Quantitative Trait Locus Analysis of Cold Tolerance in Maize

With booming populations soon to overwhelm the world's food production capabilities, studying what makes crops, like maize, efficient is crucial to ensure that the demand for food is met. In Minnesota and other northern states, planting earlier in the spring would lengthen the crop season and result in larger yields. However, the crops need to be tolerant to early spring’s low night temperatures. The goal of the study was to discover genomic regions harboring genes that could confer cold tolerance to maize lines. A quantitative trait locus analysis was conducted using a cold tolerant Mo17 line and a cold resistant B73 line and 97 recombinant inbred lines produced from these two lines. Cold tolerance was quantified after 8 hour incubation at 40C as leaf chlorophyll concentration, proportion of the leaf remaining green calculated by a computer image analysis, and a qualitative visual assessment of stress response. Four chromosomal regions (quantitative trait loci, QTLs) on chromosomes 1, 3, 5, and 7 were identified as containing genes conferring cold stress tolerance to maize seedlings. These regions were well supported by combinations of our phenotypic data. Genes controlling cold tolerance are likely located in these regions and are activated or silenced in response to cold stress. Gene expression data were used to identify genes within the four QTL regions that were up- or down-regulated in response to cold stress. Fourteen genes exhibiting natural variation in cold stress response between B73 and Mo17 were identified in the four QTL regions. These genes potentially explain the difference in cold stress response between B73 and Mo17 and could be selected for to breed cold tolerance in maize.