Comparison of four inoculation methods and three Fusarium species for phenotyping stalk rot resistance among 22 maize hybrids (Zea mays)

Fusarium stalk rot (FSR) is among the most destructive maize diseases causing significant global yield losses. Resistance of 22 maize hybrids to FSR was tested using four inoculation methods in each of two locations in 2021 and 2022. The inoculation methods included needle injection (NI), toothpick method (TM), stick method (SM) and mycelium method (MM), and the inoculated fungi were Fusarium culmorum, F. graminearum and F. temperatum. NI displayed the highest FSR infection among maize hybrids followed by TM and SM. MM showed the least infection. From five stalk rot-related traits, full-length infection and internode proportion, that is, the percentage of visible infection summed up over internodes, captured most of the genetic variation. The latter was the trait with the highest heritability (0.90). No significant (p > 0.05) genotype x method and genotype x fungus interaction variances were observed for any traits. For F. graminearum inoculation, NI showed the highest internode proportion followed by TM and SM, with F. culmorum responding in a similar way. For F. temperatum, TM outranked all other methods. F. graminearum was the most aggressive fungal pathogen compared to F. culmorum and F. temperatum. For phenotyping maize lines with varying degrees of resistance to FSR, we recommend needle injection and internode proportion.