ORIGINAL ARTICLE Peanut Resistance Gene Expression in Response to Aspergillus flavus Infection During Seed Germination Huili Zhang 1 , Leslie Scharfenstein 2 , Dunhua Zhang 3 , Perng-Kuang Chang 2 , Beverly G. Montalbano 2 , Baozhu Guo 4 , Xianjun Meng 5 and Jiujiang Yu 6 1 Light Industry College, Liaoning University, Huanggu, Shenyang, China 2 Southern Regional Research Center, USDA/ARS, New Orleans, LA 70124, USA 3 Aquatic Animal Health Research, USDA/ARS, Auburn, AL 36832, USA 4 Crop Protection and Management, USDA/ARS, Tifton, GA 31793, USA 5 College of Food Science, Shenyang Agricultural University, Dongling, Shenyang, China 6 Beltsville Agricultural Research Center, USDA/ARS, Beltsville, MD 20705, USA Keywords Aspergillus flavus, fungal resistance, gene expression, peanut, plant–fungus interaction, real-time PCR Correspondence J. Yu, Beltsville Agricultural Research Center, USDA/ARS, Beltsville, MD 20705, USA. E-mail: Jiujiang.yu@ars.usda.gov Received: April 14, 2014; accepted: August 4, 2014. doi: 10.1111/jph.12311 Abstract Aspergillus flavus produces potent mutagenic and carcinogenic polyketide- derived secondary metabolites known as aflatoxins. Development of host plant resistance in peanut and other crops is the most environmentally friendly and cost-effective method to eliminate the serious problem of aflatoxin contamination in grains. To confirm that putative peanut genes identified in a previous microarray study were involved in peanut resis- tance to A. flavus infection, 14 genes were selected for further investiga- tion through real-time PCR. The results revealed diverse patterns of gene expression during seed germination after A. flavus inoculation. Based on the expression levels and the relative-expression patterns over a 7-day period, the 14 host genes could be classified into six different groups belonging to three main biochemical and genetic defence processes of lipid metabolism, oxidative signalling and cell-wall synthesis during counter- attack. A network of gene expression patterns was activated in sequential order in response to A. flavus invasion in both resistant and susceptible peanut lines during seed germination. Understanding gene expression patterns in peanut will be useful to breeders and other scientists interested in incorporating genetic resources of resistance against A. flavus into pea- nut germplasm and/or commercial cultivars via conventional and/or molecular methods. Introduction Aspergillus flavus produces the most potent mycotoxins known as aflatoxins that are mutagenic and carcino- genic polyketide-derived secondary metabolites. Aflatoxin contamination occurs when the toxin- producing fungi infect crops such as corn, peanut, cotton seed and tree nuts before harvest in the field and postharvest in stored grains. Elimination of afla- toxin contamination is a serious challenge facing the world today due to its economic and health impacts. Development of host plant resistance in peanuts would be a cost-effective and practical approach to prevent aflatoxin contamination (Holbrook et al. 2000; Guo et al. 2008). For this reason, peanut culti- vars with resistance to preharvest A. flavus infection have been the target of investigation for plant pathol- ogists and plant breeders around the world. In the past 20 years, several resistant maize lines have been identified and developed through field screening (Scott and Zummo 1988; Guo et al. 2005). With the development of maize kernel gene and pro- tein markers resistant to A. flavus infection/aflatoxin production, identification of natural resistance traits Ó 2014 Blackwell Verlag GmbH 1 J Phytopathol