic variances were generally higher for LP than for TP in each testcross set. Correlations between LP and TP were moderate ((r) over cap (p) <= 0.57) for GER rating and DON concentration. We recommend multi-stage selection to develop GER resistant maize hybrids based on evaluation of GER resistance under artificial inoculation for (1) LP in one environment followed by (2) TP evaluation in two to three environments. Only the most promising testcrosses should be tested for DON concentration.