Mapping the Effect of the LOX Gene Family on Aflatoxin Accumulation Resistance in Maize.

Maize (Zea mays L.) is a staple food and one of the most important cereal grains in the world. It is prone to contamination by aflatoxin, a secondary carcinogenic metabolite produced by the fungus Aspergillus flavus. An efficient approach to combat the accumulation of aflatoxin is the development of germplasm resistant to infection and spread of A. flavus. Lipoxygenases (LOXs) are a group of non heme iron containing dioxygenase enzymes that catalyze oxygenation of polyunsaturated fatty acids (PUFAs), and LOX derived oxilipins play critical roles in plant defense against pathogens such as A. flavus. The objectives of this study were to map the effect of all LOX genes in the maize genome on aflatoxin accumulation via linkage and association mapping. In total, 13 LOX genes were identified, characterized, and mapped. Genes GRMZM2G102760 in bin 5.02 and GRMZM2G104843 in bin 2.04 fell under previously published QTL in one of four mapping populations and appear to have a measurable effect on the reduction of aflatoxin in maize grains. Association mapping results find 19 of the total 215 SNPs tested from within the sequence of five genes GRMZM2G070092, GRMZM2G109130, GRMZM2G015419, GRMZM2G104843 and GRMZM2G102760 were associated with reduced aflatoxin levels at 7.51x10^-4 ≤ p ≤ 8.43 x 10^-5. In addition to confirming the importance of some lipoxygenases for fungal resistance, markers from within or linked to the sequence of these genes may be used for marker assisted selection and the creation of new resistant germplasm.