Selecting South American Popcorn Germplasm for Bipolaris maydis Resistance at Contrasting Nitrogen Levels

Nitrogen (N) availability plays a crucial role in plant development. However, studies indicate that the pathosystem of pathogenic fungi, such as Bipolaris maydis, which causes Southern Corn Leaf Blight (SCLB) in popcorn, interacts with N availability. Therefore, this study seeks to select popcorn inbred lines (ILs), considering contrasting environments regarding N availability (low N-LN and optimal N-ON). For this, 90 ILs from 16 populations from tropical and temperate climates from South America were evaluated in five experiments using a randomized complete block design (three replications), with four common controls. From the tests, the level of severity of the ILs to SCLB was evaluated. Three trials showed greater severity in ON, one trial had higher severity in LN, and one trial did not show significant differences. However, the genotype x nitrogen level (GxN) interaction was always present. Of the 90 ILs, 73 showed resistance in both N levels, three only in LN, and four only in ON, while 10 were susceptible in both environments. On average, the lines were more susceptible in ON, and the observed GxN interactions indicate that there is a distinct behavior of the genotypes regarding the response to N in the soil, which reinforces the importance of selection in contrasting environments.