Resistance Breeding to Northern Corn Leaf Blight with Dominant Genes, Polygene, and Their Combinations—Effects to Yield Traits

Resistance breeding is the most economic method to control northern corn leaf blight (NCLB). The objectives of these studies were: To assess effects of dominant genes (Ht(s)), polygene (PG), and combinations on percent leaf area affected (PLAA), yield, kernel moisture, kernel number per ear, and 100-kernel weight; to understand genetic action of combinations; to predict losses and effects of resistant genes for yield traits with PLAA; and to assess yield under different NCLB epidemic conditions. Two experiments were conducted. E1 had 120 crosses, their parents, and ten hybrid checks, inoculated NCLB twice in 2015 and 2016; and E2 had 85 crosses and 10 hybrids, with none, one, and two inoculation treatments in 2015. E1 results showed the order of PLAA was Ht3 ≈ Ht2 ≈ PGHtm1 ≈ PGHt1< PGHt3 ≈ PGHt2 < PGHtn1 < PG < Ht1 < Htn1 ≈ Htm1. The order of Ht(s) effects for yield was Ht2 > Ht3 > Ht1 > Htm1 > Htn1. Gene effects of cross ≈ gene effects of (female + male) for all five traits. Predicted losses and predicted effects of resistant genes between yield traits with PLAA were determined. E2 results indicated resistant genes increased yield more efficiently under NCLB epidemic environments.