Evaluation of fall armyworm resistance in maize germplasm lines using visual leaf injury rating and predator survey

After examining ear-colonizing pest resistance, 20 maize lines from the USDA-ARS Germplasm Enhancement of Maize (GEM) Program were evaluated for whorl-feeding fall armyworm (FAW) (Spodoptera frugiperda) resistance using 4 maize inbred lines as the resistant and susceptible controls. Both FAW injury ratings at 7- and 14-d after infestation, and predator abundance and diversity at whorl stage (V6-V8) were recorded in 2009 and 2010. The survey of the diversity and abundance of predators in each experimental plot were conducted 7 d after the FAW infestation. Of the 20 germplasm lines examined, 3 of them (i.e., entries 9, 15, and 19 that were derived from tropical maize germplasm lines were originated from Uruguay, Cuba, and Thailand, respectively) were identified as the best FAW-resistant germplasm lines using the leaf injury ratings and predator survey data. In addition, the abundance and diversity of the predators were greater in 2010 than in 2009, which might have caused the low level of the FAW injury ratings on all lines examined in 2010. The 2-year data showed that the FAW injury ratings were negatively correlated to the predator abundance and diversity, which is also influence by genotype × environment interactions. The findings suggested that tropical germplasm is an important source of native resistance to the FAW and the corn earworm. At the same time, the maize genotype × environment interaction (e.g., predator attractiveness, and varying weather conditions) should be included in the multiple-year evaluations of insect and disease resistance of maize germplasm lines under field conditions.