Maize leaf spots

The main causal agents of leaf spots include Cochliobolus heterostrophus, Setosphaeria turcica, Cercospora zeae-maydis, Cochliobolus carbonum, and Physoderma zeae-maydis, as well as bacterial pathogens Pseudomonas and Xanthomonas. Symptoms vary from streaks and stripes to rectangular or oval necroses, often delimited by leaf veins, with disease development typically starting from the lower canopy.

Genetic protection is based on specific genes, such as Hm1, responsible for the detoxification of Cochliobolus carbonum metabolites, and a series of Ht genes (Ht1, Ht2, Ht3, Htm1, Htn1) that reduce the severity of Setosphaeria turcica infection. In addition to monogenic resistance, quantitative resistance controlled by multiple QTLs is widely used in breeding, with its level evaluated using scoring scales.